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Bones - Anatomy & Physiology (view source)
Revision as of 14:38, 6 January 2011
, 14:38, 6 January 2011no edit summary
[[Image:Horse Skeleton.jpg|thumb|right|250px|Horse Skeleton - Copyright Nottingham]]
[[Image:Horse Skeleton.jpg|thumb|right|250px|Horse Skeleton - Copyright Nottingham]]
==Bone Growth==
===Length===
The '''epiphyseal growth plate (EPG)''' allows the [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|bone]] to continue to grow in length after birth. The EPG is a region of continuous chondroblast differentiation and maturation and can be divided into five zones:
# '''Germinal Zone''' - chondroblast division at a low rate, and self renewal.
# '''Proliferation Zone''' - chondroblast division at a fast rate.
# '''Maturation Zone''' - chondroblast differentiation into chondrocytes.
# '''Hypertrophic Zone''' - chondrocytes enlarge and then die.
# '''Dead cells''' become the matrix for bone growth.
===Girth===
The '''periosteum''' lines the outer surface of the diaphysis of the bone. It has a cellular inner layer, consisting of osteoblasts, and a fibrous outer layer. The '''endosteum''' lines the inner surface of the diaphysis of the bone. It contains osteoblasts ''and'' osteoclasts. Bone growth occurs by a shift in the equilibrium between osteoblasts and osteoclasts. Osteoblasts on the outside in the periosteum add bone to increase the bone's diameter. Osteoclasts on the inside in the endosteum remove this bone to maintain the bone diameter. When osteoclasts start removing less bone, or osteoblasts start adding more bone, the girth increases.