Skeletal system Flashcards
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The various vertebrae are named according to their location in the vertebral column. The cervical vertebrae are located in the neck. The first cervical vertebra, called the atlas, holds up the head and allows it to tilt side to side. It is so named because Atlas, of Greek mythology, held up the world. The second cervical vertebra is called the axis, because it allows a degree of rotation. The thoracic vertebrae have long, thin spinous processes (Fig. 12.7a). The thoracic vertebrae articulate with one another and with the ribs at articular facets. Lumbar vertebrae have large bodies and thick processes. The five sacral vertebrae are fused together in the sacrum. The coccyx, or tailbone, is usually composed of four fused vertebrae.
Types of Vertebrae
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need atp to attach myasin heads to actin
need in form of Adp and phosphate form
triggers
What role does atp in muscle contraction
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Extra
BIOLOGY TODAY Science
Osteoarthritis and Joint Replacement Surgery
Osteoarthritis is a condition that afflicts nearly everyone, to a greater or lesser degree, as each person ages. The bones that unite to form joints, or articulations, are covered with a slippery cartilage. This articular cartilage wears down over time, as friction in the joint wears it away (Fig. 12B). By age 80, people typically have osteoarthritis in one or more joints. By contrast, rheumatoid arthritis is an autoimmune disorder (see Section 7.5) that causes inflammation within the joint. Unlike osteoarthritis, which typically affects older people, rheumatoid arthritis can afflict a person of any age, even young children. Both forms of arthritis cause a loss of the joint’s natural smoothness. This is what causes the pain and stiffness associated with arthritis. Arthritis is first treated with medications for joint inflammation and pain and with physical therapy to maintain and strengthen the joint. If these treatments fail, a total joint replacement is often performed. Successful replacement surgeries are now routine, thanks to the hard work and dedication of the British orthopedic surgeon Dr. John Charnley.
Figure 12B Osteoarthritis. A comparison of a normal knee (a) and a knee with osteoarthritis (b).
(both): ©Puwadol Jaturawutthichai/Alamy
Early experimental surgeries by Charnley and others had been very disappointing. Fused joints were immobile, and fusion didn’t always relieve the patient’s pain. Postsurgical infection was common. The bones attached to the artificial joint eroded, and the supporting muscles wasted away because the joint wasn’t useful. Charnley wanted to design a successful prosthetic hip, with the goal of replacing both parts of the diseased hip joint: the acetabulum, or “socket,” as well as the ball-shaped head of the femur. Charnley soon determined that surgical experimentation alone wasn’t enough. He studied bone repair, persuading a colleague to operate on Charnley’s tibia, or shinbone, to see how repair occurred. He studied the mechanics of the hip joint, testing different types of synthetic materials. He achieved his first success using a hip socket lined with Teflon but soon discovered that the surrounding tissues became inflamed. After multiple attempts, his perfected hip consisted of a socket of durable polyethylene. Polyethylene is still used today as the joint’s plastic component. The head of his prosthetic femur was a small, highly polished metal ball. Stainless steel, cobalt, and titanium, as well as chrome alloys, form the metal component today. Various techniques for cementing the polyethylene socket onto the pelvic bone had failed when bone pulled away from the cemented surface and refused to grow. Charnley’s surgery used dental cement, slathered onto the bone surfaces. When the plastic components were attached, cement was squeezed into every pore of the bone, allowing the bone to regenerate and grow around the plastic. Finally, Charnley devised a specialized surgical tent and instrument tray to minimize infection.
Charnley’s ideas were innovative and unorthodox, and he was reassigned to a former tuberculosis hospital, which he converted into a center for innovation in orthopedic surgery. His colleagues developed a prosthetic knee joint similar to the Charnley hip. In knee replacement surgery (see the chapter opener), the damaged ends of bones are removed and replaced with artificial components that resemble the original bone ends. Hip and knee replacements remain the most common joint replacement surgeries, but ankles, feet, shoulders, elbows, and fingers can also be replaced. Though many improvements on the procedure continue, the Charnley hip replacement remains the technique after which all others are modeled.
When a joint replacement is complete, the patient’s hard work is vital to ensure the success of the procedure. Exercise and activity are critical to the recovery process. After surgery, the patient is encouraged to use the new joint as soon as possible. The extent of improvement and range of motion of the joint depend on its stiffness before the surgery, as well as the amount of patient effort during therapy following surgery. A complete recovery varies in time from patient to patient but typically takes several months. Older patients can expect their replacements to last about 10 years. However, younger patients may need a second replacement if they wear out their first prosthesis. Still, individuals who have joint replacement surgery can expect an improved quality of life and a bright future with greater independence and healthier, pain-free activity.
Questions to Consider
Compare each component of Charnley’s artificial joint with that of a real synovial joint.
Explain why rheumatoid arthritis is actually a disorder of the immune system.
Movements Permitted by Synovial Joints
Intact skeletal muscles are attached to bones by tendons that span joints. When a muscle contracts, one bone moves in relation to another bone. The more common types of movements are described in Figure 12.11.
Figure 12.11 Synovial joints allow for a variety of movement. a. Flexion and extension. b. Adduction and abduction. c. Rotation and circumduction. d. Inversion and eversion. Red dots indicate pivot points.
CHECK YOUR PROGRESS 12.4
List the three major types of joints.
Answer
Fibrous, cartilaginous, synovial.
Describe the basic movements of cartilaginous and fibrous joints, and give an example of each in the body.
Answer
Cartilaginous joints are slightly movable and found in the rib cage and intervertebral discs; fibrous joints are not movable and are found in the sutures of the skull.
Describe the different movements of synovial joints, and give an example of each in the body.
Answer
Flexion and extension—knee; adduction and abduction—hip and shoulder; rotation—arm; circumduction—hip and shoulder; inversion and eversion—foot and ankle.
CONNECTING THE CONCEPTS
For more information on ligaments and tendons, refer to the following discussion:
Section 4.2 describes the connective tissue found in the tendons and ligaments.
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tendon
endomesium - delicate connective tissue sheet- particular fibers- individual cell
perimecium- fascilcle- bundling together
endomesium- outside
tendon- connective tissue- forms - fusion- of all connective tissue sheets conencting muscle to bone
origin and insertion- attachment of muscle on stationary bone- insertion- attachment on bone that moves
How are skeletal muscles attached ; hierarchy of organization
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12.3 Bones of the Appendicular Skeleton
LEARNING OUTCOMES
Upon completion of this section, you should be able to
Identify the bones of the pelvic and pectoral girdles.
Identify the bones of the upper and lower limbs.
Bones of the Appendicular Skeleton
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Dense, smooth, homogeneous Composed of osteons with a central canal containing blood vessels Contains living bone cells called osteocytes in chambers called lacunae
Compact bone
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The skeletal system
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Metathesis- where epiphiyses and diaphyses meet
growth plate
spongey bone- red bone marrow
Epiphyses
How do bones grow, remodel, and repair?
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posture- stay upright
attach to skeleton- muscles contract
constant body temperature
movement of cardiovascular vessels
protects internal organs
stabilizes joints- tendons- joints tighter
Skeletal muscle
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shoulder girdle, pectoral girdle, arms, hands, pelvic girdle or hip girdle and lower limbs
Appendicular skeleton
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Look at slide 12. 14
The coxal bones support the abdominal cavity.
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Identify the regions of the vertebral column.
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designed for strength
unorganized appearance
cells receive nutrients through canaliculi
contains trabeculae
These are characteristics of spongy bone marrow
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- not as strong as bone, but it more flexible
- matrix is gel-like and contains many collagenous and elastic fibers.
- The cells, called chondrocytes, lie within lacunae that are irregularly grouped.
- Cartilage has no nerves, making it well suited for padding joints where the stresses of movement are intense.
- Cartilage also has no blood vessels and relies on neighboring tissues for nutrient and waste exchange. This makes it slow to heal.
The three types of cartilage differ according to the type and arrangement of fibers in the matrix.
- Hyaline cartilage is firm and somewhat flexible. The matrix appears uniform and glassy, but actually it contains a generous supply of collagen fibers. Hyaline cartilage is found at the ends of long bones, in the nose, at the ends of the ribs, and in the larynx and trachea.
- Fibrocartilage is stronger than hyaline cartilage, because the matrix contains wide rows of thick, collagenous fibers. Fibrocartilage is able to withstand both tension and pressure and is found where support is of prime importance—in the disks between the vertebrae and in the cartilage of the knee.
- Elastic cartilage is more flexible than hyaline cartilage, because the matrix contains mostly elastin fibers. This type of cartilage is found in the ear flaps and the epiglottis.
Cartilage characteristics and three types
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The most prominent of the facial bones are the mandible, the maxillae (sing., maxilla), the zygomatic bones, and the nasal bones.
The mandible, or lower jaw, is the only movable portion of the skull, and it forms the chin (Fig. 12.4 and Fig. 12.5). The maxillae form the upper jaw and a portion of the eye socket. Further, the hard palate and the floor of the nose are formed by the maxillae (anterior) joined to the palatine bones (posterior). Tooth sockets are located on the mandible and on the maxillae. The grinding action of the mandible and maxillae allows us to chew our food.
The Facial Bones
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contraction cycle
if calcium present- repeats
each time- actin moves closer
Actin filament- thin - filament - two other proteins associated triponin tropomyasin
- calcium - released sarcoplasmic reticulum- shifts position- threads- tropomyasin- myasin binding sites exposed along
heads- golf club- atp binding sites- atp binds- adp and phosphate-
breakdown of atp- myosin heads crossbridge to actin filament-
atp - and phosphate released- changes position- powerstroke- actin filament- pulls towards sarcomere
atp - heads detach actin filament
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knees elbows, movable, ?
synovial
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intramembraneous ossificaiton
connective tissues becomes osteoblasts- mesochuymal
secreting ossification center- matrix
bony matrix- collagen fibers and muco polysaccharides
will lay calcium there- by osteoblasts
calcification- part of the process -
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The spinal cord extends from the base of the brain and down through the vertebral column.
- Passes through the foramen magnum into the vertebral canal, which is created by openings in vertebrae
- Spinal nerves project from the spinal cord between vertebrae.
- Protection of the spinal cord
- Bony vertebrae surround spinal cord
- Fluid-filled intervertebral disks cushion and separate vertebrae
- Protective membranes called meninges wrap around the spinal cord
Spinal cord and surrounding structures
- long, thin spinous processes (Fig. 12.7a)
- articulate with one another and with the ribs at articular facets
- between cervicle and lumbar vertebrae
What characterizes the thoracic vertebrae? What do they articulate with? What 2 types of vertebrae is the thoracic vertebrae located between?
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What are some bone- and joint-associated injuries or conditions?
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Vertebral column
concave, convex,
structure- helps - stability carry body weight
curvature
(
There are several general classes of synovial joints, two of which are shown in Figure 12.10. Figure 12.10b illustrates the general anatomy of a freely movable synovial joint. Ligaments connect bone to bone and support or strengthen the joint. A fibrous joint capsule formed by ligaments surrounds the bones at the joint. This capsule is not shown in Figure 12.10b so that the inner structure of the joint may be revealed. The joint capsule is lined with synovial membrane, which secretes a small amount of synovial fluid to lubricate the joint. Fluid-filled sacs called bursae (sing., bursa) ease friction between bare areas of bone and overlapping muscles or between skin and tendons. The full joint contains menisci (sing., meniscus), which are C-shaped pieces of fibrocartilage cartilage between the bones. These give added stability and act as shock absorbers.
The ball-and-socket joints at the hips and shoulders (Fig. 12.10c) allow movement in all planes, even rotational movement. The elbow and knee joints are synovial joints called hinge joints (Fig. 12.10d). Like a hinged door, they largely permit movement in one direction only. The Science feature “Osteoarthritis and Joint Replacement Surgery” examines the history of how joint replacement therapy was developed.
BIOLOGY TODAY Science
Osteoarthritis and Joint Replacement Surgery
Osteoarthritis is a condition that afflicts nearly everyone, to a greater or lesser degree, as each person ages. The bones that unite to form joints, or articulations, are covered with a slippery cartilage. This articular cartilage wears down over time, as friction in the joint wears it away (Fig. 12B). By age 80, people typically have osteoarthritis in one or more joints. By contrast, rheumatoid arthritis is an autoimmune disorder (see Section 7.5) that causes inflammation within the joint. Unlike osteoarthritis, which typically affects older people, rheumatoid arthritis can afflict a person of any age, even young children. Both forms of arthritis cause a loss of the joint’s natural smoothness. This is what causes the pain and stiffness associated with arthritis. Arthritis is first treated with medications for joint inflammation and pain and with physical therapy to maintain and strengthen the joint. If these treatments fail, a total joint replacement is often performed. Successful replacement surgeries are now routine, thanks to the hard work and dedication of the British orthopedic surgeon Dr. John Charnley.
Figure 12B Osteoarthritis. A comparison of a normal knee (a) and a knee with osteoarthritis (b).
(both): ©Puwadol Jaturawutthichai/Alamy
Early experimental surgeries by Charnley and others had been very disappointing. Fused joints were immobile, and fusion didn’t always relieve the patient’s pain. Postsurgical infection was common. The bones attached to the artificial joint eroded, and the supporting muscles wasted away because the joint wasn’t useful. Charnley wanted to design a successful prosthetic hip, with the goal of replacing both parts of the diseased hip joint: the acetabulum, or “socket,” as well as the ball-shaped head of the femur. Charnley soon determined that surgical experimentation alone wasn’t enough. He studied bone repair, persuading a colleague to operate on Charnley’s tibia, or shinbone, to see how repair occurred. He studied the mechanics of the hip joint, testing different types of synthetic materials. He achieved his first success using a hip socket lined with Teflon but soon discovered that the surrounding tissues became inflamed. After multiple attempts, his perfected hip consisted of a socket of durable polyethylene. Polyethylene is still used today as the joint’s plastic component. The head of his prosthetic femur was a small, highly polished metal ball. Stainless steel, cobalt, and titanium, as well as chrome alloys, form the metal component today. Various techniques for cementing the polyethylene socket onto the pelvic bone had failed when bone pulled away from the cemented surface and refused to grow. Charnley’s surgery used dental cement, slathered onto the bone surfaces. When the plastic components were attached, cement was squeezed into every pore of the bone, allowing the bone to regenerate and grow around the plastic. Finally, Charnley devised a specialized surgical tent and instrument tray to minimize infection.
Charnley’s ideas were innovative and unorthodox, and he was reassigned to a former tuberculosis hospital, which he converted into a center for innovation in orthopedic surgery. His colleagues developed a prosthetic knee joint similar to the Charnley hip. In knee replacement surgery (see the chapter opener), the damaged ends of bones are removed and replaced with artificial components that resemble the original bone ends. Hip and knee replacements remain the most common joint replacement surgeries, but ankles, feet, shoulders, elbows, and fingers can also be replaced. Though many improvements on the procedure continue, the Charnley hip replacement remains the technique after which all others are modeled.
When a joint replacement is complete, the patient’s hard work is vital to ensure the success of the procedure. Exercise and activity are critical to the recovery process. After surgery, the patient is encouraged to use the new joint as soon as possible. The extent of improvement and range of motion of the joint depend on its stiffness before the surgery, as well as the amount of patient effort during therapy following surgery. A complete recovery varies in time from patient to patient but typically takes several months. Older patients can expect their replacements to last about 10 years. However, younger patients may need a second replacement if they wear out their first prosthesis. Still, individuals who have joint replacement surgery can expect an improved quality of life and a bright future with greater independence and healthier, pain-free activity.
Questions to Consider
Compare each component of Charnley’s artificial joint with that of a real synovial joint.
Explain why rheumatoid arthritis is actually a disorder of the immune system.
Movements Permitted by Synovial Joints
Intact skeletal muscles are attached to bones by tendons that span joints. When a muscle contracts, one bone moves in relation to another bone. The more common types of movements are described in Figure 12.11.
Figure 12.11 Synovial joints allow for a variety of movement. a. Flexion and extension. b. Adduction and abduction. c. Rotation and circumduction. d. Inversion and eversion. Red dots indicate pivot points.
CHECK YOUR PROGRESS 12.4
List the three major types of joints.
Answer
Fibrous, cartilaginous, synovial.
Describe the basic movements of cartilaginous and fibrous joints, and give an example of each in the body.
