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The Digestive System

  • The mouth is a site of both mechanical and chemical digestion. The salivary glands secrete amylase, an enzyme that hydrolyzes starch into polysaccharides and disaccharides.
  • The rhythmic contractions of the esophagus, called peristalsis, move food into the stomach.
  • Gastric glands in the stomach secrete gastric juices, which contain hydrochloric acid and pepsin. Pepsin breaks proteins down into polypeptides.
  • Digestion of starches, proteins and fats takes place in the small intestine. The pancreas secretes bicarbonate and enzymes into the duodenum. Additional enzymes are produced by the epithelial cells of the small intestine.
  • The villi and microvilli of the small intestine provide a large surface area for the digestion and absorption of nutrients.
  • The liver produces bile, which is stored by the gall bladder and secreted into the duodenum. Bile emulsifies fat, facilitating the breakdown of fat by lipases.
  • The large intestine consists of the cecum, colon and rectum. Major functions of the large intestine are the absorption of water and minerals and the storage of waste.
  • Digestion is regulated by the hormones gastrin, secretin and cholecystokinin (CCK).

The Digestive System

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

AP Biology Intro