Sci/241 Digestive System

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Digestive System

Joseph Cascio

The digestive process begins as soon as food is seen and smelled; when food enters the mouth saliva begins to immediately break down sugars and starches, while the teeth grind the food into what is called a bolus. The bolus then enters the esophagus and is swallowed, where it enters the stomach for further breakdown from stomach acids. Very little of the food is actually digested in the stomach. Instead, the acids work to break down the food for easier digestion in the intestines, while the stomach contracts and relaxes to increase the amount of food the acids that come in contact with. As the food is broken down to a thick paste-like substance known as chyme, it moves past the pyloric sphincter which protects food from re-entering the stomach, and into the small intestine. The first section of the small intestine, the duodenum, secretes digestive enzymes like amylase, maltase, sucrase, lactase, lipase and pepsin, to break down the chyme into even smaller parts that the body can then convert into usable energy. Several other organs secrete chemicals to aid in the digestion process as well. The pancreas secretes trypsin and chymotripsin. The liver and gall bladder secrete bile, used for the emulsification of fats. The second section of the small intestine, the jejunum, is where the majority of food is absorbed into the bloodstream. The last section of the small intestine, the ileum, is where the remainder of nutrients is absorbed. What is not absorbed by the small intestine passes into the large intestine, which includes the colon and rectum. Here, peristalsis (the contractions of the muscles around the stomach and intestines that assist in moving food through the system) slows, allowing the growth of bacteria, which aids in the digestion of fiber and the absorption of some vitamins. The colon absorbs water, vitamins and minerals not absorbed by the small intestine. Anything that has not been absorbed by this point is...
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