Lab 1 Module 3: Posterior Triangle of the Neck - Page 1 of 5

READINGS:

Gray's Anatomy for Students (Fourth Edition): Pages: 1012-1019

The neck is divided into a number of triangles for the purposes of description. The two main triangles are the Anterior Triangle and the Posterior Triangle. Each of these two triangles can be broken down into smaller sub-triangles. We will discuss the specifics of those triangles during the GI theme. At this time we are only concerned with the Posterior Triangle.

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	Begin with the Trapezius added to the shoulder.
	The Sternocleidomastoid divides the neck into the anterior and posterior triangles. The posterior triangle is bounded by the posterior border of the sternocleidomastoid muscle (anteriorly) and the anterior border of the trapezius muscle (posteriorly) and by the middle 1/3 of the clavicle inferiorly.

Origin - manubrium of the sternum and medial 1/3 of the clavicle.

Insertion - mastoid process of the temporal bone (and a small part of the occipital bone).

Innervation - Spinal Accessory Nerve (Cranial Nerve XI).

Action - Unilaterally causes the contralateral rotation of the face and ipsilateral neck side bending. When acting bilaterally they help flex the neck.

Remove the Sternocleidomastoid and add the Splenius Capitus – runs from the ligamentum nuchae and spinous processes of the superior thoracic vertebrae to the mastoid process and superior nuchal line. *DO NOT WORRY ABOUT THIS MUSCLE NOW. IT WILL BE COVERED IN NEURO I THEME. YOU SHOULD BE ABLE TO IDENTIFY IT AT THIS POINT BUT THAT IS ALL. *

Add the Posterior Scalene.

Origin - Posterior tubercles of transverse processes of C5-C7 vertebrae.

Insertion - external border of the second rib.

Innervation - ventral rami of cervical nerves C7 and C8.

Action - flexes the neck laterally; elevates the second rib during forced inspiration.

Add the Middle Scalene.

Origin - Posterior tubercles of transverse processes of C5-C7 vertebrae.

Insertion - superior surface of the first rib’ posterior to the groove for subclavian artery.

Innervation - ventral rami of cervical spinal nerves.

Action - flexes the neck laterally; elevates the first rib during forced inspiration.

Add the Anterior Scalene.

Origin - Transverse processes of C3-C6

Insertion - 1st Rib

Innervation - cervical spinal nerves C4-C6

Action - Flex the head.

	The roots of the Branchial Plexus emerge from the cervical spine and travel between the anterior and middle scalene muscles as they begin to form the rest of the brachial plexus. This is a clinically relevant area for the administration of anesthetic when performing surgery on the upper limb.
	The roof of the Posterior Triangle is formed by the deep fascia which covers the space between the trapezius and sternocleidomastoid muscles. The roof is covered by skin, superficial fascia, the platysma muscle, and superficial veins and nerves.