Answer
Cartilaginous joints are slightly movable and found in the rib cage and intervertebral discs; fibrous joints are not movable and are found in the sutures of the skull.
Describe the different movements of synovial joints, and give an example of each in the body.
Answer
Flexion and extension—knee; adduction and abduction—hip and shoulder; rotation—arm; circumduction—hip and shoulder; inversion and eversion—foot and ankle.
CONNECTING THE CONCEPTS
For more information on ligaments and tendons, refer to the following discussion:
Section 4.2 describes the connective tissue found in the tendons and ligaments.
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dense connective tissue (same with tendons)
ligaments
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The vertebral column consists of 33 vertebrae (Fig. 12.6). These are named by their region and by number. Normally, the vertebral column has four curvatures that provide more resilience and strength for an upright posture than a straight column could provide. Scoliosis is an abnormal lateral (sideways) curvature of the spine. There are two other well-known abnormal curvatures. Kyphosis is an abnormal posterior curvature that often results in a “hunchback.” An abnormal anterior curvature results in lordosis, or “swayback.”
The Vertebral Column
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13.2 Skeletal Muscle Fiber Contraction
LEARNING OUTCOMES
Upon completion of this section, you should be able to
Identify the structures of a muscle fiber.
Explain how the sliding filament model is responsible for muscle contraction.
Summarize how activities within the neuromuscular junction control muscle fiber contraction.
We have already examined the structure of skeletal muscle, as seen with the light microscope (see Fig. 13.1). Skeletal muscle tissue has alternating light and dark bands, giving it a striated appearance. These bands are due to the arrangement of myofilaments in a muscle fiber.
Muscle Fibers and How They Move
A muscle fiber is a cell containing the usual cellular components (see Section 3.2), but special names have been assigned to some of these components (Table 13.1). For example, the plasma membrane is called the sarcolemma (sarco means “muscle”); the cytoplasm is the sarcoplasm; and the endoplasmic reticulum is the sarcoplasmic reticulum. A muscle fiber also has some unique anatomical characteristics. One feature is its T (for transverse) system. The sarcolemma forms T (transverse) tubules, which penetrate, or dip down, into the cells. The transverse tubules come into contact—but do not fuse—with expanded portions of the sarcoplasmic reticulum. The expanded portions of the sarcoplasmic reticulum are calcium storage sites. Calcium ions (Ca2+), as we will see, are essential for muscle contraction. Glycogen, a complex carbohydrate (see Section 2.4), is the preferred energy source for muscle contraction.
Table 13.1Anatomy of a Muscle Fiber
Table Summary:
NameFunction
SarcolemmaThe plasma membrane of a muscle fiber that forms T tubules.
SarcoplasmThe cytoplasm of a muscle fiber that contains the organelles, including myofibrils.
MyoglobinA red pigment that stores oxygen for muscle contraction.
T tubuleAn extension of the sarcolemma that extends into the muscle fiber and conveys impulses that cause +Ca2+ to be released from the sarcoplasmic reticulum.
Sarcoplasmic reticulumThe smooth endoplasmic reticulum (ER) of a muscle fiber that stores +Ca2+.
MyofibrilA bundle of myofilaments that contracts.
MyofilamentAn actin or a myosin filament, whose structure and functions account for muscle striations and contractions.
The sarcolemma encases hundreds and sometimes even thousands of myofibrils, each about 1 μm in diameter. Myofibrils are the contractile portions of the muscle fibers. Any other organelles, such as mitochondria, are located in the sarcoplasm between the myofibrils. The sarcoplasm also contains glycogen, which provides stored energy for muscle contraction. In addition, sarcoplasm includes the red pigment myoglobin, which binds oxygen until it is needed for muscle contraction.
SCIENCE IN YOUR LIFE
Why don’t muscle cells use hemoglobin?
Hemoglobin is the primary transport pigment of oxygen in the bloodstream. However, as the temperature of the tissue rises and the pH becomes more acidic, hemoglobin loses its ability to bind the oxygen molecules. This is where myoglobin comes in. Like hemoglobin, myoglobin binds oxygen molecules. However, myoglobin has a higher affinity (attraction) for oxygen than hemoglobin. So when you exercise or use a muscle group, the increase in temperature causes the oxygen in the hemoglobin to be transferred to the myoglobin of the muscle cells. This allows for an efficient transfer of oxygen to those muscles that are actively contracting.
Skeletal Muscle Contraction: Muscle Anatomy
Myofibrils and Sarcomeres
Figure 13.6 illustrates the structure of a skeletal myocyte, also called a muscle fiber. Notice that the muscle fiber is roughly cylindrical in shape. Grouped inside this larger cylinder are smaller cylinders called myofibrils (Fig 13.6a). Myofibrils run the entire length of the muscle fiber. Myofibrils are composed of even smaller cylinders called myofilaments. Thus, the muscle cell is a set of small cylinders (myofilaments) assembled into larger cylinders (myofibrils) clustered within the largest cylinder (the muscle fiber).
Figure 13.6 The structure of a skeletal muscle fiber. a. A muscle fiber contains many myofibrils divided into (b) sarcomeres, which are contractile. c. When the myofibrils of a muscle fiber contract, the sarcomeres shorten. d. The actin (thin) filaments slide past the myosin (thick) filaments toward the center. Notice that the Z lines move inward and the H band is reduced in size.
(photos) (a): ©Fuse/Getty Images; (b): ©Thomas Deerinck, NCMIR/Science Photo Library/Getty Images
Tutorial: Skeletal Muscle Contraction
The light microscope shows that skeletal muscle fibers have light and dark bands called striations (Fig. 13.6b). At the higher magnification provided by an electron microscope, one can see that the striations of skeletal muscle fibers are formed by the placement of myofilaments within myofibrils. There are two types of myofilaments. Thick myofilaments are made up of a protein called myosin, and thin myofilaments are composed of a second protein termed actin. Myofibrils are further divided vertically into sarcomeres. A sarcomere extends between two dark vertical lines called the Z lines. The I bands on either side of the Z line are light colored, because each contains only the thin actin myofilaments. The dark central A band within the sarcomere is composed of overlapping actin and myosin myofilaments. Centered within the A band is a vertical H band. In an uncontracted sarcomere, the H band lacks thin actin myofilaments and contains only thick myosin myofilaments.
The thick and thin filaments differ in the following ways:
Thick filaments. A thick filament is composed of several hundred molecules of the protein myosin. Each myosin molecule is shaped like a golf club, with the straight portion of the molecule ending in a globular head. The heads occur on each side of a sarcomere but not in the middle (Fig. 13.6).Page 264
Thin filaments. Primarily, a thin filament consists of two intertwining strands of the protein actin. Two other proteins, called tropomyosin and troponin, also play a role, as we will discuss later in this section.
The Sliding Filament Model
As we will see next, when muscles are stimulated, electrical signals travel across the sarcolemma and then down a T tubule. In turn, this signals calcium to be released from the sarcoplasmic Page 265reticulum. Now the muscle fiber contracts as the sarcomeres within the myofibrils shorten. As you compare the relaxed sarcomere with the contracted sarcomere (Fig. 13.6c), note that the filaments themselves remain the same length. When a sarcomere shortens, the actin (thin) filaments approach one another as they slide past the myosin (thick) filaments. This causes the I band to shorten, the Z line to move inward, and the H band to almost or completely disappear (Fig. 13.6d). The sarcomere changes from a rectangular shape to a square as it shortens.
Sarcomere Contraction
The movement of actin filaments in relation to myosin filaments is called the sliding filament model of muscle contraction. ATP supplies the energy for muscle contraction. Although the actin filaments slide past the myosin filaments, it is the myosin filaments that do the work. Myosin filaments break down ATP, and their cross-bridges pull the actin filament toward the center of the sarcomere.
Skeletal Muscle Contraction: The Sliding Filament Model
As an analogy, think of yourself and a group of friends as myosin. Collectively, your hands are the cross-bridges, and you are pulling on a rope (actin) to get an object tied to the end of the rope (the Z line). As you pull the rope, you grab, pull, release, and then grab farther along on the rope.
Muscle Fiber Contraction
Muscle fibers are stimulated to contract by motor neurons whose axons are grouped together to form nerves. The axon of one motor neuron can stimulate from a few to several muscle fibers of a muscle, because each axon has several branches (Fig. 13.7a). Each branch of Page 266an axon ends in an axon terminal that lies in close proximity to the sarcolemma of a muscle fiber. A small gap, called a synaptic cleft, separates the axon terminal from the sarcolemma (Fig. 13.7b). This entire region is called a neuromuscular junction.
Figure 13.7 Neuromuscular junctions. a. The branch of a motor nerve fiber terminates in an axon terminal. b. A synaptic cleft separates the axon terminal from the sarcolemma of the muscle fiber. c. Nerve impulses traveling down a motor fiber cause synaptic vesicles to discharge acetylcholine, which diffuses across the synaptic cleft and binds to ACh receptors. Impulses travel down the T tubules of a muscle fiber, and the muscle fiber contracts.
(photo): ©Ed Reschke/Oxford Scientific/Getty Images
Axon terminals contain synaptic vesicles filled with the neurotransmitter acetylcholine (ACh). Nerve signals travel down the axons of motor neurons and arrive at an axon terminal. The signals trigger the synaptic vesicles to release ACh into the synaptic cleft (Fig. 13.7c). When ACh is released, it quickly diffuses across the cleft and binds to receptors in the sarcolemma. Now, the sarcolemma generates electrical signals that spread across the sarcolemma and down the T tubules. Recall that the T tubules lie adjacent to the sarcoplasmic reticulum, but the two structures are not connected. Nonetheless, signaling from the T tubules causes the release of Ca2+ from the sarcoplasmic reticulum, which leads to sarcomere contraction, as explained in Figure 13.8.
Figure 13.8 The role of calcium ions and ATP during muscular contraction. a. Calcium ions +(Ca2+) bind to troponin, exposing myosin-binding sites. b. Follow steps 1 through 4 to see how myosin uses ATP and does the work of pulling actin toward the center of the sarcomere, much as (c) a group of people pulling a rope.
Tutorial: Skeletal Muscle Contraction
Two other proteins are associated with an actin filament. Threads of tropomyosin wind about an actin filament, covering binding sites for myosin located on each actin molecule. Troponin occurs at intervals along the threads. When Ca2+ is released from the sarcoplasmic reticulum, it combines with troponin. This causes the tropomyosin threads to shift their position, exposing myosin-binding sites. In other words, myosin can now bind to actin (Fig. 13.8a).
Skeletal Muscle Contraction: Regulation by Calcium Ions
To fully understand muscle contraction, study Figure 13.8b. (1) The heads of a myosin filament have ATP-binding sites. At this site, ATP is hydrolyzed, or split, to form ADP and Ⓟ. (2) The ADP and Ⓟ remain on the myosin heads, and the heads attach to an actin-binding site. Joining myosin to actin forms temporary bonds called cross-bridges. (3) Now, ADP and Ⓟ are released and the cross-bridges bend sharply. This is the power stroke that pulls the actin filament toward the center of the sarcomere. (4) When ATP molecules again bind to the myosin heads, the cross-bridges are broken. Myosin heads detach from the actin filament. This is the step that does not happen during rigor mortis. Relaxing the muscle is impossible, because ATP is needed to break the bond between an actin-binding site and the myosin cross-bridge.
Breakdown of ATP and Cross-Bridge Movement
Page 267
BIOLOGY TODAY Science
Botox and Wrinkles
Several of the most important bacterial pathogens that cause human diseases—including cholera, diphtheria, tetanus, and botulism—do so by secreting potent toxins capable of sickening or killing their victims. The botulinum toxin, produced by the bacterium Clostridium botulinum, is one of the most lethal substances known. Less than a microgram (µg) of the purified toxin can kill an average-size person, and 4 kilograms (kg) (8.8 pounds [lb]) would be enough to kill all humans on Earth! Given this scary fact, it seems that the scientists who discovered the lethal activity of this bacterial toxin nearly 200 years ago could never have anticipated that the intentional injection of a very dilute form of botulinum toxin (now known as Botox) would become the most common nonsurgical cosmetic procedure performed by many physicians. As with many breakthroughs in science and medicine, the pathway from thinking about botulism as a deadly disease to using botulinum toxin as a beneficial treatment involved the hard work of many scientists, mixed with a considerable amount of luck.
In the 1820s, a German scientist, Justinus Kerner, was able to prove that the deaths of several people had been caused by their consumption of spoiled sausage (in fact, botulism is named for the Latin word for “sausage,” botulus). A few decades later, a Belgian researcher named Emile Pierre van Ermengem identified the specific bacterium responsible for producing the botulinum toxin, which can cause symptoms ranging from droopy eyelids to paralysis and respiratory failure.
By the 1920s, medical scientists at the University of California had obtained the toxin in pure form, which allowed them to determine that it acts by preventing nerves from communicating with muscles, specifically by interfering with the release of acetylcholine from the axon terminals of motor nerves.
Scientists soon began testing very dilute concentrations of the toxin as a treatment for conditions in which the muscles contract too much, such as crossed eyes or spasms of the facial muscles or vocal cords. In 1989, the FDA first approved diluted botulinum toxin (Botox) for treating specific eye conditions called blepharospasm (eyelid spasm) and strabismus (crossing of the eyes).
Right around this time, a lucky break occurred that eventually would open the medical community’s eyes to the greater potential of the diluted toxin. A Canadian ophthalmologist, Jean Carruthers, had been using it to treat her patients’ eye conditions when she noticed that some of their wrinkles had also subsided. One night at a family dinner, Dr. Carruthers shared this information with her husband, a dermatologist, who decided to investigate whether he could reduce the deep wrinkles of some of his patients by injecting the dilute toxin into their skin. The treatment worked well, and after trying it on several more patients (as well as on themselves!), the Canadian doctors spent several years presenting their findings at scientific meetings and in research journals. Although they were initially considered “crazy,” the Carrutherses eventually were able to convince the scientific community that diluted botulinum toxin was effective in treating wrinkles; however, they never patented it for that use, so they missed out on much of the $1.3 billion in annual sales the drug now earns for the company that did patent it.
The uses of diluted botulinum toxin seem to be growing since it was FDA approved for the treatment of frown lines in 2002 (Fig. 13A). In March 2010, it was approved for the treatment of muscle stiffness in people with upper limb spasticity, and the company has approval for as many as 90 uses of diluted botulinum toxin, including treatment of migraine headaches.
Figure 13A Botox Treatment. This woman’s wrinkles are being treated with diluted botulinum toxin.
©Thinkstock/Getty Images
Questions to Consider
Considering that botulism is caused by a preformed toxin, how do you suppose it can be treated?
Do you think companies should be allowed to patent a naturally occurring molecule such as botulinum toxin? Why or why not?
Page 268
In living muscle, the cycle begins again and myosin reattaches farther along the actin filament. The cycle recurs until calcium ions are actively returned to the calcium storage sites. This step also requires ATP.
CHECK YOUR PROGRESS 13.2
Explain the role of the myofibril, myofilament, and sarcomere in a muscle fiber.
Answer
A myofibril is a bundle of myofilaments that contract; myofilaments are actin (thin) or myosin (thick) filaments whose structure and functions account for muscle striations and contractions; a muscle fiber contains many myofibrils divided into sarcomeres, which are contractile.
Explain how the thin and thick filaments interact in the sliding filament model.
Answer
The actin filaments (thin filaments) slide past the myosin filaments (thick filaments) toward the center. The Z lines move and the H band gets smaller to the point of disappearing.
Describe the role of both ATP and calcium ions in muscle contraction.
Answer
Calcium binds to troponin, exposing myosin-binding sites. Myosin uses ATP in doing the work of pulling actin toward the center of the sarcomere.
CONNECTING THE CONCEPTS
For more information on ATP and how the nervous system controls the contraction of skeletal muscle, refer to the following discussions:
Figure 3.21 illustrates the ATP–ADP cycle.
Section 14.2 explains the role of neurotransmitters, such as acetylcholine, in the nervous system.
Figure 14.5 illustrates the action of neurotransmitters in the synaptic cleft.
