Page 519 - Anatomy and Physiology of Farm Animals, 8th Edition

504 / Anatomy and Physiology of Farm Animals

There may also be diverticula (pockets) in Pelvic brim
the wall of the gland cistern.
VetBooks.ir The teat cistern is continuous with the

exterior of the teat through a narrow open-
Lateral Medial
ing in the end of the teat, the papillary suspensory suspensory
duct (commonly called streak canal or lamina lamina
teat canal), which opens at the ostium
papillae. The bovine streak canal is about
8.5 mm long, and its lumen is normally
closed by epithelial folds that project
inward from the wall of the streak canal,
leaving only a star‐shaped potential open-
ing. A sphincter of smooth muscle fibers
surrounds the streak canal at the distal end
of the teat.

Suspensory Apparatus

The udder of a lactating dairy cow can
weigh as much as 60 kg (132 lb), so the
organ is supported by a dense system of
fibroelastic ligaments called the suspen-
sory apparatus. The primary supportive
elements of the suspensory apparatus are
its two medial laminae, which take their
origin together from the midline linea alba
of the abdominal wall and the symphysis of Figure 29-2. Suspensory apparatus of the cow.
the pelvis (Fig. 29‐2). Each medial lamina Udder is shown in transverse section through
passes ventrad between the two halves of hindquarters.
the udder so that one layer intimately cov-
ers the medial side of each half. The two wall near the external inguinal ring and
medial laminae can be readily separated, as more caudally from the regions of the pelvic
they are united only by a small amount of symphysis and prepubic tendon (the tendon
loose areolar connective tissue; practically of insertion of the m. rectus abdominis).
no vessels or nerves pass through the From its origins, the lateral lamina passes
medial ligament from one half of the udder ventrad and around the lateral side of each
to the other. Proximally (close to the body half of the mammary gland, meeting the
wall), the laminae are thickest. As they medial lamina at the cranial and caudal
descend, they give off sheets of connective aspects of each half. Like the medial lamina,
tissue that diverge from the midline and the lateral lamina is thick close to the body
interdigitate into the parenchyma of the wall and thins progressively ventrally as it
udder so that the two medial laminae are gives off sheets of connective tissue into the
thinnest near the intermammary groove. substance of the gland.
The lateral laminae of the suspensory
apparatus are composed largely of dense
white fibrous connective tissue, making Blood Supply
them less elastic than the medial laminae,
which are mostly elastic connective tissue. The blood supply to the udder is primarily
The cranial part of the lateral lamina derives through the external pudendal artery
from the aponeurotic tissues of the body (Fig. 29‐3), a branch of the pudendoepigastric