Bone and Osseous Tissue

Bone and Osseous Tissue

Osseous Tissue

the major structural component of bones

a connective tissue composed of a bone matrix made of Calcium Phosphate and Collagen Fibers

Lacunae - spaces within the bone matrix

Osteocytes - the bone cells in the lacunae

Canaliculi - channels in the bone matrix for nourishing bone cells

Dense (Compact) Bone

located mainly in the diaphysis of a bone

Osteon (Haversian System) - basic unit of organization with a Central Canal (Haversian Canal) for passage of blood vessels

Osteocytes - the bone cells in the lacunae

Periosteum - covering around the outside of a bone, composed of Dense Irregular (Fibrous) Connective Tissue

Spongy (Cancellous) Bone

located mainly in the heads of bone and near the marrow cavity

Trabeculae - basic unit of organization, somewhat like an osteon with Osteocytes

Endosteum - lining inside a bone ( marrow cavity), composed of an epithelial cellular layer with:

Osteoblasts - cells responsible for producing new bone matrix

Osteoclasts - cells responsible for destroying old bone matrix

Mineral metabolism and Bone remodeling

Calcitonin

secreted in response to elevated blood levels of calcium

inhibits osteoclast activity

decreases rate of intestinal absorption of calcium

increases rate of calcium excretion by kidney

Parathormone

secreted in response to low blood levels of calcium

stimulates osteoclast activity

increases rate of intestinal absorption of calcium

decreases rate of calcium excretion by kidney

About one-fifth of skeleton is demolished and rebuilt each year

osteocytes maintain matrix by removing and replacing calcium salts

osteoclasts dissolve bone matrix

osteoblasts synthesize the new bone matrix