Osteogenesis and Joints Flashcards
In intramembranous bone formation, what do mesenchymal cells differentiate into?
osteoblasts
In intramembraneous bone formation, what do osteoblasts secrete?
osteoid; it traps some of the osteoblasts.
What is another term for trapped osteoblasts in the osteoid?
osteocytes
In intramembranous bone formation, what do the osteocytes form?
A functional syncytium
In intramembranous bone formation, what ion causes mineralization?
calcium ions
What does osteoid include?
collagen I and non-collagen proteins.
What do primary ossification centers become?
a trabecula.
What do numerous trabeculae fuse together to become?
spongy bone
In intramembranous bone formation, what is the initial type of bone formed?
woven bone; its collagen fibers are arranged randomly.
What type of bone includes aligned collagen fibers?
lamellar bone
In endochondral bone formation, what is cartilage replaced by?
bone
In endochondral bone formation, what do chondrocytes release?
vascular endothelial growth factor
In endochondral bone formation, when do chondrocytes apoptose?
After vessels have formed
In endochondral bone formation, what cells used calcified strands as substrates for deposition of osteoid?
osteoblasts
Where does secondary ossification occur?
in the epiphyses
What are the epiphyses and diaphyses separated by?
A growth plate
What are the four zones of the growth plate?
reserve zone, proliferative zone, hypertrophic zone, vascular invasion zone
What occurs in the reserve zone?
primitive hyaline cartilage is found; it is responsible for the growth in length of bone and erosion/deposition process advances.
What is the epiphysis made of?
hyaline cartilage
What occurs in the proliferative zone?
chondrocytes mitotically divide and form stacks parallel to cartilage.
What occurs in the hypertrophic zone?
chondrocytes apoptose and calcification occurs
What occurs in the vascular invasion zone?
vessels invade the bone.
Where does ossification first occur?
The diaphysis (midsection) of a long bone
During ossification, what lays periosteal bone on top of endochondral bone?
perisoteum
Each epiphysis plate is separated from the diaphysis by what?
a plate of hyaline cartilage
During endochondral bone formation, what is the role of the osteoclast?
to break down bone in the center of diaphysis and form a medullary cavity.
During endochondral bone formation, cartilage is continually added to what end of the ephiphyseal plate?
distal end
During endochondral bone formation, cartilage is replaced by bone at what end?
proximal end; this increases bone length.
What kind of cartilage remains at either end of the bone?
articular cartilage
What are the 3 zones of the epiphyseal plate?
zone of proliferation, hypertrophy/calcification and ossification
What is proliferation stimulated by?
Indian hedgehod (ihh); it also prevents hypertrophy of chondrocytes.
What is a joint?
Where two bones come together
What are the 3 major classes of joints?
cartilaginous, fibrous and synovial
What are the types of cartilaginous joints, and what are they composed of?
symphysis (fibrocartilage), synchondrosis (hyaline cartilage)
What are examples of symphysis and synchondrosis joints
intervertebral discs, pubic symphsis (symphysis); epiphyseal plate and first sternocostal joint (synchondrosis)
What are the types of fibrous joints, and what are they composed of?
suture, gomphosis and syndesmosis; collagenous or elastic fibrous CT
What are examples of suture, gomphosis and syndesmosis joints?
calvaria (suture), teeth in socket (gomphosis), membrane of fibia and tibia (syndesmosis)
What is a feature of synovial joints?
they are surrounded by a fluid-filled capsule.
What are the 3 types of synovial joints?
monaxial, biaxial and triaxial
What are examples of the 3 types of synovial joints?
hinge/knee (monaxial), finger/atlantooccipital/saddle (diaxial); ball-and-socket (triaxial)
What type of cartilage is found in synovial joints?
articular (hyaline) cartilage
