The Skeletal System Bone Anatomy

I. Bone Functions A. Support B. Protection-skull, vertebral column and ribs serve to protect C. Movement-bones attach to muscles by tendons D. Mineral storage- store many types of inorganic minerals, most important are calcium and phosphate. E. Blood cell formation-called hematopoiesis and occurs inside marrow cavities.

II. Classification of Bones A. Long bones-all limb bones but patella, wrist and ankle. Mostly compact bone through diaphysis. B. Short bones-wrist and ankle bones, cube-like shape. C. Flat bones-ribs, scapula, pelvis and some bones of the skull D. Irregular bones-vertebrae, mostly spongy bone. E. Sesamoid bones (round bones)-small, round bones embedded in tendons adjacent to joints. Ex. Patella (knee cap)

Bone Shapes

III. Anatomy of Bones A. Long bones-consist of epiphysis, diaphysis, membranes such as the periosteum, osteoblasts and osteoclasts. Spongy bone and compact bone. B. All other bones-not cylindrical, contain periosteum, compact and spongy bone. C. Compact Bone-continuous extracellular matrix with no spaces made up of minerals-gives strength. The main unit is called an osteon (Haversian system). These are tiny weight bearing pillars. Blood vessels and nerves run through them. Osteocytes are bone cells found in chambers called lacunae around the osteon. D. Spongy bone-contain structures called trabeculae which are bony plates made of osteocytes interspersed by spaces filled with marrow.

ANATOMY OF A BONE

COMPACT BONE

Compact Bone

SPONGY BONE

Epiphyseal plate -cartilage band indicates ossification is occurring and spongy bone is being deposited.