The upper limb is divided into distinct muscle compartments by deep fascia, intermuscular septa, and bones. These compartments house functionally related muscles, along with their associated nerves and blood vessels. Compartmentalization allows for coordinated movement, efficient neurovascular routing, and containment of infections or pressure-related conditions.
1. Arm (Brachium) Compartments
The arm is divided into two main compartments by the medial and lateral intermuscular septa:
Anterior Compartment (Flexor Compartment)
Posterior Compartment (Extensor Compartment)
2. Forearm (Antebrachium) Compartments
The antebrachial fascia and interosseous membrane divide the forearm into two main compartments:
Anterior Compartment (Flexor-Pronator Compartment)
Posterior Compartment (Extensor-Supinator Compartment)
- Superficial Muscles: Brachioradialis, Extensor carpi radialis longus & brevis, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris
- Deep Muscles: Supinator, Abductor pollicis longus, Extensor pollicis brevis & longus, Extensor indicis
- Function: Extension of wrist, fingers, and thumb; forearm supination
- Innervation: Radial nerve (deep branch → posterior interosseous nerve)
- Blood Supply: Posterior interosseous artery
3. Hand Compartments
The hand is organized into several functional compartments:
Thenar Compartment
- Muscles: Abductor pollicis brevis, Flexor pollicis brevis, Opponens pollicis
- Innervation: Recurrent branch of median nerve
- Function: Thumb movement (abduction, flexion, opposition)
Hypothenar Compartment
Central Compartment
- Muscles: Lumbricals
- Tendons: Flexor digitorum superficialis and profundus
- Innervation: Median nerve (lateral 2 lumbricals), Ulnar nerve (medial 2 lumbricals)
- Function: MCP flexion and IP extension
Adductor Compartment
- Muscle: Adductor pollicis
- Innervation: Deep branch of ulnar nerve
- Function: Thumb adduction
Interosseous Compartments
- Muscles: Palmar and dorsal interossei
- Innervation: Deep branch of ulnar nerve
- Function: Finger adduction (palmar) and abduction (dorsal), assist lumbricals
Clinical Significance
- Compartment Syndrome: Raised pressure within a muscle compartment (commonly forearm) can lead to ischemia and nerve damage; requires prompt fasciotomy.
- Nerve Injury Diagnosis: Patterns of muscle weakness or atrophy can help localize nerve damage to specific compartments.
- Surgical Planning: Knowledge of compartments is crucial in trauma, reconstructive surgery, and targeted nerve blocks.
Comparative Anatomy
In non-human primates, compartmentalization is present but less refined. In humans, the complexity and separation of compartments reflect the advanced motor control required for tool use, writing, and precise hand function.
Published on May 12, 2025
Last updated on May 12, 2025