The intestines receive food from the stomach, digest nourishment and liquid from it and pass the remaining waste on for elimination from the anus. Because the intestines are, technically, in direct contact with the world outside, they are exposed to an enormous variety of challenges, from germs, parasites, poisons, undigestible foreign matter and other "insults". The most common medical condition associated with the intestines, diarrhea, is often not a medical condition itself but rather your pet's way of coping with an irritant. Diarrhea may also occur as a result of damage to the digestive system. Constipation is also often caused by damage. Both of these conditions may also be caused by conditions outside the digestive tract. The intestines are an important part of the immune system. A variety of inflammatory bowel diseases and dietary sensitivities are associated with an inappropriate response from the immune system.
Digestion In The Small Intestine
The lining of the small intestines is covered in microscopic finger-like projections called villi. This is where nutrients from food are absorbed into the blood stream. Food is broken down into its smallest components by digestive enzymes from the pancreas and liver but also with help from the 'good' bacteria in the intestines. Any condition that damages the villi, either temporarily or permanently, or upsets the natural balance of digestive bacteria, upsets digestion and usually (but not always) causes diarrhea.
The Intestines Defend The Whole Body
The small intestines form a major, indeed vital part of the immune system. Throughout the intestinal lining are special immune system cells called "Mucosa-associated lymphoid tissue" or "MALT". MALT secretes immunoglobulin (IgA) that quite literally paints the entire lining of the intestines. These defend your pet not only from harmful viruses and bacteria that enter the digestive system but also from other potential harmful antigens in food. The signs of food allergy occur when MALT mistakenly responds to a perfectly normal protein in food.
Diarrhea In General
Diarrhea is the most common manifestation of intestinal disease. It may be accompanied by vomiting, tummy rumbles, burping or passing wind. It may contain mucus or blood. It can be associated with an increased appetite or loss of appetite, normal behaviour or severe lethargy. Here are some characteristics of diarrhea and common causes.