Mechanical Digestion in the Small Intestine
2 types of movements: Segmentations and Migrating Motility Complexes (a type of peristalsis). Both are mainly governed by the myenteric plexus. Segmentations : localized mixing contractions that occur in portions of the intestine distended by a large volume of chyme. Segmentations mix chyme with digestive juices and bring particles of food in contact with the mucosa for absorption; they do not push contents along the tract. Essentially, the chyme sloshes back and forth. Migrating Motility Complex (MMC): begins in the lower portion of the stomach and pushes chyme forward along a short stretch of the small intestine before dying out. The MMC slowly migrates down the small intestine reaching the end of the ileum in 90-120 minutes. Another MMC then begins in the stomach. All totaled, chyme remains in the small intestine for 45 min -3 hours, depending on the diet.
Chemical Digestion in the Small Intestine
Chyme entering the small intestine contains partially digested carbohydrates, proteins and lipids. The completion of the digestion of these is a collective effort of pancreatic juice, bile, and intestinal juice in the small intestine.
The digestion of carbohydrates occurs with the following enzymes:
Amylase – breaks starch down to simple sugars α – Dextrinase, Sucrase, Lactase, Maltase (all brush-border enzymes) assist with starch breakdown Digestion of carbohydrates ends with the production of monosaccharides, which the digestive system is able to absorb. Carbohydrates exist in the equine diet in several forms: Simple sugars mono and disaccharides – found in grains, molasses, fruit, some in grasses carbohydrates polysaccharides Starch in hay and grain Fibre (branched chains of glucose units) in hay and grain.
In the horse, the main dietary components are starch and fibre (cellulose)
Digestion of Proteins occurs with the following enzymes:
Proteases such as Pepsin, enzymes of pancreatic juice and Peptidases (brush-border enzymes) break proteins into amino acids.
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