The Upper Extremities
by Dr. Gary Farr on 3 August 2003

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1

The upper extremities are connected to the trunk via the shoulder girdle.

The upper limbs include:

• shoulder girdle with shoulder blade and collar bone;
• upper arm with humerus;
• lower arm with ulna and radius;
• hand with carpus; metacarpus and fingers.

The shoulder girdle consists of the collar bone (clavicle) and the shoulder blade (scapula).

The collar bone can be felt below the {skin} skin along its entire length and, together with the radius in the arm, is the bone most frequently broken in the human body. The shoulder blades are located behind the {musles_thorax} thorax. They {joints} articulate to the collar bone by means of a bone extension. Their tops form the flat articular cavities joining up with the articular heads in the upper arms to form ball-and-socket joints.

The upper arm (humerus) is connected at the elbow joint to the two lower arm bones ulna (ulna) and spoke bone (radius), the ulna to the little finger side and the spoke bone to the thumb side. The elbow joint permits stretching and flexing movements of the lower arm.

The hand can be divided up into three sections:

• scarpus (wrist bone)
• metacarpus (five bones connecting wrist to fingers)
• finger bones (ossa digitorum manus)

The eight carpal bones (ossa carpi) are ordered in two rows.

The first row (proximal), situated between the radius and ulna on one side and the second row on the other comprises:

• scaphoid bone
• lunate bone
• triquetral bone
• pisiform bone

The second row (distal), situated between the metacarpal bones on one side and the first row on the other, comprises:

• trapezium
• trapezoid bone
• capitate bone
• hamate bone

The metacarpal bones consist of five tubular bones arranged like a fan, whereby only the first one is connected with complete mobility via a {joints} saddle joint to the carpus (thumb saddle joint).

The other four are connected to the carpus via sprung, taut joints.

The 14 finger bones (phalanges) are extremely mobile compared with the metacarpal bones, made possible by a series of {musculoskeletal_system} muscles.

Apart from the thumb (which has no middle joint) all of the fingers can be divided into three sections:

• proximal phalanx
• medial phalanx
• distal phalanx

The Latin terms for the fingers are as follows:

• thumb (pollex)
• index finger (index)
• middle finger (digitus medius)
• ring finger (digitus anularis)
• little finger (digitus minimus).

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