Dorsally on each side of the trunk, the triangle of auscultation is the area bounded by:
- medially: the lateral border of the inferior part of trapezius
- laterally: the vertebral border of the scapula
- inferiorly: the superior border of latissimus dorsi
Increasing the size of these boundaries by drawing the scapulae forward, for example by folding the arms across the chest, uncovers the deeper structures. They are, from superficial to deep:
- the rhomboid muscles
- the sixth and seventh ribs bounding the seventh intercostal space
Therefore with relatively few and thin muscular layers, the triangle provides a particularly favourable site for auscultation of breath sounds.