Skeletal Muscle Fiber contraction
- download images
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The rib cage
Rib(s) Protect the heart and lungs Flattened bone originating from the thoracic vertebrae 12 pairs 7 pairs true ribs = vertebrosternal 3 pairs false ribs = vertebrochondral 2 pairs floating ribs = vertebral (note the names come from what the ribs articulate (meet up) with: vertebrosternal = vertebrae and sternum, for example) Sternum the breastbone T
Many fibrous joints, such as the sutures between the cranial bones, are immovable.
Fibrous joints
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Bones of the Axial System
12.2 Bones of the Axial Skeleton
LEARNING OUTCOMES
Upon completion of this section, you should be able to
Identify the bones of the skull, the hyoid, vertebral column, and rib cage.
Identify the regions of the vertebral column.
Explain the function of the sinuses and intervertebral discs.
The 206 bones of the skeleton are classified according to whether they occur in the axial skeleton or the appendicular skeleton (Fig. 12.3). The axial skeleton lies in the midline of the body and consists of the skull, hyoid bone, vertebral column, and the rib cage.
Figure 12.3 The axial and appendicular skeletons. Axial skeleton bones are colored blue. Bones of the appendicular skeleton are tan. a. Frontal view. b. Dorsal view.
SCIENCE IN YOUR LIFE
Does everyone have the same number of bones?
A newborn has nearly 300 bones, some of which fuse together as the child grows. The adult human skeleton has approximately 206 bones, but the number varies between individuals. Some people have extra bones, called Wormian bones, that help fuse skull bones together. Others may have additional small bones in the ankles and feet.
The Skull
The skull is formed by the cranium (braincase) and the facial bones. However, some cranial bones contribute to the structure of the face.
The Cranium
The cranium protects the brain. In adults, it is composed of eight bones fitted tightly together. In newborns, certain cranial bones are not completely formed. Instead, these bones are joined by membranous regions called fontanels. The fontanels usually close by the age of 16 months (see Section 12.5).
The major bones of the cranium have the same names as the lobes of the brain: frontal, parietal, occipital, and temporal. On the top of the cranium (Fig. 12.4a), the frontal bone forms the forehead, the parietal bones extend to the sides, and the occipital bone curves to form the base of the skull. Here, there is a large opening, the foramen magnum (Fig. 12.4b), through which the spinal cord passes. Below the much larger parietal bones, each temporal bone has an opening (external auditory canal) that leads to the middle ear.
Figure 12.4 The bones of the skull. a. Lateral view. b. Inferior view.
The sphenoid bone, shaped like a bat with outstretched wings, extends across the floor of the cranium from one side to the other. The sphenoid is the keystone of the cranial bones, because all the other bones articulate with it. The sphenoid completes the sides of the skull and contributes to forming the orbits (eye sockets). The ethmoid bone, which lies in front of the sphenoid, also helps form Page 240the orbits and the nasal septum. The orbits are completed by various facial bones. The eye sockets are called orbits because we can rotate our eyes.
Some of the bones of the cranium contain the sinuses, air spaces lined by mucous membrane. The sinuses reduce the weight of the skull and give a resonant sound to the voice. Sinuses are named according to the bones in which they are located. The major sinuses are the frontal, sphenoid, ethmoid, and maxillary. A smaller set of sinuses, called the mastoid sinuses, drain into the middle ear. Mastoiditis, a condition that can lead to deafness, is an inflammation of these sinuses.
The Facial Bones
The most prominent of the facial bones are the mandible, the maxillae (sing., maxilla), the zygomatic bones, and the nasal bones.
The mandible, or lower jaw, is the only movable portion of the skull, and it forms the chin (Fig. 12.4 and Fig. 12.5). The maxillae form the upper jaw and a portion of the eye socket. Further, the hard palate and the floor of the nose are formed by the maxillae (anterior) joined to the palatine bones (posterior). Tooth sockets are located on the mandible and on the maxillae. The grinding action of the mandible and maxillae allows us to chew our food.
Figure 12.5 The bones of the face and the location of the hyoid bone. a. The frontal bone forms the forehead and eyebrow ridges; the zygomatic bones form the cheekbones; and the maxillae have numerous functions. They assist in the formation of the eye sockets and the nasal cavity. They form the upper jaw and contain sockets for the upper teeth. The mandible is the lower jaw with sockets for the lower teeth. The mandible has a projection we call the chin. b. The maxillae, frontal, and nasal bones help form the external nose. c. The hyoid bone is located as shown.
(b): ©Image100/Corbis
The lips and cheeks have a core of skeletal muscle. The zygomatic bones form the cheekbone prominences, and the nasal bones form the bridge of the nose. Other bones (e.g., ethmoid and vomer) are a part of the nasal septum, which divides the interior of the nose into two nasal cavities. The lacrimal bone (see Fig. 12.4a) contains the opening for the nasolacrimal canal, which drains tears from the eyes to the nose.
Certain cranial bones contribute to the face. The temporal bone and the wings of the sphenoid bone account for the flattened areas we call the temples. The frontal bone forms the forehead and has supraorbital ridges, where the eyebrows are located. Glasses sit where the frontal bone joins the nasal bones.
The exterior portions of ears are formed only by cartilage and not by bone. The nose is a mixture of bones, cartilages, and connective tissues. The cartilages complete the tip of the nose, and fibrous connective tissue forms the flared sides of the nose.
The Hyoid Bone
The hyoid bone is not part of the skull but is mentioned here because it is a part of the axial skeleton. It is the only bone in the body that does not articulate with another bone (Fig. 12.5c). It is attached to the temporal bones by muscles and ligaments and to the larynx (see Fig. 10.1) by a membrane. The hyoid Page 241bone anchors the tongue and serves as the site for the attachment of muscles associated with swallowing. Due to its position, the hyoid bone does not fracture easily. In cases of suspicious death, however, a fractured hyoid is a strong indication of manual strangulation.
The Vertebral Column
The vertebral column consists of 33 vertebrae (Fig. 12.6). These are named by their region and by number. Normally, the vertebral column has four curvatures that provide more resilience and strength for an upright posture than a straight column could provide. Scoliosis is an abnormal lateral (sideways) curvature of the spine. There are two other well-known abnormal curvatures. Kyphosis is an abnormal posterior curvature that often results in a “hunchback.” An abnormal anterior curvature results in lordosis, or “swayback.”
Figure 12.6 The vertebral column. The vertebral column is made up of 33 vertebrae separated by intervertebral discs. The intervertebral discs make the column flexible. The vertebrae are named for their location in the vertebral column. For example, the thoracic vertebrae are located in the thorax. Humans have a coccyx, which is also called a tailbone.
As the individual vertebrae are layered on top of one another, they form the vertebral column. The vertebral canal is in the center of the column, and the spinal cord passes through this canal. The intervertebral foramina (sing., foramen, “a hole or opening”) are found on each side of the column. Spinal nerves branch from the spinal cord and travel through the intervertebral foramina to locations throughout the body. Spinal nerves control skeletal muscle contraction, among other functions. If a vertebra is compressed, or slips out of position, the spinal cord and/or spinal nerves might be injured. The result can be paralysis or even death.
The spinous processes of the vertebrae can be felt as bony projections along the midline of the back. The transverse processes extend laterally. Both spinous and transverse processes serve as attachment sites for the muscles that move the vertebral column.
Types of Vertebrae
The various vertebrae are named according to their location in the vertebral column. The cervical vertebrae are located in the neck. The first cervical vertebra, called the atlas, holds up the head and allows it to tilt side to side. It is so named because Atlas, of Greek mythology, held up the world. The second cervical vertebra is called the axis, because it allows a degree of rotation. The thoracic vertebrae have long, thin spinous processes (Fig. 12.7a). The thoracic vertebrae articulate with one another and with the ribs at articular facets. Lumbar vertebrae have large bodies and thick processes. The five sacral vertebrae are fused together in the sacrum. The coccyx, or tailbone, is usually composed of four fused vertebrae.
Figure 12.7 The thoracic vertebrae, ribs, and sternum. a. Structure of a thoracic vertebra. b. The rib cage consists of the 12 thoracic vertebrae, the 12 pairs of ribs, the costal cartilages, and the sternum. The rib cage protects the lungs and the heart.
Intervertebral Discs
Between the vertebrae are intervertebral discs composed of fibrocartilage that act as padding. The discs prevent the vertebrae from grinding against one another. They also absorb shock caused Page 242by movements such as running, jumping, and even walking. The presence of the discs allows the vertebrae to move as we bend forward, backward, and from side to side. Unfortunately, these discs become weakened with age and can herniate and rupture. Pain results if a disc presses against the spinal cord and/or spinal nerves. If that occurs, surgical removal of the disc may relieve the pain.
The Rib Cage
The rib cage, also called the thoracic cage, is composed of the thoracic vertebrae, the ribs and their associated cartilages, and the sternum (Fig. 12.7b). The rib cage is part of the axial skeleton.
The rib cage demonstrates how the skeleton is protective but also flexible. The rib cage protects the heart and lungs, yet it swings outward and upward upon inspiration and then downward and inward upon expiration (see Fig. 10.8).
The Ribs
A rib is a flattened bone that originates at the thoracic vertebrae and proceeds toward the anterior thoracic wall. There are 12 pairs of ribs. All 12 pairs connect directly to the thoracic vertebrae in the back. A rib articulates with the body and transverse process of its corresponding thoracic vertebra. Each rib curves outward and then forward and downward.
The upper seven pairs of ribs (ribs 1 through 7; Fig. 12.7b) connect directly to the sternum by means of a long strip of hyaline cartilage called costal cartilage. These are called “true ribs.” Ribs 8 through 12 are called “false ribs” because their costal cartilage at the end of the ribs does not connect directly to the sternum. Ribs 11 and 12 are also called “floating ribs” because they have no connection with the sternum.
The Sternum
The sternum lies in the midline of the body. Along with the ribs, it helps protect the heart and lungs. The sternum, or breastbone, is a flat bone that has the shape of a knife.
The sternum is composed of three bones. These bones are the manubrium (the handle), the body (the blade), and the xiphoid process (the point of the blade). The manubrium articulates with the clavicles of the appendicular skeleton. Costal cartilages from the first pair of ribs also join to the manubrium. The manubrium joins with the body of the sternum at an angle. This is an important anatomical landmark, because it occurs at the level of the second rib and therefore allows the ribs to be counted. Counting the ribs is sometimes done to determine where the apex of the heart is located—usually between the fifth and sixth ribs.
The xiphoid process is the third part of the sternum. The variably shaped xiphoid process serves as an attachment site for the diaphragm, which separates the thoracic cavity from the abdominal cavity.Page 243
CHECK YOUR PROGRESS 12.2
List the bones of the axial skeleton.
Answer
Skull, hyoid bone, vertebral column, rib cage.
Identify the bones of the cranium and face, and describe how they contribute to facial features.
Answer
Frontal bone forms the forehead; parietal bones extend to the sides; occipital bone curves to form the base of the skull; each temporal bone is located below the parietal bones; sphenoid bone extends across the floor of the cranium from one side to the other; the ethmoid bone lies in front of the sphenoid. The mandible forms the lower jaw and chin, maxillae form the upper jaw and the anterior portion of the hard palate, zygomatic bones are the cheekbone prominences, and the nasal bones form the bridge of the nose.
Describe the various types of vertebrae.
Answer
Cervical vertebrae (7), including C1 (atlas) and C2 (axis)—located in the neck and allow movement of the head; thoracic vertebrae (12)—form the thoracic curvature and have long, thin, spinous processes and articular facets for the attachment of the ribs; lumbar vertebrae (5)—form the lumbar curvature and have a large body and thick processes; sacral vertebrae (5)—fused together, forming the pelvic curvature; coccyx (3-5)—fused vertebrae that form the tailbone.
CONNECTING THE CONCEPTS
For more information on the interaction of the axial skeleton with other organ systems in the body, refer to the following discussions:
Section 10.4 examines how the rib cage is involved in respiration.
Section 14.2 details how the vertebral column and skull protect components of the central nervous system.
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• Stored in the muscle • Glycogen • Lipid • In the blood • Glucose • Fatty acids
Where are the fuel sources for muscle contraction?
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This is what the deal is with the vertebral column
What is the intervertebral foramina
Where are the spinal nerves and what do they do?
What happens if the vertebra is compressed?
Where are the spinous processes and how are they felt?
What are the transverse processes and where are they found?
What is the function of both transverse and spinous processes?
vertebral canal: center of the column, and the spinal cord passes through this canal
The intervertebral foramina (sing., foramen, “a hole or opening”) are found on each side of the column.
Spinal nerves branch from the spinal cord and travel through the intervertebral foramina to locations throughout the body. Spinal nerves control skeletal muscle contraction, among other functions.
If a vertebra is compressed, or slips out of position, the spinal cord and/or spinal nerves might be injured. The result can be paralysis or even death.
The spinous processes of the vertebrae can be felt as bony projections along the midline of the back. The transverse processes extend laterally. Both spinous and transverse processes serve as attachment sites for the muscles that move the vertebral column.
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I am the cranium’s four parts.
major brains share those of the brain: frontal, parietal, occipital, and temporal.
On the top (Fig. 12.4a), the frontal bone forms the forehead
the parietal bones extend to the sides, and the
occipital bone curves to form the base of the skull. Here, there is a large opening, the foramen magnum (Fig. 12.4b), through which the spinal cord passes.
Below the much larger parietal bones, each temporal bone has an opening (external auditory canal) that leads to the middle ear.
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12.1 Overview of the Skeletal System
LEARNING OUTCOMES
Upon completion of this section, you should be able to
State the functions of the skeletal system.
Describe the structure of a long bone and list the types of tissues it contains.
List the three types of cartilage found in the body and provide a function for each.
The skeletal system consists of two types of connective tissue: bone and the cartilage found at joints, which is the point where two joints come together. In addition, ligaments, formed of fibrous connective tissue, join the bones.
Functions of the Skeleton
The skeleton does more than merely provide a frame for the body. In addition, it has the following functions:
Support. The bones of the legs support the entire body when we are standing, and bones of the pelvic girdle support the abdominal cavity.
Movement. The skeletal system works with the muscular system to provide movement.
Protection. The bones of the skull protect the brain; the rib cage protects the heart and lungs; and the vertebrae protect the spinal cord, which makes nervous connections to all the muscles of the limbs.
Production of blood cells. The skeleton plays an important role in the formation of blood. In the fetus, all bones have red bone marrow to produce new blood cells. However, in adults, only certain bones produce blood cells.
Storage of minerals and fat. All bones have a matrix that contains calcium phosphate, a source of calcium ions and phosphate ions in the blood. Fat is stored in yellow bone marrow.
Anatomy of a Long Bone
The bones of the body vary greatly in size and shape. To better understand the anatomy of a bone, we will use a long bone (Fig. 12.1), a type of bone common in the arms and legs. The shaft, or main portion of the bone, is called the diaphysis. The diaphysis has a large medullary cavity, whose walls are composed of compact bone. The medullary cavity is lined with a thin, vascular membrane (the endosteum) and is filled with yellow bone marrow, which stores fat.
Figure 12.1 The anatomy of a long bone. A long bone is formed of an outer layer of compact bone. The central shaft of a long bone contains yellow marrow, a form of stored fat. Periosteum, a fibrous membrane, encases the bone except at its ends, which are covered by hyaline cartilage.
The expanded region at the end of a long bone is called an epiphysis (pl., epiphyses). The epiphyses are separated from the diaphyses by a small region of mature bone called the metaphysis, which contain the epiphyseal plate, a region of cartilage that allows for bone growth.
The epiphyses are composed largely of spongy bone that contains red bone marrow, where blood cells are made. The epiphyses are coated with a thin layer of hyaline cartilage, which is also called articular cartilage, because it occurs at a joint.
Except for the articular cartilage on the bone’s ends, a long bone is completely covered by a layer of fibrous connective tissue called the periosteum. This covering contains blood vessels, lymphatic vessels, and nerves. Note in Figure 12.1 how a blood vessel penetrates the periosteum and enters the bone. Branches of the blood vessel are found throughout the medullary cavity. Page 238Other branches can be found in hollow cylinders called central canals within the bone tissue. The periosteum is continuous with ligaments and tendons connected to a bone.
