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posterior primary rami - saonew
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10-31-2006, 06:52 AM
Which muscle is innervated by posterior primary rami?
A) Latissimus dorsi B) Levator scapulae C) Rhomboideus major D) Erector spinae E) Trapezius
10-31-2006, 06:59 AM
The correct answer is: erector spinae
Of all the answer choices, erector spinae is the only true back muscle listed. True back muscles act on the vertebral column, producing its movements and maintaining posture. These true back muscles are innervated by posterior (dorsal) primary rami. The other four muscles are superficial back muscles that aid with the movements of the limbs as well as with respiration. They mostly receive their nerve supply from the ventral rami of cervical nerves. Latissimus dorsi is innervated by the thoracodorsal nerve, which is made from branches of the ventral primary rami of C5 and C6. Levator scapulae and rhomboideus major are innervated by the dorsal scapular nerve, a branch of the ventral primary rami of C5. (The superior part of levator scapulae also receives some innervation from the ventral primary rami of C3 and C4.) Lastly, trapezius is innervated by the accessory nerve (CN XI) but also receives innervation from C3 and C4 ventral primary rami for proprioception. |
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