Unit Two Flashcards
What percentage does bone tissue weight in the human body?
18%
What are the functions of Bone?
- Support
- Protection
- Movement
- Mineral Homeostasis - Stores minerals (like calcium and phosphorus) and releases minerals into blood when other organs and muscles need them
- Blood Cell Production - Hemopoiesis (production of RBCs, WBCs, and platelets) occurs in red bone marrow inside bone
- Triglyceride Storage - Triglycerides are high energy source and stored in yellow bone marrow (consists of high concentration of adipose cells) and found within the bone
Regions of long bones:
Diaphysis - Central shaft of the bone
Epiphysis - The distal and proximal ends of the bone
Metaphysis - Regions where diaphysis meets the epiphysis (contains epiphyseal plate of hyaline cartilage responsible for growth and becomes epiphyseal line when bone stops growing)
Structures of long bones:
Articular Cartilage - Hyaline cartilage covering epiphysis, reduce friction and absorbs shock in the joint
Periosteum - Dense irregular tissue surrounds bone surface.
Medullary Cavity - Space in the Diaphysis that contain fatty yellow bone marrow in adult long bones and red marrow in flat bones
Endosteum - Thin membrane of bone forming cells that lines the medullary cavity
Functions of Periosteum
Allow bone to grow in width, protection, nourishment, and an attachment point for ligaments and tendons
Sharpy’s fibers are collagen fibers that attach the periosteum to the bone
What is the extracellular matrix of bone tissue made of?
25% water, 25% collagen (flexibility), and 50% crystallized mineral salt
(calcium phosphate salts - reason for hardness)
Process of calcification:
Mineral salts are deposited in the framework formed by the collagen fibers, then crystallize causing the tissue to harden
What does a bone’s hardness depend on?
The crystallized mineral salt
What does a bone’s flexibility depend on?
The collagen fibers
What are the cells of the bone?
Osteogenic cells
Osteoblasts
Osteocytes
Osteoclasts
What are Osteogenic cells
Unspecialized stem cells that undergo mitosis and differentiation and become osteoblasts
Where do you find Osteogenic cells?
Mostly in endosteum but also a little in periosteum
What bone cells undergo cell devision?
Osteogenic cells
What are Osteoblasts?
Bone-building cells that synthesize collagen to build the extracellular matrix and initiate calcification
They become trapped in extracellular matrix and develop into osteocytes
What are Osteocytes?
Mature bone cells that maintain the bone metabolism and nutrient/waste exchange with the blood
(Keep bone tissue healthy)
What are Osteoclasts?
Large cells produced from the fusion of around 50 monocytes (type of WBC)
Responsible for resorption of bone (breakdown of bone’s extracellular matrix for development, growth and repair)
Where are Osteoclasts found?
Endosteum
What is bone remodelling?
Interaction where osteoclasts breakdown bone and osteoblasts build new bone
What is the strongest form of bone tissue?
Compact bone
What percentage of compact bone makes up the skeleton?
80%
Where is compact bone found?
Outer portion of the bone, under the periosteum
What are the structures of compact bone?
Haversian Canal - tubes where arteries and veins pass through
Concentric Lamellae - calcified extracellular matrix surrounding the haversian canal
Lacunae - spaces between the lamellae that house the osteocytes
Canaliculi - small canals that connect the lacunae and eventually lead to the haversian canal (so osteocytes can communicate and nutrient/waste can travel through)
Interstitial lamellae - Areas between osteons (concentric lamellae) that has been broken down by osteoclasts
Circumferential Lamellae - Lamellae that encircle the medullary cavity just beneath the periosteum
What type of bone does not contain osteons?
Spongy bone
What is the lamellae in spongy bone called?
Trabeculae
What surrounds the trabeculae?
Spaces
Are there lacunae and canaliculi in the trabecula?
Yes
Function of the space between trabeculae?
Makes bone lighter and contains red bone marrow which feeds the osteocytes directly with blood from the marrow
Where do you find spongy bone?
