Anatomy and Physiology: Physiology of Bone

ossification

formation/conversion into bone or boney substance

ossification process

osteoblasts form a new bone and become mature osteocytes

Bone is comprised of what?

1/3 organic and 2/3 inorganic substances

how is true bone formed

through the deposition of calcium salts upon an organic framework

bone can form in what 3 days?

endochondral, intramembranous, heteroblastic ossification

endochondral ossification

uses cartilaginous framework to convert cartilage bars laid down in embryo to bone (long/majority of bones)

intramembranous ossification

bone formed within fibrous membranes laid down in embryo (flat bones)

heteroblastic ossification

bone formation in bones other than the skeleton (os cordis, in cattle hearts)

bone lengthening (long bones)

articular/epiphyseal cartilage grows, thickens, is replaced by bone

when does bone lengthening stop?

when all cartilage is replaced

bone thickening (periosteum)

periosteum proliferates osteoblasts, secretes matrix, mineralizes

bone thickening (endosteum)

contains osteoblasts that remove formed bone, allows thickening without weight

Types of cell bones

osteoblasts, osteocytes, osteoclasts

osteoblasts

immature, large, bone forming cells that produce osteoid

osteocytes

mature cells, derived from osteoblasts, occupy a lacunae in bone

osteoclasts

reabsorb cartilage and bone matrix, can dissolve matrix and release minerals

simple fracture

across bone, heals well

oblique fracture

diagonally across bone

comminuted fracture

fragmented but no break in skin

spiral fracture

travels around bone

greenstick fracture

incomplete, only on one side

transverse fracture

straight across

epiphyseal fracture

separation between epiphysis and diaphysis

compound fracture

ends of bone break skin and protrude

bone healing

fracture/inflammatory phase, granulation tissue formation, callus formation, lamellar bone deposition, remodelling