LAB: Back & Shoulder
Created by Rachel Karin, '09 and Nick Cohen, '09
LEARNING OBJECTIVE:
SLIDE #1
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Superficial Muscles of the Back
The first layer (depicted on the left side of this image) consists of the Trapezius and the Latissimus Dorsi Muscles. The Trapezius
arises from the external occipital protuberance, nuchal ligament, and spinous processes of C7-T12 to insert onto the lateral third of
the clavicle, the acromion, and the scapular spine. Its fibers run in several different directions creating 3 functional groups. The
superficial, middle, and inferior groups of fibers serve to elevate, retract, and depress the scapula respectively. Remember that this
muscle receives motor innervation from Cranial Nerve XI. The Latissimus Dorsi arises from the spinous processes of T7-T12, the
thoracolumbar fascia and the iliac crest to insert on the anterior of the humerus by making an unusual 180 degree twist. This muscle
functions to adduct and extend the arm and to medially rotate the humerus.