Abundant in flat and irregularly shaped bones
Bones that are not heavily stressed
What is a Bone Scan?
Radiological diagnostic procedure where the body is injected intravenously with a small amount of radioactive tracer (dye). Then body is scanned by a gamma camera to measure the amount of radiation emitted from the bones.
What are “cold spots” indicated by in bone scans and what can they mean?
Lighter areas - decreased metabolism/blood flow
Can indicate osteoporosis, infections, and inflammatory arthridities (rheumatoid arthritis)
What identifies normal bones after doing a bone scan?
Gray color - indicates a uniform uptake of the tracer by the bone
What are “hot spots” indicated by in bone scans and what can they mean?
Darker spots - areas of increased metabolism/blood flow
Can indicate bone cancer, fractures, or abnormal growth
Why are bones so abundant with blood vessels?
- Accommodate the constant metabolism, remodeling and growth of the bone
- To deliver the newly manufactured blood out from the red marrow to the rest of the body
What are periosteal arteries?
Arteries accompanying nerves that travel through the Volkman’s canals (nutrient foramen) into the diaphysis, supplying the periosteum and the outer compact bone
Where are nerves and free nerve endings abundant within bone?
The periosteum
(reason why fractures and bone tumors are so painful)
What are the terms for bone formation?
Ossification or osteogenesis
What does Osteogenesis involve?
Either the replacement of preexisting connective tissue with bone or the replacement of cartilage with bone
What are the two methods of osteogenesis?
Intramembranous and endochondral ossification
Where does intramembranous ossification occur?
Flat bones and skull bones
What are the steps of Intramembranous ossification?
- Development of the ossification center
- Calcification
- Trabeculae Formation
- Periosteum Development
What occurs during the development of the ossification center for Intramembranous Ossification?
During fetal development: mesenchymal cells (tissue from which all CT arises) cluster together, forming the ossification center. These cells then differentiate into osteogenic cells then into osteoblasts. The osteoblasts start secreting the extracellular matrix
What occurs during the calcification step in Intramembranous Ossification?
After the extracellular matrix formation stops, the osteoblasts mature and become osteocytes. After a few days the calcium and mineral salts are deposited and the extracellular matrix calcifies and hardens
What occurs during the Trabeculae formation step in Intramembranous Ossification?
As the extracellular matrix forms, it develops into trabeculae forming spongy bone. Blood vessels grow in the spaces between the trabeculae and form red bone marrow
What occurs during the Periosteum Development step in intramembranous Ossification?
On the outside of the bone, mesenchymal cells condense and form the periosteum
What is Endochondral Ossification?
Replacement of cartilage by bone
What type of bone undergoes Endochondral Ossification?
Long bones
What are the steps for Endochondral Ossification?
- Development of the Cartilage model
- Growth of the Cartilage model
- Development of the primary ossification center
- Development of the medullary cavity
5.Development of the secondary ossification centers - Formation of the articular cartilage and the epiphyseal plate
What occurs during the development of the cartilage model in Endochondral Ossification?
During fetal development: mesenchymal cells form the shape of the future bone and differentiate into chondroblasts.
Chondroblasts are immature cartilage cells that secrete hyaline cartilage and produce a cartilage model of the long bone.
Also, a membrane called the perichondrium develops around the cartilage model.
What occurs during the growth of the cartilage model in Endochondral Ossification?
Chondroblasts mature and become chondrocytes. The chondrocytes
undergo continual mitosis causing the cartilage model to increase in length (interstitial growth)
The cartilage model increases in width by continual mitotic activity of chondroblasts in the perichondrium. (Appositional growth)
As the cartilage model continues to grow, chondrocytes grow in size and the surrounding cartilage extracellular matrix begins to calcify.
Soon the chondrocytes begin to die
because nutrients cannot diffuse across the calcified matrix and reach the chondrocyte. As the chondrocytes die, lacunae form.
