Muscles of the Back and Shoulder

10/24/14 and 10/27/14

Focus Question: Identify the superficial and deep muscles of the back and shoulder.

Procedure:

1. Recognize where the latissimus dorsi and the external oblique are located (the latissimus dorsi being superior (above) the external oblique). Both muscles should be located on the cat’s posterior (back). Identify the spinotrapezius, acromiotrapezius and clavotrapezius, located further up the cat’s posterior (back). The spinotrapezius is superior (above) the latissimus dorsi and inferior (below) the acromiotrapezius. The clavotrapezius is superior (above) the acromiotrapezius. The acromiotrapezius being intermediate between the clavotrapezius and the spinotrapezius. Review the diagrams in the Anatomy booklet for further direction on the location of these superficial muscles.
2. With a scalpel, make an incision outlining these superficial back muscles then take a picture.
3. Identify the superficial muscles of the shoulder: clavobrachialis (clavodeltoid), acromiodeltoid, spinodeltoid, and the triceps brachii. The levator scapulae ventralis is intermediate between the acromiodeltoid and the acromiotrapezius. The spinodeltoid is intermediate between the triceps brachii and the acromiotrapezius. The spinodeltoid and the levator scapulae are next to each other. The triceps brachii take up the outer-side of the arm and are inferior (below) to the acromiodeltoid and the spinodeltoid. Left to the triceps brachii is the clavobrachialis (clavodeltoid), which is inferior (below) to the clavotrapezius. Review the diagrams in the Anatomy booklet for further direction on the location of these superficial muscles.
4. With a scalpel, clearly outline each of these superficial shoulder muscles, which are located on the cat’s shoulder and upper arm area. Take a picture.
5. Next with a scalpel and surgical tweezers, remove the superficial muscles of the shoulder in order to identify the deep muscles of the shoulder. The following deep shoulder muscles should be identified: Supraspinatus, infraspinatus and teres major. The supraspinatus is superior (above) the infraspinatus muscle. The teres major is a small muscle inferior (below) the infraspinatus. The infraspinatus being intermediate between the supraspinatus and teres major. Review the diagrams in the Anatomy booklet for further direction on the location of these deep muscles.
6. Attached to the back side of the shoulder is the levator scapulae ventralis, rhomboideus capitis and the rhomboideus muscle. These are deep back muscles attached to the shoulder. The levator scapulae ventralis is superior (above) the rhomboideus capitis. The rhomboideus is inferior (below) the rhomboideus capitis. The rhomboideus capitis is intermediate between the levator scapulae ventralis and the rhomboideus. Review the diagrams in the Anatomy booklet for further direction on the location of these deep muscles. With your fingers, delicately separate these three muscles. Use your scalpel if needed.
7. Once clearly identified, take a picture of all the deep shoulder muscles.
8. With a scalpel and surgical tweezers, make an incision in the clavotrapezius in order to identify the splenius. The splenius is a deep neck muscle located underneath the clavotrapezius.
9. Once clearly identified, take a picture of the incision of the clavotrapezius and the splenius muscle.
10. Next with a scalpel and surgical tweezers, make an incision down the midline of the cat’s posterior (back) in order to identify the deep muscles of the cat. The following deep back muscles should be identified: the spinalis dorsi, the longissimus and the iliocostalis. The spinalis dorsi is medial to the iliocostalis. In other words, the spinalis dorsi is closest to the midline and the iliocostalis are lateral or away from the midline. The longissimus is intermediate between the spinalis dorsi and the iliocostalis. Also, identify the fascia intermediate the superficial back muscles and the deep back muscles.
11. Once clearly identified, take a picture of the fascia and the deep back muscles.

Materials: scalpel and surgical tweezers.

Data and Observations: 
All of Samara's superficial and deep muscles of the back and shoulder were in great condition and in the correct spot. The different muscles were able to be clearly identified due to the striations of the muscles, especially the deep muscles of the back. Pictures of the data collected are shown below.

Human Corresponding Muscles of the Back and Shoulder

Conclusion: 
I found the superficial and deep back muscles easy. It was slightly harder to cut through the superficial muscle to get to the deep muscle because of the fascia on the cat’s posterior but, I was able to identify all the muscles easily. Unfortunately, I struggled to locate and identify the superficial and the deep muscles of the shoulder and often questioned if I was dissecting my cat correctly. These muscles were very confusing to me and I had a terribly hard time labeling my pictures. Once I finished labeling my pictures and diagrams, I did gain a new knowledge of the superficial and deep muscles of the back and shoulder. I am glad I had the opportunity to observe how the muscles of the back connect to the shoulder. It was very cool to see the muscles contract and observing this gave me a better understanding of the anatomy.