Bone
Compact bone is highly organized and composed of tubular units called osteons (Fig. 12.2). In a cross-section of an osteon, bone cells called osteocytes lie in lacunae (sing., lacuna), tiny chambers arranged in concentric circles around a central canal (Fig. 12.1). Matrix fills the space between the rows of lacunae. Tiny canals called canaliculi (sing., canaliculus) run through the matrix. These canaliculi connect the lacunae with one another and with the central canal. The cells stay in contact by strands of cytoplasm that extend into the canaliculi. Osteocytes nearest the center of an osteon exchange nutrients and wastes with the blood vessels in the central canal. These cells then pass on nutrients and collect wastes from the other cells via gap junctions (see Fig. 3.17).
Figure 12.2 Anatomy of compact bone. Compact bone is composed of cylinder-shaped structures called osteons, which contain osteocytes.
(photos) (compact bone): ©Ed Reschke; (osteocyte): ©Biophoto Associates/Science Source
Compared with compact bone, spongy bone has an unorganized appearance (Fig. 12.2). It contains numerous thin plates, called trabeculae, separated by unequal spaces. Although this makes spongy bone lighter than compact bone, spongy bone is still designed for strength. Just as braces are used for support in Page 239buildings, the trabeculae follow lines of stress. The spaces of spongy bone are often filled with red bone marrow, a specialized tissue that produces all types of blood cells. The osteocytes of spongy bone are irregularly placed within the trabeculae. Canaliculi bring them nutrients from the red bone marrow.
Cartilage
Cartilage is not as strong as bone, but it is more flexible. Its matrix is gel-like and contains many collagenous and elastic fibers. The cells, called chondrocytes, lie within lacunae that are irregularly grouped. Cartilage has no nerves, making it well suited for padding joints where the stresses of movement are intense. Cartilage also has no blood vessels and relies on neighboring tissues for nutrient and waste exchange. This makes it slow to heal.
The three types of cartilage differ according to the type and arrangement of fibers in the matrix. Hyaline cartilage is firm and somewhat flexible. The matrix appears uniform and glassy, but actually it contains a generous supply of collagen fibers. Hyaline cartilage is found at the ends of long bones, in the nose, at the ends of the ribs, and in the larynx and trachea.
Fibrocartilage is stronger than hyaline cartilage, because the matrix contains wide rows of thick, collagenous fibers. Fibrocartilage is able to withstand both tension and pressure and is found where support is of prime importance—in the discs between the vertebrae and in the cartilage of the knee.
Elastic cartilage is more flexible than hyaline cartilage, because the matrix contains mostly elastin fibers. This type of cartilage is found in the ear flaps and the epiglottis.
Fibrous Connective Tissue
Fibrous connective tissue contains rows of cells called fibroblasts separated by bundles of collagenous fibers (see Section 4.2). This tissue makes up ligaments and tendons. Ligaments connect bone to bone. Tendons connect muscle to bone at a joint (also called an articulation).
CHECK YOUR PROGRESS 12.1
List the functions of the skeletal system.
Answer
Support, movement, protection, production of blood cells, storage of minerals and fat.
Summarize the structure of a long bone by describin
Skeletal system part one
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line
epiphial plate becomes
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- flexible connective tissue
- categorized by type and arrangement of matrix fibers (collagen and elastic)
- Found where support under pressure is important and some movement is done
- Chondrocytes- cartilage cells
What is cartilage tissue?
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Skeletal muscle
posture- stay upright
attach to skeleton- muscles contract
constant body temperature
movement of cardiovascular vessels
protects internal organs
stabilizes joints- tendons- joints tighter
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How are hormones involved in bone growth?
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The hyoid bone is not part of the skull but is mentioned here because it is a part of the axial skeleton. It is the only bone in the body that does not articulate with another bone (Fig. 12.5c). It is attached to the temporal bones by muscles and ligaments and to the larynx (see Fig. 10.1) by a membrane. The hyoid Page 241bone anchors the tongue and serves as the site for the attachment of muscles associated with swallowing. Due to its position, the hyoid bone does not fracture easily. In cases of suspicious death, however, a fractured hyoid is a strong indication of manual strangulation.
The Hyoid Bone
What are joints and what kind of movements do they allow?
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Bone Growth and Homestasis
12.5 Bone Growth and Homeostasis
LEARNING OUTCOMES
Upon completion of this section, you should be able to
Summarize the process of ossification and list the types of cells involved.
Describe the process of bone remodeling.
Explain the steps in the repair of bone.
The importance of the skeleton to the human form is evident by its early appearance during development. The skeleton starts forming at about 6 weeks, when the embryo is only about 12 mm (0.5 in.) long. Most bones grow in length and width through Page 247adolescence, but some continue enlarging until about age 25. In a sense, bones can grow throughout a lifetime, because they are able to respond to stress by changing size, shape, and strength. This process is called remodeling. If a bone fractures, it can heal by bone repair.
BIOLOGY TODAY Science
Identifying Skeletal Remains
Regardless of how, when, and where human bones are found unexpectedly, many questions must be answered. How old was this person at the time of death? Are these the bones of a male or female? What was the ethnicity? Are there any signs this person was murdered?
Clues about the identity and history of the deceased person are available throughout the skeleton (Fig. 12A). Age is approximated by dentition, or the structure of the teeth in the upper jaw (maxilla) and lower jaw (mandible). For example, infants between 0 and 4 months of age will have no teeth present; children approximately 6 to 10 years of age will have missing deciduous, or “baby,” teeth; young adults acquire their last molars, or “wisdom teeth,” around age 20. The age of older adults can be approximated by the number and location of missing or broken teeth. Studying areas of bone ossification also gives clues to the age of the deceased at the time of death. In older adults, signs of joint breakdown provide additional information about age. Hyaline cartilage becomes worn, yellowed, and brittle with age, and the hyaline cartilages covering bone ends wear down over time. The amount of yellowed, brittle, or missing cartilage helps scientists guess the person’s age.
Figure 12A Forensic investigators uncover a skeleton. A knowledge of bone structure and how bones age will help identify these remains.
©Michael Donne/Science Source
If skeletal remains include the individual’s pelvic bones, these provide the best method for determining an adult’s gender. The pelvis is shallower and wider in the female than in the male. The long bones, particularly the humerus and femur, give information about gender as well. Long bones are thicker and denser in males, and points of muscle attachment are bigger and more prominent. The skull of a male has a square chin and more prominent ridges above the eye sockets, or orbits.
Determining ethnic origin of skeletal remains can be difficult, because so many people have a mixed racial heritage. Forensic anatomists rely on observed racial characteristics of the skull. In general, individuals of African or African American descent have a greater distance between the eyes, eye sockets that are roughly rectangular, and a jaw that is large and prominent. Skulls of Native Americans typically have round eye sockets, prominent cheek (zygomatic) bones, and a rounded palate. Caucasian skulls usually have a U-shaped palate, and a suture line between the frontal bones is often visible. Additionally, the external ear canals in Caucasians are long and straight, so that the auditory ossicles can be seen.
Once the identity of the individual has been determined, the skeletal remains can be returned to the family for proper burial.
Questions to Consider
Why do you think long bones are most often found by forensic investigators?
How does an examination of bone ossification provide an indication of age?
Bones are living tissues, as shown by their ability to grow, remodel, and undergo repair. Several different types of cells are involved in bone growth, remodeling, and repair:
Osteoblasts are bone-forming cells. They secrete the organic matrix of bone and promote the deposition of calcium salts into the matrix.
Osteocytes are mature bone cells derived from osteoblasts. They maintain the structure of bone.
Osteoclasts are bone-absorbing cells. They break down bone and assist in returning calcium and phosphate to the blood.
Throughout life, osteoclasts are removing the matrix of bone and osteoblasts are building it up. When osteoblasts are surrounded by calcified matrix, they become the osteocytes within lacunae.
Bone Development and Growth
The term ossification refers to the formation of bone. The bones of the skeleton form during embryonic development in two distinctive ways: intramembranous ossification and endochondral ossification.
Intramembranous Ossification
Flat bones, such as the bones of the skull, are examples of intramembranous bones. In intramembranous ossification, bones develop between sheets of fibrous connective tissue. Here, cells derived from connective tissue cells become osteoblasts located in ossification centers. The osteoblasts secrete the organic matrix Page 248of bone. This matrix consists of mucopolysaccharides and collagen fibrils. The osteoblasts promote ossification of the matrix by adding calcium salts.
Ossification results in the formation of soft sheets, or trabeculae, of spongy bone. Spongy bone remains inside a flat bone. A periosteum forms outside the spongy bone. Osteoblasts derived from the periosteum carry out further ossification. Trabeculae form and fuse to become compact bone. The compact bone forms a bone collar that surrounds the spongy bone on the inside.
Endochondral Ossification
Most bones of the human skeleton are formed by endochondral ossification, which means the bone forms within the cartilage (Fig. 12.12). During endochondral ossification, bone replaces the cartilaginous (hyaline) models of the bones. Gradually, the cartilage is replaced by the calcified bone matrix that makes these bones capable of bearing weight. Inside, bone formation spreads from the center to the ends. The steps of endochondral ossification include:
The cartilage model (Fig 12.12a). In the embryo, chondrocytes lay down hyaline cartilage, which is shaped like the future bones. Therefore, they are called cartilage models of the future bones. As the cartilage models calcify, the chondrocytes die off.
The bone collar (Fig 12.12b). Osteoblasts are derived from the newly formed periosteum. Osteoblasts secrete the organic bone matrix, and the matrix undergoes calcification. The result is a bone collar, which covers the diaphysis. The bone collar is composed of compact bone. In time, the bone collar thickens.Page 251
The primary ossification center (Fig 12.12c). Blood vessels bring osteoblasts to the interior, and they begin to lay down spongy bone. This region is called a primary ossification center, because it is the first center for bone formation.
The medullary cavity and secondary ossification sites (Fig. 12.12d). The spongy bone of the diaphysis is absorbed by osteoclasts, and the cavity created becomes the medullary cavity. Shortly after birth, secondary ossification centers form in the epiphyses. Spongy bone persists in the epiphyses, and it persists in the red bone marrow for quite some time. Cartilage is present at two locations: the epiphyseal (growth) plate and articular cartilage, which covers the ends of long bones.
The epiphyseal (growth) plate (Fig 12.12e). A band of cartilage called the epiphyseal plate (also called a growth plate) remains between the primary ossification center and each secondary center (see Fig. 12.1). The limbs keep increasing in length as long as the epiphyseal plates are still present.
Figure 12.12 Bone growth by endochondral ossification. In endochondral ossification, the bone begins as hyaline cartilage. Bone cells called osteoblasts colonize the cartilage, then ossify to turn cartilage into bone.
Bone Growth
Figure 12.13 shows that the epiphyseal plate contains four layers. The layer nearest the epiphysis is the resting zone, where cartilage remains. The next layer is the proliferating zone, in which chondrocytes are producing new cartilage cells. In the third layer, the degenerating zone, the cartilage cells are dying off; and in the fourth layer, the ossification zone, bone is forming. Bone formation here causes the length of the bone to increase. The inside layer of articular cartilage also undergoes ossification in the manner described.
Figure 12.13 Increasing bone length. a. Length of a bone increases when cartilage is replaced by bone at the growth plate. Arrows indicate the direction of ossification. b. Chondrocytes produce new cartilage in the proliferating zone, and cartilage becomes bone in the ossification zone closest to the diaphysis.
The diameter of a bone enlarges as a bone lengthens. Osteoblasts derived from the periosteum are active in new bone deposition as osteoclasts enlarge the medullary cavity from inside.
Final Size of the Bones
When the epiphyseal plates close, bone lengthening can no longer occur. The epiphyseal plates in the arms and legs of women typically close at about age 16 to 18, and they do not close in men until about age 20. Portions of other types of bones may continue to grow until age 25.
Hormones, chemical messengers that are produced by one part of the body and act on a different part of the body, are secreted by the endocrine glands and distributed about the body by the bloodstream. Hormones control the activity of the epiphyseal plate, as is discussed next.
Hormones Affect Bone Growth
Several hormones play an important role in bone growth.
Vitamin D is formed in the skin when it is exposed to sunlight, but it can also be consumed in the diet. Milk, in particular, is often fortified with vitamin D. In the kidneys, vitamin D is converted to a hormone that acts on the intestinal tract. The chief function of vitamin D is intestinal absorption of calcium. In the absence of vitamin D, children can develop rickets, a condition marked by bone deformities, including bowed long bones.
Growth hormone (GH) directly stimulates growth of the epiphyseal plate, as well as bone growth in general. However, growth hormone is somewhat ineffective if the metabolic activity of cells is not promoted. Thyroid hormone, in particular, promotes the metabolic activity of cells (see Section 16.6). Too little growth hormone in childhood results in dwarfism. Too much growth hormone during childhood (prior to epiphyseal fusion) can produce excessive growth and even gigantism (see Fig. 16.9). Acromegaly results from excess GH in adults following epiphyseal fusion. Page 252This condition produces excessive growth of bones in the hands and face (see Fig. 16.10).
Adolescents usually experience a dramatic increase in height, called the growth spurt, due to an increased level of sex hormones. These hormones apparently stimulate osteoblast activity. Rapid growth causes epiphyseal plates to become “paved over” by the faster-growing bone tissue within 1 or 2 years of the onset of puberty.
Bone Remodeling and Calcium Homeostasis
Bone is constantly being broken down by osteoclasts and re-formed by osteoblasts in the adult. As much as 18% of bone is recycled each year. This process of bone renewal, often called bone remodeling, normally keeps bones strong. In Paget disease, new bone is generated at a faster-than-normal rate. This rapid remodeling produces bone that’s softer and weaker than normal bone and can cause bone pain, deformities, and fractures.
Bone recycling allows the body to regulate the amount of calcium in the blood. To illustrate that the blood calcium level is critical, recall that calcium is required for blood to clot (see Section 6.4). Also, if the blood calcium concentration is too high, neurons and muscle cells no longer function. If calcium falls too low, nerve and muscle cells become so excited that convulsions occur. Calcium ions are also necessary for the regulation of cellular metabolism by acting in cellular messenger systems. Thus, the skeleton acts as a reservoir for storage of this important mineral—if the blood calcium rises above normal, at least some of the excess is deposited in the bones. If the blood calcium dips too low, calcium is removed from the bones to bring it back up to the normal level.
Two hormones in particular are involved in regulating the blood calcium level. Parathyroid hormone (PTH) stimulates osteoclasts to dissolve the calcium matrix of bone. In addition, parathyroid hormone promotes calcium reabsorption in the small intestine and kidney, increasing blood calcium levels. Vitamin D is needed for the absorption of Ca2+ from the digestive tract, which is why vitamin D deficiency can result in weak bones. It is easy to get enough of this vitamin, because your skin produces it when exposed to sunlight, and the milk you buy at the grocery store is fortified with vitamin D.
Calcitonin is a hormone that acts opposite to PTH. The female sex hormone estrogen can actually increase the number of osteoblasts; the reduction of estrogen in older women is often given as reason for the development of weak bones, called osteoporosis. Osteoporosis is discussed in the Health feature “You Can Avoid Osteoporosis.” In the young adult, the activity of osteoclasts is matched by the activity of osteoblasts, and bone mass remains stable until about age 45 in women. After that age, bone mass starts to decrease.
BIOLOGY TODAY Health
You Can Avoid Osteoporosis
Osteoporosis is a condition in which the bones are weakened due to a decrease in the bone mass that makes up the skeleton. The skeletal mass continues to increase until ages 20 to 30. After that, there is an equal rate of formation and breakdown of bone mass until ages 40 to 50. Then, reabsorption begins to exceed formation, and the total bone mass slowly decreases (Fig. 12C).
Figure 12C Preventing osteoporosis. a. Normal bone. b. Bone from a person with osteoporosis.
(a): ©Susumu Nishinaga/Science Source; (b): ©Ed Reschke/Photolibrary/Getty Images
Over time, men are apt to lose 25% and women 35% of their bone mass. But we have to consider that men—unless they have taken asthma medications that decrease bone formation—tend to have denser bones than women anyway. Whereas a man’s testosterone (male sex hormone) level generally declines slowly after the age of 45, estrogen (female sex hormone) levels in women begin to decline significantly at about age 45. Sex hormones play an important role in maintaining bone strength, so this difference means that women are more likely than men to suffer a higher incidence of fractures, involving especially the hip, vertebrae, long bones, and pelvis. Although osteoporosis may at times be the result of various disease processes, it is essentially a disease that occurs as we age.
