Fig. 50-28. A, The cupola of the pleura, anterior scalene, and longus colli; anterior aspect and slightly from the right side. The cupola projects upward between the scalenes and the longus colli, about 3 cm above the medial third of the clavicle (interrupted line). B, The third part of the subclavian artery and the brachial plexus between the anterior scalene and the middle scalene. The lower trunk of the plexus lies posterior to the artery. The phrenic nerve, which descends almost vertically on the obliquely set anterior scalene, is bound to the front of the muscle by the transverse cervical and suprascapular arteries. The anterior scalene, longus colli, and first part of the subclavian artery form a triangle. The carotid tubercle of C6 lies at the apex, and the vertebral artery ascends through the triangle to reach the foramen transversarium of C6. (A is based on von Lanz and Wachsmuth.) Click for high resolution image.