Deep head of pronator teres

At a glance

English

Deep head of pronator teres

Latin (TA2)

Caput profundum pronatoris teretis

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the deep head of pronator teres

Pronator teres is the rounded muscle that crosses the front of the upper forearm obliquely and turns the palm downward. It has two heads: a large superficial head from the medial epicondyle of the humerus and a much smaller deep head from the ulna, also called the ulnar head. The deep head is a thin bundle that is occasionally missing.

The deep head starts on the inner side of the ulna's coronoid process, the projection on the front of the upper ulna just below the elbow joint. Its fibres run downward and outward and meet the deep surface of the superficial head at a sharp angle. The united muscle then crosses the forearm to end in a flat tendon on a rough area in the middle of the lateral surface of the radius, the pronator tuberosity, at the point of greatest convexity of the bone.

The importance of the deep head lies in its relations. The median nerve enters the forearm by passing between the two heads, with the deep head behind the nerve. The ulnar artery lies deeper still, separated from the nerve by the deep head. Acting with the superficial head, it turns the forearm into pronation, rotating the radius over the ulna, and assists weakly in bending the elbow. The deep head is supplied by the median nerve (C6, C7), and it receives blood from the anterior ulnar recurrent artery and small branches of the ulnar artery.

Compression of the median nerve as it passes between the two heads is the main cause of pronator syndrome. It produces aching in the front of the forearm and numbness in the thumb and fingers, made worse by repeated forceful turning of the forearm, and it is distinguished from carpal tunnel syndrome by tenderness over the muscle and altered sensation over the palm. A fibrous band at the edge of the deep head can add to the squeeze.

Attachments, action and supply

Origin

Coronoid process of the ulna, on its medial side.

Insertion

Joins the superficial head; together they insert on the pronator tuberosity, mid-lateral surface of the radius.

Action

Pronates the forearm with the superficial head; weakly assists flexion of the elbow.

Nerve supply

Median nerve (C6, C7).

Blood supply

Anterior ulnar recurrent artery and muscular branches of the ulnar artery.