Lecture 22 9/27/23 Flashcards
What is endochondral ossification?
replacement of hyaline cartilage template by bone
What is the responsibility of the physis?
longitudinal growth of bone
In what direction does the physis grow bone?
towards the diaphysis
What are the layers of the physis?
-resting chondrocytes
-proliferating chondrocytes
-hypertrophied chondrocytes
-calcified cartilage matrix
Which region of the physis is the weakest?
hypertrophied chondrocytes
Why is the hypertrophied chondrocyte layer of the physis the weakest?
-large cells filled with glycogen
-no matrix
What happens to the chondrocytes in the calcified matrix?
they undergo apoptosis
How do osteoblasts interact with the calcified matrix?
it turns the calcified matrix into osteoid
How does the epiphysis grow bone?
from the articular-epiphyseal cartilage complex (growth plate)
How long does the physis persist?
until skeletal maturity
Which type of cartilage remains following skeletal maturity?
articular cartilage
What is a type one Salter-Harris fracture?
physis fracture at resting chondrocytes layer
What is a type two Salter-Harris fracture?
physis fracture at the hypertrophied chondrocytes layer
What are the characteristics of type 3 and type 4 Salter-Harris fractures?
-partial fractures at physis
-some of bone continues to grow, other has altered growth
How does type # relate to severity of the Salter-Harris fracture?
-higher type # is associated with greater disruption to normal function and growth
What is intramembranous ossification?
replacement of mesenchymal template from bone
What are the characteristics of intramembranous ossification?
-bone forms from condensed mesenchymal cells
-cartilage not involved
-forms flat bones of skull and clavicle
What are the characteristics of bone remodeling?
-occurs constantly, even in adults
-weight bearing determines bone density
What are the characteristics of fibrous joints?
-bones connected by dense collagen
-little to no movement
-skull sutures
What are the characteristics of cartilaginous joints?
-bones connected by fibrocartilage
-little to no movement
-intervertebral discs
What are the characteristics of synovial joints?
-ends of bones covered by hyaline cartilage
-bones connected by ligaments and fibrous joint capsule
What is the synovial membrane?
-lining on the inside of the synovial joint capsule
-synoviocytes produce the synovial fluid
What are the functions of the synovial fluid?
-lubricate the joint
-provide nutrients to the cartilage
