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31 Lecture Ppt

  1. 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 31 Digestive Systems and Nutrition
  2. 2. Animals Must Obtain and Process Their Food 31-
  3. 3. 31.1 A digestive system carries out ingestion, digestion, absorption, and elimination <ul><li>Digestion contributes to homeostasis by providing body’s cells with nutrients they need to continue living </li></ul><ul><li>Ingestion - act of taking in food during the process of feeding </li></ul><ul><li>Digestion </li></ul><ul><ul><li>Mechanical digestion can be accomplished by chewing in with mouthparts such as teeth </li></ul></ul><ul><ul><li>Chemical digestion requires enzymes secreted by the digestive tract or by glands </li></ul></ul><ul><li>Absorption - occurs when nutrients are taken into the body, often into the bloodstream </li></ul><ul><li>Elimination (defecation) - removal of waste products that pass through the anus </li></ul>31-
  4. 4. Figure 31.1A The four phases of digestion 31-
  5. 5. Figure 31.1B Chemical digestion 31-
  6. 6. 31.2 Animals exhibit a variety of feeding strategies <ul><li>Bulk feeders bite off chunks of food, or take in a whole organism, in one feeding </li></ul><ul><ul><li>Humans are bulk feeders that use utensils </li></ul></ul><ul><ul><li>Tend to eat discontinuously - they have discrete periods of eating and not eating </li></ul></ul><ul><li>Filter feeders (suspension feeders) sift small food particles from the water </li></ul><ul><ul><li>Baleen whales are filter feeders that eat tons of small, shrimplike animals called krill </li></ul></ul><ul><li>Fluid feeders include parasites that live in body fluid of a host, and external parasites, which tap into host’s vascular system </li></ul><ul><ul><li>A vampire bat has fangs (pointed incisors) for piercing the skin of its host in order to get at its blood </li></ul></ul><ul><li>Substrate feeders live on, or in, the material they eat </li></ul><ul><ul><li>Caterpillars live and feed on leaves </li></ul></ul>31-
  7. 7. Figure 31.2A A great blue heron, a bulk feeder 31-
  8. 8. Figure 31.2B Baleen whale, a filer feeder 31-
  9. 9. Figure 31.2C Vampire bat, a fluid feeder <ul><li>Figure 31.2D Caterpillar, </li></ul><ul><li>a substrate feeder </li></ul>31-
  10. 10. 31.3 A complete digestive tract has specialized compartments <ul><li>Incomplete Digestive Tract </li></ul><ul><ul><li>Begins at mouth and pharynx </li></ul></ul><ul><ul><li>Gastrovascular cavity branches through body </li></ul></ul><ul><ul><li>Saclike because pharynx serves as an entrance and exit for food </li></ul></ul><ul><li>Complete Digestive Tract in an Earthworm </li></ul><ul><ul><li>Muscular pharynx draws in food with a sucking action </li></ul></ul><ul><ul><li>Food enters crop, storage area with expansive walls </li></ul></ul><ul><ul><li>Food goes to gizzard to crush food with pebbles </li></ul></ul><ul><ul><li>Typhlosole an intestinal fold for increased absorption </li></ul></ul><ul><li>Complete Digestive Tract in Birds </li></ul><ul><ul><li>Some birds are discontinuous bulk feeders, and have a crop which serves as a storage area so they can ‘eat and run’ </li></ul></ul><ul><ul><li>Attached to the large intestine are two long ceca ( cecum sing.), a blind sac that helps with digestion of cellulose </li></ul></ul><ul><ul><li>Elimination occurs at cloaca , which receives indigestible material and urine from the bladder and gametes from the testes or ovaries </li></ul></ul>31-
  11. 11. Figure 31.3A Incomplete digestive tract of a planarian 31-
  12. 12. Figure 31.3B Complete digestive tract of an earthworm 31-
  13. 13. Figure 31.3C Complete digestive tract of a bird 31-
  14. 14. Complete Digestive Tract in Mammalian Herbivores <ul><li>Modified to provide a special compartment for microbes that can digest cellulose </li></ul><ul><ul><li>Ruminants, such as cows, sheep, and giraffes, have large divided stomachs with four chambers, one of which is the rumen </li></ul></ul><ul><ul><ul><li>Rumen is a large fermentation chamber that contains microbes and up to 50 gallons of undigested plant material </li></ul></ul></ul><ul><ul><li>Mammalian herbivores, such as rabbits and hares, are not ruminants and instead use a single, large cecum at the start of the large intestine </li></ul></ul><ul><ul><ul><li>Contains microorganisms that digest cellulose </li></ul></ul></ul><ul><li>Carnivores (foxes, dogs, cats, lions, and tigers) have a much shorter digestive tract than herbivores because their food is much easier to digest </li></ul>31-
  15. 15. Figure 31.3D A ruminant’s stomach 31-
  16. 16. Figure 31.3E Digestive tract of a carnivore compared to a ruminant herbivore 31-
