Shoulder

Brachium

Antebrachium

Facial and Masticatory Muscles

Thorax and Heart

Brain

Body Wall

Hip and Thigh

Shank and Foot

Digestive System

Urinary and Reproductive Systems

Hip and Tail

Deep Hip and Tail of the Cat (Felis catus)

Photos and text by Adam Hartstone-Rose

Introduction:

Though cats are very agile creatures, their deep hip and tail muscles are not particularly different from those of many other quadrupedal mammals.  This is partially due to the fact that cats generally move their legs in the sagittal plane (thus there is no necessity for large abduction, adduction and rotation motions which are those produced by the deep hip muscles) and use their tails only for balance [1].  In this way, the muscles of the cat’s hip and tail are fairly representative of the typical mammalian condition [2] whereas some of the other mammals in the class, namely the opossum and beaver, have much more specialized tails and more elaborate hip musculature.

Dissection Technique:

The muscles that attach to the proximal end of the femur are deep to many of the thigh muscles and the abdominal viscera.  As such, some of the hip muscles (described in the thigh lab) will have to be removed from their pelvic origins, and the abdominal viscera will have to be reflected or removed.

To reflect the abdominal viscera follow the instructions in the digestive system lab (to remove the gut tube) and then sever the great vessels (the aorta and postcaval vein) just cranial to the origin of the renal vessels and reflect them- along with the kidneys and ureters caudad and to one side.  Once this is done, the psoas major and minor and quadratus lumborum muscles are visible.  The two psoas muscles join with the iliacus muscle (forming the iliopsoas m.) and act as major hip flexors and lateral rotators.

The gluteus medius muscle should be dissected away from its origin close to the spinous processes of the sacrum and from its insertion on the greater trochanter of the femur to reveal the deep hip muscles.  The other superficial muscles that attach to the proximal femur (see thigh lab) should also be reflected or removed to leave a clear view of the hip muscle insertions.

Table 1.  Deep hip muscles.  Adapted from [2 & 3].

Tail:

As noted above, the cat uses its tail mainly for balance.  The tail is heavy (to counter the shifts of the center of balance) and usually about as long as the combined head and body length[3], but not very dexterous or otherwise specialized [1].  Anatomically, the cat’s tail is fairly flexible and muscular, though these muscles are long and strap-like and span the whole length of the tail almost continuously, unlike in a prehensile tail in which the muscles are highly differentiated (see opossum dissection).

The muscles in the tail are derivations of the epaxial back muscles and are renamed (from dorso-medial to ventro-medial) sacrocaudalis dorsalis medialis, sacrocaudalis dorsalis lateralis, sacrocaudalis ventralis lateralis, sacrocaudalis ventralis medialis.  Each of these muscle bundles has a small but visible arterial supply.  Along the ventral midline of the tail runs one relatively large vein and a smaller artery on either side of it.

Discussion:

Some cats rely heavily on their tails for balance.  The cheetah (Acinonyx jubatus) for instance, has a relatively long and heavy tail.  By quickly moving it in the opposite direction it is turning in during running pursuit, the cheetah can outmaneuver its prey with sharp turns.  During such movements, its relatively tailless prey is disadvantaged.  Other cats have smaller tails for various reasons.  The lynx (Felis lynx), for instance, has a small tail, perhaps as a reflection of the fact that a) it does not sprint after its prey like a cheetah but pounces on it (negating the need for counterbalance) and lives in a particularly cold environment in which long extremities may be a hindrance.  [1]

References:

1. Turner A. 1997.  The Big Cats and Their Fossil Relatives.  New York: Columbia Univ.

2. Reighard, J. & Jennings H.S. 1935.  Anatomy of the Cat.  New York: Henry Holt and Co.

3. Walker, W. F. 1970. Vertebrate Dissection.  Philadelphia: W. B. Saunders Co.

4. Kitchener, A. 1991. The Natural History of the Wild Cats. Comstock Publishing Associates. Ithaca.