The dissection of the posterior triangle highlites the brachial plexus branches of the subclavian and axillary arteries.

Basic concepts:
You may wish to review the basic concepts for the upper limb at this time. The link opens a new window which you will need to close to return to this page.

Specific Learning Objectives:

1. Describe the relationships of structures found in the posterior triangle. For example, the anterior scalene separates the subclavian vein from the subclavian artery. (Entrapment of the subclavian artery between the anterior and middle scalenes has potentially important clinical ramifications.) Another example is the relationship of the roots of the brachial plexus to the scalene muscles.
2. List all of the components of the brachial plexus.
3. Recall which spinal segments contribute to each peripheral nerve (e.g., axillary = C5,6).
4. Identify anatomic structures in radiographic studies including X-ray, CT scans and MRI films.

Difficult parts of the dissection:

1. The most difficult part of this dissection is the tough cervical fascia in the posterior triangle. You need to be patient and careful in removing this fascia to expose nerves and arteries in this region.
2. The suprascapular artery and vein are frequently destroyed because they are covered by the clavicle. Carefully slide your dental forceps along the undersurface of the bone to free the vessels. See Step 3 of the dissection of the posterior triangle.
3. Another difficult aspect of this dissection is that the clavicle and the pectoralis minor muscle tend to be in the way. Removing the bone and muscle might seem the obvious answer, but doing so distorts the relationships that we strive so hard to teach. Our compromise is to remove the clavicle and reflect the pectoralis minor muscle on one side only as described in Step 1 of the dissection of the axilla.