Chapter 51

Summary		Questions		Media Resources
51.1 Animals employ a digestive system to prepare food for assimilation by cells.
• The digestive system of vertebrates consists of a gastrointestinal tract and accessory digestive organs. • Different regions of the digestive tract display specializations of structure and function.		1.  What are the layers that make up the wall of the vertebrate gastrointestinal tract? What type of tissue is found in each layer?		•Digestive Tract Wall •Introduction to Digestion •Human Digestion •Specialization of Digestive Tract
51.2 Food is ingested, swallowed, and transported to the stomach.
• The teeth of carnivores are different from those of herbivores • The esophagus contracts in peristaltic waves to drive the swallowed food to the stomach. • Cells of the gastric mucosa secrete hydrochloric acid, which activates pepsin, an enzyme that promotes the partial hydrolysis of ingested proteins.		2. How does tooth structure vary among carnivores, herbivores, and omnivores? 3. What normally prevents regurgitation in humans, and why can't horses regurgitate? 4. What inorganic substance is secreted by parietal cells?		•Digestive System •Teeth •Mouth •Swallowing •Glottis Function •Digestion •Mouth to Stomach •Stomach •Stomach Digestion •Ulcers •Mouth and Esophagus •Stomach *Activities: - Digestion - Stomach •Digestion in Birds •Stomach and Duodenum •Stomach Mucosa-Gastric Glands
51.3 The small and large intestines have very different functions.
• The duodenum receives pancreatic juice and bile, which help digest the chyme that arrives from the stomach through the pyloric sphincter. • Digestive enzymes in the small intestine finish the breakdown of food into molecules that can be absorbed by the small intestine. • The large intestine absorbs water and ions, as well as certain organic molecules such as vitamin K; the remaining material passes out of the anus.		5. How are the products of protein and carbohydrate digestion absorbed across the intestinal wall, and where do they go after they are absorbed? 6. What anatomical and behavioral specializations do ruminants have for making use of microorganisms?		•Small Intestine Anatomy •Hepatic Lobules •Stomach to Small Intestine •Small Intestine Digestion •Small Intestines •Large Intestines •Protein and Carbohydrate Absorption •Absorption of Fats •Stomach of Ruminants •Digestive System Variations (1) •Digestive System Variations (2)
51.4 Accessory organs, neural stimulation, and endocrine secretions assist in digestion.
• Pancreatic juice contains bicarbonate to neutralize the acid chyme from the stomach. Bile contains bile pigment and bile salts, which emulsify fat. The liver metabolizes toxins and hormones that are delivered to it in the hepatic portal vein; the liver also helps to regulate the blood glucose concentration. • The stomach secretes the hormone gastrin, and the small intestine secretes various hormones that help to regulate the digestive system.		7. What are the main exocrine secretions of the pancreas, and what are their functions? 8. What is the function of bile salts in digestion? 9. Describe the role of gastrin and secretin in digestion.		•Digestive System A •Digestive System B •Formation of Gallstones •Accessory Organs •Enzymes and Hormones •Liver and Pancreas •Activity: Intestines • Actions of Insulin and Glucagon •Hormonal Control of Digestion
51.5 All animals require food energy and essential nutrients.
• The basal metabolic rate (BMR) is the lowest level of energy consumption of the body. • Vitamins, minerals, and the essential amino acids and fatty acids must be supplied in the diet.		10.  What is a vitamin? What is the difference between an essential amino acid and any other amino acid?		•Nutrition • Bulimia •Weight Loss Drug •Impossible Dreams: Fad Diets •Why Fat People are Hungrier •Thanksgiving Day Pounds •Diabetes-Obesity Link

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