d. Diaphragm/Skirt. The diaphragm or skirt is the flat muscle that separates
the thoracic cavity from the abdominal cavity. This is the muscle which, when
contracted, allows the thoracic cavity to expand and bring air into the lungs. The skirt is
completely covered with serous membrane.
e. Kidney Knob. The kidney knob is a large glob of fat and an encased kidney;
it is located in the lumbar region of the abdominal cavity.
In addition to the terms in paragraphs 2-1 and 2-2, the following terms are
applicable to a beef hindquarter.
a. Flank Pocket. This is the internal surface of the abdominal cavity or flank, at
the posterior end is the flank pocket formed by the folding over of the flank. This is an
area of concern since it is a site of early deterioration due to the lack of air circulation.
b. Hind Shank and Gambrel Cord. On the distal end of the hindquarter we
have the hind shank. It contains both the hind shank muscles and the hind shank
bones (tibia and fibula). Also in the hind shank is the Achilles tendon or gambrel cord,
which attaches the gastrocnemius (heel) muscle to the anklebone. It is behind this
tendon that the slaughtering plant passes a metal hook, called a gambrel hook, in order
to hang the side or hindquarter from the meat rail.
c. Gracilis Muscle. On the inside of the hindquarter along the median plane,
and adjacent to the aitch bone (pubis) is the exposed, cut surface of the gracilis muscle.
Its importance will be discussed in the next section under the topics of sex
determination (paragraphs 2-4).
Section II. GRADING OF BEEF
The inspector must be able to distinguish the sex of a beef carcass because the
inspection data packet will often specify steers or heifers. If it is not specified, either is
acceptable. The military does not purchase bulls, cows, or bullocks.
a. Five Classes of Carcasses. The sex of a carcass falls within one of five
classes, depending on the maturity and apparent sex condition at the time of slaughter.
(1) Steer. A steer is a male bovine that was castrated (had his testicles
removed) prior to reaching sexual maturity (puberty) and has characteristics of youth
such as red bones, buttons, and slight ossification of the sacral vertebras. On steers,
the cod fat is rough and knobby and the gracilis muscle is somewhat triangular in
shape. The aitch bone terminates into lean at the dorsal posterior tip ("bone to lean").
The steer has a smaller neck than a stag or bull, a less pronounced pizzle eye, and
more cod fat.