CORACOBRACHIALIS MUSCLE: CHARACTERISTICS, ORIGIN, FUNCTIONS - ANATOMY AND PHYSIOLOGY - 2025

The coracobrachialis muscle is scientifically called Musculus coracobrachialis. It is a muscle that is anatomically located in the arm, specifically in the anterior face. It arises from the upper part of the apophysis of the shoulder blade bone or also called the scapula. This region is called the coracoid process of the scapula. Hence, part of the name of this muscle comes from.

It is a long muscle, with a certain thickness. This ends in the central segment of the diaphysis of the humerus bone, one third from the lower or distal end of the bone. It is innervated by the musculocutaneous nerve that comes from the brachial plexus, being able to find from 1 to 3 branches innervating the muscle. On the other hand, the muscle is supplied vascularly by the brachial artery.

Coracobrachialis muscle highlighted in purple. Source: Me

The function of this muscle can be summarized as follows: it allows moving the arm forward (anteversion), towards the midline of the body (adduction), internal rotation (medial rotation) and return to the starting position (neutralization). In addition, it performs other functions such as the longitudinal coaptador muscle of the arm, protecting the shoulder joint.

characteristics

Coracobrachial is a compound word. While "coraco" comes from the word coracoides honoring the place where the muscle begins, the term brachialis, comes from the Latin brachialis, which refers to the anatomical site of the arm. This muscle is characterized by being long and thick.

Origin

The coracobrachialis muscle originates from the coracoid complex or process (coracoid process of the shoulder blade). From there he departs in company with the short head of the biceps brachii.

Insertion

It is nailed on the internal face of the diaphysis of the humerus bone, specifically one third of the lower or distal end of the mentioned bone.

Innervation

The coracobrachialis muscle is innervated by one or more branches of the lateral cord of the brachial plexus, called the musculocutaneous nerve. This generally passes between the muscle fibers. It should be noted that this nerve not only innervates this muscle, but also other muscles in the area.

The number of nerve branches that innervate the coracobrachialis muscle can vary from one individual to another, as demonstrated by Olave in 2004, who performed dissections of 42 upper limbs (right and left) from Brazilian cadavers, which had previously been fixed in formalin.

Olave found considerable variability, reporting the observation of a bouquet in 11 members on the left side and in 6 members on the right side. While with two bouquets he found a total of 7 for the left side and 11 for the right. And with 3 branches he found 3 on the left side and 4 on the right. These results are summarized as follows: 40.5% was innervated by a single branch, 42.9% by 2 branches, and 16.6% with 3 branches.

This study also determined the origin of the ramifications, where 88.1% originated from the musculocutaneous nerve and 11.9% originated from the lateral cord of the brachial plexus.

Finally, regarding its path, Olave observed that in 83.3% of the cases it passed through the muscle fibers, the rest did so outside of it.

Other studies such as that of Tavares et al. In 2008, found a small percentage of individuals where the musculocutaneous nerve was absent.

Research has shown that this anomaly does not cause symptoms in the patient, since it is generally replaced by the median nerve and less frequently by nascent motor fibers from the lateral root of the median nerve or also from the lateral bundle of the brachial plexus.

Irrigation

The coracobrachialis muscle is supplied by the brachial artery.

Features

The coracobrachialis muscle fulfills several functions, among them the following can be mentioned: movement of the arm together with shoulder flexion, maintenance of the joint of the shoulder joint and balancer.

Movement

It is responsible for the movements of anteversion (forward), adduction (towards the midline of the body), as well as allowing the movement of internal rotation of the shoulder (medial rotation) and return to the starting position (neutralization).

The movements can be carried out at the desired speed, either slow, moderate or fast, since this muscle is more related to the speed of the movement, than to strength.

Maintaining the union of the shoulder joint

The coracobrachialis muscle participates in the coaptation of the shoulder muscles, that is, in maintaining the union of the humerus joint with the shoulder blade.

As it is a joint with great movement and very frequent use, it must be well protected, both by ligaments and muscles. Both will allow the proximal epiphysis of the humerus (head of the humerus) to remain anchored to the glenoid cavity, avoiding joint dislocation.

A set of transverse and longitudinal coaptator muscles participate in this function. Some are located in the anterior part of the joint and others in the posterior part.

In the case of the coracobrachialis muscle, it is a longitudinal co-receptor that acts on the anterior aspect. At this level it works together with the following muscles: supraspinatus, deltoids, triceps brachii, clavicular part of the pectoralis major, and long head of the biceps brachii tendon.

Balancer

Produces stability to the joint.

Syndrome

Trigger point formation

They are pain nodules that are formed by overloading the muscle. It is common for them to occur in the coracobrachialis muscle, especially when performing activities that involve squeezing the arms toward the body. Example: athletes who practice lifting weights in a lying position (bench press) or do dips on rings (ring dips).

Related disorders

Rotator cuff wear

The set of muscles that act as longitudinal coaptators of the shoulder joint - where the coracobrachialis muscle participates - can, at any given time, cause wear on the muscles that make up the rotator cuff.

The latter is formed by the supraspinatus, infraspinatus, subscapularis and teres minor.

Wear of the rotator cuff can cause a lot of pain to the patient, preventing him from making some arm movements.

A common mistake is to try to strengthen only the rotator cuff muscles, since as already seen, they are not the only muscles of importance in the function of the shoulder joint.

It is also a mistake to try to strengthen the bicep, tricep and deltoid muscles and neglect those of the rotator cuff.

References

1. Olave E. Anatomical and biometric aspects of the innervation of the coracobrachialis muscle and its motor points. Int. J. Morphol, 2004; 2 (4): 323-326. Available in: scielo.
2. Silva L, Muñoz D, Pérez J, Correa A, Ania J, Junquera C, Cuevas A, et al. (2002). Auxiliaries / Technicians of Sanitary Transport. Editorial Mad. Sevilla Spain.
3. "Coracobrachialis muscle" Wikipedia, The Free Encyclopedia. 8 Sep 2018, 13:35 UTC. 22 Aug 2019, 04:05 wikipedia.org.
4. Álvarez O, Campohermoso O, Álvarez Durán G. High bifurcation of the brachial (humeral) artery. Quad. Hosp. Clin. 2014; 55 (2): 68-75. Available at: scielo.org.
5. Tavares F, Macéa M, Pereira C, Barros M, Macéa J. Absence of the musculocutaneous nerve: a rare anatomical variation with possible clinical-surgical implications. Sao Paulo Med. J. 2008; 126 (5): 288-290. Available from: scielo.