The coracobrachialis muscle is the smallest of the three muscles that attach to the

coracoid process The coracoid process (from Greek κόραξ, raven) is a small hook-like structure on the lateral edge of the superior anterior portion of the scapula (hence: coracoid, or "like a raven's beak"). Pointing laterally forward, it, together with the ...

of the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

. (The other two muscles are

pectoralis minor Pectoralis minor muscle () is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major in the human body. Structure Attachments Pectoralis minor muscle arises from the upper margins and outer surfaces ...

and the short head of the biceps brachii.) It is situated at the upper and medial part of the arm.

Structure

Coracobrachialis muscle arises from the apex of the

, in common with the short head of the biceps brachii, and from the intermuscular septum between the two muscles. It is inserted by means of a flat tendon into an impression at the middle of the medial surface and border of the

body of the humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

(shaft of the humerus) between the origins of the

triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally respon ...

and brachialis.

Innervation

Coracobrachialis muscle is perforated by and innervated by the

musculocutaneous nerve The musculocutaneous nerve arises from the lateral cord of the brachial plexus, opposite the lower border of the pectoralis major, its fibers being derived from C5, C6 and C7. Structure The musculocutaneous nerve arises from the lateral cor ...

, which arises from the anterior division of the

upper trunk The upper (superior) trunk is part of the brachial plexus. It is formed by joining of the ventral rami of the fifth (C5) and sixth (C6) cervical nerves. The upper trunk divides into an anterior and posterior division. The branches of the upper tru ...

( C5, C6) and middle trunk ( C7) of the

brachial plexus The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...

Development

Variation

Function

The action of the coracobrachialis is to flex and adduct the arm at the

glenohumeral joint The shoulder joint (or glenohumeral joint from Greek ''glene'', eyeball, + -''oid'', 'form of', + Latin ''humerus'', shoulder) is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint ...

(shoulder joint). Also, the coracobrachialis resists deviation of the arm from the frontal plane during abduction. Therefore, the contraction of the coracobrachialis leads to two distinct movements at the shoulder joint. It both draws the humerus forward, causing flexion of the arm, and draws the humerus toward the torso, causing adduction of the arm. To a smaller extent, it also turns the humerus inwards, causing internal rotation."Coracobrachialis Muscle." Anatomy, Function and Pathology. KenHub. Another important function of the coracobrachialis is the stabilization of the humeral head within the shoulder joint, especially when the arm is hanging freely at a person's side.

Clinical significance

The overuse of the coracobrachialis can lead to stiffening of the muscle. Common causes of injury include chest workouts or activities that require one to press the arm very tight towards the body, e.g. work on the rings in gymnastics. Symptoms of overuse or injury are pain in the arm and shoulder, radiating down to the back of the hand. In more severe cases, the

can get trapped, causing disturbances in sensation to the skin on the radial part of the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anat ...

and weakened

flexion Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

of the elbow, as the nerve also supplies the biceps brachii and brachialis muscles. Actual

rupture Rupture may refer to: General * Rupture (engineering), a failure of tough ductile materials loaded in tension Anatomy and medicine * Abdominal hernia, formerly referred to as "a rupture" * Achilles tendon rupture * Rupture of membranes, a "wate ...

to the coracobrachialis muscle is extremely rare. Very few case reports exist in the literature, and it is reported to be caused by direct trauma to the contracted muscle. Avulsion of the muscle's origin from the

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...

as a result of indirect forces is even more unusual.Iannotti, Joseph P. and Gerald R. Williams. ''Disorders of the Shoulder: Diagnosis & Management, Volume 1'' Philadelphia: Lippincott Williams and Wilkins, 2007. 271–73. Print.

References

Additional images

File:Coracobrachialis muscle - animation01.gif, Position of coracobrachialis muscle (shown in red). Animation. File:Coracobrachialis muscle - animation05.gif, Close up. Seen from below. Ribs are not shown. File:Coracobrachialis muscle07.png, Still image. Lateral view. File:Gray1231.png, Front of right upper extremity. (Coracobrachialis labeled at right, fourth from the bottom.) File:Slide7n.JPG, Coracobrachialis muscle (shown in green text) File:Slide5B.JPG, Coracobrachialis muscle (shown in green text).

Horizontal section The transverse plane (also known as the horizontal plane, axial plane and transaxial plane) is an anatomical plane that divides the body into superior and inferior sections. It is perpendicular to the coronal and sagittal planes. List of cli ...

of arm. File:Slide1HHH.JPG, Coracobrachialis muscle (shown in green text) File:Slide1JJJ.JPG, Coracobrachialis muscle (shown in green text) File:Slide3OOO.JPG, Coracobrachialis muscle (shown in green text)

External links

PTCentral
{{Authority control Muscles of the upper limb