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The coracobrachialis muscle is located in the upper medial part of the arm, within the anterior compartment. It is responsible for flexion and adduction at the glenohumeral joint (shoulder joint). The musculocutaneous nerve, a major peripheral nerve of the upper limb, innervates the coracobrachialis muscle. This nerve arises from the lateral cord of the brachial plexus (C5-C7) and pierces the coracobrachialis muscle near its point of insertion on the humerus. The musculocutaneous nerve also innervates the biceps brachii and brachialis muscles, supplying motor innervation for flexion at the elbow.
| Characteristics | Values |
|---|---|
| Location | Upper medial part of the arm |
| Compartment | Anterior |
| Origin | Coracoid process of scapula |
| Insertion | Mid-medial surface of humerus |
| Innervation | Musculocutaneous nerve |
| Function | Adduction and flexion of the arm |
| Blood supply | Brachial artery |
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What You'll Learn
The musculocutaneous nerve
The nerve gives rise to the lateral cutaneous nerve of the forearm, which innervates the lateral aspect of the forearm. It passes down the flexor compartment of the upper arm, superficial to the brachialis but deep to the biceps brachii muscle. It pierces the deep fascia lateral to the biceps brachii to emerge lateral to the biceps tendon and brachioradialis.
In the region of the elbow, the nerve runs deep to the brachial fascia, over the brachialis muscle. Past the elbow, the nerve continues as a pure sensory nerve, known as the musculocutaneous sensory or lateral antebrachial cutaneous sensory nerve. It becomes subcutaneous and separates into two terminal divisions (anterior and posterior) to supply sensation to the lateral half of the forearm.
The nerve is well-protected within the axilla, and injury is relatively uncommon. However, penetrating trauma to the axilla, such as a stabbing wound, can result in injury to the nerve.
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The coracobrachialis is one of three muscles in the anterior compartment of the arm
The coracobrachialis is innervated by the musculocutaneous nerve, which arises from the lateral cord of the brachial plexus and is formed by spinal nerves C5-C7. This nerve passes through the axilla, pierces and innervates the coracobrachialis, and then travels under the biceps brachii. The musculocutaneous nerve supplies motor innervation to the coracobrachialis, biceps brachii, and brachialis muscles, enabling flexion at the elbow. It then continues into the forearm as the lateral cutaneous nerve, providing sensory innervation to the lateral aspect of the forearm.
The brachialis muscle also receives some innervation from the radial nerve, although this is considered clinically insignificant. The coracobrachialis is often difficult to isolate and test due to its position beneath the biceps brachii muscle. To confirm contraction of the coracobrachialis, a therapist may ask the client to flex the elbow, which will show biceps brachii contraction but not that of the coracobrachialis.
The coracobrachialis muscle is classified into superficial and deep layers, with varying degrees of separation between these layers in different individuals. This muscle can be strained or ruptured, causing symptoms such as pain and tenderness in the upper arm, radiating down to the back of the hand. In more severe cases, the musculocutaneous nerve can become trapped, leading to disturbances in sensation in the forearm.
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The coracobrachialis arises from the coracoid process
The coracobrachialis is a long and slender muscle in the upper medial part of the arm, specifically within the anterior compartment of the arm. It is one of three muscles that comprise the anterior compartment, alongside the biceps brachii and the brachialis. The coracobrachialis arises from the coracoid process of the scapula, inserting onto the middle of the medial aspect of the body of the humerus.
The coracobrachialis muscle is innervated by the musculocutaneous nerve, which arises from the anterior division of the upper trunk (C5-C7). This nerve is a major peripheral nerve of the upper limb and gives rise to the lateral cutaneous nerve of the forearm, which innervates the lateral aspect of the forearm. The musculocutaneous nerve pierces the coracobrachialis muscle near its point of insertion on the humerus. It can pass through the coracobrachialis, or it may pass under it and/or through the biceps brachii.
