Anterior Compartment of the Arm
Anterior compartment of arm contains biceps brachii and brachialis innervated by the musculocutaneous nerve.
The anterior compartment of the arm (also called the flexor compartment) contains muscles responsible for flexion of the elbow and shoulder, as well as forearm supination. It is bounded by the brachial fascia and separated from the posterior compartment by the medial and lateral intermuscular septa. It also houses major neurovascular structures including the musculocutaneous nerve and brachial artery.
Boundaries
| Structure | Description |
|---|---|
| Anterior | Brachial fascia and skin |
| Posterior | Humerus and intermuscular septa |
| Medial & Lateral | Medial and lateral intermuscular septa |
Muscles of the Anterior Compartment
| Muscle | Origin | Insertion | Function | Innervation |
|---|---|---|---|---|
| Biceps brachii |
Long head: supraglenoid tubercle Short head: coracoid process |
Radial tuberosity and bicipital aponeurosis | Flexes elbow, supinates forearm, weak shoulder flexion | Musculocutaneous nerve (C5–C6) |
| Brachialis | Distal anterior surface of humerus | Coronoid process and tuberosity of ulna | Main flexor of the elbow (regardless of forearm position) | Musculocutaneous nerve (C5–C6), radial nerve (partial) |
| Coracobrachialis | Coracoid process of scapula | Medial surface of humerus (midshaft) | Flexes and adducts the shoulder | Musculocutaneous nerve (C5–C7) |
Contents
- Musculocutaneous nerve: Innervates all three muscles; emerges as lateral cutaneous nerve of forearm
- Brachial artery: Main arterial supply; gives off profunda brachii and nutrient branches
- Median nerve and ulnar nerve: Pass through the compartment but do not innervate it
- Basilic vein: Travels medially in the superficial fascia
Function
- Elbow Flexion: Primarily by brachialis and biceps brachii
- Forearm Supination: Biceps brachii (when forearm is flexed)
- Shoulder Flexion and Adduction: Coracobrachialis and biceps (short head)
Blood Supply
- Brachial artery: Continuation of axillary artery; supplies all muscles and gives branches to the humerus
Innervation
- Musculocutaneous nerve (C5–C7): Sole motor nerve of this compartment
Clinical Significance
- Compartment Syndrome: Increased pressure within the anterior compartment can compromise perfusion and nerve function, requiring fasciotomy
- Biceps Tendon Rupture: Results in a “Popeye” deformity and loss of supination power
- Musculocutaneous Nerve Injury: Rare but can cause weakness in elbow flexion and loss of lateral forearm sensation
Comparative Anatomy
In quadrupeds, the anterior compartment is less prominent due to reduced elbow flexion demands. In humans, it is well-developed to support carrying, lifting, and tool manipulation — functions dependent on controlled forearm positioning and strength.
Last updated on May 12, 2025
