Chapter 10 | Nutrition and the Digestive System

  1. Figure 10.11 Which of the following statements about the digestive system is false?
    1. Chyme is a mixture of food and digestive juices that is produced in the stomach.
    2. Food enters the large intestine before the small intestine.
    3. In the small intestine, chyme mixes with bile, which emulsifies fats.
    4. The stomach is separated from the small intestine by the pyloric sphincter.
      Illustration shows the human lower digestive system, which begins with the stomach, a sac that lies above the large intestine. The stomach empties into the small intestine, which is a long, highly folded tube. The beginning of the small intestine is called the duodenum, the long middle part is called the jejunum, and the end is called the ileum. The ileum empties into the large intestine on the right side of the body. Beneath the junction of the small and large intestine is a small pouch called the cecum. The appendix is at the bottom end of the cecum. The large intestine travels up the left side of the body, across the top of the small intestine, then down the right side of the body. These parts of the large intestine are called the ascending colon, the transverse colon and the descending colon, respectively. The large intestine empties into the rectum, which is connected to the anus. The pancreas is sandwiched between the stomach and large intestine. The liver is a triangular organ that sits above and slightly to the right of the stomach. The gallbladder is a small bulb between the liver and stomach.
      Figure 10.11 The human stomach has an extremely acidic environment where most of the protein gets digested. (credit: modification of work by Mariana Ruiz Villareal)
  2. Figure 10.12 Which of the following statements about the small intestine is false?
    1. Absorptive cells that line the small intestine have microvilli, small projections that increase surface area and aid in the absorption of food.
    2. The inside of the small intestine has many folds, called villi.
    3. Microvilli are lined with blood vessels as well as lymphatic vessels.
    4. The inside of the small intestine is called the lumen.
      Illustration shows a cross section of the small intestine, the lumen, or inside of which has many fingerlike projections called villi. Muscle layers wrap around the outside of the intestine, and blood vessels interact with the muscle layer. A blowup shows that capillaries and lymphatic vessels travel up inside the villi. The surface of each villus is covered with hairline microvilli.
      Figure 10.12 Villi are folds on the small intestine lining that increase the surface area to facilitate the absorption of nutrients.
  3. Figure 10.19 Which of the following statements about digestive processes is true?
    1. Amylase, maltase and lactase in the mouth digest carbohydrates.
    2. Trypsin and lipase in the stomach digest protein.
    3. Bile emulsifies lipids in the small intestine.
    4. No food is absorbed until the small intestine.
      Steps in mechanical and chemical digestion are shown. Digestion begins in the mouth, where chewing and swallowing mechanically breaks down food into smaller particles, and enzymes chemically digest carbohydrates. In the stomach, mechanical digestion includes peristaltic mixing and propulsion. Chemical digestion of proteins occurs, and lipid-soluble substances such as aspirin are absorbed. In the small intestine, mechanical digestion occurs through mixing and propulsion, primarily by segmentation. Chemical digestion of carbohydrates, lipids, proteins and nucleic acid occurs. Peptides, amino acids, glucose, fructose, lipids, water, vitamins, and minerals are absorbed into the bloodstream. In the large intestine, mechanical digestion occurs through segmental mixing and mass movement. No chemical digestion occurs except for digestion by bacteria. Water, ions, vitamins, minerals, and small organic molecules produced by bacteria are absorbed into the bloodstream.
      Figure 10.19 Mechanical and chemical digestion of food takes place in many steps, beginning in the mouth and ending in the rectum.

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