Osteoporosis
How to Avoid Osteoporosis
Everyone can take measures to avoid having osteoporosis later in life. Adequate dietary calcium throughout life is an important protection against osteoporosis. The National Osteoporosis Foundation (www.nof.org) recommends that adults under the age of 50 take in 1,000 mg of calcium per day. After the age of 50, the daily intake should exceed 1,200 mg per day.
A small daily amount of vitamin D is also necessary for the body to use calcium correctly. Exposure to sunlight is required to allow skin to synthesize a precursor to vitamin D. If you reside on or north of a “line” drawn from Boston to Milwaukee, to Minneapolis, to Boise, chances are you’re not getting enough vitamin D during the winter months. Therefore, you should take advantage of the vitamin D present in fortified foods such as low-fat milk and cereal. If you are under age 50, you should be receiving 400–800 IU of vitamin D per day. After age 50, this amount should increase to 800–1,000 IU of vitamin D daily.
Very inactive people, such as those confined to bed, lose bone mass 25 times faster than people who are moderately active. On the other hand, moderate weight-bearing exercise, such as regular walking or jogging, is another good way to maintain bone strength (Fig. 12C).
Diagnosis and Treatment
Postmenopausal women with any of the following risk factors should have an evaluation of their bone density:
White or Asian race
Thin body type
Family history of osteoporosis
Early menopause (before age 45)
Smoking
A diet low in calcium or excessive alcohol consumption and caffeine intake
Sedentary lifestyle
Bone density is measured by a method called dual-energy X-ray absorptiometry (DEXA). This test measures bone density based on the absorption of photons generated by an X-ray tube. Blood and urine tests are used to detect the biochemical markers of bone loss. Over the past several years, it has become easier for physicians to screen older women and at-risk men for osteoporosis.
If the bones are thin, it is worthwhile to take all possible measures to gain bone density, because even a slight increase can significantly reduce fracture risk. Although estrogen therapy does reduce the incidence of hip fractures, long-term estrogen therapy is rarely recommended for osteoporosis. Estrogen is known to increase the risk of breast cancer, heart disease, stroke, and blood clots. Other medications are available, however. Calcitonin, a thyroid hormone, has been shown to increase bone density and strength while decreasing the rate of bone fractures. Also, the bisphosphonates are a family of nonhormonal drugs used to prevent and treat osteoporosis. To achieve optimal results with calcitonin or one of the bisphosphonates, patients should also receive adequate amounts of dietary calcium and vitamin D.
Questions to Consider
How may long-term digestive system problems promote the chances of developing osteoporosis?
Why are individuals at risk for osteoporosis encouraged to increase their exercise regimes, including load-bearing exercises?
Page 253Bone remodeling also accounts for why bones can respond to stress. If you engage in an activity that calls upon the use of a particular bone, the bone enlarges in diameter at the region most affected by the activity. During this process, osteoblasts in the periosteum form compact bone around the external bone surface and osteoclasts break down bone on the internal bone surface around the medullary cavity. Increasing the size of the medullary cavity prevents the bones from getting too heavy and thick. Today, exercises such as walking, jogging, and weightlifting are recommended. These exercises strengthen bone because they stimulate the work of osteoblasts instead of osteoclasts.
Bone Repair
Repair of a bone is required after it breaks or fractures. Fracture repair takes place over a span of several months in a series of four steps, shown in Figure 12.14:
Hematoma. After a fracture, blood escapes from ruptured blood vessels and forms a hematoma (mass of clotted blood) in the space between the broken bones. The hematoma forms within 6 to 8 hours.
Fibrocartilaginous callus. Tissue repair begins, and a fibrocartilaginous callus fills the space between the ends of the broken bone for about 3 weeks.
Bony callus. Osteoblasts produce trabeculae of spongy bone and convert the fibrocartilage callus to a bony callus that joins the broken bones together. The bony callus lasts about 3 to 4 months.
Remodeling. Osteoblasts build new compact bone at the periphery. Osteoclasts absorb the spongy bone, creating a new medullary cavity.
Figure 12.14 Bone repair following a fracture. The stages in the repair of a fracture.
In some ways, bone repair parallels the development of a bone except that the first step, hematoma, indicates that injury has occurred. Further, a fibrocartilaginous callus precedes the production of compact bone.
The naming of fractures tells you what type of break has occurred. A fracture is complete if the bone is broken clear through, and incomplete if the bone is not separated into two parts. A fracture is simple if it does not pierce the skin, and is compound if it does pierce the skin. Impacted means that the broken ends are wedged into each other. A spiral fracture occurs when the break is ragged due to twisting of a bone.
Blood Cells Are Produced in Bones
The bones of your skeleton contain two types of marrow: yellow and red. Fat is stored in yellow bone marrow, thus making it part of the body’s energy reserves.
Red bone marrow is the site of blood cell production. The red blood cells are the carriers of oxygen in the blood. Oxygen is Page 254necessary for the production of ATP by aerobic cellular respiration. White blood cells also originate in the red bone marrow. The white cells are involved in defending your body against pathogens and cancerous cells; without them, you would soon succumb to disease and die.
CHECK YOUR PROGRESS 12.5
Describe how bone growth occurs during development.
Answer
Through intramembranous ossification, in which bone develops between sheets of fibrous connective tissue, and endochondral ossification, in which bone replaces a cartilage model.
Summarize the stages in the repair of bone.
Answer
A hematoma is formed. Next, tissue repair begins, and a fibrocartilaginous callus is formed between the ends of the broken bone. Then, the fibrocartilaginous callus is converted into a bony callus and remodeled by osteoblasts and osteoclasts.
Explain how the skeletal system is involved in calcium homeostasis.
Answer
When blood calcium is low, parathyroid hormone is secreted, causing osteoclasts to dissolve the bone matrix, releasing calcium into the blood. When blood calcium is high, calcitonin from the thyroid gland activates the bone-forming activity of osteoblasts.
CONNECTING THE CONCEPTS
For more on bone development and the hormones that influence bone growth, refer to the following discussions:
Section 9.6 provides additional information on inputs of vitamin D and calcium in the diet.
Section 16.2 examines the role of growth hormones in the body.
Section 16.3 describes the action of the hormones calcitonin and PTH.
CONCLUSION
For the first painful month or so after having her knee replaced, Jackie wondered if she had made the right decision. Just walking down the hall or up stairs was excruciating at first. Within 2 months, however, she was walking and swimming. Her physical therapist attributed her rapid return to her previous habits of staying in shape. But Jackie knows that without twenty-first-century medicine, she might have a difficult time walking by the time she is 60. Still, she has been reminded by her doctor that all bones, even those of adults, are dynamic structures. Whereas her bone could be replaced by bone remodeling, the plastic and ceramic parts of her knees would eventually wear out. So there was a very good chance she would have to undergo a repeat replacement of her knee in about 20 years. For Jackie, the ability to once again lead an active lifestyle was a worthwhile trade for a few months of discomfort.
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Ligaments and tendons.
Ligaments connect bone to bone. Tendons connect muscle to bone at a joint (also called an articulation).
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posterior
traps
lats
triceps- straighten forearm- antagonistic biceps
extensor
extensor
gluteus -
hamstrings- three muscles- biceps - semi tendinosis -
bends leg at knee
gastro- turn foot downwards- standing on toes
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The skeleton starts forming at about 6 weeks, when the embryo is only about 12 mm (0.5 in.) long. Most bones grow in length and width through adolescence, but some continue enlarging until about age 25. In a sense, bones can grow throughout a lifetime, because they are able to respond to stress by changing size, shape, and strength. This process is called remodeling. If a bone fractures, it can heal by bone repair.
This is when the skeleton starts forming. This is the life trajectory of bones.
This is the name of the process of bones changing size, shape, and strength.
How are hormones involved in bone growth?
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Hormones-
bony matrix - homeostasis
parathyroid hormone- works whole life
- never know when need calcium- signal osteoclasts- break down bony matrix- calcium
Calcitonin- doesn’t really work as much after teenagers; doesn’t work so well
why take calcium- as long as blood calcium - stable- don’t have to have parathyroid hormone- kick in -
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List the three types of cartilage in the blood and provide and functioning for each.
1) hyaline 2) fibroelastic 3) elastic
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What role does atp in muscle contraction
need atp to attach myasin heads to actin
need in form of Adp and phosphate form
triggers
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Osteoblasts- osteocytes- mature osteoblasts- maintain
osteoclasts- from macrophages- hydrolytic enzymes, break down bony matrix, put calcium back in blood stream-
work swith blasts in remodeling
chondrocytes- cartilage forming cells
osteoblasts- put in calcium
Bone growth, repair
and cells
Rib(s) Protect the heart and lungs Flattened bone originating from the thoracic vertebrae 12 pairs 7 pairs true ribs = vertebrosternal 3 pairs false ribs = vertebrochondral 2 pairs floating ribs = vertebral (note the names come from what the ribs articulate (meet up) with: vertebrosternal = vertebrae and sternum, for example) Sternum the breastbone
Ribs
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concave, convex,
struture- helps - stability carry body weight
curvature
Vertebral column
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Spongy Bone
- unorganized appearance (Fig. 12.1).
- numerous thin plates, trabeculae: follow lines of stress; separated by unequal spaces: red bone marrow: a specialized tissue that produces all types of blood cells.
- lighter than compact bone,
- still designed strength. the trabeculae filled with
- The osteocytes of spongy bone are irregularly placed within the trabeculae. Canaliculi bring them nutrients from the red bone marrow
Made of small, needle-like plates with spaces filled with red bone marrow (trabeculae)
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How do you know the names of ribs
The names come from what the ribs articulate from or meet up wtih
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Bones3
Pectoral girdle and upper limb Pelvic girdle and lower limb 12.3 Bones of the Appendicular Skeleton THE APPENDICULAR SKELETON 2 THE APPENDICULAR SKELETON Pectoral girdle Scapula and clavicle Upper limb Arm (humerus, radius, ulna) and hand bones (carpals, metacarpals, phalanges) clavicle scapula humerus radius ulna head of ulna carpals metacarpals phalanges Copyright © The McGraw-Hill Companies, Inc. Permission required for r
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Periosteum – outer covering of fibrous connective tissue found spanning the long bone, except where articular cartilage is found Ligaments – fibrous connective tissue that connects bones to bones 12.1
WHAT IS THE ANATOMY OF A LONG BONE?
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Articulations
Bones are joined at the joints, also called articulations, which are classified as fibrous, cartilaginous, or synovial. Many fibrous joints, such as the sutures between the cranial bones, are immovable. Cartilaginous joints may be connected by hyaline cartilage, as in the costal cartilages that join the ribs to the sternum. Other cartilaginous joints are formed by fibrocartilage, as in the intervertebral discs. Cartilaginous joints tend to be slightly movable. Synovial joints are freely movable (Fig. 12.10).
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Support, Movement, Protection, RBC Production, Storage of Minerals and Fat
Support: body, internal framework, leg bones: whole body, bone pelvic girdle- abdomenal cavity
Movement: attached skeletal muscles (by tendons); works with muscular system to provide movement
Protection: Protects the soft organs; skull: protect brain; rib cage: heart and lungs; vertebrae- spinal cord- making nervous connections along limb
Production of blood cells: hematopoiesis takes place in red bone marrow formation of blood; in fetus all bones have red bone marrow to produce blood, but in adults only certain bones have it
Storage of minerals and fat: calcium phosphate matrix- blood source of calcium and phosphate ions; Fat stored in yellow bone marrow; Stores minerals (mainly calcium and phosphate) and fat
What are the functions of the skeletal system?
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Types of Vertebrae
named according to their location in the vertebral column. The cervical vertebrae are located in the neck. The first cervical vertebra, called the atlas, holds up the head and allows it to tilt side to side. It is so named because Atlas, of Greek mythology, held up the world. The second cervical vertebra is called the axis, because it allows a degree of rotation. The thoracic vertebrae have long, thin spinous processes (Fig. 12.7a). The thoracic vertebrae articulate with one another and with the ribs at articular facets. Lumbar vertebrae have large bodies and thick processes. The five sacral vertebrae are fused together in the sacrum. The coccyx, or tailbone, is usually composed of four fused vertebrae.
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Study this diagram
Upper Respiratory Tract
What are some bone- and joint-associated injuries or conditions?
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Process of bone fracture **
1) hematoma - first 6-8 hours- blood clot- forms- scab inside- bones- vasculature- blood flow
2) fibracartilagenous callous- fibrocartilage- where hemotoma was- make sure all in alignment before fracture- sturdy- bones come together
3) replaced by bony callous - 3-4 months afterwards- spongey bone
4) remodeling- mechanical stress location- how use to what degree- reinforce that area- old bone tissue- replaced by new - some compact not just spongey
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Bones of the Appendicular Skeleton
12.3 Bones of the Appendicular Skeleton
LEARNING OUTCOMES
Upon completion of this section, you should be able to
Identify the bones of the pelvic and pectoral girdles.
Identify the bones of the upper and lower limbs.
The appendicular skeleton consists of the bones within the pectoral and pelvic girdles and their attached limbs. A pectoral (shoulder) girdle and upper limb are specialized for flexibility. The pelvic (hip) girdle and lower limbs are specialized for strength.
The Pectoral Girdle and Upper Limb
The body has left and right pectoral girdles. Each consists of a scapula (shoulder blade) and a clavicle (collarbone) (Fig. 12.8). The clavicle extends across the top of the thorax. It articulates with (joins with) the sternum and the scapula, a visible bone in the back. The muscles of the arm and chest attach to the scapula. The glenoid cavity of the scapula articulates with and is much smaller than the head of the humerus. This allows the arm to move in almost any direction but reduces stability. This is the joint most apt to dislocate. Ligaments and tendons stabilize this joint. Tendons that extend to the humerus from four small muscles originating on the scapula form the rotator cuff. Vigorous circular movements of the arm can lead to rotator cuff injuries.
Figure 12.8 The bones of the pectoral girdle and upper limb. The pectoral girdle consists of the clavicle and the scapula. The humerus is the single bone of the arm. The forearm is formed by the radius and ulna. A hand contains carpals, metacarpals, and phalanges.
Pectoral girdle
Scapula and clavicle
Upper limb
Upper arm: humerus
Forearm: radius and ulna
Hand: carpals, metacarpals, and phalanges
The components of a pectoral girdle freely follow the movements of the upper limb, which consists of the humerus in the upper arm and the radius and ulna in the forearm. The humerus has a smoothly rounded head that fits into the glenoid cavity of the scapula, as mentioned. The shaft of the humerus has a tuberosity (protuberance) where the deltoid, a shoulder muscle, attaches. You can determine, even after death, whether the person did a lot of heavy lifting during his or her lifetime by the size of the deltoid tuberosity. The far end of the humerus has two protuberances that articulate respectively with the radius and the ulna at the elbow.
When the upper limb is held so that the palm is turned forward, the radius and ulna are about parallel to each other. When the upper limb is turned so that the palm is turned backward, the radius crosses in front of the ulna, a feature that contributes to the easy twisting motion of the forearm.
The hand has many bones, and this increases its flexibility. The wrist has eight carpal bones, which look like small pebbles. From these, five metacarpal bones fan out to form a framework for the palm. The metacarpal bone that leads to the thumb is opposable to the other digits. (The term digits refers to either fingers or toes.) An opposable thumb can touch each finger separately or Page 245cross the palm to grasp an object. The knuckles are the enlarged distal ends of the metacarpals. Beyond the metacarpals are the phalanges, the bones of the fingers and the thumb. The phalanges of the hand are long, slender, and lightweight.
SCIENCE IN YOUR LIFE
Why are human toes shorter than the fingers?
Though some scientists believe that toes are an example of a vestigial organ, there is growing evidence that short toes played an important role in our evolutionary history. According to some scientists, the shortness of our toes contributes to our ability to run long distances, a rare trait in the animal kingdom. Studies have shown that long toes require more energy to start and stop running. In most animals with toes, the fingers and toes are approximately the same length. As toe length shortens, the ability of the animal to run long distances increases. The shortness of our toes may have contributed to the success of our species in hunting large prey on the open plains of Africa.
