I.A.2 Back: Muscles (Superficial, Intermediate, Deep)

I.A.2 Back: Muscles (Superficial, Intermediate, Deep): Page 2 of 3

Now let's add the members of the intermediate back muscles and discuss their function. These muscles assist in respiration.

	Step 9: Add the serratus posterior superior which elevates ribs II to V.
	Step 10: Add the serratus posterior inferior which depresses ribs IX to XII.

	What is the sum of these actions?
It assists in inspiration by increasing thoracic volume.

Now let's add in the members of the superficial back muscles. In general these muscles assist in movement of the shoulder by:

	Step 11: Add the latissimus dorsi which extends, adducts and medially rotates the humerus.
	Step 12: Demonstrate this manuver on one of your classmates. ***Note that the Latissimus dorsi is innervated by a branch of the brachial plexus, the thoracodorsal nerve. There will be more information about this when we conver the brachial plexus in week 4.
	Step 13: Add the levator scapulae which as it's name implies, elevates the scapula.
	Step 14: Add the rhomboid minor.
	Step 15: Add the rhomboid major.

Both rhomboids elevate and retract (adduct) the scapula.