Scalene muscles

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The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene. They originate from the lateral processes from the cervical vertebrae of C3 to C7 and insert onto the first and second ribs. They are innervated by the spinal nerves C3-C8. The action of the anterior and middle scalene muscles is to elevate the first rib and rotate the neck to the opposite side; the action of the posterior scalene is to elevate the second rib and tilt the neck to the same side.

The scalene muscles have an important relationship to other structures in the neck. The brachial plexus and subclavian artery pass between the anterior and middle scalenes. The subclavian vein passes arteriorly to the anterior scalene as it crosses over the first rib.

They also act as accessory muscles of inspiration, along with the sternocleidomastoid.

The passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles constitute the scalneus hiatus. The region in which this lies is referred to as the scaleotracheal fossa. It is bound by the clavical inferior anteriorly, the trachea medially, posteriorly by the trapezius, and anteriorly by the platisma muscle. If you look closely, you can also see the brances off that subclavian which will form the common carotid artery, which will further go up and split into the two branches, internal and external located at the junction of the carotid sinus. (Refer to Netter's Atlas of Human Anatomy for proper picturing.) With these you will also see a long string that appears white to cream color and can be tugged on firmly. This will be the Vagus Nerve (Cranial Nerve X)