Page 97 - Anatomy and Physiology of Farm Animals, 8th Edition

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(A) (B)
VetBooks.ir

Wings

Pelvic sacral
foramina

Figure 4-10. Ventral view of the sacrum. Cranial is toward the top. (A) Bovine. (B) Equine.

ventral rows of sacral foramina on dor- Table 4-4. Rib and sternebra numbers
sal and ventral (or pelvic) sides of the
sacrum. These foramina, as with other Species True Ribs False Ribs Sternebrae
intervertebral foramina, give passage to Horse 8 10 7
spinal nerves. Ruminant 8 5 7
Caudal vertebrae form the bony basis Pig 7 7‐8 6
for the tail. Depending on the length of the
tail, the number varies considerably from
species to species and even within the same The ribs form the lateral walls of the
species. Size of the vertebrae decreases bony thorax. Usually, the number of pairs
rapidly in a caudal direction, until the last of ribs is the same as the number of thoracic
few caudal vertebrae are merely small rods vertebrae. Rarely, an extra rib or pair of ribs
of bone. As animals lack the curved, fused lies either cranial or caudal to the thoracic
coccyx of human beings, the human vertebrae. The dorsal extremity of a typical
anatomical term coccygeal to describe the rib consists of a rounded head which artic-
vertebrae of the tail is discouraged. ulates with two adjacent vertebral bodies
and a tubercle which articulates with the
transverse process of the vertebra. The
Sternum and Ribs body of the rib is flattened in cross‐section
and more‐or‐less curved (depending on
The sternum forms the ventrum of the the region of the thoracic wall from which
bony thorax and gives attachment to the it came) as it approaches its sternal extrem-
costal cartilages of the ribs as well as pro- ity. At this end, the bone of the rib attaches
viding a bony origin for the pectoral mus- to a costal cartilage through which it is
cles (Table 4-4). The cranial extremity of attached to the sternum. Both costoverte-
the sternum is the manubrium; the middle bral articulations and the costosternal
portion is the body; and the caudal extrem- joints are all synovial in nature.
ity is the xiphoid process, which is either The sternal extremities of the more
in part or wholly cartilaginous. The ster- cranial ribs are connected directly to the
num initially consists of individual bones sternum by the costal hyaline cartilage;
called sternebrae that may fuse as the indi- ribs so attached are called sternal (true)
vidual ages. ribs. More caudally, the costal cartilages