The fat is absorbed by the lacteal into the. The carbohydrates and proteins in the chyme enter the bloodstream passively via the vein and artery. When that slurry passes into the small intestine, it comes into contact with the villi. Absorption of these minerals from the hind-gut is negligible. The small intestine finishes the process of digestion, absorbs the nutrients, and passes the residue on to the large intestine. When food is broken down in the stomach, it forms a substance called chyme, which is a slurry of nutrients. Absorption is controlled homeostatically, and vitamin D takes part in the regulation of both calcium and phosphorus absorption. Bile contains bile salts, lecithin, and substances derived from cholesterol so it acts as an emulsifier. The ileum function involves absorption of vitamin B12, bile salts and all digestion products which were not. As stomach contents enter the small intestine, the digestive system sets out to manage a small hurdle, namely, to combine the separated fats with its own watery fluids. Both minerals are secreted into the digestive tract by saliva and gastric and intestinal juices. The jejunum also functions to absorb most fats. Potassium is absorbed in the small intestine (65-70%) and may be absorbed or secreted in the hind-gut depending on mineral status.Ĭalcium is absorbed in the first part of the small intestine where the gut contents are acidic, while phosphorus is absorbed in the middle and terminal parts of the small intestine. It is the kidneys, and not the gut, which regulate the body stores of minerals such as sodium, potassium and chloride. When the dietary supply of salt is marginal compared to requirements, the horse can absorb as much as 99% of these minerals from the faeces. Sodium and chloride absorption in caecum and colon provided the osmotic potential to facilitate water resorption - osmosis. The highest loss of water with faeces occurs on roughage diets. In the large intestine 70-90% of secreted water is re-absorbed, depending upon the rate of passage of the intestinal digesta and the water-binding capacity of the undigested parts of the feed. The ingestion of 1 kg of dry matter as hay or straw requires the secretion of 12-14 litres of water while 1 kg of concentrate requires only 7 litres.įlows of liquid and electrolytes in the gut of the horse:ĭaily flow of liquid and electrolytes from the small to the large inte stine: The amount of water secreted into the gastrointestinal tract is 15-20 litres per 100 kg of body weight per day (Table 9).This fluid contains high concentrations of sodium and chloride, but efficient absorption mechanisms in the small and large intestines effectively re-absorb both water and minerals back to the blood. But the somatic nervous system also plays a role to control the timing of elimination.Large amounts of water and electrolytes are exchanged daily between the contents of the gastrointestinal tract and the blood. ![]() The defecation reflex is mostly involuntary, under the command of the autonomic nervous system. This process, called defecation, involves contraction of rectal muscles, relaxation of the internal anal sphincter, and an initial contraction of the skeletal muscle of the external anal sphincter. The body expels waste products from digestion through the rectum and anus. ![]() Defecation Eliminates Waste From the Body The large intestine temporarily stores the feces prior to elimination. ![]() Most absorption of water and electrolytes occurs in the small intestine, with some water absorbed in the colon as well. It continues to move through the descending and sigmoid colons. The average adult usually ingests 1-2 L of water each day, but the fluid load to the small intestine is 9 to 10 L, 8 to 9 L being added by secretions of the GI system. This dehydration, combined with peristaltic waves, helps compact the chyme. Any remaining nutrients and some water are absorbed as peristaltic waves move the chyme into the ascending and transverse colons. The Large Intestine Completes Absorption and Compacts WasteĬhyme passes from the small intestine through the ileocecal valve and into the cecum of the large intestine. Other absorbed nutrients enter the bloodstream through the capillary beds and are taken directly to the liver, via the hepatic vein, for processing. Fatty acids absorbed from broken-down chyme pass into the lacteals. The large intestine absorbs water, salt, and other waste material from the digestive product and solidifies the waste into stool, which passes into the rectum. Villi contain capillary beds, as well as lymphatic vessels called lacteals. Villi that line the walls of the small intestine absorb nutrients into capillaries of the circulatory system and lacteals of the lymphatic system. Villi That Line the Walls of the Small Intestine Absorb Nutrients The small intestine (or small bowel) is a 20-25 foot long, specialized tube (between the stomach and colon) that absorbs nutrients, salt and water from.
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