Explore Anatomy
AC

Anterior Compartment of the Arm

Anterior compartment of arm contains biceps brachii and brachialis innervated by the musculocutaneous nerve.

RegionUpper Limb
SystemMusculoskeletal System

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

StructureDescription
AnteriorBrachial fascia and skin
PosteriorHumerus and intermuscular septa
Medial & LateralMedial 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.

Published on May 12, 2025
Last updated on May 12, 2025
Disclaimer: The content on this site is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.