Anatomy IV -- external occipital protuberance, superficial back muscles, triangles

The external occipital protuberance. 3cm inferolaterally in the thick fascia, we have the greater occipital nerve penetrating the trapezius. It innervates the back of the scalp. Laterally to that we find the occipital artery, which supplies the back of scalp, sternocleidomastoid muscles, and other deep muscles of the back and neck.

The skin of the back is thick. Funny story: someone suggested this is an evolutionary adaptation against being backstabbed.

The trapezius is a kite-shaped muscle attaching to the lateral third of clavicle, acromion, and spine of scapula. It can raise, retract, and lower the scapula. It is innervated by the accessory nerve and the ventral rami of C3/C4 spinal nerves. Blood supply: transverse cervical artery (branch of thyrocervical trunk).

The latissimus dorsi muscle attaches proximally to T7-T12, thoracolumbar fascia, iliac crest, ribs 9-12 and distally terminates in intertubercular sulcus of anterior side of humerus. It receives blood and nerve supply from the thoracodorsal artery and nerve.

Rhomboids, major and minor. Minor attaches proximally to nuchal ligament and C7/T1, distally to medial border of scapula at the level of the spine. Major attaches proximally to T2-T5, distally to medial border of scapula below level of the spine. Both rhomboids retract the scapula. They are supplied by dorsal scapular nerve and artery. Dorsal scapular artery may branch directly from subclavian or may be a branch off transverse cervical artery (normal anatomical variation).

Levator scapulae. Proximal attachment: transverse processes of C1-C4. Distal attachment: scapula, superior angle. Dorsal scapular nerve and artery supply it. It elevates scapula and rotates scapula to depress glenoid cavity.

Triangle of auscultation: latissimus dorsi, trapezius (inferior part), rhomboid major. Lung sounds clearly heard here.

Lumbar triangle: latissimus dorsi, external oblique, iliac crest. Floor of lumbar triangle is internal oblique. Can be site of lumbar hernia.