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Bone & Cartilage Development - Anatomy & Physiology (view source)
Revision as of 10:01, 31 August 2008
, 10:01, 31 August 2008no edit summary
#'''Endochondrial Ossification''' - mesechymal tissue first differentiates into cartilage, then into bone. This occurs in the production of limb and axial skeleton.
#'''Endochondrial Ossification''' - mesechymal tissue first differentiates into cartilage, then into bone. This occurs in the production of limb and axial skeleton.
#*Limb cartilage is produced in a proximal to distal direction as a continuous structure. It becomes punctuated with joints later, and then converted to bone.
#*Limb cartilage is produced in a proximal to distal direction as a continuous structure. It becomes punctuated with joints later, and then converted to bone.
==Endochondrial Ossification==
*''Bone formation via cartilage.''
#Proliferating limb mesenchyme condenses.
#The increased cell density triggers mesenchymal cells to differentiate into chondrocytes. Proliferation continues.
#The bone shape is formed, with a diaphysis (shaft) and epiphysis (bulbous ends).
#Chondrocytes in the middle of the diaphysis stop proliferating and undergo '''hypertrophy'''.
#*''The shaft is surrounded by the '''perichondrium''', a restrictive membrane. This means that the bone can only grow in length, not width. The epiphysis are pushed away from each other.''
#After chondrocytes have undergone hypertrophy, they die.
#*'''Osteoblasts''' on the inner side of the perichondrium invade the cartilage matrix.
#*They then secrete the extra - cellular matrix characteristic of bone.
#*''Ossification occurs from the outside - in. This is called primary ossification, or perichondrial ossification.''
#Blood vessels invade the central region of the diaphysis to transport bone marrow stem cells and osteoclasts.
#*The osteoclasts break down the cartilage matrix to allow room for the bone marrow.