Coracobrachialis muscle

At a glance

English

Coracobrachialis muscle

Latin (TA2)

Musculus coracobrachialis

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the coracobrachialis muscle

Coracobrachialis is the least of the three muscles in the front (flexor) compartment of the arm, the others being biceps and brachialis. It lies in the upper, inner part of the arm, deep to the short head of biceps, and it is one of three muscles fixed to the coracoid process, the others being pectoralis minor and biceps by its short head.

It arises from the tip of the scapula's coracoid process, sharing a tendon with the short head of biceps. Its belly runs down along the medial side of the humerus and ends by a flat tendon on a rough mark halfway down the shaft's medial surface, between the attachments of brachialis in front and the medial head of triceps behind. The musculocutaneous nerve usually pierces the muscle a few centimetres below the coracoid, a useful landmark; the brachial artery and median nerve run close along its medial border, and its tendon is used to locate them.

Coracobrachialis flexes the arm at the shoulder and draws it towards the trunk (adduction). It may turn the humerus inwards slightly. It also helps to hold the head of the humerus in the socket, particularly when the arm hangs by the side and when it carries a load, and it resists the arm being pulled out of line during abduction. Its nerve is the musculocutaneous nerve (C5 to C7), the same nerve that supplies biceps and brachialis, and its blood comes from muscular branches of the brachial artery and the anterior circumflex humeral artery.

Overuse, for example in gymnastics on the rings or in heavy chest exercises, can make the muscle tight and painful, with pain spreading down the arm. Because the musculocutaneous nerve runs through it, a tight or enlarged muscle can rarely compress the nerve, weakening elbow flexion and causing numbness on the outer forearm. Tears of the muscle itself are very rare and are usually due to a direct blow.

Attachments, action and supply

Origin

Coracoid process tip, shared with the short head of biceps.

Insertion

Medial surface of the humeral shaft, about halfway down.

Action

Flexes and adducts the arm at the shoulder; helps steady the humeral head in the glenoid cavity.

Nerve supply

Musculocutaneous nerve (C5, C6, C7).

Blood supply

Muscular branches of the brachial artery and the anterior circumflex humeral artery.