Osteology

Axial Skeleton

The part of the skeleton that includes the skull, vertebral column, ribs, and sternum.

Appendicular Skeleton

The part of the skeleton that includes the pectoral girdle, upper limbs, pelvic girdle, and lower limbs.

Functions of the Skeletal System

Includes protection, support, leverage, blood cell production, and storage of minerals.

Protection

Function of the skeletal system where the ribs protect the heart and lungs, skull protects the brain, vertebrae protect the spinal cord, and pelvic bones protect reproductive organs.

Support

The skeletal system provides a framework for the attachment of organs.

Leverage

Muscles pull on bones to produce movement.

Blood Cell Production

Bone marrow produces erythrocytes, leukocytes, and platelets.

Storage of Minerals

Bones store minerals such as calcium ions (98% of the body's total) and phosphate ions.

Long Bones

Typically longer than they are wide, consisting of a shaft and two ends.

Flat Bones

Thin and flattened, often curved bones.

Round/Short Bones

Cube-shaped bones such as the wrist and ankle bones.

Sesamoid Bones

Special short bones enclosed in tendons.

Irregular Bones

Bones with complicated shapes that do not fit into other classifications.

Bone Markings

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

Osseous Tissue

A supportive connective tissue that forms the skeletal system.

Bone Matrix

The calcified structure of bone consisting of collagen fibers, which contribute to tensile strength.

Osteoblasts

Bone cells that synthesize and secrete osteoid, the initial semi-solid form of the bone matrix.

Osteocytes

Mature bone cells derived from osteoblasts; maintain the protein and mineral content of the matrix.

Osteoclasts

Cells that break down bone through acidic secretions and lysosomal enzymes.

Compact Bone

The dense outer layer of a long bone that appears smooth and solid.

Spongy Bone

Bone made up of a honeycomb of small needle-like pieces of bone called trabeculae.

Diaphysis

The tubular shaft of a long bone, consisting of compact bone surrounding the central medullary cavity.

Epiphyses

The ends of long bones that are covered by articular cartilage.

Periosteum

A white double-layered membrane covering external surfaces of bones except at joints.

Endosteum

A delicate connective tissue membrane covering the internal surface of bone.

Haversian Canal

Central canal that runs through the core of an osteon, containing blood vessels and nerves.

Volkmann’s Canals

Canals that connect blood vessels and nerves of the periosteum to the central canal.

Lacunae

Small cavities that contain osteocytes.

Canaliculi

Hairlike canals connecting lacunae to each other and to the central canal.

Ossification

The process of bone tissue formation.

Endochondral Ossification

Bone formation by replacing hyaline cartilage.

Intramembranous Ossification

Bone formation that occurs directly from mesenchymal tissue.