Unformatted text preview: PowerLecture: Chapter 41 Hominids, Hips, and Hunger Section 41.0: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Videos: CNN Ask your Thomson Sales Representative for these volumes on CD or VHS Genetics, 2003, Vol. 1, Fat Hormone (2:33) A&P, 2004, Vol. 8, Teen Obesity Surgery (2:00) Impacts, Issues: Hominids, Hips, and Hunger Adipose cells are fat-storing cells, an adaptation that helped our ancestors survive times of food scarcity Adipose cells produce leptin, a hormone which acts on the brain to control hunger Impacts, Issues: Hominids, Hips, and Hunger Americans are among the fattest people in the world 60% of adults are overweight Obesity is overabundance of fat in adipose tissue Obese people do not have less leptin than normal, but leptin receptors may not work properly Gastric bypass – surgery to close off part of stomach and most of small intestine Impacts, Issues: Hominids, Hips, and Hunger Cholecystokinin may promote appetite suppression Elderly tend to have low appetites that sometimes endanger health New drugs that block cholecystokinin may help elderly stay nourished Impacts, Issues Video Section 41.1: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Fighting Fat Fat-storing cells are an adaptation for survival in lean times Once formed, fat cells are forever Dieting decreases amount of fat in cells Dieting triggers metabolic slowdown Eating Disorders Anorexia nervosa Potentially fatal eating disorder based on a flawed assessment of body weight Bulimia Out-of-control “oxlike” appetite Binge-purge can damage teeth, gut lining Digestive System Tasks Break up, mix, and move food material Secrete enzymes into tube where digestion occurs Digest (break down) food particles into smaller molecules Absorb nutrients and fluids Eliminate wastes and residues Two Types of Systems Incomplete digestive system One-way, saclike digestive cavity Complete digestive system A tube with an opening at each end Two Types of Systems Examples of digestive systems Digestive Specialization Digestive system is often subdivided into functional regions Specialization reflects feeding behavior Specialized Teeth Structure of teeth reflects feeding behavior Antelope brush teeth against dirt as they eat; wear down crowns Antelope Stomach Multiple chambers allow rechewing and breakdown of cellulose Antelope Stomach Antelope stomach function Human Digestive System A complete system with many specialized organs About 6.5 to 9 meters long if extended Lined with mucus-secreting epithelium Movement is one way, from mouth to anus Section 41.2: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Videos: CNN Ask your Thomson Sales Representative for these volumes on CD or VHS Anatomy and Physiology, 2002, Vol. 6, Video Pill (1:32) Major Components Mouth (oral cavity) Pharynx (throat) Esophagus Gut Stomach Small intestine Large intestine Rectum Anus Human digestive system Accessory Organs Salivary glands Secrete saliva Liver Secretes bile Gallbladder Stores and concentrates bile Pancreas Secretes digestive enzymes Section 41.3: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Human Teeth Normal adult number is 32 Human teeth Saliva Produced by salivary glands at back of mouth and under tongue Saliva includes Salivary amylase (enzyme) Bicarbonate (buffer) Mucins (bind food into bolus) Water Swallowing Complex reflex Tongue forces food into pharynx Epiglottis and vocal cords close off trachea; breathing temporarily ceases Bolus moves into esophagus, then through esophageal sphincter into stomach Section 41.4: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Structure of the Stomach J-shaped organ lies below the diaphragm Sphincters at both ends Outer serosa covers smooth muscle layers Inner layer of glandular epithelium faces lumen Digestive Enzymes Stomach Secretions Secreted into lumen (gastric fluid) Hydrochloric acid (HCl) Mucus (protective) Pepsinogen (inactive form of a protein-digesting enzyme) Stomach cells also secrete the hormone gastrin into the bloodstream Mixing Chyme A thick mixture of food and gastric fluid High acidity kills many pathogens Mixed and moved by waves of stomach contractions (peristalsis) Peristalsis Protein Digestion in Stomach High acidity of gastric fluid denatures proteins and exposes peptide bonds Pepsinogen secreted by stomach lining is activated to pepsin by HCl Pepsin breaks proteins into fragments Ulcer An erosion of the wall of the stomach or small intestine Can result from undersecretion of mucus and buffers, or oversecretion of pepsin Most ulcers involve Helicobacter pylori bacteria and can be treated with antibiotics Into the Small Intestine Movement into duodenum controlled by pyloric sphincter Only a small amount of chyme passes through sphincter at a given time Fat content of chyme affects the rate of stomach emptying Intestinal Secretions Wall of the duodenum secretes Disaccharidases - digest disaccharides to monosaccharides Peptidases - break protein fragments down