Module 4: The Skeletal System: Histology and Movement Flashcards
What type of tissue is bone classified as?
Connective tissue.
What does the function of connective tissue (whether it is bone, connective tissue proper, cartilage, or blood) depend upon?
It depends on the composition. The bone matrix determines the function.
Blast
Immature cell
Cyte
Mature cell
Osteo
Bone
Osteoblast
A bone-forming cell.
Osteocyte
A mature bone cell surrounded by bone matrix.
What is the function of osteoblasts?
They produce bone matrix.
When is an osteoblast considered an osteocyte?
Once the matrix is fully formed and the cells are surrounded.
Lacuna
The microscopic space within the matrix that houses the osteocytes.
Osteoclast
A large, multinucleated cell that breaks down bone.
Clast
To break.
Why does the body need osteoclasts?
Bones deteriorate on their own, so the body must be able to break down bone in order to build it up again. When the body need minerals that are stored in bone, the osteoclasts break down the bone tissue and release those minerals.
What are the three basic types of bone cells?
Osteoblasts, osteocytes, and osteoclasts.
What is the bone matrix like?
It contains protein in the form of collagen fibers and calcium salts.
What % of bone is collagen?
30%.
Where do the collagen fibers in the bone matrix come from?
They are secreted by the osteoblasts as they build the bone matrix.
What is the function of collagen in bone?
It gives the tissue flexibility and tensile strength.
What are some other names for calcium salts?
Calcium minerals, bone salts, or bone minerals.
Calcium salt
An ionic compound that contain calcium ions.
What does mineral refer to in “calcium mineral”?
Inorganic crystalline compounds.
What are most of the calcium salts in the bone matrix?
Hydroxyapatite.
What is the chemical formula for hydroxyapatite?
Ca10(PO4)6(OH)2
How do calcium salts come to be in the bone matrix?
Unlike other connective tissue matrices, the cells do not produce the calcium salts. Instead, the blood brings the salts into the bone matrix.
What % calcium is bone made of?
40%.
What % phosphorous is bone made of?
20%.
What qualities does hydroxyapatite give bone?
Hardness and compressive strength.
Compressive strength
The kind of strength that holds weight. (Ex. A metal rod.)
Describe the mixture of substances in bone.
Collagen provides tensile strength with flexibility and the calcium salts provide compressive strength so the bones can bear weight.
How does vinegar break down hydroxyapatite?
Vinegar is an acid. The hydroxide ion in hydroxyapatite reacts with the vinegar and destroys the calcium salt, and the Ca2+ ions dissolve into the solution. In the end, the bone matrix loses its calcium salt and loses its compressive strength.
What causes rickets?
Low calcium levels in the body that lead to a lack of hydroxyapatite in the bones, making them rubbery. The bones are made of 30% collagen and that is what mostly remains with rickets.
What is the function of Vitamin D with relation to the bones?
It absorbs calcium out of the intestines and into the blood. Rickets is a lack of Vitamin D.
What would bone be like without collagen fibers?
It would be brittle and hard with no flexibility. Only calcium salts would be left behind.
Trabeculae
The beams that form the latticework of cancellous bone.
What is found in between the trabeculae?
Bone marrow and blood vessels.
Osteons
Tightly-packed cylinders that compact bone tissue is arranged in.
What did osteons used to be called?
Haversian systems.
The central canal
The hollow tube in the middle of an osteon sometimes called the Haversian canal. Blood vessels run through the central canal.
Concentric lamellae
Tubes of bone tissue that surround the blood vessels that run through the central canal that make up the osteon.
Interstitial lamellae
Bony layers of tissue in between the osteons that do not form cylinders. Can be thought of as the “packing material” around the osteons.
How are osteocytes shaped?
They are shaped like spiders because they have microscopic “legs” called processes that extend from the main cell body.
What is the purpose of an osteocyte’s processes?
They allow the cell to communicate with other cells.
How do osteocytes’ processes communicate with one another?
The process of one cell touches another and links the cells together.
Canaliculi
Channels in the bone through which the osteocytes’ processes run. Latin for “tiny canals.”
Describe the process of ossification.
The chondrocytes near the epiphyseal plates (made of hyaline cartilage) undergo mitosis and create new cartilage. The older chondrocytes near the diaphysis enlarge and increase the size of their lacunae. At the same time, calcium salts accumulate in the older cartilage. As they accumulate, the chondrocytes die and leave behind holes. Then blood vessels grow in the lacunae (the holes) and bring in osteoblasts and osteoclasts. The osteoblasts lay bone matrix on top of the calcified cartilage and form new cancellous bone. The process is complete.
