Appendicular skeleton

Of the 206 bones in the human skeleton, the appendicular skeleton comprises 126. Functionally it is involved in locomotion (lower limbs) of the axial skeleton and manipulation of objects in the environment (upper limbs).

The appendicular skeleton forms during development from cartilage, by the process of endochondral ossification.

The appendicular skeleton is divided into six major regions:

1. Shoulder girdles (4 bones) - Left and right clavicle (2) and scapula (2).
2. Arms and forearms (6 bones) - Left and right humerus (2) (arm), ulna (2) and radius (2) (forearm).
3. Hands (54 bones) - Left and right carpals (16) (wrist), metacarpals (10), proximal phalanges (10), intermediate phalanges (8) and distal phalanges (10).
4. Pelvis (2 bones) - Left and right hip bone (2).
5. Thighs and legs (8 bones) - Left and right femur (2) (thigh), patella (2) (knee), tibia (2) and fibula (2) (leg).
6. Feet and ankles (52 bones) - Left and right tarsals (14) (ankle), metatarsals (10), proximal phalanges (10), intermediate phalanges (8) and distal phalanges (10).

It is important to realize that through anatomical variation it is common for the skeleton to have many accessory bones (sutural bones in the skull, cervical ribs, lumbar ribs and even extra lumbar vertebrae).

The appendicular skeleton of 126 bones and the axial skeleton of 80 bones together form the complete skeleton of 206 bones in the human body. Unlike the axial skeleton, the appendicular skeleton is unfused. This allows for a much greater range of motion.[2]

• 
  Appendicular skeleton (shown in red).
• 
  Illustration depicting anterior and posterior view of appendicular skeleton

• Axial skeleton
• pectoral girdle
• pelvic girdle
• Legs
• Bones