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Small Intestine: Most of the digestion of food occurs in the small intestine, which is supplied with digestive enzymes from its own cells and from the pancreas. Bile from the liver and gall bladder also enters the small intestine through the bile ducts. At the junction of the large and small intestines there are two long Blind pouches, called ceca, which play a minor role in digestion. The ceca may be 4 to 6 inches (10 to 15 cm) long in adults. The large intestine in chickens is extremely short and appears to have relatively little function other than as a passage from the small intestine to the cloaca. The undigested food wastes of the intestine and the products of the kidneys and reproductive organs all pass through a common chamber, the cloaca, which opens to the outside through the vent, or anus.
As might be expect the reproductive system of the hen is highly veloped. The hen possesses two ovaries, though only the left ovary is functional. It hen producing eggs regularly, the ovary appe as a cluster of folh'cles.
Equine ascariasis is an infection by large roundworms called Parascaris equorum. These parasites are 6 to 9 inches (15-23 cm) in length and white in color. The adult life of the parasite is spent in the horse's intestine. Its eggs pass in die feces, develop on the ground, and are ingested in feed or water. The eggs hatch in the small intestine, where the larvae penetrate the intestinal Wall and enter the liver and lungs, which may be seriously damaged. Once in the lungs they travel up the windpipe (trachea) to the gullet (pharynx) and are swallowed and returned to the small intestine, where they complete their life cycle.
The tendency of specialists is to consider the rectum as only that part of the bowel below the third sacral vertebra and devoid of mesentery, and to divide it into two portions, the fixed rectum and movable rectum. The rectum is in close opposition with large pelvic vessels and nerves and a portion of the small intestine; also, in the male, with the bladder, urethra and prostate gland, and in the female, with the uterus, vagina and Douglas' cul-de-sac. Its lower portion is surrounded by the haemor-rhoidal plexus of veins.
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