Calcified cartilage
The point in ossification in which the chondrocytes have died and left behind holes. Calcium salts are accumulating at this time.
Describe the direction of growth in the ossification of the epiphyseal plate.
The epiphyseal plates stay the same thickness, but the diaphysis forms new bone on its end and increases the length of the bone.
Epiphyseal line
The bony marking that replaces the epiphyseal plate in ossification.
How is the growth of the epiphysis different from the growth of the diaphysis?
In the epiphysis, the articular cartilage never fully ossifies.
Appositional bone growth
The growth of a bone in diameter when osteoblasts lay new bone matrix on the surface of a bone.
Bone remodeling
The process by which osteoclasts break down worn-out bone and rebuild it.
If a person is bed-ridden and does not move much or loses weight, what will happen to their bones?
The bone will gradually be removed by the osteoclasts because of the lack of stress on the bone.
If a person is very active or gains weight, what will happen to their bones?
The bones will be stressed and will respond by increasing their mass to become more firm.
What does an osteoclast do when it experiences excessive stress?
Stress, which is a compressive force, “squashes” the osteoclasts. They do not like to be stressed, so they secrete a protective shell around themselves made of more bone.
What nutrients are necessary to build strong bone?
Protein, calcium, phosphorus, and others.
Describe the general basics of how orthodontics work.
The maxilla and mandible are encouraged to remodel due to the stress of the wire bands. When a tooth is pulled in one direction, its ligaments stress the bone, and more bone is laid. On the opposite side of the tooth, there is compression on the tooth’s ligament, and the bone is gradually removed by osteoclasts. This causes the tooth to move into the newly remodeled socket.
Why must orthodontic patients wear a retainer after their treatment?
The ligaments that hold tooth to bone have long memories. They have been stretched and want to pull back to their original position. Without a retainer, they will remodel the bone toward the original.
How do osteoclasts dissolve bone salts? (Bone minerals, calcium salts)
They secrete an acid that reacts with hydroxyapatite. The hydroxide ion (a base) in hydroxyapatite reacts with the acid and cause the calcium ion to dissolve. Another way they dissolve salts is to secrete proteolytic enzymes that digest protein.
Proteolytic enzymes
Enzymes that digest protein, especially collagen.
Describe the process by which bone heals itself.
When a bone is broken, the blood vessels are broken and blood flows out and forms a hematoma. The hematoma forms a clot and the bone tissue surrounding the break dies. After the clot is formed, a callus forms. As the callus forms, blood vessels grow into the internal callus and fibroblasts start producing collagen. Chondroblasts start producing cartilage. Phagocytic cells break down the blood clot and clean the debris. Osteoclasts break down dead bone tissue and osteoblasts lay down new bone tissue. The cartilage ossifies and forms new bone.
Hematoma
A mass of blood that is confined to a limited space.
Callus
A mass of connective tissue that connects the ends of a broken bone.
Internal callus
The callus that forms between the breaks in the bone.
External callus
The callus that forms around the outside of the bone.
What is the role of the external callus in healing a bone?
It provides stable support for the bone like pieces of tape on the outside of two pieces of wood glued together.
Why don’t people who break a bone have to wait a year to remove their cast?
They only have to wait long enough for the bone to be healed enough to stay together. This is the point at which cancellous bone has been formed but has not yet been remodeled.
Why doesn’t the body repair broken bones with compact bone right away?
It would take much too long. By utilizing the quick repair of calluses, cartilage, and cancellous bone, it allows the bone to achieve functionality much faster.
What does the parathyroid hormone do?
It regulates the concentration of calcium ions in the blood.
What does calcitonin do?
It is involved in regulating the concentration of calcium in the blood but is not essential for life.
How do low calcium levels in the blood affect the body?
The neurons become overactive and overstimulate the muscles, leaving the muscles unable to relax. In severe cases, the diaphragm cannot relax and the person may asphyxiate.
What do calcium ions in the blood affect?
Blood clotting, neuron-to-neuron communication, and heart muscle contraction.
What do parathyroid glands do when the level of calcium in the blood decreases?
They detect the decrease and release PTH. The PTH causes osteoclasts to increase their activity and break down more bone. This releases calcium into the blood and returns the calcium levels to normal.
How do the kidneys regulate calcium levels in the blood?
Kidneys can control the levels of many chemicals in the blood. PTH stimulates the kidneys to decrease the amount of calcium in the urine and increase the amount left in blood.
How does PTH affect vitamin D?
It stimulates the production of vitamin D, which in turn increases the amount of calcium that the body can absorb from food.