  17. 17. 31.4 Both mechanical and chemical digestion occur in the mouth <ul><li>Mouth serves multiple functions </li></ul><ul><ul><li>Roof of mouth separates nasal cavities from oral cavity and has two parts: anterior hard palate and a posterior soft palate </li></ul></ul><ul><ul><li>Tonsils contain lymphatic tissue and help protect the body against infections, but when inflamed it is called tonsillitis </li></ul></ul><ul><li>Salivary Glands </li></ul><ul><ul><li>Saliva contains antibacterial agents, including lysozyme and an enzyme called salivary amylase that begins the process of digesting starch </li></ul></ul><ul><ul><li>Tongue, composed of skeletal muscle, mixes chewed food with saliva and forms mixture into a mass called a bolus </li></ul></ul><ul><li>The Teeth </li></ul><ul><ul><li>We use our teeth to chew food into pieces convenient for swallowing </li></ul></ul><ul><ul><li>Tooth decay, called dental caries , or cavities, occurs when bacteria within the mouth metabolize sugar and give off acids, which erode teeth </li></ul></ul><ul><li>Gum Disease </li></ul><ul><ul><li>Bacteria accumulate in plaque and cause inflammation of the gums (gingivitis), which can spread to the periodontal membrane, which lines the tooth sockets </li></ul></ul>31-
  18. 18. Figure 31.4A The human digestive tract 31-
  19. 19. Figure 31.4B Adult teeth 31-
  20. 20. 31.5 The esophagus conducts food to the stomach <ul><li>Esophagus - muscular tube that passes from the pharynx through the thoracic cavity and diaphragm into the abdominal cavity, where it joins the stomach </li></ul><ul><li>Pharynx - region that receives air from the nasal cavities and food from the mouth </li></ul><ul><ul><li>Swallowing in the pharynx is a reflex action performed automatically </li></ul></ul><ul><ul><li>Soft palate moves back to close off the nasopharynx and the trachea moves up under the epiglottis to cover the glottis </li></ul></ul><ul><ul><ul><li>Glottis - opening to the larynx (voice box), the air passage </li></ul></ul></ul><ul><li>A rhythmic contraction called peristalsis pushes bolus (chewed and swallowed food) along digestive tract </li></ul><ul><ul><li>Sphincters are muscles that encircle tubes and act as valves </li></ul></ul><ul><li>Gastroesophageal Reflux Disease (GERD) </li></ul><ul><ul><li>Refluxed stomach acid touches the lining of the esophagus and causes a burning sensation in the chest called heartburn, or acid indigestion </li></ul></ul>31-
  21. 21. Figure 31.5A Swallowing 31-
  22. 22. Figure 31.5B Peristalsis, a rhythmic progressive wave of muscular contraction, pushes the food bolus along the digestive tract 31-
  23. 23. 31.6 Food storage and chemical digestion take place in the stomach <ul><li>The stomach is a thick-walled organ that is continuous with the esophagus above and duodenum of small intestine below </li></ul><ul><ul><li>Stores food, initiates digestion of protein, and controls movement of chyme into small intestine </li></ul></ul><ul><li>Wall of stomach contains three layers of smooth muscle that allow stomach to stretch and mechanically break food into smaller fragments </li></ul><ul><ul><li>Oblique, Circular, and Longitudinal layers </li></ul></ul><ul><li>Food leaves stomach as a thick, soupy liquid called chyme </li></ul><ul><ul><li>Chyme enters the small intestine in squirts by way of the pyloric sphincter, which acts like a valve, repeatedly opening and closing </li></ul></ul>31-
  24. 24. Figure 31.6 Anatomy of the stomach wall 31-
  25. 25. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 31.7 Bacteria contribute to the cause of ulcers <ul><li>In 1983, Dr. Barry Marshall proposed that ulcers were caused by the bacterium Helicobacter pylori </li></ul><ul><ul><li>Initially, the idea was met with scorn and ridicule </li></ul></ul><ul><ul><li>Dr. Marshall used himself as a guinea pig and drank a tube of Helicobacter pylori </li></ul></ul><ul><ul><li>One week later, he began suffering painful symptoms of stomach inflammation </li></ul></ul><ul><ul><li>He treated himself by taking a combination of antibiotics to kill the bacteria and an acid-blocking drug to ease the symptoms </li></ul></ul><ul><li>Today doctors treat ulcers with antibiotics, coupled with an acid-reducing drug to allow the stomach lining to heal </li></ul>31-
  26. 26. 31.8 In the small intestine, chemical digestion concludes, and absorption of nutrients occurs <ul><li>The small intestine is about 6 meters long, but only about 2.5 cm wide </li></ul><ul><ul><li>First 25 cm is called the duodenum </li></ul></ul><ul><ul><li>Bile from the liver emulsifies fat, causing fat droplets to disperse in water </li></ul></ul><ul><li>Anatomic features increase the surface area of the small intestine </li></ul><ul><ul><li>Wall of small intestine contains fingerlike villi (sing., villus ) that have extensions called microvilli </li></ul></ul><ul><ul><ul><li>Microvilli greatly increase the surface area of the villus for the absorption of small nutrient molecules </li></ul></ul></ul><ul><ul><li>Villi also bear enzymes that finish chemical digestion </li></ul></ul><ul><li>Nutrient molecules are absorbed into the vessels of a villus, which contains blood capillaries and a lymphatic capillary called a lacteal </li></ul>31-
