Exam 3 Review:  Chapter 23:  Large Intestine Physiology

gastroileal reflex - One of the visceral reflexes involved in the regulation of digestion in which sensory signals from gastric distension as a meal is ingested stimulate increased motility = peristalsis in the ileum and relaxation of the ileocecal valve; therefore, chyme moves through the ileocecal valve into the large intestine; it is mediated by gastrin release from G cells in the stomach and possibly also supported by parasympathetic autonomic motor impulses.

haustral churning - Slow segmenting movements within the large intestine; as each haustral pouch is filled with chyme, the walls contract which assists in reabsorbing the water added to the chyme by the secretions of the digestive system, and compressing and compacting the remaining wastes into feces; after the compaction movement, the chyme/feces is slowly moved forward to the next haustral pouch; it is mediated by parasympathetic autonomic motor impulses.

mass peristalsis - Forcible peristaltic movements of short duration, occurring only three or four times a day, which move the contents of the large intestine from one division to the next, as from the ascending to the transverse colon; it is mediated by parasympathetic autonomic motor impulses; it is often stimulated by gastric filling, the gastrocolic reflex.

gastrocolic reflex - One of the visceral reflexes involved in the regulation of digestion in which sensory signals from distension of the stomach stimulate a mass peristaltic (coordinated, rhythmic, smooth muscle contraction which acts to force food through the digestive tract) movement of the colon that often occurs fifteen to thirty minutes after eating a meal; it is mediated by parasympathetic autonomic motor impulses.

feces - The excrement discharged from the intestines, consisting of bacteria, exfoliated from the intestines, secretions, chiefly of the liver and a small amount of food residue.  aka - stool

dietary fiber - The bulky residue of food, primarily cellulose, which cannot be broken down by enzymes in the small intestine of the digestive system; almost all natural fiber comes from plants; although fiber has little nutritional value, it offers other health benefits; people with a high-fiber diet experience lower rates of cancer because food passes through the body more rapidly; by adding bulk to the diet, fiber also prevents constipation, minimizes intestinal disorders, and may serve as an aid in dieting.  [Note:  The benefits of consuming foods high in fiber include lower blood levels of cholesterol and triglycerides. Foods high in fiber include legumes, green, leafy vegetables, whole fruits, and unrefined foods such as bran and sprouted seeds.] aka -  roughage

defecation reflex - One of the visceral reflexes involved in the regulation of digestion in which sensory signals from distension of the rectum as feces accumulate there (after peristalsis moves them from the sigmoid colon) stimulates the involuntary relaxation of the internal anal sphincter; if voluntary relaxation of the external anal sphincter follows, feces will be discharged; if there is no voluntary relaxation of the external anal sphincter, the feces move back to the sigmoid colon until the next peristaltic wave; it is mediated by parasympathetic autonomic motor impulses.

For some additional useful information, visit "Understanding Your Bowels."

19.  the functions of the large intestine.

          (1)  absorption of residual water and electrolytes from digestion
          (2)  absorption of any residual nutrients from food as well as the few nutrients and vitamins (B complex and K) generated by intestinal normal flora metabolism
          (3)  conversion of remnants of chyme into feces by compaction (haustral churning)
          (4)  addition of mucus to feces to lubricate feces for movement through the large intestine
          (5)  storage of feces
          (6)  expulsion of feces = defecation