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Reading Notes Section 6.2 Pages 217-231 The Digestive System The organs that make up the human digestive tract are the ___________, ______________, stomach, ___________ intestine, large intestine, ___________, and anus. The accessory organs are the salivary glands, ___________, gall bladder, and _____________. PHYSICAL DIGESTION BEGINS The _____________ (physical) digestion of food begins in the mouth because you use your ___________ to chew your food. Water and mucus in saliva aid the teeth as they tear and grind food into smaller pieces, increasing the ___________ available for the __________ digestion of any __________ that has been ingested. Chemical digestion starts in the mouth, when an enzyme in saliva, called ________________, begins to break down starch into simpler sugars (________________). The __________ moves through the _____________ partly by ____________ but mainly through a wave-like series of muscular ________________ and _________________ called ________________. As _______________ continues, food is propelled through the ____________ toward the _______________, where the next stage of digestion occurs. Entry to the ______________ is controlled by a ring-like muscular structure called the ____________________. Relaxation of the ______________________ allows the bolusto pass into the ________________. ________________ of this sphincter usually prevents the _______________ contents of the ________________ from backing up into the esophagus. STORING, DIGESTING AND PUSHING FOOD: THE STOMACH Both _________________ and _________________ digestion occur in the stomach. Waves of __________________ push food against the bottom of the stomach, churning it backward, breaking it into ____________ pieces, and mixing it with ____________ to produce a thick liquid called _____________. Once active, ____________ hydrolyzes proteins to yield ________________—a first step in protein digestion in the digestive tract. Very few substances are absorbed from the chyme in the stomach because most substances in the chyme have not yet been broken down _________________. The stomach does absorb some ____________ and salts, however, as well as certain anti-inflammatory medications, such as ____________, and ________________. In the ___________________, bands of circular _______________ briefly contract forming closed _______________. This process is called _____________. __________ is sloshed back and forth within the segment, causing _______________ digestion and mixing the nutrient ________________ with digestive ______________. Such movement increases contact between nutrients and the intestinal wall which enhances nutrient ______________. Peristalsis also occurs, mixing food and enzymes and pushing it on toward the _____________ intestine. DIGESTING AND ABSORBING NUTRIENTS: THE SMALL INTESTINE The ridges in the inner lining of the small intestine are covered in tiny projections called _____________, which, in turn, are covered in microvilli. Together, the ridges, ____________, and ____________ vastly increase the absorptive _______________of the small intestine. The _______________, _____________, and gall bladder produce and/or store secretions necessary for digestion of macromolecules. _______________: The pancreas delivers about 1 L of pancreatic fluid to the _________________ each day. Pancreatic fluid contains a multitude of ____________, including: ■ trypsin and ______________, which are proteases that digest ______________; ■ pancreatic ______________, which is a ________________ that digests _______________ in the small intestine; and ■ ________________, which digests fat. Liver: The liver is the _______________ internal organ of the human body. The main digestion-related secretion of the liver is ___________, a greenish-yellow fluid mixture that is made up of ________________ and bile _____________. Bile salts assist ____________ in accessing fats because they are partly soluble in ___________ and partly soluble in _____________. Bile salts work like a ______________, dispersing large fat droplets into a fine __________________ of ______________ droplets in the chyme. This ___________________ process produces a _________________ surface area of fats on which the ________________ can act. _______________: After bile is produced in the liver, it is stored in the ___________. The arrival of ___________, with a high __________ concentration, in the duodenum stimulates the _____________ to contract. This causes bile to be transported through a __________ (shared by both the gall bladder and the liver) and injected into the ___________. Most of the digestion of __________________ does not take place until the chyme enters the small intestine, where the pH is about ____________. In the ________________, pancreatic amylase completes the digestion of starch into ________________-. Other carbohydrases hydrolyze the disaccharides into ___________________, such as glucose and ________________. _________________ are absorbed by active transport into the cells of the intestinal _____________. The _________________ of glucose and other monosaccharides requires ______, which is produced in the _____________ of cells. From the cells of the intestinal lining, the _______________ enter the bloodstream and are transported directly to the ____________. The arrival of ___________ (fats) in the duodenum stimulates the secretion of __________, which ____________ the fat droplets. The breakdown of fats by hydrolysis is carried out by ___________ secreted in the duodenum. The resulting ________________ and _____________ are absorbed into the cells of the villi by simple ________________. In the small intestine, _____________ are digested by enzymes, called nucleases, to yield ________________. The nucleotides are hydrolyzed to their constituent _____, ______________, ______________. These molecules are then ____________, like glucose and amino acids, into the bloodstream by active transport. ______________, produced by the lower part of the stomach, enters the bloodstream and stimulates the upper part of the stomach to produce more gastric juice. Secretin and CCK, produced by the duodenal wall, stimulate the ______________ to secrete its digestive juice and the gall bladder to release ___________.