Classification and Gross Anatomy of Bone

Axial Skeleton

Long axis of body (Skull, vertebral colum, and rib cage)

Appendicular Skeleton

Bones of upper and lower limbs

Bones are classified according to their

Shape

Long bones

Longer than they are wide

Short bones

Cube-shaped bones (in wrist and ankle)

Sesamoid

a short bone embedded within a tendon (patella)

Flat bones

Thin, flat, slightly curved (example: Sternum, scapulae, ribs, most skull bones)

Irregular bones

Complicated shapes (example: Vertebrae and hip bones)

Compact bone (lamellar bone)

dense outer layer on every bone that appears smooth and solid

Spongy bone (diploe)

made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae

Structure of short, irregular, and flat bones

Thin plates of spongy bone covered by compact bone.

Periosteum

white, double-layered connective tissue membranes that cover the outside of compact bone and external surfaces, except joints.

Periosteum contains

Contains many nerve fibers and blood vessels and anchor points for tendons and ligaments

endosteum

connective tissue membranes that covers inside portion of compact bone

Structure of long bone

All long bones have a diaphysis, epiphyses, and membranes

Diaphysis

Tubular shaft that forms the long axis of bone. Compact bone surrounds the medullary cavity, filled with yellow marrow in adults.

Epiphyses

ends of long bones that consist of compact bone externally and spongy bone internally

epiphyseal line (growth line)

signifies the end of bone growth in a particular bone

epiphyseal plate

allowing bones to increase in length until skeletal maturity

Medullary cavity

the central, hollow space within the diaphysis of long bones stores bone marrow for blood cell and fat production.

Bone markings

Sites of muscle, ligament, and tendon attachment, and areas involved in joint formation.

Projection bone marking

outward bulge of bone

Depression bone marking

bowl- or groove-like cut-out that can serve as passageways for vessels and nerves, or plays a role in joints

Opening bone marking

hole or canal in bone that serves as passageways for blood vessels and nerves