The structure indicated is the intertubercular sulcus of the humerus.

The intertubercular sulcus, also known as the intertubercular groove, or bicipital groove, is a groove separating the greater and lesser tubercles of the humerus.

The tendon of the long head of the biceps muscle runs in this groove and attaches on the supraglenoid tubercle of the scapula. The short head of the biceps muscle on the other hand has its origin on the coracoid process of the scapula.

The intertubercular sulcus is the site of three important muscle attachments:

1. Pectoralis major
2. Latissmus dorsi
3. Teres major

The pectoralis major attaches to the lateral lip of the intertubercular sulcus. The latissimus dorsi attaches to the floor of the intertubercular sulcus. The teres major attaches to the medial lip of the intertubercular sulcus. The insertion point of the latissimus dorsi is therefore sandwiched between the insertion points of the teres major and the pectoralis major. This anatomical relationship can be remembered with the mnemonic “the lady between two majors”.

Learn more about the anatomy of the humerus in this tutorial.