to amino acids Nucleases - digest nucleotides down to nucleic acids and monosaccharides Pancreatic Enzymes Secreted into duodenum Pancreatic amylase Trypsin and chymotrypsin Carboxypeptidase Lipase Pancreatic nucleases Fat Digestion Liver produces bile Bile is stored in gallbladder, then secreted into duodenum Bile emulsifies fats; breaks them into small droplets This gives enzymes a greater surface area to work on Hormones and Digestion Gastrin Secretin Cholecystokinin (CCK) GIP (glucose insulinotropic peptide) Section 41.5: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Walls of Small Intestine Projections into the intestinal lumen increase the surface area available for absorption Structure of the small intestine Absorption of Nutrients Passage of molecules into internal environment Occurs mainly in jejunum and ileum of small intestine Segmentation mixes the lumen contents against wall and enhances absorption Absorption Mechanisms Monosaccharides & amino acids are actively transported across plasma membrane of epithelial cells, then from cell into internal environment Fat Absorption Digestion and Absorption Absorption Into the Blood Glucose and amino acids enter blood vessels directly Triglycerides enter lymph vessels, which eventually drain into blood vessels Section 41.6: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Videos: CNN Ask your Thomson Sales Representative for these volumes on CD or VHS Biology, 2001, Vol. 5, Screening for Colon Cancer (1:54) Large Intestine (Colon) Concentrates and stores feces Sodium ions are actively transported out of lumen and water follows Lining secretes mucus and bicarbonate Structure of the large intestine Bacteria in Colon Slow movement of material through colon allows growth of bacteria Harmless--unless they escape into abdominal cavity Some produce vitamin K, which is absorbed through intestinal wall Movement through Colon During a meal, gastrin and autonomic signals trigger contraction of ascending and transverse colon Material moves along to make room for incoming food Feces is stored in last part of colon Defecation Distension of the last part of the colon triggers a reflex action Smooth muscle of anal sphincter relaxes Voluntary contraction of external sphincter can prevent defecation Colon Malfunction Appendicitis Constipation Colon cancer Symptoms include blood in feces Can be caused by a genetic defect Low-fiber diet is a predisposing factor Section 41.7: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Pathways of Organic Metabolism Section 41.8: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Videos: CNN Ask your Thomson Sales Representative for these volumes on CD or VHS Biology, 2004, Vol. 8, Fat Facts (2:29) Genetics, 2004, Vol. 2, Gene Therapy for Diabetes (2:16) Food Pyramid Carbohydrates Body’s main energy source Foods high in complex carbohydrates are usually high in fiber; promote colon health Simple sugars lack fiber as well as minerals and vitamins of whole foods; intake should be minimized Lipids Most fats can be synthesized Essential fatty acids must be obtained from food Fats should be about 30 percent of diet Excess saturated fats can raise cholesterol level and contribute to heart disease Proteins Body cannot build eight of the twenty amino acids These essential amino acids must be obtained from diet Animal proteins are complete; supply all essential amino acids Plant proteins are incomplete; must be combined Dietary Essentials Vitamins Essential organic substances Minerals Essential inorganic substances Food Pyramid Section 41.9: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Vitamins Fat soluble Excess accumulates in tissue Vitamins A, D, E, K Vitamins Major Minerals Calcium Chloride Copper Fluorine Iodine Sulfur Iron Magnesium Phosphorus Potassium Sodium Zinc Section 41.10: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Videos: CNN Ask your Thomson Sales Representative for these volumes on CD or VHS Anatomy and Physiology, 2003, Vol. 7, Obesity and Infertility (2:16) Obesity Increasing numbers of Americans are obese Obesity-related conditions Type 2 diabetes Breast cancer Heart disease Colon cancer Hypertension Gout Gallstones Osteoarthritis Body-Mass Index An indicator of obesity-related health index BMI = Weight (lbs) X 700 ----------------------------Height (inches)2 BMI greater than or equal to 27 indicates health risk Body mass index Caloric requirements Maintaining Weight Caloric input must equal caloric use Calories burned depends upon Activity level Age Height and build Leptin Hormone that affects appetite and metabolic rate Product of the Ob gene Faulty Ob gene may contribute to some human obesity Effects of leptin on bone may complicate use of leptin to treat obesity Chronology of leptin research Ghrelin Newly discovered peptide hormone Secreted mainly by cells of the stomach lining Directly stimulates the appetite control center Makes you feel hungry ...
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