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Anterior Arm Muscles

Musculi brachii (pars anterior)

For medical students2 min readUpdated 2026-10-10

The anterior compartment of the arm includes three main muscles: the biceps brachii, coracobrachialis, and brachialis. The primary function of this group is flexion at the shoulder and elbow joints. A key anatomical feature is their shared innervation by the musculocutaneous nerve.

Muscle Group CompositionConsists of only 3 muscles: the biceps brachii, coracobrachialis, and brachialis.
Primary FlexorThe brachialis muscle is the primary flexor of the forearm at the elbow joint.
Nerve TopographyThe musculocutaneous nerve frequently perforates the coracobrachialis muscle.
Joint ProtectionFibers of the brachialis muscle blend into the joint capsule, preventing its impingement.

Biceps Brachii

The biceps brachii (m. biceps brachii) is a powerful flexor and supinator of the forearm. As the name implies, it has two heads originating on the scapula.

Both heads merge and insert via a common tendon onto the radial tuberosity (tuberositas radii). An important structure is the bicipital aponeurosis (aponeurosis m. bicipitis brachii), which branches off the main tendon and blends into the antebrachial fascia (medially, toward the cubital fossa).

Functions: In addition to powerful flexion and supination of the forearm, the long head assists in shoulder flexion and weak abduction, while stabilizing the humeral head. The short head assists in shoulder adduction.

Topography and Blood Supply: The medial and lateral bicipital grooves (sulcus bicipitalis medialis et lateralis) run along the sides of the muscle belly. The bicipitoradial bursa (bursa bicipitoradialis) is located near the insertion site. Blood supply is provided by branches of the brachial artery (a. brachialis), including the radial recurrent artery (a. recurrens radialis), as well as the superior and inferior ulnar collateral arteries (aa. collaterales ulnaris superior et inferior).

Coracobrachialis

The coracobrachialis (m. coracobrachialis) is located in the upper arm. It originates from the apex of the coracoid process of the scapula (processus coracoideus) via a common tendon with the short head of the biceps.

The muscle runs inferiorly and inserts onto the medial surface of the humerus at its middle third (along the medial brachial line / linea brachii medialis).

Functions: The muscle flexes and adducts the arm at the shoulder joint and plays a key role in stabilizing the humeral head.

Clinical Features: The musculocutaneous nerve (n. musculocutaneus, segments C5–C7), which innervates the entire anterior compartment, frequently perforates (pierces) the coracobrachialis muscle. Blood supply is provided by the anterior and posterior circumflex humeral arteries (aa. circumflexae humeri anterior et posterior).

Brachialis

The brachialis (m. brachialis) lies deep to the biceps brachii and is the primary flexor of the forearm at the elbow joint.

It originates from the anterior surface of the distal (lower) half of the humerus, as well as from the medial and lateral intermuscular septa of the arm. The muscle inserts onto the ulnar tuberosity (tuberositas ulnae) and the coronoid process (processus coronoideus).

Clinical Significance: Some muscle fibers of the brachialis blend directly into the anterior wall of the elbow joint capsule. This is an important protective mechanism that prevents the joint capsule from being pinched during flexion.

Innervation and Blood Supply: Like the other muscles in this group, it is innervated by the musculocutaneous nerve (n. musculocutaneus, C5–C7). However, the lateral part of the muscle often receives additional branches from the radial nerve (n. radialis). Blood is supplied by branches of the brachial artery (a. brachialis), collateral ulnar arteries (aa. collaterales ulnaris sup./inf.), and the radial recurrent artery (a. recurrens radialis).

Mnemonic

General innervation rule for the anterior compartment: all three muscles receive branches from the musculocutaneous nerve (n. musculocutaneus).

Frequently asked questions

What vessels and nerves pass through the medial bicipital groove of the arm?

Passing through the medial bicipital groove are:

  • medial cutaneous nerve of the arm (n. cutaneus brachii medialis);
  • medial cutaneous nerve of the forearm (n. cutaneus antebrachii medialis).

The basilic vein (v. basilica) runs along the medial surface of the arm; in the lower third of the arm, it pierces the deep fascia and goes deep.

What function does the bicipital aponeurosis perform in relation to the neurovascular bundle?

The bicipital aponeurosis (aponeurosis m. bicipitis brachii, or lacertus fibrosus) extends medially and blends into the antebrachial fascia, separating superficial veins from deeper neurovascular structures.

What terminal sensory branch does the musculocutaneous nerve give off in the forearm?

The musculocutaneous nerve continues into the forearm as the lateral cutaneous nerve of the forearm (n. cutaneus antebrachii lateralis), which innervates the skin of the lateral forearm.

Which muscle is the primary flexor of the forearm?

The primary flexor of the forearm at the elbow joint is the brachialis muscle (m. brachialis), not the biceps brachii, as is commonly mistaken.

Which structure shares the common origin of the short head of the biceps and the coracobrachialis?

Both muscles originate via a common tendon from the apex of the coracoid process of the scapula (processus coracoideus).

Which nerve pierces the coracobrachialis muscle?

It is frequently perforated by the musculocutaneous nerve (n. musculocutaneus), which then proceeds to supply the remaining muscles of the anterior compartment.

How does the brachialis muscle protect the elbow joint?

Some of its fibers blend directly into the anterior wall of the elbow joint capsule, pulling it taut during contraction to prevent impingement.

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