Ossification

Question 1

What are the two types of ossification?

Answer 1

intramembranous and endochondral

Question 2

What is the most common type of ossification and when does the uncommon type happen & why?

Answer 2

endochondral

intramembranous is not as common but it happens for the skull cap, mandible and clavicle (all help protect the baby)

Question 3

What are the cells involved in ossification and bone resorption/destruction?

Answer 3

Mesenchyme - immature embryonic connective tissue, the precursor for many cells
Osteogenic cell
Osteoblast - forms bone, secretes calcium matrix
Osteocyte - maintains the bone - calcium matrix hardens

Osteoclast - resorption/destruction of bone matrix, formed from monocytes/macrophages, has nucleotides and a ruffled border to increase surface area

Question 4

What is a lacuna?

Answer 4

it is a small space containing an osteocyte or chrondrocyte

Question 5

What are the 4 steps for intramembranous ossification?

Answer 5

1. development of center of ossification (mesenchyme - osteoblast - osteoid matrix - Calcium - osteocytes - lacuna)
2. Osteocytes deposit mineral salts ( calcification)
3. Formation of trabeculae (thin columns of bone that fuse into spongy bone)
4. development of periosteum, spongy bone (bone remolding to osteons into: compact bone)

Question 6

What are the 5 steps for endochondral ossification?

Answer 6

1. development of cartilage model (mesenchyme condenses - chondroblasts - cartilage to matrix - perichondrium grows around catilage)
2. Growth of cartilage model (increase cartilage matrix (interstitial growth) + appositional growth (thickness) - periosteum develops + nutrient artery
3. development of primary ossification center (osteogenic cells - osteoblasts - bone matrix - bone collar - replace cartilage matrix - spongy bone - capillaries grow)
4. Development of secondary ossification center (medullary cavity replaces)
5. Formation of articular cartilage and epiphyseal plate