Ossification starts from before birth. Growth ceases during adolescence to adulthood. After growth ceases, you don't get taller but bone still remodels.
Mesenchymal condensation occurs in area where cartilage formation is to take place, pre chondroblasts proliferate to form mass in cartilage
Condensed mesenchymal cells become round and secrete basophilic ECM.
Cells differentiate into chondroblasts and produce ECM.
Cartilage model surrounded by perichondrium
Bone growth:
Mesenchymal cells that undergo intramembranous ossification or transform into cartilage which undergo endochondral ossification.
Intramembranous ossification:
1.Mesenchymal condensation occurs and cells become small, spindle shaped with parallel orientation.
2.Mesenchymal cells produce collagen
3.Some cells differentiate into osteoblasts
4.Osteoblasts produce ECM called osteoid
5. Become highly vascular
6. Osteoblasts trigger deposition of Ca salts
7. Osteoblasts trapped in matrix become osteoclasts
8. Centre of ossification established. Layer of vascular mesenchyme condenses on bone( periosteum).
9. Inner periosteum cells differentiate into osteoblasts which lay down bone as parallel plates or lamellae.
Endochondral ossification-Most bones.
1. Mesenchymal condensation occurs in area where bone formation is taking place, cells proliferate to form a mass in shape of future bone.
2.Condensed mesenchymal cells become round and secrete basophilic ECM substance cells.
3. The cells differentiate into chondroblasts and produce ECM
4.Catilage model surrounded by perichondrium.
5. Week 8 ossification occurs in middle of shaft
6.Cartilage cells in middle shaft enlarge and calcium salts are deposited in the matrix.
7.Calcification inhibit nutrient diffusion so cartilage cells degenerate, leaving large spaces. At the same time, cells of perichondrium become active and become osteoblasts( now periosteum) and start laying down compact bone.
8. Vascular tissue invades areas of calcified matrix, bringing in chondroclasts and osteoblasts.
9. Chondroclasts break down lacunawalls and osteoblasts lay down bone in these spaces and primary centre of ossification established.
From UTAS notes: This is not a comprehensive guide, its my summary.