QUESTIONS and ANSWERS:

1. What are the names of the nerves that innervate the subcutaneous tissue and skin?

The posterior cutaneous branches of the dorsal rami innervate the subcutaneous tissue and skin of the back. Their origins are the dorsal rami of the spinal nerves running from C2 to the coccyx.

2. What is the function of the investing fascia?

The investing fascia (deep fascia) invests the muscles and associated tendons up to their attachment to bone and is itself attached to the periosteum of the bones. Parts of it are named for the muscle being invested. For example, the thoracolumbar fascia encloses the deep muscles of the back in the thoracic and lumbar regions. Furthermore, groups of muscles with similar functions may be contained in a common compartment formed by the investing fascia. These fascial compartments often contain or direct the spread of an infection or a tumor.

3. Between some muscles there is loose fascia, fat and connective tissue. What is the function of this fascia?

Loose fascia and fat are located throughout the body at sites which require padding or mobility, where friction is a concern, where blood vessels and/or nerves require padding.

4. Why do nerves, arteries, and veins branch in different manners?

Nerves, arteries, and veins all have different embryological origins, different anatomical sources, different targets, and obviously different functions. But, just like different people travel on the same interstate highway to go to different places, nerves, arteries, and veins can start somewhere, jump into a neurovascular bundle in order to travel a distance, then jump off to reach their destination.

5. Where do nerves C3 and C4 (branching off of anterior primary rami of spinal nerves) combine to form the subtrapezial plexus?

C3, C4, and the accessory nerve (CN XI) combine at the C5 level to form the subtrapezial plexus. Together they innervate the trapezius muscle. The accessory nerve carries the motor fibers, while C3 and C4 carry the proprioceptive sensory fibers.

6. What is the thoracolumbar fascia (aponeurosis)?

The thoracolumbar fascia is an extensive fascial sheet that splits into anterior and posterior layers, thereby enclosing the deep back muscles. It is thin and transparent where it covers the thoracic parts of the deep muscles but is thick and strong in the lumbar region. The lumbar part of the thoracolumbar fascia, extending between the 12th rib superiorly and the iliac crest inferiorly, is a point of origin for the internal oblique and transverse abdominal muscles.

7. In reference to latissimus dorsi: How are the costal attachments of the muscle related to adjacent muscles? Is there an attachment to the scapula?

The serratus posterior inferior muscle and serratus anterior muscle (to be dissected later) lie deep to the latissimus dorsi, attaching to the costal surfaces. Between the scapula and the iliac crest, the latissimus dorsi muscle is attached to ribs 9 through 12.  Additionally, the latissimus dorsi often has a small attachment to the inferior angle of the scapula.