Latissimus Dorsi Muscle - Triangles

Triangles

• The lateral margin of the latissimus dorsi is separated below from the obliquus externus abdominis by a small triangular interval, the lumbar triangle of Petit, the base of which is formed by the iliac crest, and its floor by the obliquus internus abdominis.

• Another triangle is situated behind the scapula. It is bounded above by the trapezius, below by the latissimus dorsi, and laterally by the vertebral border of the scapula; the floor is partly formed by the rhomboideus major. If the scapula is drawn forward by folding the arms across the chest, and the trunk bent forward, parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for auscultation. The space is therefore known as the triangle of auscultation.

• The Latissimus Dorsi can be remembered best for insertion as "The Lady Between Two Majors". As the Latissimus Dorsi inserts into the floor of the intertubercular groove of the humerus it is surrounded by two major muscles. The Teres Major inserts medially on the medial lip of the intertubercular groove and laterally the Pectoralis Major inserts into the lateral lip.