Module 3.5: Bone Structure

Marrow Cavity

The longitudinal section of a typical long bone, filled with bon marrow

Diaphysis

Shaft or center length of the bone

Compact Bone

The solid outer layer of the bone

Epiphysis 

The ends of each long bone 

Spongy Bone (Trabecular Bone)

The ends of each long bone

Metaphysics

Where epiphysis and diaphysis meet

Cortex

Spongy bone that is found in between two layers of compact bone 

Diploë

Layer of spongy bone in the cranium

Osteons

Compact bone contains many of these in which osteocytes can be found in tiny, open chambers

Canaliculi

Small, narrow channels found in between the lacunae; allow osteocytes to receive nutrients, remove wastes, and allow for communication between cells

Lamellae

The layers of matrix surrounding lacunae 

Central Canals

Contain blood vessels and nerves

Perforating Canals (Volkmann’s Canals)

Run perpendicular to the bone surface and carry blood vessels into the bone and bone marrow

Periosteum 

Protective membrane that has a tough fibrous outer and an inner cellular layer; separates bone from the surrounding structures and provides a structure for the bast amount of blood vessels that go into bone tissue; covers superficial layer of compact bone, except within joint cavities 

Perforating Fibers

Made of strong collagen fibers that help connect the periosteum to the bone

Endosteum

Lines marrow cavity; membrane lining that lines all the internal cavities inside the bone

Trabeculae

The open network in spongy bones, which lacks capillaries and venules 

Hydroxyapatite

Calcium phosphate and calcium carbonate combine

Ostogenic Cells

Stem cells whose divisions produce osteoblasts

Osteoblasts

Immature bone cells that secrete organic components of matrix (osteoid); deposit calcium into bone

Osteocytes

Mature bone cells that maintain the bone matrix and cellular activities like exchanging wastes and nutrients for the bone

Osteoclasts

Multinucleate cells that secrete acids and enzymes to dissolve bone matrix