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Core
There are four muscles in the upper arm. They can be compartmentalised into anterior and posterior compartments.
It is also very important when studying muscles that you are comfortable with anatomical terminology, as a lot is used in these articles. For more information, please check out our Anatomical Terminology Article.
There are three muscles in the anterior compartment of the arm. Biceps brachii and brachialis contribute to flexion at the elbow. Coracobrachialis does not cross the elbow; it flexes and weakly adducts the arm at the shoulder. The musculocutaneous nerve (a branch of the brachial plexus) is the main nerve supply to this compartment, with an additional radial nerve contribution to brachialis.
This muscle has two heads. The long head originates from the supraglenoid tubercle, found on the scapula, whilst the short head originates from the coracoid process. These heads converge to form a main belly which inserts into the radial tuberosity of the radius. The main function of the biceps is to supinate the forearm. It is also responsible for flexion at the elbow and shoulder joints as it crosses both of these joints.
Found deep to the biceps brachii, this muscle is the main elbow flexor. It originates from the humeral shaft and inserts into the ulna tuberosity.
This muscle originates from the coracoid process. It attaches to the medial humeral shaft. As this muscle does not cross the elbow joint, it doesn’t perform elbow flexion. It does, however, flex the arm at the shoulder joint.
The anterior muscles of the arm can be remembered by the acronym 'BBC'.
Diagram - Illustrates the location of biceps brachii and brachialis. The coracobrachialis cannot be seen in this illustration, however, it would be found deeper to these muscles. If trying to locate the coracobrachialis, try and work down from the coracoid process
Creative commons source by CFCF, edited by Dr. Sachin Sudhakaran [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
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