What occurs during the development of the primary ossification center in Endochondral Ossification?
A nutrient artery penetrates the perichondrium and travels to the middle of the cartilage model. The blood supply stimulates the osteogenic cells in the perichondrium to become osteoblasts. The perichondrium starts to form bone and becomes the periosteum.
In the middle of the cartilage model, the nutrient artery branches into capillaries and fills the already disintegrating calcified cartilage, forming the primary ossification center. This is the region where bone tissue will start being deposited over remnants of calcified cartilage, forming spongy bone trabeculae.
What occurs during the development of the medullary cavity in Endochondral Ossification?
As the primary ossification center
expands toward the ends of the bones,
osteoclasts start to break down some of
the newly formed spongy trabeculae.
This leaves a central cavity in the
diaphysis which becomes the medullary
cavity that will contain the marrow.
What occurs during the development of the secondary ossification centers in Endochondral Ossification?
This occurs at the time of birth. Branches of the
epiphyseal artery enters the epiphyses, where the sites of the secondary ossification centers are located. The blood supply stimulates the formation of osteogenic cells that quickly differentiate into osteoblasts. The osteoblasts start to deposit bone tissue over the remnants of calcified cartilage forming spongy bone.
What occurs during the formation of the articular cartilage and the epiphyseal plate in Endochondral Ossification?
The hyaline cartilage of the preexisting cartilage
model remains over the epiphyses and
becomes the articulating cartilage.
Hyaline cartilage also remains between
the diaphysis and the epiphysis forming
the epiphyseal plate, responsible for the
lengthening of long bone.
What is the difference between primary and secondary ossification centers?
The primary ossification center occurs in the diaphysis and forms the medullary cavity.
The secondary ossification centers occurs in the epiphyses, the spongy bone remains and is not replaced by the
medullary cavity
What is the Epiphyseal plate?
A layer of hyaline cartilage in the metaphysis of long bones
What are the Zones of the Epiphyseal plate?
- Zone of resting cartilage
- Zone of proliferating cartilage
- Zone of Hypertrophic Cartilage
- Zone of Calcified Cartilage
What is the Zone of Resting Cartilage?
A layer of small chondrocytes that is closest to the epiphysis and functions to anchor the epiphyseal plate
What is the Zone of Proliferating Cartilage?
Layer of larger chondrocytes that divide to replace dead chondrocytes at the diaphyseal side of the epiphyseal plate
What is the zone of Hypertrophic Cartilage?
Layer of large, maturing chondrocytes arranged in columns
What is the Zone of Calcified Cartilage?
Layer of mostly dead, calcified chondrocytes. Osteoclasts will dissolve the calcified cartilage while osteoblasts and vessels from the diaphysis invade the area and lay down new bone.
Where does the length of the bone increase?
The diaphyseal end of the epiphyseal plate
Explain Appositional Growth:
- Cells in the periosteum differentiate into osteoblasts. The osteoblasts secrete collagen and extracellular matrix until they become surrounded by it. They then become osteocytes. This process forms bone ridges on either sides of a periosteal blood vessel, which continues to grow forming grooves for the vessel.
- Eventually the ridges fold over the vessel and fuse, causing the groove to become a tunnel that encloses the blood vessel. The former periosteum becomes the endosteum that line the tunnel.
- Osteoblasts in the endosteum lays down more bony matrix forming new concentric lamellae around the vessel. This continues until the vessel is firmly anchored, forming the osteon.
- Osteoblasts under the periosteum deposit new outer circumferential lamellae, increasing the width of the bone.
Where do osteoclasts destroy bone tissue?
In the Medullary cavity
Why is Bone remodeling important?
Allows for increased growth of a bone
Also removes injured bone, replacing with a new stronger and thicker bone, that is more fracture resistant
What can happen if there is too much activity from osteoclasts and too little activity from osteoblasts?
