Which muscle borders both the triangle of auscultation and the triangle of Petit?

Which muscle borders both the triangle of auscultation and the triangle of Petit?

• A. Trapezius
• B. Latissimus dorsi
• C. Serratus anterior
• D. Teres major

Answer: (B)

Latissimus dorsi is the muscle that borders both regions. In the triangle of auscultation, latissimus dorsi forms the lower boundary, with trapezius above and the medial border of the scapula forming the other edge, creating a relatively thin spot for listening to the lungs. In the lumbar region, the triangle of Petit is bordered medially by the latissimus dorsi, laterally by the external oblique, and inferiorly by the iliac crest (with internal oblique as the floor). So the same muscle lines the border of both spaces, making it the correct answer. The other muscles don’t form borders for both triangles.

Latissimus dorsi is the muscle that borders both regions. In the triangle of auscultation, latissimus dorsi forms the lower boundary, with trapezius above and the medial border of the scapula forming the other edge, creating a relatively thin spot for listening to the lungs. In the lumbar region, the triangle of Petit is bordered medially by the latissimus dorsi, laterally by the external oblique, and inferiorly by the iliac crest (with internal oblique as the floor). So the same muscle lines the border of both spaces, making it the correct answer. The other muscles don’t form borders for both triangles.