The musculocutaneous nerve provides motor functions to the coracobrachialis, biceps brachii, and brachialis muscles, enabling flexion at the shoulder and elbow. It also provides sensory functions, giving rise to the lateral cutaneous nerve of the forearm, which provides sensory innervation to the lateral aspect of the forearm.
The main actions of the coracobrachialis muscle are to produce flexion and adduction of the arm at the shoulder joint. It acts as an antagonist to the deltoid muscle, particularly when the arm is abducted and extended. The coracobrachialis receives its blood supply from the muscular branches of the brachial artery, with additional supply from the anterior circumflex humeral and thoracoacromial arteries.
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The nerve branches off the lateral cord of the brachial plexus
The musculocutaneous nerve is a major peripheral nerve of the upper limb. It is the nerve that innervates the coracobrachialis muscle. This nerve branches off the lateral cord of the brachial plexus, passing through the axilla and piercing the coracobrachialis muscle.
The musculocutaneous nerve arises directly from the lateral cord of the brachial plexus, specifically from the anterior division of the upper trunk (C5, C6, and C7). It pierces the coracobrachialis muscle near its point of insertion on the humerus. The nerve then continues its path, passing through the flexor compartment of the upper arm, deep to the biceps brachii muscle and superficial to the brachialis muscle.
The musculocutaneous nerve provides motor innervation to the coracobrachialis muscle, enabling flexion and adduction of the arm at the shoulder joint. It also innervates the biceps brachii and brachialis muscles, supplying motor function for flexion at the elbow.
In the region of the elbow, the musculocutaneous nerve runs deep to the brachial fascia, just above the brachialis muscle. Beyond the elbow, the nerve's terminal extension continues as a sensory nerve, known as the musculocutaneous sensory nerve or the lateral antebrachial cutaneous sensory nerve. This sensory nerve supplies sensation to the lateral aspect of the forearm.
The musculocutaneous nerve is well-protected within the axilla, and injuries are relatively uncommon. However, penetrating trauma to the axilla, such as a stabbing injury, or iatrogenic injury during surgical procedures, can damage the nerve.
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The nerve pierces the coracobrachialis muscle
The coracobrachialis muscle is located in the upper arm, specifically in the anterior or front compartment of the arm. It is one of three muscles that make up the anterior compartment, alongside the deltoid and brachialis muscles. The coracobrachialis is responsible for flexion and adduction at the glenohumeral joint, which is located in the shoulder.
The musculocutaneous nerve is a major peripheral nerve of the upper limb, and it is this nerve that pierces the coracobrachialis muscle. The nerve arises from the lateral cord of the brachial plexus, specifically from spinal nerves C5-C7. It passes through the axilla, or armpit, and pierces the coracobrachialis muscle near its point of insertion on the humerus, or upper arm bone. The musculocutaneous nerve innervates the coracobrachialis muscle, as well as the biceps and brachialis muscles.
The musculocutaneous nerve then continues past the elbow as a pure sensory nerve, known as the musculocutaneous sensory or lateral antebrachial cutaneous sensory nerve. In the forearm, the nerve becomes subcutaneous and separates into two terminal divisions (anterior and posterior) to supply sensation to the lateral half of the forearm. The musculocutaneous nerve is well-protected within the axilla, and injury is relatively uncommon. However, penetrating trauma to the axilla, such as a stabbing, can cause damage to the nerve.
The coracobrachialis muscle is classified into distinct superficial and deep layers. In most individuals, there is no discernible separation of these layers, but in some cases, the muscle may be fully or partially divided into these layers. The coracobrachialis is considered functionally insignificant, as it is a weak flexor and adductor of the arm. However, overuse of the muscle can lead to stiffening and injury, causing pain in the arm and shoulder.
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Frequently asked questions
The musculocutaneous nerve innervates the coracobrachialis muscle.
The musculocutaneous nerve is a major peripheral nerve of the upper limb. It gives rise to the lateral cutaneous nerve of the forearm, which innervates the lateral aspect of the forearm.
The musculocutaneous nerve innervates the biceps, brachialis, and coracobrachialis muscles.
