Anatomy Unit 4: Skeletal Systems

Main functions of the skeletal system

Support the body, protect soft organs, facilitate movement, storage of minerals and fats, and blood cell formation.

Parts of the skeletal system

Bones, joints, cartilages, and ligaments.

Axial skeleton

The part of the skeleton that forms the longitudinal axis of the body.

Appendicular skeleton

Bones of the limbs and girdles.

Compact bone

Dense and homogeneous type of bone.

Spongy bone

Type of bone made of small needle-like pieces with many open spaces.

Long bones

Bones that are longer than they are wide, with a shaft and heads at both ends; contain mostly compact bone.

Short bones

Cube-shaped bones that mostly contain spongy bone, e.g., carpals and tarsals.

Flat bones

Thin and flattened bones, usually curved, with two layers of compact bone surrounding a layer of spongy bone; e.g., skull, ribs.

Irregular bones

Bones with irregular shapes that do not fit into other categories; e.g., vertebrae, pelvis.

Diaphysis

The shaft of a long bone composed of compact bone.

Epiphysis

The ends of a long bone composed mostly of spongy bone.

Periosteum

The outside covering of the diaphysis, a fibrous connective tissue membrane.

Articular cartilage

Hyaline cartilage that covers the external surface of epiphyses, decreasing friction at joint surfaces.

Medullary cavity

The cavity within the shaft of a long bone that contains yellow marrow in adults and red marrow in infants.

Osteon

The structural unit of compact bone.

Osteocytes

Mature bone cells housed in lacunae.

Osteoblasts

Bone-forming cells responsible for new bone formation.

Osteoclasts

Bone-destroying cells that break down bone matrix for remodeling and releasing calcium.

Bone remodeling

The process where bone is continuously being broken down and rebuilt.

Hematoma formation

The first step in fracture repair, where a blood-filled swelling occurs.

Fibrocartilage callus formation

The second step in fracture repair where a callus forms around the break.

Bony callus formation

Replaces fibrocartilage callus in fracture repair.

Axial skeleton overview

The axial skeleton forms the longitudinal part of the body, divided into the skull, vertebral column, and bony thorax.

Subdivisions of the skull

Cranium and facial bones, with bones joined by sutures.

Hyoid bone

The only bone that does not articulate with another bone, serving as a movable base for the tongue.

Vertebral column parts

Divided into cervical, thoracic, lumbar regions, sacrum, and coccyx.

Pectoral girdle

Composed of the clavicle and scapula, allows free movement of the upper limb.

Pelvic girdle structure

Composed of ilium, ischium, and pubic bone; supports the weight of the upper body.

Synarthroses

Immovable joints.

Diarthroses

Freely movable joints.

Bursitis

Inflammation of a bursa usually caused by blow or friction.

Arthritis

Inflammatory or degenerative diseases of joints.

Gouty arthritis

Inflammation of joints caused by deposition of urate crystals from the blood, controllable by diet.