Prelab Images - Superficial Back

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

Step 1. Prepare the cadaver for dissection as described under Care for the Cadaver. (Play movie)

Plate N152 or TG1-01 shows the surface anatomy of the back.

Step 2. Review the bony anatomy. (Play movie)

External occipital protuberance and mastoid process are on plates N4 or TG7-05 and N8 or TG7-06. The acromion process and spine of the scapula are in N420 or TG2-03B and N421 or TG2-03A. Plates N17 or TG1-03D and N13 or TG1-04 show the spinous process of the cervical vertebrae with the spina prominens labeled on plate N21 or TG1-01. Plate N153 or TG1-02 shows a view of the entire spinal column. The crest of the ilium (AKA iliac crest) is shown on plates N486 or TG3-04A and TG3-04B and N174 or TG5-03. Finally, the sacrum and coccyx are illustrated on plate N157 or TG1-08.

Step 3. Begin to remove the skin from the back as shown in Figure 1. (Play movie), Step4. Separate skin from subcutaneous connective tissue. (Play movie), and Step 5. Complete the removal of skin and superficial fascia of the back. (Play movie)

These steps describe how to skin the back (see the diagram in the lab manual). First, make a long incision all the way down the spine starting from the skull. Try to stay on top of the spinous processes of the vertebrae. Next, make cuts perpendicular to this cut to create flaps of skin that you can pull back. Try to reflect only the skin and leave as much subcutaneous tissue on the back as possible. Surface anatomy of the back is shown on plate N152 or TG1-01.

Step 6. Dissect out an exemplary cutaneous nerve or two and clean the trapezius and latissimus dorsi muscles. (Play movie)

Plate N177 or TG1-12 gives you an idea of what the cutaneous nerves will look like in lab, except they will be much smaller and there will be subcutaneous tissue covering the muscles. Plates N180 or TG1-17 and N258 are similar and they show how the dorsal primary rami innervate the deep back muscles and skin of the back after branching off the spinal nerve. They also show how the ventral primary rami wrap around the body with the ribs and send branches to innervate the lateral and anterior skin of the trunk. Plates N170 and N192 may also be helpful or TG4-11 and TG4-12. The blood supply to the skin of the back is seen in plate N172 or TG1-21. Finally, the superior cluneal nerves (dorsal primary rami of L1, L2, and L3) are labeled in plate N177 or TG1-12.

Step 7. Reflect trapezius, identify its blood and nerve supply, and locate the greater occipital nerve. (Play movie

The first part of step 4 describes what to pay attention to when dissecting muscles (origin, insertion, neurovascular supply, muscle actions, etc.) and how to clean a muscle. This information is extremely important. The trapezius can be seen posteriorly in plate N174 or TG1-12 (the part that attaches to the clavicle is seen anteriorly in plate N27 or TG7-16). The ligamentum nuchae is also seen in plate N174 or TG1-13 as the white, tendinous attachment of the trapezius to the cervical vertebrae, but it is not labeled. It is labeled in plate N21 or TG1-09, which shows the spine from a side view. The rest of step 4 can be summed up in the following: you need to cut through the attachment of the trapezius to the spines of the vertebrae and the acromion process and then fold the muscle laterally without damaging the underlying neurovasculature. When you have done this it should look similar to plate N177 or TG1-13. Plate N178 or TG1-16 shows the greater occipital nerve. The transverse cervical artery will start in the neck as a branch of the thyrocervical trunk (plate N33 or TG7-14 shows its origin which will be seen in a later lab and it shows it moving posteriorly to supply the trapezius). You will see this artery later in its course and it will look similar to plate N177 or TG1-13. The spinal accessory nerve (cranial nerve XI) starts from the brainstem and unites with C3 and C4 (plate N127 or TG7-17) to form the subtrapezial plexus. The view you will see of these nerves in the lab looks like plate N177 or TG1-13.

Step 8. Reflect latissimus dorsi, levator scapulae, and the rhomboids and identify their blood and nerve supply. ( Play movie)

The latissimus dorsi muscle is identified in plate N174 or TG1-12. The thoracolumbar fascia is also seen in plate N174 or TG1-13 and you can appreciate how it invests the deep back muscles by the cross section on page N179 that shows its layers. The neurovascular supply of the latissimus dorsi will be seen later, but if you are curious the thoracodorsal artery is shown branching off the axillary artery in plates N427 or TG2-15 and N429 and the thoracodorsal nerve is shown coming from the brachial plexus in plate N430 and innervating the latissimus dorsi anteriorly in plate N429. You need to reflect this muscle laterally also, but you cut through the body of the muscle near the tendon and not the tendon itself (be careful not to cut too deeply and reflect serratus posterior inferior muscle shown in plate N174 or TG1-13 with it). See plates N420 or TG2-06 and N421 or TG2-06B for the insertion of the trapezius and latissimus dorsi muscles.

Plate N424 or TG2-07 shows the rhomboid major, rhomboid minor, and levator scapulae muscles.  The dorsal scapular nerve is shown at its origin in plate N430 or TG2-13, uniting with the dorsal scapular artery in plate N429, and eventually innervating the levator scapulae (lower part) and both rhomboid muscles in plate N477. The origin of the dorsal scapular artery from the subclavian artery is in the neck region and will be seen in a later lab (plates N429 and N33 or TG7-15). Plate N427 or TG2-09 shows this artery medial to the scapula where you will find it in the lab. It sends branches to the rhomboid muscles, levator scapulae, and the scapula itself. You will need to reflect the rhomboids laterally and be careful not to destroy the dorsal scapular artery and nerve. Also make sure not to reflect serratus posterior superior (N174 or TG1-13) with the rhomboids. The insertions of these muscles are shown in plate N421 or TG2-06B.

Updated: 17 Aug 2011