Excessive loss of calcium and mineral content leading to osteoporosis, rickets, and osteomalasia
What can happen if there is too much activity from osteoblasts and too little activity from osteoclasts?
Lead to abnormally thick and heavy bones or the formation of osteophytes (bone spurs)
What are factors that can affect bone growth?
Minerals
Vitamins
Hormones
What Vitamin is essential for collagen formation?
Vitamin C
What Vitamins are needed for bone protein synthesis?
Vitamin K and B12
What Vitamin stimulates osteoblastic activity?
Vitamin A
What Vitamin allows calcium to be absorbed from the GI tract into the blood?
Vitamin D
What hormones affect bone growth?
Insulin-like Growth Factors (IGFs), bone growth hormone (from pituitary lobe), thyroid hormones, estrogen, and testosterone
What happens if there is an oversecretion of human growth hormone?
If occurred during childhood: results in gigantism
If occurred during adulthood: results in acromegaly (become very thick/broad)
What happens if there is an under-secretion of human growth hormone?
Dwarfism
What is a fracture?
Any break of the bone
What are the steps to repairing fractures?
- Fracture hematoma occurs. Bone cells die due to loss of blood supply. And inflammatory response begins. Osteoclasts start to remove dead bone tissue and WBCs remove any other injured tissue
- Fibroblasts and chondrocytes from the periosteum invade the fracture side and deposit collagen fibers and fibrocartilage respectively. This forms fibrocartilage callus (tissue mass connecting broken ends of the bone)
- As vascular supply is repaired and restored, osteoblasts are formed and start forming spongy bone. Osteoblasts start converting fibrocartilage callus into spongy bone, forming bony callus
- Remodeling of the body callus occurs. Osteoclasts resorbs dead bone and osteoblasts replace spongy bone with compact bone at the bone surface
What is fracture hematoma?
When blood vessels leak blood and form a clot around the site of the fracture
How long does the formation of a fibrocartilage callus take?
3 weeks
How long does the bony callus lasts?
3-4 months
What is the body’s calcium reservoir?
Bone - stores 99% of the body’s calcium
What is calcium essential for?
muscle contraction, nerve conduction, blood clotting, and heart function
What happens when the calcium concentration in blood in low?
Parathyroid hormone (PTH) is secreted by the parathyroid glands
Hormone stimulates osteoclasts to breakdown more bone tissue to release calcium into the blood
What happens when calcium concentration in blood is too high?
Hormone calcitonin is released from the thyroid gland
Calcitonin decreases osteoclast activity and stimulates osteoblastic activity, to remove calcium from the blood
What is Wolff’s law
When bones are under mechanical stress (weight-bearing exercise) the bone becomes stronger
How many bones are there?
206
What is the Axial skeleton?
Bones that lie around the longitudinal axis
How many bones do the axial skeleton consist of?
80
What is the Appendicular skeleton?
Bones that form the upper and lower limbs
How many bones are in the appendicular seleton?
126
How many bones make up the sections of the axial skeleton?
Cranial bones - 8
Facial bones - 14
Hyoid bone - 1
Auditory ossicles - 6
Vertebrae - 26
Thorax - 1 sternum; 24 ribs
What are the classifications of bone shape?
Long bones - greater length than width
Short bones - usually cube shaped
Flat bones - thin bones function to protect
Irregular bones - complex shaped bones
Sesamoid bones - bones formed within tendons to improve the mechanical efficiency of a joint
What type of bones is the axial skeleton composed of?
Flat and irregular bones
What are the types of bone markings?
