Page 102 - Anatomy and Physiology of Farm Animals, 8th Edition

The Skeletal System / 87

Porcine Ruminant (bovine) Equine
VetBooks.ir

III+IV III
V
II
III IV

Figure 4-14. Digits. Each weight‐bearing digit comprises three phalanges. Yellow bones are metacar-
pals. Red, proximal phalanx; green, middle phalanx; blue, distal phalanx.

fetlock. The region of the digit between the the pubis. All three of these participate in
fetlock and the hoof is the pastern. the formation of the acetabulum of the
The ox, sheep, and goat have two prin- hip joint.
cipal digits, the third and fourth, whereas The ilium is the largest and most dorsal
the second and fifth digits are represented of the pelvic bones. It is irregularly triangu-
only by the small dewclaws at the back of lar, with the apex at the acetabulum and
the pastern. These do not have boney the base projecting craniodorsad. The
elements within them. In the pig, how- medial angle, the tuber sacrale, is close to
ever, the dewclaws are fully developed as the sacroiliac joint near the midline. The
digits with the normal complement of lateral angle, the tuber coxae, is known as
phalanges within each (Fig. 4‐13). When the point of the hip (often called the hook
standing on a firm substrate, the dew- bone by cattlemen). A fracture of the tuber
claws of swine do not touch the ground, coxae in the horse results in obvious asym-
but on soft surfaces (e.g., sand or mud), metry in the two points of the hips, as
they bear some weight. viewed from behind. Horsemen call this
condition a knock‐down hip.
Pelvic Limbs The broad, flat portion between the
tuber coxae and tuber sacrale is the wing of
The pelvis consists of a circle of bones by the ilium, and the dorsal margin is the iliac
which the pelvic limbs articulate with the crest. The body of the ilium projects
vertebral column. Each hemipelvis (half ventrad and caudad between the wing and
a pelvis) comprises three bones, which acetabulum and helps form the lateral wall
are fused to form the os coxae, or pelvic of the pelvic cavity.
bone (Fig. 4‐15). These two ossa cox- The ischium projects backward and
arum are firmly attached to one another ventrad from the acetabulum, forming
at the pelvic symphysis ventrally and are much of the floor of the pelvic cavity. The
joined to the sacrum of the axial skeleton ischium has a large roughened caudal
by two strong sacroiliac joints. The three prominence, the tuber ischiadicum (also
bones entering into the formation of each ischial tuber), commonly called the pin
ox coxae are the ilium, the ischium, and bone in cattle.