Page 549 - Anatomy and Physiology of Farm Animals, 8th Edition

534 / Anatomy and Physiology of Farm Animals

Plasma uric acid levels can be used, but for ovulation. Just prior to “coming into lay,”
the ovary will resemble a bunch of grapes.
VetBooks.ir these levels can increase normally after equivalent to the yolk of the egg; it will
The mature ovum is more‐or‐less
a meal and because most uric acid enters
tubular fluid by secretion, significant
renal tubular dysfunction must occur be released at ovulation and received into
before plasma uric acid increases. the expanded terminus of the oviduct,
Within renal tubules of avian kidneys, the infundibulum (Fig. 30‐11). It is in the
unique, extremely small (3 to 13 µm), infundibulum that fertilization will take
spherical concretions or particles form, place if the bird was allowed to breed. The
and these contain uric acid, albumin, and oviduct is variable in size, being maximally
inorganic ions. The accumulation of multi- expanded and lengthened during the lay
ple osmotic particles into a single particle (60 to 70 cm long in the hen) and regress-
effectively reduces the osmolality of the ing in size during nonlaying periods such
tubular fluid and permits additional water as broodiness and the molt. The oviduct
reabsorption. Albumin is readily available possesses grossly identifiable sections (the
in the tubular fluid of birds for it contains magnum, isthmus, uterus, and vagina) that
significantly more plasma protein than in correlate with the important tasks of
mammals. producing the albumen (the “white” of
As discussed earlier, urine may be the egg) and the laying down of the egg
moved from the urodeum by reverse
peristalsis to the ceca, and additional
absorption of water and electrolytes Oocytes
may occur in the coprodeum, rectum,
and ceca. In dehydrated birds, 15% of
urine water can be reabsorbed by the
colon. Stress‐induced defecation will Envelops Infundibulum
reduce this reabsorption, resulting in oocyte
very moist excrement. Uric acid in the
urine entering the cloaca may precipitate
on feces, and these are seen as a white
pasty part of the droppings. Secretes
albumen Magnum
Female Reproductive System

The production of eggs for human con- Secretes
sumption is a primary reason for keeping shell membrane Isthmus
poultry worldwide. Among female birds,
both right and left ovaries and oviducts are Secretes hard Uterus
present embryologically, but in chickens, shell; adds cuticle
turkeys, and domestic geese the right Nothing added;
organs regress early in development and sperm storage Vagina
only the left side develops (both sides per-
sist and develop in ducks). The ovaries are Cloaca
located cranioventral to the corresponding
kidney, and the size varies with the repro- Vent
ductive status of the bird. Prior to the onset
of the first laying period, the small ovary is Figure 30-11. Simplified version of the female
smooth; as puberty is approached, it begins avian genitourinary tract. Source: adapted from
to develop a granular, then cobblestone Reece, 2009. Reproduced with permission of John
appearance as follicles enlarge in preparation Wiley & Sons, Inc.