Depressions and openings: Grooves, holes or pits in bone that allow the passage or nerves, vessels, ligaments, tendons, or muscle, and contribute to the shape of the joint
Processes: projections or outgrowths on bone that form joints, or attachment points for ligaments and tendons
Examples of Depression and openings:
Fissure: slits in bone that house vessels
Foramen: holes in bone where nerves, vessels, or ligaments pass
Fossa: Shallow depression/pit that house muscle
Sulcus: Groove on the bone surface that contains nerve, vessels, or tendon
Meatus: Tube-like opening or tunnel
Examples of Processes that have articular cartilage:
Condyle: Large, round protuberance at the end of bone
Facet: Smooth flat articular surface
Head: Rounded articular projection at the end of bone
Examples of Processes that do NOT have articular cartilage:
Crest: Prominent ridge
Epicondyle: Projection above a condyle
Line: Long narrow ridge, less than a crest
Spinous Process: Sharp, slender projection
Trochanter: Very large projection
Tubercle: Small, rounded projection
Tuberosity: Large, rounded and rough projection
What space is found within the Frontal bone?
Frontal sinuses
How many nasal bones are there?
Two
How many Maxillae bones are there?
Two
What bones contain sinuses?
Frontal bone, sphenoid bone, ethmoid bone, maxilla bone
How many bones make up the orbits (eye sockets)?
7 bones
What bones make up the orbits?
Frontal, Sphenoid, Palatine, Maxilla, Zygomatic, Lacrimal, Ethmoid
What bone is the “cheek bone”
Zygomatic bone
Where are tears stored?
In the lacrimal sack, in the lacrimal bone
A deviated septum can lead to:
chronic infections, congestion, sinusitis, etc.
When you break your nose it is normally damage to:
The septal cartilage rather than the nasal bones or vomer
What is a suture?
Immovable joint in adults found between the skull bones
What is a sutures function?
Hold the skull bones together
What are the sutures and what bones do they connect?
Coronal - frontal and parietal bones
Sagittal - united both parietal bones
Lambdoid - parietal and occipital bones
Squamous - parietal and temporal bones
What is the function of the paranasal sinuses?
Produce mucus and resonating chambers for sound when speaking/singing
What are paranasal sinuses?
Cavities lined with mucous membranes
What are Fontenelles?
“Soft spots” on the baby’s head found between the cranial bones
Areas of unossified mesenchyme
Around what age does intramembranous ossification form the sutures and get rid of fontanelles?
Around 2 years of age
What is the function of fontenelles?
Allows the fetal head to be flexible to pass through the birth canal
What bones in the axial skeleton do not articulate with other bones?
Hyoid bone
What is the function of the hyoid bone?
Provide attachment site for ligaments, tendons, and some tongue, neck and pharynx muscles
How many bones fuse together to make the sacrum and coccyx?
Sacrum - 5
Coccyx - 4
What is the function of the vertebral column?
Protect spinal cord
Support head
Attachment for the ribs, pelvis, and muscles of the back
How many vertebrae are there in each region?
Cervical - 7
Thoracic - 12
Lumbar - 5
Sacrum - 1 fused from 5
Coccyx - 1 fused from 4
What is a “C” curve in the spine with its concavity posterior called? And where is the curve found?
Lordosis
Found in the cervical and lumbar regions
What is a “C” curve in the spine with its concavity anterior called? And where is the curve found?
Kyphosis
Thoracic and sacral regions
What is a lateral deviation of the spine called?
Scoliosis
What is the composition of intervertebral discs?
Outside layer - annulus fibrosus composed of fibrocartilage
Inside the disc - “Jelly” called nucleus pulposus
What is a herniated disc?
An injury where the nucleus pulposus breaks and goes through annulus fibrosis
What are the names of C1 and C2 and C7?
C1 - Atlas
C2 - Axis
C7 - Vertebral prominens
What does C1 allow us to do?
Flex and extend our head - motion of saying yes
What does C2 allow us to do?
Rotate head left and right - motion of saying no
What is the function of the processes of the vertebrae?
Sites for muscle attachments
Transverse processes function as rib attachments in the thoracic spine
What vertebrae are the largest and strongest?
Lumbar vertebrae
Around what ages does the sacrum begin and end fusing?
Begin around age 16
Ends around age 30
What is the lateral portions of the sacrum called?
Sacral ala
What is the tail-bone called?
