Muscles of the Posterior Compartment of the Arm

Overview

The posterior compartment of the arm is one of the two compartments in the arm. The brachial fascia (sheath of deep fascia) surrounds the arm and is divided into anterior and posterior compartments by two intermuscular septa (medial and lateral) which extend from it to attach to the humerus at the medial condylar ridge and lateral supracondylar ridge, respectively.

Muscles

Triceps Brachii

• Origin:
  • Long head – infraglenoid tubercle of scapula.
  • Lateral head – humerus, superior to the radial groove.
  • Medial head – humerus, inferior to the radial groove.
• Insertion: The three heads converge onto a single tendon inserting into the olecranon of the ulna.
• Action: Extension of the arm at the elbow.
• Innervation: Radial nerve (C5 – T1)

Anconeus muscle

• Origin: Lateral epicondyle of the humerus
• Insertion: Olecranon of the ulnar
• Action: Weak elbow extension
• Innervation: Radial nerve (C5 – T1)
• Arterial Supply: Posterior interosseous recurrent artery – branch of the common interosseus artery (arising from the ulnar artery)

Articularis cubiti muscle

• Origin: Posterior surface of the distal humerus
• Insertion: Posterior surface of the elbow joint capsule
• Innervation: Radial nerve (C5 – T1)
• Action: Tenses the posterior elbow joint capsule during elbow extension

Innervation

Radial nerve. A tap on the triceps tendon tests spinal segment C7.

Anatomical Variants

• Long head of the triceps brachii innervated by the axillary nerve