1.6 Interstitial Growth
Width
increases via appositional growth along bone collar
Resorbtion
when osteoclasts release Ca into blood
Remodeling
when osteoclasts take up Ca from blood and incorporate it into bone
Interstitial growth
bone lengthening; occurs within epiphyseal plate; 5 zones; the first being most near the epiphysis and last being most far away (towards diaphysis)
Osteopropgenitor
cells that develop into osteoblasts
Epiphyseal plate
hyaline cartilage at the boundary of the epiphysis and diaphysis; site of interstitial growth of cartilage
Arterial supply
important because it supplies blood vessels that penetrate periosteum, osteoblasts enter via periosteal bud, blood brings osteogenic cells and CaPO4
Length
increases via interstitial growt of cartilage that is ossified
Osteoclasts
very large cell that is active during bone remodeling; turn woven bone into lamellar bone, responsible for remodeling and resorbtion
Ossification
zone interstitial growth where walls that were calcified between lacunae break down, forming longitudinal channels for capillaries to invade, now considered bone
Resting
zone of cartilage in interstitial growth that has not yet begun to divide; nearest to epiphyseal plate, composed of small chondrocytes, secures epiphysis to epiphyseal plate
Hypertrophic
zone of cartilage in interstitial growth that is characterized by large, dying chondrocytes whose matrix is all that remains of the cell; chondrocytes cease dividing and begin to hypertrophy, resorbing the cartilage matrix; lacunae become thin
Calcified
zone of cartilage in interstitial growth that is only a few cells thick, minerals are deposited in matrix between lacunae columns; calcification kills chondrocytes; matrix is opaque, not yet bone
Proliferating
zone of cartilage in interstitial growth; staking, chondrocytes are undergoing rapid mitotic cell division enlargement and become aligned like a stack of coins into columns of flattened lacunae