The Pelvic Girdle and Lower Limb
Figure 12.9 shows how the lower limb is attached to the pelvic girdle. The pelvic girdle (hip girdle) consists of two heavy, large hip bones, also known as os coxa. The pelvis is a basin composed of the pelvic girdle, sacrum, and coccyx. The pelvis bears the weight of the body, protects the organs within the pelvic cavity, and serves as the place of attachment for the legs.
Each hip bone has three parts: the ilium, the ischium, and the pubis, which are fused in the adult (Fig. 12.9). The hip socket, called the acetabulum, is where these three bones meet. The ilium is the largest part of the hip bones. We sit on the ischium, which has a posterior spine for muscle attachment. The pubis, from which the term pubic hair is derived, is the anterior part of a hip bone. The two pubic bones are joined by a fibrocartilaginous joint called the pubic symphysis.
Figure 12.9 The bones of the pelvis and lower limb. The ilium, ischium, and pubis join at the acetabulum to form the hip bone. The pelvis is completed by the addition of the sacrum and coccyx. The femur, tibia, and fibula form the leg. Tarsals, metatarsals, and phalanges construct the foot.
Pelvic girdle
Hip bones (os coxa)
Lower limb
Thigh: femur
Leg: tibia and fibula
Foot: tarsals, metatarsals, and phalanges
The male pelvis is different than the female pelvis. In the female, the iliac bones are more flared and the pelvic cavity is shallower, but the outlet is wider. These adaptations facilitate the birthing process during vaginal delivery.
The femur (thighbone) is the longest and strongest bone in the body. The head of the femur articulates with the hip bones at the acetabulum, and the short neck better positions the legs for walking. The femur has two large processes, which are places of attachment for thigh muscle and buttock muscles. At its distal end, the femur articulates with the tibia of the leg. This is the region of the knee and the patella, or kneecap. The patella is held in place Page 246by the quadriceps tendon, which continues as a ligament that attaches to the tibial tuberosity. The fibula is the more slender bone in the leg. The fibula has a head that articulates with the tibia.
Each foot has an ankle, an instep, and five toes. The many bones of the foot give it considerable flexibility, especially on rough surfaces. The ankle contains seven tarsal bones, one of which (the talus) can move freely where it joins the tibia and fibula. The calcaneus, or heel bone, is also considered part of the ankle. The talus and calcaneus support the weight of the body.
The instep has five elongated metatarsal bones. The distal ends of the metatarsals form the ball of the foot. If the ligaments that bind the metatarsals together become weakened, flat feet are apt to result. The bones of the toes are called phalanges, just like those of the fingers. In the foot, the phalanges are stout and extremely sturdy.
CHECK YOUR PROGRESS 12.3
List the bones of the pectoral girdle and the upper limb.
Answer
Pectoral girdle—scapula, clavicle; upper limb—humerus, radius, ulna, carpals, metacarpals, phalanges.
List the bones of the pelvic girdle and the lower limb.
Answer
Pelvic girdle—two coxal bones composed of ilium, pubis, and ischium; lower limb—femur, patella, tibia, fibula, tarsals, metatarsals, phalanges.
Describe how you can tell the difference in gender from looking at the bones of the pelvic girdle.
Answer
In the female the iliac bones are more flared, the pelvic cavity is shallower, but the outlet is wider.
CONNECTING THE CONCEPTS
For more information on the limbs of the body, refer to the following discussions:
Figure 5.12 diagrams the major blood vessels of the arms and legs.
Figure 13.5 illustrates the major muscles of the arms and legs.
Section 14.2 details the areas of the brain responsible for the movement of the arms and legs.
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Muscles mentioned in lecture
anterior muscles
muscle structures-
names and functions of each one of organs in chart
winking and blinking- eye
kiss and love- oral
orbit - circular
pectoral- pecks
serratus anterior- serrated knife- pulls scapular forward- boxer’s muscle- pulls fowrward
external abdomenal oblique-
rectus abdomenal
massider- mastication
deltoid- brings arms away form side
biceps brachea- bends forearm at
elbow
flexors
quads- set of 4 muscles straighten leg at knee raises thigh
tibia anterior- tibius - medial
raises toe
adductor- set of three- rhonus- moves thigh towrads midline
sartoriois- raises and laterally rotates thigh- rotates - cross legs- tailors - crosslegge-d sew
Major Skeletal Muscles and Functions
Commit to memory
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isometric contractions
load is too heavy - press against a wall- don’t see movement
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bone remodeling
as get bigger- bones- bigger diameter- actual thickness not much different, add bony matrix from outside- take away bony matrix from inside
osteoblasts- add from outside- and take awya car form inside
bigger diameter bone on the outside- but not anymore solid- too heavy- don’t want that
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Describe the skull.
The skull is formed by the cranium (braincase) and the facial bones. However, some cranial bones contribute to the structure of the face.
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Synovial joints and structures
The structure of this joint:
- Figure 12.10
- . Synovial joints are movable and therefore flexible. b. The bones of joints are joined by ligaments that form a capsule. The capsule is lined with synovial membrane, which gives off synovial fluid as a lubricant. Bursae are fluid-filled sacs that reduce friction. Menisci (sing., meniscus), formed of cartilage, stabilize a joint, and articular cartilage caps the bones. c. Ball-and-socket joints form the hip and shoulder. d. Hinge joints construct the knee and elbow.
(a) : ©Dmitry Tsvetkov/Shutterstock
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Vertebrae
Costal,
transverse processes
– These are the 2 attachments where they connect
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electrical impulses travel down somatic - neuromuscular junciton- meeting of where neuron and muscle cell interact with each other- somatic motor neuron
skeletal muscle cell-
nerve impulse- sodium rushing across cell membrane ad changing charge of membrane itself
reaches ends of neuron- axon-
axon terminals- causes calcium channels to open-
calcium rushes in
exocytosis- brain - acetocholyne- to go through exocytosis- membrane bound vesicle carrying acetycholine
neuron- muscle fiber- synaptic cleft- filled with water- actl- attaches to motor end of sarcolemma- closest to neuromuscular junction- diffused across membrane
sarcolemma- temporarily permeable to sodium- aciton potential
inwward- rush- excess positive ions- inside- trigger action potential
sodium entering through membrane- through sarcolema t tubule- cause calcium to be released
reticulum-
released calcium - combines with triponin-
attached to troplomyacin
changed triponin- lifts up tropamyacin- noramlly covered-
cross bridges
ATP- used for energy- break apart right away through hydrolysis-
energy contained after breakup- move actin filaments- to sarcomere-
contraction occurs-
axons- end of neuron axon terminals - sodium channels open all the way through nerve impulse- calcium enter- into axon terminals-
vesicles- contains acetylcholine- exocytosis- synaptic cleft- bind to recepts on motor end plate of sarcolemma of muscle cell
enough bind- another action potential- sodium rush in at the level of the muscle cell
Process of muscle contraction
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muscle structures-
names and functions of each one of organs in chart
winking and blinking- eye
kiss and love- oral
orbit - circular
pectoral- pecks
serratus anterior- serrated knife- pulls scapular forward- boxer’s muscle- pulls fowrward
external abdomenal oblique-
rectus abdomenal
massider- mastication
deltoid- brings arms away form side
biceps brachea- bends forearm at
elbow
flexors
quads- set of 4 muscles straighten leg at knee raises thigh
tibia anterior- tibius - medial
raises toe
adductor- set of three- rhonus- moves thigh towrads midline
sartoriois- raises and laterally rotates thigh- rotates - cross legs- tailors - crosslegge-d sew
Muscles mentioned in lecture
anterior muscles
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There are several general classes of synovial joints, two of which are shown in Figure 12.10. Figure 12.10b illustrates the general anatomy of a freely movable synovial joint. Ligaments connect bone to bone and support or strengthen the joint. A fibrous joint capsule formed by ligaments surrounds the bones at the joint. This capsule is not shown in Figure 12.10b so that the inner structure of the joint may be revealed. The joint capsule is lined with synovial membrane, which secretes a small amount of synovial fluid to lubricate the joint. Fluid-filled sacs called bursae (sing., bursa) ease friction between bare areas of bone and overlapping muscles or between skin and tendons. The full joint contains menisci (sing., meniscus), which are C-shaped pieces of fibrocartilage cartilage between the bones. These give added stability and act as shock absorbers.
The ball-and-socket joints at the hips and shoulders (Fig. 12.10c) allow movement in all planes, even rotational movement. The elbow and knee joints are synovial joints called hinge joints (Fig. 12.10d). Like a hinged door, they largely permit movement in one direction only. The Science feature “Osteoarthritis and Joint Replacement Surgery” examines the history of how joint replacement therapy was developed.
Synovial joint capsules and bursae, etc.
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Calcium interacts with triponin that makes tripmyacin move
Take a look at how all animations
CHECK YOUR PROGRESS 13.5
Summarize the importance of movement in homeostasis.
Answer
Muscle movement allows body movement in response to environmental change. It is also necessary for breathing, peristalsis, moving gametes, and childbirth. Also, it moves fluid in blood and lymph vessels, ureters, and the urinary bladder.
Summarize how the muscular system works to maintain body temperature.
Answer
Smooth muscles in blood vessels at body surfaces can constrict, diverting blood internally to conserve heat; contraction of skeletal muscle and involuntary shivering can produce heat.
Explain how the muscular system interacts with the digestive system.
Answer
Muscle contraction accounts for chewing and peristalsis; the digestive system absorbs nutrients needed for muscle contraction.
CONNECTING THE CONCEPTS
For more information on calcium and body temperature homeostasis, refer to the following discussions:
Section 4.8 explores how the body maintains homeostasis using feedback mechanisms.
Figure 4.18 examines how the hypothalamus is involved in body temperature regulation.
Section 16.3 describes how the thyroid and parathyroid glands are involved in calcium homeostasis.
CONCLUSION
There are several different classes of muscular dystrophy. In the most common types of muscular dystrophy, symptoms occur very early in life. In Kate’s case, the relatively late onset of the disease suggested she had a rarer form called Becker muscular dystrophy. For Kate, the good news was that this is a much slower-progressing form of the disease, with most patients living well into their thirties. Furthermore, many of the symptoms of Becker muscular dystrophy can be controlled with medication. Becker muscular dystrophy is known to cause heart problems later in life, but researchers are actively studying whether it may be possible to use gene therapy (see Section 22.4) to replace the defective dystrophin gene. In the interim, patients of Becker muscular dystrophy, such as Kate, are recommended to regularly exercise to slow the loss of muscle tissue over time.
Check yourself - homestasis muscle and skeletal
Cartilaginous joints may be connected by hyaline cartilage, as in the costal cartilages that join the ribs to the sternum. Other cartilaginous joints are formed by fibrocartilage, as in the intervertebral discs. Cartilaginous joints tend to be slightly movable. Synovial joints are freely movable (Fig. 12.10).
Cartilaginous joints
major brains share those of the brain: frontal, parietal, occipital, and temporal.
On the top (Fig. 12.4a), the frontal bone forms the forehead
the parietal bones extend to the sides, and the
occipital bone curves to form the base of the skull. Here, there is a large opening, the foramen magnum (Fig. 12.4b), through which the spinal cord passes.
Below the much larger parietal bones, each temporal bone has an opening (external auditory canal) that leads to the middle ear.
I am the cranium’s four parts.
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The skull and crainium. Study this slide and the image.
The sphenoid bone, shaped like a bat with outstretched wings, extends across the floor of the cranium from one side to the other. The sphenoid is the keystone of the cranial bones, because all the other bones articulate with it. The sphenoid completes the sides of the skull and contributes to forming the orbits (eye sockets). The ethmoid bone, which lies in front of the sphenoid, also helps form Page 240the orbits and the nasal septum. The orbits are completed by various facial bones. The eye sockets are called orbits because we can rotate our eyes.
Some of the bones of the cranium contain the sinuses, air spaces lined by mucous membrane. The sinuses reduce the weight of the skull and give a resonant sound to the voice. Sinuses are named according to the bones in which they are located. The major sinuses are the frontal, sphenoid, ethmoid, and maxillary. A smaller set of sinuses, called the mastoid sinuses, drain into the middle ear. Mastoiditis, a condition that can lead to deafness, is an inflammation of these sinuses.
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Fused vertebrae
You have to know all the numbers
4 - Coccyx and tale bone- between 3 and 5
I eat cereal for breakfast at 7, I eat a turkey sandwich at 12, I eat lasagna for dinner at 5 -
I secretly eat cookies
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This is the compact bone that is forming the outer boundaries of long bone
This is called cortical bone as well as compact bone
The skeletal system
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building up muscle
increasing number of mitochondria, myoglobin
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bones add cartilage from epiphyseal, turn into bone diathesial side
resting zone- cartialge- mitosis- proliferating zone- more arranged fashions- even bigger- there hypertrophic zone- degenerating zone
ossification zone- calcium start replacing dying cartilage cell replacing -
osteoblasts- remain ing
epiphyseal plate
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Articulations
12.4 Articulations
LEARNING OUTCOMES
Upon completion of this section, you should be able to
List the three types of joints.
Describe the structure and operation of a synovial joint.
Summarize the types of movement made possible by a synovial joint.
I am the vertebrae in order from top to bottom and the chief characteristics of each
Cartilaginous joints
Cartilaginous joints may be connected by hyaline cartilage, as in the costal cartilages that join the ribs to the sternum. Other cartilaginous joints are formed by fibrocartilage, as in the intervertebral discs. Cartilaginous joints tend to be slightly movable. Synovial joints are freely movable (Fig. 12.10).
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• Action: muscles work in pairs or groups • Prime mover- the muscle that does most of the work • Synergist – muscle or muscles that help the prime mover for a common action • Antagonist – muscle that acts opposite to a prime mover Figure 13.3 Skeletal muscles often work in pairs.
2 is better than one
Types of muscles- check out Figure 13.3
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Pectoral girdle and upper limb Pelvic girdle and lower limb
12.3 Bones of the Pectoral girdle Scapula and clavicle Upper limb
Pelvic girdle: Arm (humerus, radius, ulna) and hand bones (carpals, metacarpals, phalanges) clavicle scapula head of ulna
Appendicular system bones
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Made of small, needle-like plates with spaces filled with red bone marrow (trabeculae)
TYPES OF BONE (OSSEOUS) TISSUE Spongy bone
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energy contained within phosphate bonds and break up apart can use energy
myasin head- cock back- meet up - form cross bridge-
power stroke- pull actin to sarcomere by myasin head
atp molecule attach-
rigor mortis- stiff as a board
Immediately ATP split=
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lud sation- bones - out of alignment -
joints- accompanied sprains, inflammation, joint immobilization
body protective- no more movement than needs to
dislocation- serious falls impact
disclocation
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Upper Respiratory Tract
Study this diagram
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WHAT IS THE ANATOMY OF A LONG BONE?
Periosteum – outer covering of fibrous connective tissue found spanning the long bone, except where articular cartilage is found Ligaments – fibrous connective tissue that connects bones to bones 12.1
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The sphenoid bone, shaped like a bat with outstretched wings, extends across the floor of the cranium from one side to the other. The sphenoid is the keystone of the cranial bones, because all the other bones articulate with it. The sphenoid completes the sides of the skull and contributes to forming the orbits (eye sockets). The ethmoid bone, which lies in front of the sphenoid, also helps form Page 240the orbits and the nasal septum. The orbits are completed by various facial bones. The eye sockets are called orbits because we can rotate our eyes.
Some of the bones of the cranium contain the sinuses, air spaces lined by mucous membrane. The sinuses reduce the weight of the skull and give a resonant sound to the voice. Sinuses are named according to the bones in which they are located. The major sinuses are the frontal, sphenoid, ethmoid, and maxillary. A smaller set of sinuses, called the mastoid sinuses, drain into the middle ear. Mastoiditis, a condition that can lead to deafness, is an inflammation of these sinuses.
The skull and crainium. Study this slide and the image.
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bind muscle to bone- at joints -
tendons
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What are the components of the axial and appendicular skeletons?
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Within each myofibriles which hold sarcomeres
Muscle cells
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vertebral canal: center of the column, and the spinal cord passes through this canal
The intervertebral foramina (sing., foramen, “a hole or opening”) are found on each side of the column.
Spinal nerves branch from the spinal cord and travel through the intervertebral foramina to locations throughout the body. Spinal nerves control skeletal muscle contraction, among other functions.