What hormone controls a high blood calcium negative feedback system?
Calcitonin, found in the thyroid gland.
How does the thyroid react to high calcium levels?
When it detects an increase in blood calcium levels, it secretes calcitonin, which decreases the activity of the osteoclasts. This decreases the amount of bone being broken down and lowers the amount of calcium released into the blood.
How do the parathyroids react to high calcium levels?
They make less PTH, which decreases osteoclast activity.
Is calcitonin increase or PTH decrease more effective in lowering calcium levels?
PTH decrease.
What gland secretes growth hormone?
The anterior pituitary gland.
What does growth hormone (GH) do?
It stimulates tissue growth and osteoblast activity.
Dwarfism
A condition in which too little GH is released and the child does not grow well, making them shorter than the average human.
Giantism
A condition in which too much GH is released, making the bones grow too rapidly and causing the person to be very tall.
What happens to an adult if their GH levels rise?
The epiphyseal plates are already ossified and the bones cannot grow longer, but the bones can grow thicker. The brow looks thick and the feet are abnormally large.
How estrogen and testosterone affect growth?
They stimulate osteoblastic activity, causing the bones to grow.
How is vitamin D essential to bone health?
It absorbs calcium.
How is magnesium essential to bone health?
It enables the calcium to be used properly in bone formation.
How is vitamin C essential to bone health?
It aids in the formation of collagen.
Joint
A place where different bones are joined that allow the skeletal system to move.
What are the three basic kinds of joints?
Fibrous, cartilaginous, and synovial.
Fibrous joint
Two bones joined together with fibrous connective tissue. They are either immovable or slightly movable.
What are the two types of fibrous joints?
Suture and syndesmosis.
Suture
A completely immovable joint found only in the skull.
Syndesmosis
A fibrous connection between two bones that are farther apart from each other compared with the tight fit of bones in a suture. Ex: The connection between the radius and the ulna.
Cartilaginous joint
The point at which bones are united with fibrocartilage or hyaline cartilage. They are either immovable or slightly moveable.
What are the two types of cartilaginous joints?
Synchondrosis and symphysis.
Synchondrosis
A joint made by hyaline cartilage. Ex: Epiphyseal plates in children and the strips of cartilage that attach the ribs to the sternum.
Symphysis
A joint consisting of bones joined by fibrocartilage. Ex: The symphysis pubis which joins the two coxal bones and the intervertebral discs.
Synovial joint
A joint that allows for free movement of the skeleton.
What is the most complex type of joint?
A synovial joint.
What is the purpose of articular cartilage in a synovial joint?
It helps the bones move smoothly inside the joint and prevents pain and inflammation. It provides a smooth “hard plastic.”
What are two consequences of friction?
It reduces the efficiency of motion and causes heat.
Articular capsule
A tough but thin sac that surrounds a synovial joint.
What are the two layers of the articular capsule?
The outer fibrous capsule and the inner synovial membrane.
Fibrous capsule
The outer layer of the articular capsule. It is made of dense irregular connective tissue and is an extension of the periosteum. It holds the bones together, and in some cases, becomes thick enough to form ligaments.
Bursa
A fluid-filled cushion between the parts of the joint and bone.
Synovial membrane
A collection of connective tissue cells that produce synovial fluid.
Synovial fluid
A fluid that lubricates the joint and reduces friction between the articular cartilage of the two bones.
What is the synovial fluid made of?
Blood plasma and chemicals secreted by the cells in the synovial membrane. Those chemicals include proteins, fats, polysaccharides, specifically hyaluronic acid.
Besides lubrication, what are some other functions of synovial fluid?
It supports the chondrocytes in the articular cartilage of the joint by supplying them with oxygen and nutrients and relieving them of carbon dioxide and metabolic waste. It also acts as a shock absorber for the joint.
List the synovial joints in order of increasing mobility. (Minus the pivot joint)
The plane or gliding joint, the hinge joint, the ellipsoid joint, the saddle joint, and the ball-and-socket joint.
Name the characteristics of a ball-and-socket joint.
- Provides for the highest range of motion. 2. Consists of a rounded head (the ball) on the end of one bone resting in a rounded depression (socket) on the end of the other bone. 3. Designed for movement in all directions.
Name an example of a ball-and-socket joint.
The hip and shoulder joints.
Name the characteristics of a hinge joint.
- Does not offer a wide range of motion. 2. Composed of a cylinder at the end of one bone, resting in a cylindrical depression at the end of the other bone. 3. Provides for motion in only one plane.
Name an example of a hinge joint.
The elbows and knees.
