Fox thigh
Photo and Text: Nick Zolkowski and Elizabeth Farrell
The main functions of the hindleg are to support the weight of the animal and to provide propulsion. The specialization of the leg seems to be in the size of the muscles based on their compartment. The lateral muscles are larger and thicker than the medial muscles.
We found it interesting that the fox had one undifferentiated adductor muscle, meaning the muscle did not further divide as is seen in many other species. Since the fox's hindlimb is restricted to parasagittal movement [1], it has little need to adduct or abduct the limb. It is possible that this resulted in these muscles never developing in significant sizes or numbers.
We started the dissection by tracing the biceps femoris muscle on the lateral side. There was not a lot of fascia to cut through, and what was present was easily removed. We then cut and reflected the biceps femoris. Deep to it, we saw the sciatic nerve running parallel to the vastus lateralis muscle, proximal to distal down the length of the thigh. Inferior to the vastus lateralis muscle and deep to the sciatic nerve are the adductor, semimembranosus, and semitendonosus muscles, which was partially visible from beyond the biceps femoris. The adductor runs most medially, with the semitendinosus the most lateral. The semimembranosus is easily distinguished, as it becomes tendinous more proximally than the semitendinosus. Cranial to the vastus lateralis muscles is the rectus femoris muscle.
Having identified all the muscles of the lateral side, we flipped the leg over to the medial side. The view here was less clear; because when the femoral vein was injected with latex coloring it burst, thus coloring the subcutaneous fascia. We spent a great deal of time removing this layer. We observed the vastus medialis, caudal to the rectus femoris.
We located the sartorius muscle, which was thin and had both cranial and caudal heads. After we split the connective tissue between the two heads, we could see the semimembranosus and semitendinosus muscles from the medial aspect. Inferior to the sartorius we viewed the gracilis. Additionally, the popliteus muscle, a small muscle located caudal to the sartorius and cranial to the gracilis, was visible.
We then dissected the gluteal area. We first located the tensor fascia lata muscle, which is dorsal and slightly caudal to the rectus femoris. We cut and reflected this thin strucure, and saw the gluteus medius muscle. Caudal and superficial to the gluteus medius is he gluteus superficialis muscle. We did not reflect the gluteus medius, but probed deep to the structure. The gluteus profundus muscle is deep to the gluteus medius, and is not visible without the gluteus medius reflected.
Once we had finished the medial leg, we began dissected the gluteal area. First, we cut and reflected the tensor fascia lata muscle, and observed the gluteus superficialis muscle. Deep to the tensor fascia and gluteus superficialis were the gluteus medius and gluteus profundus muscles.
| Muscle | Origin | Insertion | Function |
| Biceps femoris | sacrotuberous ligament and sciatic tuberosity | patella via fascia lata crucial fascia | extend hip and hock, flex stifle |
| Rectus femoris | iliopubic eminence | tibial tuberosity | extend stifle |
| Vastus lateralis | lateral lip of femur | tibial tuberosity | extend stifle |
| Vastus medialis | medial lip of femur | tibial tuberosity | extend stifle |
| Semimembranosus | sciatic tuberosity | medial lip of femur | extend hip, flex stifle |
|
Semitendinosus |
sciatic tuberosity | shaft of the tibia | extend hip, flex stifle |
| Sartorius | |||
|
Cranial belly
|
crest of ilium and lumbodorsal fascia | patella | flex hip, extend stifle |
|
Caudal belly
|
cranial ventral iliac spine | tibial crest | flex the hip and stifle |
| Gracilis | pelvic symphysis by subpubic tendon | tibial crest and tuber calcis | adduct the limb, flex stifle, extend hip |
| Adductor | pubic symphysis | rough face of femur | adduct the limb and extend the hip |
| Popliteus | lateral epicondyle of femur | proximal third of tibia | flex the stifle |
| Tensor fascia latae | cranial ventral iliac spine | lateral femoral fascia | flex the hip, extend the stifle |
| Gluteus superficialis | cranial dorsal iliac spine via gluteal fascia | third trochanter | extend the hip and abduct the leg |
| Gluteus medius | crest, gluteal surface, angles of the ilium | greater trochanter | Extend and abduct the hip |
|
Gluteus profundus |
body of the ilium, gluteal line, sciatic spine | greater trochanter | abduct and extend the limb |
Adapted from Miller (1952) [2]
1. Alderton, David. 1994. Foxes, Wolves, and Wild Dogs of the World. Facts
on File,
New York.
2. Miller, Malcolm E. 1952. Guide to the Dissection of the Dog. (3rd Ed). Edward
Brothers Inc., New York.