If a vertebra is compressed, or slips out of position, the spinal cord and/or spinal nerves might be injured. The result can be paralysis or even death.
The spinous processes of the vertebrae can be felt as bony projections along the midline of the back. The transverse processes extend laterally. Both spinous and transverse processes serve as attachment sites for the muscles that move the vertebral column.
This is what the deal is with the vertebral column
What is the intervertebral foramina
Where are the spinal nerves and what do they do?
What happens if the vertebra is compressed?
Where are the spinous processes and how are they felt?
What are the transverse processes and where are they found?
What is the function of both transverse and spinous processes?
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Rib cage
Between the vertebrae are intervertebral discs composed of fibrocartilage that act as padding. The discs prevent the vertebrae from grinding against one another. They also absorb shock caused Page 242by movements such as running, jumping, and even walking. The presence of the discs allows the vertebrae to move as we bend forward, backward, and from side to side. Unfortunately, these discs become weakened with age and can herniate and rupture. Pain results if a disc presses against the spinal cord and/or spinal nerves. If that occurs, surgical removal of the disc may relieve the pain.
I have smaller, branching cells • connected cells, contract together
• usually 1 nucleus/cell • Striated • Neighboring cells connected at intercalated disks Function • involuntary, pumps blood M
I am Cardiac Muscle
Darker areas- lacunae- osteocytes- maintain bone maintenance
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The vertebral column consists of 33 vertebrae (Fig. 12.6). These are named by their region and by number. Normally, the vertebral column has four curvatures that provide more resilience and strength for an upright posture than a straight column could provide. Scoliosis is an abnormal lateral (sideways) curvature of the spine. There are two other well-known abnormal curvatures. Kyphosis is an abnormal posterior curvature that often results in a “hunchback.” An abnormal anterior curvature results in lordosis, or “swayback.”
The Vertebral Column
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functions of joints
joint, articulation, arthrosis,
arthritis- problems with joints
skeleton mobility and hold it together- bigger range of motion- weaker joints are - ligaments longer- less stabilty
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12.4 Articulations
LEARNING OUTCOMES
Upon completion of this section, you should be able to
List the three types of joints.
Describe the structure and operation of a synovial joint.
Summarize the types of movement made possible by a synovial joint.
Bones are joined at the joints, also called articulations, which are classified as fibrous, cartilaginous, or synovial. Many fibrous joints, such as the sutures between the cranial bones, are immovable. Cartilaginous joints may be connected by hyaline cartilage, as in the costal cartilages that join the ribs to the sternum. Other cartilaginous joints are formed by fibrocartilage, as in the intervertebral discs. Cartilaginous joints tend to be slightly movable. Synovial joints are freely movable (Fig. 12.10).
Figure 12.10 The structure of a synovial joint. a. Synovial joints are movable and therefore flexible. b. The bones of joints are joined by ligaments that form a capsule. The capsule is lined with synovial membrane, which gives off synovial fluid as a lubricant. Bursae are fluid-filled sacs that reduce friction. Menisci (sing., meniscus), formed of cartilage, stabilize a joint, and articular cartilage caps the bones. c. Ball-and-socket joints form the hip and shoulder. d. Hinge joints construct the knee and elbow.
(a): ©Dmitry Tsvetkov/Shutterstock
There are several general classes of synovial joints, two of which are shown in Figure 12.10. Figure 12.10b illustrates the general anatomy of a freely movable synovial joint. Ligaments connect bone to bone and support or strengthen the joint. A fibrous joint capsule formed by ligaments surrounds the bones at the joint. This capsule is not shown in Figure 12.10b so that the inner structure of the joint may be revealed. The joint capsule is lined with synovial membrane, which secretes a small amount of synovial fluid to lubricate the joint. Fluid-filled sacs called bursae (sing., bursa) ease friction between bare areas of bone and overlapping muscles or between skin and tendons. The full joint contains menisci (sing., meniscus), which are C-shaped pieces of fibrocartilage cartilage between the bones. These give added stability and act as shock absorbers.
The ball-and-socket joints at the hips and shoulders (Fig. 12.10c) allow movement in all planes, even rotational movement. The elbow and knee joints are synovial joints called hinge joints (Fig. 12.10d). Like a hinged door, they largely permit movement in one direction only. The Science feature “Osteoarthritis and Joint Replacement Surgery” examines the history of how joint replacement therapy was developed.
BIOLOGY TODAY Science
Osteoarthritis and Joint Replacement Surgery
Osteoarthritis is a condition that afflicts nearly everyone, to a greater or lesser degree, as each person ages. The bones that unite to form joints, or articulations, are covered with a slippery cartilage. This articular cartilage wears down over time, as friction in the joint wears it away (Fig. 12B). By age 80, people typically have osteoarthritis in one or more joints. By contrast, rheumatoid arthritis is an autoimmune disorder (see Section 7.5) that causes inflammation within the joint. Unlike osteoarthritis, which typically affects older people, rheumatoid arthritis can afflict a person of any age, even young children. Both forms of arthritis cause a loss of the joint’s natural smoothness. This is what causes the pain and stiffness associated with arthritis. Arthritis is first treated with medications for joint inflammation and pain and with physical therapy to maintain and strengthen the joint. If these treatments fail, a total joint replacement is often performed. Successful replacement surgeries are now routine, thanks to the hard work and dedication of the British orthopedic surgeon Dr. John Charnley.
Figure 12B Osteoarthritis. A comparison of a normal knee (a) and a knee with osteoarthritis (b).
(both): ©Puwadol Jaturawutthichai/Alamy
Early experimental surgeries by Charnley and others had been very disappointing. Fused joints were immobile, and fusion didn’t always relieve the patient’s pain. Postsurgical infection was common. The bones attached to the artificial joint eroded, and the supporting muscles wasted away because the joint wasn’t useful. Charnley wanted to design a successful prosthetic hip, with the goal of replacing both parts of the diseased hip joint: the acetabulum, or “socket,” as well as the ball-shaped head of the femur. Charnley soon determined that surgical experimentation alone wasn’t enough. He studied bone repair, persuading a colleague to operate on Charnley’s tibia, or shinbone, to see how repair occurred. He studied the mechanics of the hip joint, testing different types of synthetic materials. He achieved his first success using a hip socket lined with Teflon but soon discovered that the surrounding tissues became inflamed. After multiple attempts, his perfected hip consisted of a socket of durable polyethylene. Polyethylene is still used today as the joint’s plastic component. The head of his prosthetic femur was a small, highly polished metal ball. Stainless steel, cobalt, and titanium, as well as chrome alloys, form the metal component today. Various techniques for cementing the polyethylene socket onto the pelvic bone had failed when bone pulled away from the cemented surface and refused to grow. Charnley’s surgery used dental cement, slathered onto the bone surfaces. When the plastic components were attached, cement was squeezed into every pore of the bone, allowing the bone to regenerate and grow around the plastic. Finally, Charnley devised a specialized surgical tent and instrument tray to minimize infection.
Charnley’s ideas were innovative and unorthodox, and he was reassigned to a former tuberculosis hospital, which he converted into a center for innovation in orthopedic surgery. His colleagues developed a prosthetic knee joint similar to the Charnley hip. In knee replacement surgery (see the chapter opener), the damaged ends of bones are removed and replaced with artificial components that resemble the original bone ends. Hip and knee replacements remain the most common joint replacement surgeries, but ankles, feet, shoulders, elbows, and fingers can also be replaced. Though many improvements on the procedure continue, the Charnley hip replacement remains the technique after which all others are modeled.
When a joint replacement is complete, the patient’s hard work is vital to ensure the success of the procedure. Exercise and activity are critical to the recovery process. After surgery, the patient is encouraged to use the new joint as soon as possible. The extent of improvement and range of motion of the joint depend on its stiffness before the surgery, as well as the amount of patient effort during therapy following surgery. A complete recovery varies in time from patient to patient but typically takes several months. Older patients can expect their replacements to last about 10 years. However, younger patients may need a second replacement if they wear out their first prosthesis. Still, individuals who have joint replacement surgery can expect an improved quality of life and a bright future with greater independence and healthier, pain-free activity.
Questions to Consider
Compare each component of Charnley’s artificial joint with that of a real synovial joint.
Explain why rheumatoid arthritis is actually a disorder of the immune system.
Movements Permitted by Synovial Joints
Intact skeletal muscles are attached to bones by tendons that span joints. When a muscle contracts, one bone moves in relation to another bone. The more common types of movements are described in Figure 12.11.
Figure 12.11 Synovial joints allow for a variety of movement. a. Flexion and extension. b. Adduction and abduction. c. Rotation and circumduction. d. Inversion and eversion. Red dots indicate pivot points.
CHECK YOUR PROGRESS 12.4
List the three major types of joints.
Answer
Fibrous, cartilaginous, synovial.
Describe the basic movements of cartilaginous and fibrous joints, and give an example of each in the body.
Answer
Cartilaginous joints are slightly movable and found in the rib cage and intervertebral discs; fibrous joints are not movable and are found in the sutures of the skull.
Describe the different movements of synovial joints, and give an example of each in the body.
Answer
Flexion and extension—knee; adduction and abduction—hip and shoulder; rotation—arm; circumduction—hip and shoulder; inversion and eversion—foot and ankle.
CONNECTING THE CONCEPTS
For more information on ligaments and tendons, refer to the following discussion:
Section 4.2 describes the connective tissue found in the tendons and ligaments.
Articulations
Fibrous joints
Many fibrous joints, such as the sutures between the cranial bones, are immovable.
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Action potential traveling down two tubules- activated calcium to activeate
calcium released into sarcoplasm
move tripnonin - causes shape chagne tropomyacin
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load is too heavy - press against a wall- don’t see movement
isometric contractions
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What is the pectoral girdle (shoulder)
Shoulder blade bone and collar blade bone, scapula and clavicle-
hook upper limbs to axial skeleton-
upper arm bone- humerus-
radius- thumbside
ulna- forearms - bend the elbow articulation with humerus that is hinge joint
wrist bone- carpals
metacarpuls- middle- back and palm of hand
finger bones - philanges- three bones per finger except for thumb - thumb two
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Explanation of skull
Figure 12.5 The bones of the face and the location of the hyoid bone. a. The frontal bone forms the forehead and eyebrow ridges; the zygomatic bones form the cheekbones; and the maxillae have numerous functions. They assist in the formation of the eye sockets and the nasal cavity. They form the upper jaw and contain sockets for the upper teeth. The mandible is the lower jaw with sockets for the lower teeth. The mandible has a projection we call the chin. b. The maxillae, frontal, and nasal bones help form the external nose. c. The hyoid bone is located as shown.
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tendons
bind muscle to bone- at joints -
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parathyroid
release calcium ions back into blood
blood calcium levels- too high-
calciums - bony matrix- secreted by thyroid gland- osteoblasts- not so effetctive after adolescence
Blood calcium levels - drop - homestasis
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This is the azial skeleton
Skull – made of cranium and facial bones Hyoid bone – only bone that does not articulate (form a joint) with any other bone in the body; found in the neck region Vertebral column – vertebrae and intervertebral disks Rib cage – ribs and sternum
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Botox
excessive sweating, migraines
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Paranasal sinuses- spaces within skull found around noise
ethnoid, sphenoid, frontal, maxillary
temporal/mastoid sinuses-
chamber in that area- not around nose- cranial sinus
Sinuses
12.4 Articulations
LEARNING OUTCOMES
Upon completion of this section, you should be able to
List the three types of joints.
Describe the structure and operation of a synovial joint.
Summarize the types of movement made possible by a synovial joint.
Articulations
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In the middle of fibercartilage, mucoid, comes out
Herniated disc
Identify the regions of the vertebral column.
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Identify what each of the bones are called in each location
Humerus- upper arm
scapula- shoulder blade
clavicle- collar bone
terms heard of - need to memorize and by pointing recognize what bone identification it is
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Skull – made of cranium and facial bones Hyoid bone – only bone that does not articulate (form a joint) with any other bone in the body; found in the neck region Vertebral column – vertebrae and intervertebral disks Rib cage – ribs and sternum
This is the azial skeleton
Skull bones learn this
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Pelvic girdle
hip girdle,
coxyl bones-
articulate- axial skeleton- sacrem
coccyx- ligaments go back and forth with that oxcoxcae
three bones- fused together- ilium, isheum, pubis -
isheul tuberosky- sit bones
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Skeletal system part one
12.1 Overview of the Skeletal System
LEARNING OUTCOMES
Upon completion of this section, you should be able to
State the functions of the skeletal system.
Describe the structure of a long bone and list the types of tissues it contains.
List the three types of cartilage found in the body and provide a function for each.
The skeletal system consists of two types of connective tissue: bone and the cartilage found at joints, which is the point where two joints come together. In addition, ligaments, formed of fibrous connective tissue, join the bones.
Functions of the Skeleton
The skeleton does more than merely provide a frame for the body. In addition, it has the following functions:
Support. The bones of the legs support the entire body when we are standing, and bones of the pelvic girdle support the abdominal cavity.
Movement. The skeletal system works with the muscular system to provide movement.
Protection. The bones of the skull protect the brain; the rib cage protects the heart and lungs; and the vertebrae protect the spinal cord, which makes nervous connections to all the muscles of the limbs.
Production of blood cells. The skeleton plays an important role in the formation of blood. In the fetus, all bones have red bone marrow to produce new blood cells. However, in adults, only certain bones produce blood cells.
Storage of minerals and fat. All bones have a matrix that contains calcium phosphate, a source of calcium ions and phosphate ions in the blood. Fat is stored in yellow bone marrow.
Anatomy of a Long Bone
The bones of the body vary greatly in size and shape. To better understand the anatomy of a bone, we will use a long bone (Fig. 12.1), a type of bone common in the arms and legs. The shaft, or main portion of the bone, is called the diaphysis. The diaphysis has a large medullary cavity, whose walls are composed of compact bone. The medullary cavity is lined with a thin, vascular membrane (the endosteum) and is filled with yellow bone marrow, which stores fat.
Figure 12.1 The anatomy of a long bone. A long bone is formed of an outer layer of compact bone. The central shaft of a long bone contains yellow marrow, a form of stored fat. Periosteum, a fibrous membrane, encases the bone except at its ends, which are covered by hyaline cartilage.
The expanded region at the end of a long bone is called an epiphysis (pl., epiphyses). The epiphyses are separated from the diaphyses by a small region of mature bone called the metaphysis, which contain the epiphyseal plate, a region of cartilage that allows for bone growth.
The epiphyses are composed largely of spongy bone that contains red bone marrow, where blood cells are made. The epiphyses are coated with a thin layer of hyaline cartilage, which is also called articular cartilage, because it occurs at a joint.
Except for the articular cartilage on the bone’s ends, a long bone is completely covered by a layer of fibrous connective tissue called the periosteum. This covering contains blood vessels, lymphatic vessels, and nerves. Note in Figure 12.1 how a blood vessel penetrates the periosteum and enters the bone. Branches of the blood vessel are found throughout the medullary cavity. Page 238Other branches can be found in hollow cylinders called central canals within the bone tissue. The periosteum is continuous with ligaments and tendons connected to a bone.
Bone
Compact bone is highly organized and composed of tubular units called osteons (Fig. 12.2). In a cross-section of an osteon, bone cells called osteocytes lie in lacunae (sing., lacuna), tiny chambers arranged in concentric circles around a central canal (Fig. 12.1). Matrix fills the space between the rows of lacunae. Tiny canals called canaliculi (sing., canaliculus) run through the matrix. These canaliculi connect the lacunae with one another and with the central canal. The cells stay in contact by strands of cytoplasm that extend into the canaliculi. Osteocytes nearest the center of an osteon exchange nutrients and wastes with the blood vessels in the central canal. These cells then pass on nutrients and collect wastes from the other cells via gap junctions (see Fig. 3.17).
Figure 12.2 Anatomy of compact bone. Compact bone is composed of cylinder-shaped structures called osteons, which contain osteocytes.
(photos) (compact bone): ©Ed Reschke; (osteocyte): ©Biophoto Associates/Science Source
Compared with compact bone, spongy bone has an unorganized appearance (Fig. 12.2). It contains numerous thin plates, called trabeculae, separated by unequal spaces. Although this makes spongy bone lighter than compact bone, spongy bone is still designed for strength. Just as braces are used for support in Page 239buildings, the trabeculae follow lines of stress. The spaces of spongy bone are often filled with red bone marrow, a specialized tissue that produces all types of blood cells. The osteocytes of spongy bone are irregularly placed within the trabeculae. Canaliculi bring them nutrients from the red bone marrow.
