Long Head of the Triceps Under the Skin, Posterior View

Description

Posterior skin-surface anatomy frames the long head of triceps brachii as it descends from the infraglenoid tubercle of the scapula, running inferiorly and slightly laterally to join the lateral and medial heads on the posterior humerus. Superficial fascia and skin lie directly posterior to the triceps mass, while the posterior deltoid caps the shoulder superiorly and the teres major forms a medial border near the posterior axillary fold. Medially, the long head creates a clear partition between the quadrangular space laterally and the triangular space medially, with the humeral shaft and posterior compartment structures sitting deep to the muscle belly. It reads as a long, fusiform strap in the upper arm. Clinically, this posterior view matters because the long head is both a shoulder and elbow extensor, and its proximal origin makes it a common pain generator in overhead athletes with posterior shoulder strain and tendinopathy near the infraglenoid region. Surgeons use the long head as a landmark when approaching the posterior shoulder and axilla, since the axillary nerve and posterior circumflex humeral artery pass lateral to it in the quadrangular space, while the radial nerve tracks inferiorly in the spiral groove deep to the triceps, a relationship that becomes relevant in midshaft humeral fractures and posterior compartment hematoma. Palpation and identification here also helps separate true triceps weakness from radial neuropathy. Use this artwork in upper limb anatomy teaching to reinforce compartmental organization and surface landmarks, in sports medicine content discussing posterior shoulder and elbow extensor injuries, or in operative atlases describing posterior approaches around the axilla and humerus where the long head defines safe dissection corridors. Anatomical accuracy verified by SciePro's Medical Advisory Board.