For comparison, see thigh dissections of a bat, a ferret, a fox, a rabbit, and a tree shrew.

Part I: Overview

A cat has longer and stronger hindlimbs than the forelimbs. The long hindlimbs increase the stride length. The muscles of the hind leg are also better developed, and seem to be able to produce larger forces. The most difficult part of this lab is removing the fat without cutting out the muscles in the gluteal area, because some superficial muscles such as the gluteus superficialis muscle are embedded in fat and fascia. Also, it is easy to cut out the anal sphincter muscle by accident when removing the skin, because from the outside, it is hard to locate this part with fur covering it. Thus, extra care is needed when removing the skin around this area, because if the anal sphincter muscle is cut out by accident, some feces will seep out. Otherwise, the skin in the hindlimb area comes off easily, and the muscles are relatively large and clearly divided enough to make identification easy.

Part II: Muscles and Their Origins, Insertions and Actions

Once the skin and fascia are removed from the hindlimb area, one of the superficial muscles immediately visible on the lateral side of the leg is the biceps femoris muscle. This is one of the largest muscles of the leg. This muscle literally covers most of the other lateral or dorsal muscles. The tensor fascia lata is also one of the muscles visible at the superficial level. The fascia is broad and tough, and it lies cranial to the biceps femoris muscle. It also lies superficial to the gluteus medius muscle and the vastus lateralis muscle. Thus it is necessary to cut and reflect the biceps femoris and the tensor fascia lata muscles in order to see other muscles.

The gluteus medius muscle is deep to the tensor fascia lata. This muscle is at the hip area of a cat, superior to the other superficial hindlimb muscles such as the vastus lateralis muscle. The vastus lateralis muscle is a broad sheath of muscle and the sartorius muscle is a long strip of muscle. However in this cat, these muscles were fused as one muscle and they both inserted onto the patellar tendon. In other carnivores, the sartorius muscle and the vastus lateralis muscles are well distinguished although their relative sizes may vary depending on the animal and its mode of locomotion. Reflecting the biceps femoris muscle, revealed the entire caudofemoralis muscle. This muscle had an interesting shape, because it starts out as a round strip of muscle, but it turns into a long tendon that inserts onto the patella.

The adductor femoris muscle is a deep muscle, located deep to the caudofemoralis muscle and the vastus lateralis muscle. It lies cranial to the semimembranosis muscle, which also lies cranial and deep to the semitendinosus muscle. Portions of the semitendinosus and semimembranosus muscles are visible before reflecting back the biceps femoris muscle. Superior to the semimembranosus muscle, the obturator internus muscle is visible. This muscle is easy to miss, because it is so small and deep. It is easier to find this muscle if the caudal portion of the hip joint is examined closely. The muscle lying superior to the obturator internus muscle is the gemellus inferior muscle. This muscle is as small as the obturator internus muscle, if not smaller. The divisions between these muscles are clear, however, because the fibers are in different directions. Inferior to these muscles lies a bigger and rectangular shaped muscle, the quadratus femoris muscle. This muscle is not part of the quadriceps muscle. The piriformis muscle and the gluteus profundus (also sometimes called the gluteus minimus muscle) lie deep to the gluteus medius muscle. The piriformis muscle is easy to find at the deep caudal side of the gluteus medius muscle and the gluteus profundus muscle is found at the deep cranial side of the gluteus medius muscle. Inferior to the piriformis muscle, the sciatic nerve is clearly visible. It comes out deep from the piriformis muscle and extends all the way down to the popliteal fossa before it splits into tibial nerve and the common peroneal nerve. The sciatic nerve innervates the posterior compartment of the leg. However, femoral nerve innervates the anterior compartment of the hind limb. Thus the quadriceps muscle is innervated by the femoral nerve. The femoral nerve crosses the inguinal ligaments in femoral sheath with the femoral artery and vein. These blood vessels are the extensions of the external iliac arteries and veins. Thus the femoral nerve is visible on the medial side of the thigh.

On the medial side of the leg, going from anterior to posterior, the gracilis and the sartorius muscles are immediately visible. The gracilis muscle is a large band of muscle covering most of the other muscles on the medial side. When the gracilis muscle is cut and reflected, the semimembranosus, the vastus medialis, adductor femoris, adductor longus, the pectineus and the rectis femoris muscles are all exposed without further dissection. The semimembranosus muscle is more clearly visible from this side. The semitendinosus muscle is deep to the semimembranosus muscle, and both are inferior to the adductor femoris muscle. Superior to the adductor femoris muscle lie the adductor longus muscle, and then superior to the adduction longus muscle lays the pectineus muscle. The vastus medialis muscle is superficial to the rectus femoris muscle, and is cranial to the semimembranosus, adductor femoris, adductor longus, and the pectineus muscles. The rectus femoris muscle is more clearly visible after reflecting back the vastus medialis muscle. The vastus medialis muscle is a deep muscle that, judging from its large cross-sectional area, seems to be able to produce a significant amount of force.

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