Lecture 11 Flashcards
List the steps in the formation of intermembranous bone
Mesenchymal cells become osteoblasts, which secrete osteoid (the organic part of bone matrix)
These blastema are now osteocytes and mineralization of the bone matrix via calcium ions occurs
The osteoblasts form an epithelial-like covering over the primary bone tissue that is formed
Further deposition of bone on trabecular surfaces creates compact bone
what happens during endochondral bone formation that does not occur in intremembranous bone formation?
Cartilage is replaced by bone
intermembranous bone forms without using a cartilage model.
List the steps that form a primary ossification center in endochondral bone
a hyaline cartilage model secretes endothelial growth factor to induce vascularization
This causes hypertrophic chondrocytes that apoptos and leave the cartilage matrix in a “honeycombed” network
This network is then calcified by the deposition of Ca2+ (NOT ossification)
Blood vessels form the periosteal bud and then branch further.
List the steps the form a secondary ossification center in endochondral bone.
Blood vessels and osteoprogenitor cells infiltrate the epiphysis on both ends of the bone
osteocytes derived from the perichondrium secrete osteoid appositionally which leads to the transformation of perichondrium to periosteum
the 2 ossification locations will reach each other, fuse the diaphysis and epiphysis at the epiphyseal line, and length growth stops.
Define the Epiphyseal growth plate, and state it’s purpose.
a cartilagenous growth plate between the epiphysis and metaphysis
it will eventually be replaced by bone, but growth in bone length must occur to overtake the epiphyseal growth plate.
Where does the first site of ossification occur?
the diaphysis and then at both epiphyses shortly after
List the zones of the epiphyseal plate from the zone closest to the epiphysis towards the metaphysis. describe them.
Reserve zone: primitive hyaline cartilage
Proliferative zone: chondrocytes align as vertical/parallel columns
Hypertrophic zone: exposure to vascular endothelial growth factor causes apoptosis of chondrocytes and calcification (not ossification) of the matrix occurs here
Vascular invasion zone: blood vessels penetrate the calcified matrix and bring in osteoprogenitor cells that will become osteocytes
explain what the chondrocytic run mechanism is and how that pertains to endochondral bone growth.
As the ossification-osteoclast front moves further into the epiphyseal plate, the chondrocytes in the plate proliferate away from the forming bone, and this elongates the bone.
List and describe the four steps in bone remodeling and the relationship between osteoclasts and osteoblasts in this process.
Activation: osteoclast precursors are recruited to the haversian canal, and osteoclasts begin bone resorption from within the canal
Resorption: additional osteoclasts are recruited via precursors and osteoblasts appear at the end of this step
Reversal: osteoblasts begin to secrete new osteoid on the inside of the canal, forming new lamellae
Formation: osteoblast activity continues until a new haversian canal, with it’s own cement line, is completed.
define joint
where 2 bones come together
Identify the major characteristic used to classify joints.
Degrees of freedom of movement
What defines a cartilaginous joint?
Cartilagenous joints: (amphiarthroses) joints joined by hyaline or fibrocartilage
list the 2 subcategories of cartilaginous joints, what differentiates them and give an example.
Symphysis: joined by fibrocartilage ; ex. Intervertebral discs and pubic symphysis
Synchondrosis: joined by hyaline cartilage ; ex. Epiphyseal plates and the first sternocostal joint
What defines a Fibrous joint?
(synarthroses) bones joined by collagenous and/or elastic fibrous CT
list the 3 subcategories of fibrous joints, what differentiates them and give an example.
Suture: ex. Joints between the bones of the calvaria
Gomphosis: “peg in socket” joints ; ex. Teeth in aleveoli
Syndesmosis: bones are joined by an interosseous fibrous membrane ; ex. the fibrous membrane between the tibia and fibula
