Appendicular Skeleton Bones

Appendicular Skeleton

• The appendicular skeleton consists of four parts: shoulder (pectoral) girdle, upper extremities, pelvic girdle, and lower extremities.

Shoulder (Pectoral Girdle)

• The shoulder girdle consists of the clavicle and scapula, which articulate with each other at the Acromioclavicular joint.
• The clavicle is a long, slender bone that lies horizontally across the root of the neck just beneath the skin.
• The clavicle articulates with the sternum and 1st costal cartilage medially and with the acromion process of the scapula laterally.
• The scapula is a flat triangular bone that lies on the posterior chest wall.
• The scapula has a spine that projects backward, forming the acromion, which articulates with the clavicle.
• The superolateral angle of the scapula forms the pear-shaped glenoid cavity, which articulates with the head of the humerus at the shoulder joint.

Upper Extremities

• The bones of the upper extremities are divided into four groups: bones of the arm, bones of the forearm, bones of the wrist, and bones of the hand.
• The humerus articulates with the scapula at the shoulder joint and with the radius and ulna at the elbow joint.
• The upper end of the humerus has a head and articulates with the glenoid cavity of the scapula.
• The lower end of the humerus possesses the rounded capitulum for articulation with the head of the radius and the pulley-shaped trochlea for articulation with the trochlear notch of the ulna.

Bones of the Forearm

• The forearm contains two bones: the radius and the ulna.
• The radius is the lateral bone of the forearm.
• The radius articulates with the humerus at the elbow joint and with the ulna at the proximal radioulnar joint.
• The distal end of the radius articulates with the scaphoid and lunate bones of the wrist at the wrist joint and with the ulna at the distal radioulnar joint.
• The ulna is the medial bone of the forearm.
• The ulna articulates with the humerus at the elbow joint and with the head of the radius at the proximal radioulnar joint.
• The proximal end of the ulna is large and is known as the olecranon process, which forms the prominence of the elbow.

Bones of the Wrist

• The wrist connects the hand to the forearm and is composed of eight carpal bones aligned in a proximal and distal row.
• The proximal row consists of the scaphoid, lunate, triquetral, and pisiform bones.