Medial intermuscular septum of arm

The brachial fascia, which envelops the arm muscles, forms two tough fibrous partitions that compartmentalize the arm's muscles: the medial and lateral intermuscular septa. The medial intermuscular septum extends from the medial lip of the intertubercular sulcus to the medial supracondylar ridge of the humerus. It's continuous with the teres major fascia proximally and blends with the coracobrachialis aponeurosis.

This septum is perforated by the ulnar nerve, along with the superior ulnar collateral artery and a branch of the inferior ulnar collateral artery. It provides attachment for the medial head of the triceps posteriorly and the brachialis anteriorly.