Anatomy of the Skeletal System: Bones, Joints, and Fractures

Skeletal system is made of

Bones, joints, cartilage, and ligaments

Axial

The center part of your body

Appendicular

The arms, legs, shoulders, and hips

Support

holds your body up like a frame

Protection

guards organs (like ribs protect heart & lungs)

Movement

muscles pull on bones to move

Storage

keeps minerals (like calcium) inside

Blood cell formation

Marrow makes blood cells

Compact bone

hard, dense outer layer

Spongy bone

lighter, honeycomb inside

Long Bone

Longer than wide; acts as a lever

Short Bone

Cube-shaped, strong but movable

Flat

Thin and flat; protects organs

Irregular

Odd shapes; protect & support

Diaphysis

The shaft or long middle part of the bone.

Epiphysis

The ends of the bone; form joints with other bones.

Periosteum

A tough outer covering that protects the bone and helps it grow or repair.

Arteries/Veins

Blood vessels that bring nutrients in and waste out of the bone.

Articular Cartilage

Smooth, slippery covering on bone ends that helps joints move easily.

Medullary Cavity

Hollow space inside the shaft that holds yellow marrow.

Yellow marrow

Stores fat (energy).

Red marrow

Makes red and white blood cells and platelets.

Osteon

Tiny cylinder-shaped units of bone

Central / Haversian canal

Center tunnel that carries blood vessels and nerves.

Perforating / Volkman's canal

Side tunnels that connect Haversian canals to each other.

Lacunae

Small spaces that house bone cells

Lamellae

Thin layers of bone tissue in an osteon.

Canaliculi

Tiny canals that connect bone cells so they can share food and messages.

Bone growth

Growth occurs at epiphyseal plates (growth plates), which become epiphyseal lines when growth stops.

Osteocyte

Maintains bone tissue.

Osteoblast

Builds new bone ("bone builder").

Osteoclast

Breaks down old bone ("bone cleaner").

Rickets

Bones become soft and bent from a lack of vitamin D or calcium.

Osteoporosis

Bones become weak and brittle because they lose minerals.

Osteosarcoma

A bone cancer that causes painful bone growths or tumors.

Closed Fracture

Bone breaks but does not go through the skin.

Open Fracture

Bone breaks and pokes through the skin.

Hematoma

Blood forms a swelling (bruise) around the break.

Fibrocartilage Callus

A soft callus forms between the bone ends.

Bony Callus

New bone forms, replacing the soft callus.

Remodeling

Bone becomes smooth and strong again as it returns to its normal shape.

Comminuted

Bone breaks into many pieces.

Compression

Bone is crushed

Depressed

Bone pushed inward

Impacted

Bone ends jam into each other

Spiral

A break caused by twisting

Greenstick

Bone bends and cracks a small part of the bone

Reduction

Restoring the correct anatomical alignment of a fractured bone

Open

Surgery is needed; the bone is fixed with pins or plates.

Closed

The doctor manually moves the bone back into place without surgery.