Cartilage
Cartilage is not as strong as bone, but it is more flexible. Its matrix is gel-like and contains many collagenous and elastic fibers. The cells, called chondrocytes, lie within lacunae that are irregularly grouped. Cartilage has no nerves, making it well suited for padding joints where the stresses of movement are intense. Cartilage also has no blood vessels and relies on neighboring tissues for nutrient and waste exchange. This makes it slow to heal.
The three types of cartilage differ according to the type and arrangement of fibers in the matrix. Hyaline cartilage is firm and somewhat flexible. The matrix appears uniform and glassy, but actually it contains a generous supply of collagen fibers. Hyaline cartilage is found at the ends of long bones, in the nose, at the ends of the ribs, and in the larynx and trachea.
Fibrocartilage is stronger than hyaline cartilage, because the matrix contains wide rows of thick, collagenous fibers. Fibrocartilage is able to withstand both tension and pressure and is found where support is of prime importance—in the discs between the vertebrae and in the cartilage of the knee.
Elastic cartilage is more flexible than hyaline cartilage, because the matrix contains mostly elastin fibers. This type of cartilage is found in the ear flaps and the epiglottis.
Fibrous Connective Tissue
Fibrous connective tissue contains rows of cells called fibroblasts separated by bundles of collagenous fibers (see Section 4.2). This tissue makes up ligaments and tendons. Ligaments connect bone to bone. Tendons connect muscle to bone at a joint (also called an articulation).
CHECK YOUR PROGRESS 12.1
List the functions of the skeletal system.
Answer
Support, movement, protection, production of blood cells, storage of minerals and fat.
Summarize the structure of a long bone by describin
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Bone and cartilage found at the joints.
Ligaments, formed of fibrous connective tissue join the bones.
These are the two types of tissue found in the skeletal system and where they are found.
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Compact Bone
highly organized
composed of tubular units called osteons
- in osteons: bone cells called osteocytes lie in lacunae (sing., lacuna), tiny chambers arranged in concentric circles around a central canal (Fig. 12.1).
- Matrix fills the space between the rows of lacunae.
- Tiny canals called canaliculi (sing., canaliculus) run through the matrix. These canaliculi connect the lacunae with one another and with the central canal. The cells stay in contact by strands of cytoplasm that extend into the canaliculi.
- Osteocytes nearest the center of an osteon exchange nutrients and wastes with the blood vessels in the central canal. These cells then pass on nutrients and collect wastes from the other cells via gap junctions (see Fig. 3.17)
- Matrix fills the space between the rows of lacunae.
Dense, smooth, homogeneous Composed of osteons with a central canal containing blood vessels Contains living bone cells called osteocytes in chambers called lacunae
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Skeletal muscle
prime mover-
helper muscle
- synergers
- help prime mover in common action
antagonist- acts opposite- to prime mover
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This is how many bones there are and how they are classified.
The axial skeleton lies here and consists of these 4 parts.
The 206 bones of the skeleton are classified according to whether they occur in the axial skeleton or the appendicular skeleton (Fig. 12.3). The axial skeleton lies in the midline of the body and consists of the skull, hyoid bone, vertebral column, and the rib cage.
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What is cervical vertebrae? Where is it located? What are the first and second called?
- like name: located in the neck
- The first cervical vertebra, called the atlas, holds up the head and allows it to tilt side to side. Atlas, of Greek mythology, held up the world.
- The second cervical vertebra is called axis: degree of rotation.
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The lips and cheeks have a core of skeletal muscle. The zygomatic bones form the cheekbone prominences, and the nasal bones form the bridge of the nose. Other bones (e.g., ethmoid and vomer) are a part of the nasal septum, which divides the interior of the nose into two nasal cavities. The lacrimal bone (see Fig. 12.4a) contains the opening for the nasolacrimal canal, which drains tears from the eyes to the nose.
Certain cranial bones contribute to the face. The temporal bone and the wings of the sphenoid bone account for the flattened areas we call the temples. The frontal bone forms the forehead and has supraorbital ridges, where the eyebrows are located. Glasses sit where the frontal bone joins the nasal bones.
The exterior portions of ears are formed only by cartilage and not by bone. The nose is a mixture of bones, cartilages, and connective tis
he cartilages complete the tip of the nose, and fibrous connective tissue forms the flared sides of the nose.
Facial muscle and bones
Where are the fuel sources for muscle contraction?
• Stored in the muscle • Glycogen • Lipid • In the blood • Glucose • Fatty acids
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type of bone found in arm and leg
diaphysis: shaft
a) medullary cavity- composed of compact bone; outer layer
b) spongy bone- lies beneath- red bone marrow
c) endosteum- thin vascular membrane- yellow bone marrow- stores fat
d) central shaft - yellow bone marrow
d) periosteum- fibrous membrane encases the bone except at ends
e) hyaline cartilage- covers the ends of the bones
Regions of the bone:
epiphysis (pl., epiphyses): expanded region at end of a long bone ; spongy bone that contains red bone marrow, where blood cells are made; coated with a thin layer of hyaline cartilage, articular cartilage, because it occurs at a joint.
metaphysis: separates epiphysis from the
diaphyses: contain the epiphyseal plate, a region of cartilage that allows for bone growth
Except articular cartilage on the bone’s ends, completely covered by a layer of fibrous connective tissue called periosteum: contains blood vessels, lymphatic vessels, and nerves. Note in Figure 12.1 blood vessel penetrates the periosteum and enters the bone. Branches of the blood vessel are found throughout the medullary cavity. Other branches can be found in hollow cylinders called central canals within the bone tissue. The periosteum is continuous with ligaments and tendons connected to a bone.
Epiphysis – ends of the bone made mostly of spongy bone Filled with red bone marrow (hematopoesis takes place here)
Diaphysis – shaft of the bone made of compact bone
Medullary cavity- filled with yellow bone marrow (fat storage)
Articular cartilage – hyaline cartilage found on the ends of long bones
Periosteum – outer covering of fibrous connective tissue found spanning the long bone, except where articular cartilage is found
Ligaments – fibrous connective tissue that connects bones to bones
Describe the structure of long bone and the types of tissues it has
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don’t have to break up the skin
closed reduction
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Lacunae
osteocytes-
canalliculae- communication, nutrients, waste products, osteon to osteon, and within lacunae to lacunae
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Blood calcium levels - drop - homestasis
parathyroid
release calcium ions back into blood
blood calcium levels- too high-
calciums - bony matrix- secreted by thyroid gland- osteoblasts- not so effetctive after adolescence
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False ribs
Next 3 pairs
vertebrae back in posterior, anterior- articulate with 7th cartilage right above it ; Don’t articulate to sternum
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What are the functions of the skeletal system?
Support, Movement, Protection, RBC Production, Storage of Minerals and Fat
Support: body, internal framework, leg bones: whole body, bone pelvic girdle- abdomenal cavity
Movement: attached skeletal muscles (by tendons); works with muscular system to provide movement
Protection: Protects the soft organs; skull: protect brain; rib cage: heart and lungs; vertebrae- spinal cord- making nervous connections along limb
Production of blood cells: hematopoiesis takes place in red bone marrow formation of blood; in fetus all bones have red bone marrow to produce blood, but in adults only certain bones have it
Storage of minerals and fat: calcium phosphate matrix- blood source of calcium and phosphate ions; Fat stored in yellow bone marrow; Stores minerals (mainly calcium and phosphate) and fat
Bone is also involved with storage of minerals and fat. Bone cells called osteoclasts break down bone and return calcium and phosphate ions to the bloodstream.
I am the vertebrae in order from top to bottom and the chief characteristics of each
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Mandible, maxillary (upper jaw), zygomatic bones (cheekbones) nasal bones -glasses rest there
Facial bones
This is the anatomy of a longbone
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highly organized
composed of tubular units called osteons
- in osteons: bone cells called osteocytes lie in lacunae (sing., lacuna), tiny chambers arranged in concentric circles around a central canal (Fig. 12.1).
- Matrix fills the space between the rows of lacunae.
- Tiny canals called canaliculi (sing., canaliculus) run through the matrix. These canaliculi connect the lacunae with one another and with the central canal. The cells stay in contact by strands of cytoplasm that extend into the canaliculi.
- Osteocytes nearest the center of an osteon exchange nutrients and wastes with the blood vessels in the central canal. These cells then pass on nutrients and collect wastes from the other cells via gap junctions (see Fig. 3.17)
- Matrix fills the space between the rows of lacunae.
Dense, smooth, homogeneous Composed of osteons with a central canal containing blood vessels Contains living bone cells called osteocytes in chambers called lacunae
Compact Bone
The joints of the skeletal system, along with muscles, permit flexible body movement.
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What are discs
The ____________prevent the vertebrae from grinding against one another. They also absorb shock caused by movements such as running, jumping, and even walking.
support abdomenal cavity
Coxal bones
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only posterior articulation, not attached to anything in front
Floating ribs
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During the procedure, a surgeon removes bone from the bottom of the femur and the top of the tibia and replaces each with caps made of metal or ceramic, held in place with bone cement. A plastic plate is installed to allow the femur and tibia to move smoothly against each other, and a smaller plate is attached to the kneecap (patella), so it can function properly.
This is what happens when you tear a ligament
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The names come from what the ribs articulate from or meet up wtih
How do you know the names of ribs
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Epiphysis – ends of the bone made mostly of spongy bone Filled with red bone marrow (hematopoesis takes place here) Diaphysis – shaft of the bone made of compact bone Medullary cavity- filled with yellow bone marrow (fat storage) Articular cartilage – hyaline cartilage found on the ends of long bones
WHAT IS THE ANATOMY OF A LONG BONE?
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Bone is also involved with storage of minerals and fat. Bone cells called osteoclasts break down bone and return calcium and phosphate ions to the bloodstream.
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Take a look at how all animations
Calcium interacts with triponin that makes tripmyacin move
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This is called cortical bone as well as compact bone
This is the compact bone that is forming the outer boundaries of long bone
Identify the bones of the skull, the hyoid, vertebral column, and rib cage.
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These are the different regions of the bone and the parts described.
diaphysis
the shaft or main portion of the bone
epiphysis
the expanded region at the end of the bone
metaphysis
a small region that contains the epiphyseal plate
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Shoulder blade bone and collar blade bone, scapula and clavicle-
hook upper limbs to axial skeleton-
upper arm bone- humerus-
radius- thumbside
ulna- forearms - bend the elbow articulation with humerus that is hinge joint
wrist bone- carpals
metacarpuls- middle- back and palm of hand
finger bones - philanges- three bones per finger except for thumb - thumb two
What is the pectoral girdle (shoulder)
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This is the structure of a synovial joint
- My joints are movable and therefore flexible.
- My bones are joined by ligaments forming capsule: lined with _______ membrane, emitting _______fluid as lubricant
- Bursae fluid-filled sacs, reduce friction.
- Menisci (sing., meniscus), formed of cartilage, stabilize a joint, and articular cartilage caps the bones.
- Ball-and-socket joints form the hip and shoulder.
- Hinge joints construct the knee and elbow.
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Identify the regions of the vertebral column.
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Figure 12.5 The bones of the face and the location of the hyoid bone. a. The frontal bone forms the forehead and eyebrow ridges; the zygomatic bones form the cheekbones; and the maxillae have numerous functions. They assist in the formation of the eye sockets and the nasal cavity. They form the upper jaw and contain sockets for the upper teeth. The mandible is the lower jaw with sockets for the lower teeth. The mandible has a projection we call the chin. b. The maxillae, frontal, and nasal bones help form the external nose. c. The hyoid bone is located as shown.
Explanation of skull
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Blank 1: spinous
Blank 2: body
Label this diagram.
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Describe the structure of long bone and the types of tissues it has
type of bone found in arm and leg
diaphysis: shaft
a) medullary cavity- composed of compact bone; outer layer
b) spongy bone- lies beneath- red bone marrow
c) endosteum- thin vascular membrane- yellow bone marrow- stores fat
d) central shaft - yellow bone marrow
d) periosteum- fibrous membrane encases the bone except at ends
e) hyaline cartilage- covers the ends of the bones
Regions of the bone:
epiphysis (pl., epiphyses): expanded region at end of a long bone ; spongy bone that contains red bone marrow, where blood cells are made; coated with a thin layer of hyaline cartilage, articular cartilage, because it occurs at a joint.
metaphysis: separates epiphysis from the
diaphyses: contain the epiphyseal plate, a region of cartilage that allows for bone growth
Except articular cartilage on the bone’s ends, completely covered by a layer of fibrous connective tissue called periosteum: contains blood vessels, lymphatic vessels, and nerves. Note in Figure 12.1 blood vessel penetrates the periosteum and enters the bone. Branches of the blood vessel are found throughout the medullary cavity. Other branches can be found in hollow cylinders called central canals within the bone tissue. The periosteum is continuous with ligaments and tendons connected to a bone.
Epiphysis – ends of the bone made mostly of spongy bone Filled with red bone marrow (hematopoesis takes place here)
Diaphysis – shaft of the bone made of compact bone
Medullary cavity- filled with yellow bone marrow (fat storage)
Articular cartilage – hyaline cartilage found on the ends of long bones
Periosteum – outer covering of fibrous connective tissue found spanning the long bone, except where articular cartilage is found
Ligaments – fibrous connective tissue that connects bones to bones
Muscle to Bone
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These are the 3 types of joints:
- Where bones are joined
- aka articulations
- Fibrous- many immovable (i.e. sutures b/t cranial bones)
- Cartilaginous- hyaline cartilage connects (i.e. costal cartilages joining ribs and sternum); others: fibrocartilage- i.e.- intervertertebral discs
- slightly movable
3. Synovial - freely movable
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The Vertebral Column
The vertebral column consists of 33 vertebrae (Fig. 12.6). These are named by their region and by number. Normally, the vertebral column has four curvatures that provide more resilience and strength for an upright posture than a straight column could provide. Scoliosis is an abnormal lateral (sideways) curvature of the spine. There are two other well-known abnormal curvatures. Kyphosis is an abnormal posterior curvature that often results in a “hunchback.” An abnormal anterior curvature results in lordosis, or “swayback.”
Muscle to Bone
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What is growth.
After a long bone has formed, it can continue to increase in length due to growth that occurs at the epiphyseal plate, which is also called the ___________ plate
- My joints are movable and therefore flexible.
- My bones are joined by ligaments forming capsule: lined with _______ membrane, emitting _______fluid as lubricant
- Bursae fluid-filled sacs, reduce friction.
- Menisci (sing., meniscus), formed of cartilage, stabilize a joint, and articular cartilage caps the bones.
- Ball-and-socket joints form the hip and shoulder.
- Hinge joints construct the knee and elbow.
This is the structure of a synovial joint
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After a long bone has formed, it can continue to increase in length due to growth that occurs at the epiphyseal plate, which is also called the ___________ plate
What is growth.
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Commit to memory
Major Skeletal Muscles and Functions
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The Facial Bones
The most prominent of the facial bones are the mandible, the maxillae (sing., maxilla), the zygomatic bones, and the nasal bones.
The mandible, or lower jaw, is the only movable portion of the skull, and it forms the chin (Fig. 12.4 and Fig. 12.5). The maxillae form the upper jaw and a portion of the eye socket. Further, the hard palate and the floor of the nose are formed by the maxillae (anterior) joined to the palatine bones (posterior). Tooth sockets are located on the mandible and on the maxillae. The grinding action of the mandible and maxillae allows us to chew our food.
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Spinal cord and surrounding structures
The spinal cord extends from the base of the brain and down through the vertebral column.
- Passes through the foramen magnum into the vertebral canal, which is created by openings in vertebrae
- Spinal nerves project from the spinal cord between vertebrae.
- Protection of the spinal cord
- Bony vertebrae surround spinal cord
- Fluid-filled intervertebral disks cushion and separate vertebrae
- Protective membranes called meninges wrap around the spinal cord
This is the anatomy of a longbone
Skull bones learn this
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Label this diagram.
Blank 1: spinous
Blank 2: body
