Biceps Brachii Location and Actions

The biceps brachii is a two-headed muscle located on the front of the arm and makes up the largest part of its bulk. The name biceps is derived from the Greek word bi, meaning “two” and the Latin caput, meaning “head.” The name brachii is a form of the Latin and Greek words brachialis and brachion, which describe something that pertains to the arm. Thus, biceps brachii means “two-headed muscle of the arm.” These two heads, one shorter than the other, arise from two separate origins which, although they partially combine into one large muscle, retain somewhat their separate features, both inserting together at the elbow. 1Doyle, James R., and Michael J. Botte. Surgical Anatomy of the Hand and Upper Extremity. Philadelphia: Lippincott Williams & Wilkins, 2003. 98-101.

See Biceps Trigger Points

The short head originates on the coracoid process of the scapula and the upper lip of the glenoid fossa. The long head originates on the supraglenoid tubercle of the scapula and the posterior portion of the glenoid labrum. Both heads insert onto the tuberosity of the radius and the bicipital aponeurosis, itself inserting into the deep fascia of the ulnar aspect of the forearm. 2Doyle, James R., and Michael J. Botte. Surgical Anatomy of the Hand and Upper Extremity. Philadelphia: Lippincott Williams & Wilkins, 2003. 98-101.,3Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998. 58. The biceps brachii should be thought of as a three-joint muscle, as it not only crosses the glenohumeral and elbow joints but also the radioulnar. 4Kendall, Florence Peterson. Muscles, Testing and Function with Posture and Pain. Baltimore, MD: Lippincott Williams & Wilkins, 2005.

Although the most well-known function of the biceps is as a strong elbow flexor, it is also a strong supinator of the forearm, a weak flexor of the shoulder joint, and a shoulder stabilizer (long head), assisting in maintaining the humeral head in the glenoid cavity. Also, since the short head has its origin on the coracoid process, it can also assist with adduction, as well as flexion, of the humerus.

biceps muscle illustration
Biceps Brachii

The biceps is most effective in elbow flexion when the forearm is supinated (palm facing up). It is joined in this role primarily by the brachialis, and brachioradialis, but also the coracobrachialis, and flexor pronators. For supination, it is most effective when the elbow is flexed. As the forearm pronates (palms facing away) the biceps becomes less effective due to the rotation of the radius giving its pull less mechanical advantage. 5Doyle, James R., and Michael J. Botte. Surgical Anatomy of the Hand and Upper Extremity. Philadelphia: Lippincott Williams & Wilkins, 2003. 98-101.,6Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998. 58.

arm muscle model with biceps brachii labeled
image by robswatski via flickr

Biceps Brachii Origin, Insertion, and Actions

Origin

  • Short head: Apex of coracoid process of the scapula in the conjoined tendon of the coracobrachialis and the upper lip of the glenoid fossa.
  • Long head: Supraglenoid tubercle of the scapula and posterior portion of the glenoid labrum, above the superior lip of the glenoid fossa.

Insertion: Bicipital tuberosity of the radius and into the bicipital aponeurosis. 7Doyle, James R., and Michael J. Botte. Surgical Anatomy of the Hand and Upper Extremity. Philadelphia: Lippincott Williams & Wilkins, 2003. 98-101.,8Kendall, Florence Peterson. Muscles, Testing and Function with Posture and Pain. Baltimore, MD: Lippincott Williams & Wilkins, 2005.

Actions: Elbow flexion with stronger action during supination, assisting abduction of the shoulder when the arm is externally rotated, weak shoulder flexion when the arm is internally rotated, supination of the forearm when the elbow is not fully extended. The long head provides stabilization of the shoulder, keeping the head of the humerus in the glenoid fossa when a heavy weight is carried at the waist. 9Kendall, Florence Peterson. Muscles, Testing and Function with Posture and Pain. Baltimore, MD: Lippincott Williams & Wilkins, 2005.,10Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998. 58.

See Biceps Trigger Points and Referred Pain

 

Sources   [ + ]

1, 2, 5, 7. Doyle, James R., and Michael J. Botte. Surgical Anatomy of the Hand and Upper Extremity. Philadelphia: Lippincott Williams & Wilkins, 2003. 98-101.
3, 6, 10. Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998. 58.
4, 8, 9. Kendall, Florence Peterson. Muscles, Testing and Function with Posture and Pain. Baltimore, MD: Lippincott Williams & Wilkins, 2005.