Coccyx
What is the thorax?
The entire chest / thoracic cage:
sternum, rubs, costal cartilages, bodies of the thoracic vertebrae
What are the 3 parts of the sternum?
Manubrium, body , Xiphoid process
What are the “true ribs”?
Ribs 1-7 because they attach directly to the sternum
What are the “false ribs”?
Ribs 8-12
Ribs 8-10 are specifically vertebral chondral ribs
Ribs 11-12 are specifically floating ribs
What is the primary function of the appendicular skeleton?
Movement
What bones make up the pectoral (shoulder) girdle and upper limbs?
Clavicle - 2
Scapula - 2
humerus - 2
ulna - 2
radius - 2
carpal bones - 16
metacarpal bones - 10
phalanges - 28
What bones make up the pelvic girdle and lower limbs?
pelvis - 2
femur - 2
patella - 2
fibula - 2
tibia - 2
tarsal bones - 14
metatarsal bones - 10
phalanges - 28
What are the ligaments function that connect to the clavicle?
Stability
Where do fractures normally occur in the clavicle?
The junction between the two curves - the middle of the clavicle
What is the longest and largest bone?
The femur
What is the medical term for tennis elbow?
Lateral epicondylitis
What is the medical term for golfers elbow?
Medial epicondylitis
What attaches the head of the ulna to the carpal bones?
A disc of fibrocartilage
What is the fibrous connective tissue that connects the ulna and radius called? And what is its function?
Interosseous membrane
Function: Provides stability
What can cause carpal tunnel syndrom?
Tunnel (formed by pisiform and hamate) narrows due to muscle tightness, inflammation, or anterior displacement of carpal bones
What are the symptoms of carpal tunnel?
Numbness and pain in the lateral half of the hand
Where do the hip bones unite anteriorly?
The pubic symphysis
What forms the pelvis?
Hip bones: iliac, ischium, pubis,
Sacrum and pubic symphysis
By what age do the hip bones fuse together?
23
What is the largest hip bone?
Ilium
What is the largest foramen in the body?
The obturator foramen (found between the pubis and ischium)
What cartilage makes up the pubic symphysis?
Fibrocartilage
What portion of the pelvic is below the pelvic brim?
True (lesser) Pelvic
What portion of the pelvis is above the pelvic brim?
False (greater) pelvis
Who’s pelvis is larger and heavier?
Males
Who’s pelvis is wider and more shallow?
Females
What cavity is the false (greater) pelvic a part of?
The abdominal cavity
Where is the pelvic outlet?
The tip of the coccyx to the bottom of the pubic symphysis
Where is the pelvic inlet?
The top of pubic symphysis to the top of where the sacrum starts to curve
What is the pelvic axis?
The middle of the pelvic inlet to the middle of the pelvic outlet
Where does the fracture for a “broken hip” occur?
The neck of the femur
What type of bone is the patella?
Sesamoid
What type of bone develops within a tendon and why?
A sesamoid bone - to increase the mechanical efficiency of a joint
How many knee joints are there?
3
What is bone grafting?
Taking a piece of a bone with its periosteum and nutrient artery and transplanting it to another part of the body where the bone is missing or damaged
What bone is often used to bone grafting and why?
The fibula because it is not a weight-bearing bone (mostly functions to stabilize the ankle and muscle attachment)
What is the largest and strongest tarsal bone?
Calcaneus
What bone forms with ankle joint with the tibia and fibula?
The talus bone
What is the arches in the foots function?
Support the weight of the body
Absorbed shock while walking
What are the arches of the foot?
The longitudinal arch
The transverse arch
What are the parts of the longitudinal arch?
The medial part
The lateral part
What is clawfoot?
Condition where the longitudinal arch is abnormally elevated
What can cause clawfoot?
Diabetes or neurological disorders
What can a failed medial longitudinal arch lead to?
Flatfoot - plantar fasciitis, Achilles tendonitis, shin splints, stress fractures