How are the elbow and knee hinge joints different?
The elbow is a true bony hinge, but the knee joint is flat. Strong ligaments around the knee ensure that only hinge motion can occur.
Name the characteristics of saddle joints.
- Provide a larger range of motion than the hinge joint, but do not allow for rotation. 2. Composed of two saddle-shaped bones that are oriented perpendicular to one another.
Name an example of a saddle joint.
The carpometacarpal joint.
Carpometacarpal joint
The saddle joint that joins the thumb’s metacarpal to the carpal in your wrist.
Name the characteristics of ellipsoid joints.
- Elliptically shaped version of a ball-and-socket joint with a more limited range of motion. 2. The range of motion is similar to that of a saddle joint: Small amount of rotation.
Name an example of an ellipsoid joint.
Joints in the wrist.
Name some characteristics of pivot joints.
- Allows only for partial rotational motion. 2. Formed when a process from one bone is surrounded by a ring of another bone.
Name an example of a pivot joint.
The second cervical vertebra (called the axis) has a long process (called the dens) that pokes through the foramen of the first cervical vertebra (called the atlas), forming a pivot joint.
Name some characteristics of plane or gliding joints.
- Very little motion. 2. Consist of two flat surfaces of about equal size that slide against one another.
Name an example of a plane or gliding joint.
A process from the scapula rubs against a process in the clavicle. Another example: a vertebra has a superior articular process which forms a synovial joint with an inferior articular process of another vertebra.
Why are there so many different kinds of joints in the body?
Each joint has a specific job, and if they were all as mobile as ball-and-socket joints, the body would lose much of its stability.
Anatomical position
The position acquired when one stands erect with the feet facing forward, the upper limbs hanging at the sides, and the palms facing forward with the thumbs to the outside.
Superior
Above
Inferior
Below
What anatomical words are used with relation to the head, neck, and trunk?
Superior and inferior.
What anatomical words are used with relation to the limbs?
Proximal and distal.
Proximal
Nearest to the attachment to the trunk.
Distal
Distant from the attachment on the trunk.
Anterior
Front
Posterior
Back
Midline
The imaginary line that runs down the center of the body, separating your right and left sides.
Midsagittal plane
A plane that runs through the midline that divides the body into two equal left and right halves.
Lateral
Located away from the midsagittal plane.
Medial
Close to the midsagittal plane.
Extension
To straighten a body part.
Which parts of the body can perform extension?
The limbs, hands, fingers, toes, head, and back can be extended. In the anatomical position, all body parts are extended.
Flexion
The opposite of extension. In flexion the angle between the bones of the joint is decreased.
Which body parts can be flexed?
The fingers, wrists, elbows, shoulders, vertebral column, thighs, legs, and toes.
Plantarflexion
The opposite of dorsiflexion. When the ankle is moved so that you are standing on your tiptoes, that is plantarflexion.
Dorsiflexion
The opposite of plantarflexion. This is when you move your ankle so that the angle between the foot and the leg decreases. This happens when standing on your heels.
Abduction
A motion in which body parts move away from the midline. The opposite of adduction.
Give an example of abduction.
When fingers spread apart, it is an example of abduction.
Adduction
The opposite of abduction. This is motion in which the body part moves toward the midline.
Give an example of adduction.
When the thighs are placed far apart from one another and then moved together to touch, that is adduction.
Inversion
A motion of the foot in which the foot points inward. The opposite of eversion.
Eversion
A motion of the foot in which the foot turns outward. The opposite of inversion.
Circumduction
A circular motion that is performed by ball-and-socket joints.
Give an example of circumduction.
When the arm is moved in a circle or the thigh, that is circumduction.
Rotation
Motion in which the joint turns a bone on its axis.
What are the two types of rotation?
Medial and lateral rotation.
Medial rotation
Rotation toward the midline.
Lateral rotation
Rotation away from the midline.
Pronation
The motion of the forearm when the palm is placed posteriorly.
Supination
Motion of the forearm where the palm is placed anteriorly.
When you shake your head no, what kind of motion is the head performing?
Rotation.
When you bend at the waist to pick something up off the ground, what motion is your vertebral column performing?
Flexion.
A ballet dancer stands in the anatomical position and then lifts his right thigh sideways, so that it is pointing to the right. What motion did the thigh perform?
Abduction.
A student stands in the anatomical position and then turns his hands so that the palms face posteriorly rather than anteriorly. What motion did the forearms perform?
Pronation.
A student stands in the anatomical position and then rotates his feet so that the toes on his left foot point to the toes on his right foot and vice-versa. What motion did the feet perform?
Inversion.
