Bone is a mineralized connective tissue.
It is comprised of two subtypes: cortical or compact bone and cancellous or trabecular bone.
Cortical bone comprises 80 percent of the skeleton and is increased in long bone shafts.
Cancellous bone is in contact with bone marrow cells and is enriched in the vertebral bodies, pelvis, and proximal ends of femora, all of which are subject to osteoporosis and fractures.
Bone is comprised mainly of type I collagen and contain three cells types:
Osteoclasts, which resorb mineralized bone
osteoblasts, which synthesize the proteins of the bone matrix
Osteocytes which are probably osteoblasts that have secreted bone matrix and become buried within it.
Osteocytes communicate with each other through a canalicular system.
The skeleton contain 99 percent of the total body calcium, 80-85 percent of the phosphorus, and 66 percent of the magnesium.