  27. 27. Figure 31.8A Anatomy of the wall of the small intestine 31-
  28. 28. Figure 31.8B Digestion and absorption of nutrients 31-
  29. 29. 31.9 The pancreas and the liver contribute to chemical digestion <ul><li>The Pancreas </li></ul><ul><ul><li>Elongated and flattened organ that has both an endocrine and an exocrine function </li></ul></ul><ul><ul><li>Produces pancreatic juice, with sodium bicarbonate (NaHCO 3 ) and digestive enzymes </li></ul></ul><ul><li>The Liver </li></ul><ul><ul><li>Largest gland in the body and lies under the diaphragm </li></ul></ul><ul><ul><li>Liver removes poisonous substances from the blood and detoxifies them </li></ul></ul><ul><ul><li>Maintains blood glucose level at about 100 mg/100 mL </li></ul></ul><ul><ul><li>If glycogen is depleted, liver converts glycerol and amino acids to glucose </li></ul></ul><ul><ul><li>Liver produces bile, which is stored in the gallbladder </li></ul></ul><ul><li>Liver Disorders </li></ul><ul><ul><li>Jaundice can result from a viral infection of the liver, called hepatitis </li></ul></ul><ul><ul><li>Cirrhosis is a chronic liver disease in which the organ first becomes fatty, and then liver tissue is replaced by inactive fibrous scar tissue </li></ul></ul>31-
  30. 30. Figure 31.9 Liver, gallbladder, and pancreas 31-
  31. 31. 31.10 The stomach and duodenum are endocrine glands <ul><li>The stomach produces gastrin, a hormone that increases the secretory activity of the gastric glands </li></ul><ul><li>Cells of duodenal wall produce two other hormones that are of particular interest </li></ul><ul><ul><li>Secretin and CCK (cholecystokinin) </li></ul></ul><ul><ul><li>After these hormones enter bloodstream, pancreas increases output of pancreatic juice </li></ul></ul>31-
  32. 32. Figure 31.10 Hormones that help regulate the digestion of food 31-
  33. 33. 31.11 The large intestine absorbs water and prepares wastes for elimination <ul><li>Large intestine - larger in diameter but shorter in length than the small intestine </li></ul><ul><ul><li>Includes the cecum, the colon, the rectum, and anus </li></ul></ul><ul><ul><li>Has a population of bacteria ( Escherichia coli) that break down nondigestible material and produce vitamins </li></ul></ul><ul><li>Cecum has small projection called the vermiform appendix </li></ul><ul><ul><li>Plays a role in fighting infections </li></ul></ul><ul><ul><li>Can become infected, called appendicitis </li></ul></ul><ul><li>Colon - subdivided into the ascending, transverse, descending, and sigmoid colons </li></ul><ul><ul><li>Sigmoid colon enters rectum , last 20 cm of large intestine </li></ul></ul><ul><ul><li>About 95% of water is absorbed by the small intestine, and the remaining portion is absorbed into the cells of the colon </li></ul></ul><ul><ul><li>Subject to the development of polyps, small growths arising from epithelial lining </li></ul></ul>31-
  34. 34. Good Nutrition and Diet Lead to Better Health 31-
  35. 35. 31.12 Carbohydrates are nutrients that provide immediate energy as well as fiber <ul><li>Carbohydrates are present in food in the form of sugars, starch, and fiber </li></ul><ul><ul><li>Fruits, vegetables, milk, and honey are natural sources of sugars </li></ul></ul><ul><ul><li>Glucose and fructose are monosaccharide sugars, lactose and sucrose are disaccharides </li></ul></ul><ul><li>Fiber includes various nondigestible plant carbohydrates </li></ul><ul><ul><li>Not a nutrient for humans, but adds bulk to fecal material, which stimulates movement in the large intestine, preventing constipation </li></ul></ul><ul><li>Nutritionists hypothesize that high intake of refined carbohydrates and fructose sweeteners may be responsible for prevalence of obesity in the United States </li></ul>31-
  36. 36. 31-
  37. 37. Figure 31.12 Fiber-rich foods 31-
  38. 38. 31.13 Lipids are nutrients that supply long-term energy <ul><li>Triglycerides (fats and oils) supply energy for cells, but fat is stored for the long term in the body </li></ul><ul><ul><li>Two unsaturated fatty acids (alpha-linolenic and linoleic acids) are essential </li></ul></ul><ul><ul><ul><li>Found in fatty fish and plant oils (canola and soybean oils) </li></ul></ul></ul><ul><ul><li>Animal-derived foods (butter, meat, milk, and cheeses) contain saturated fatty acids </li></ul></ul><ul><li>Cholesterol - a lipid that can be synthesized by the body </li></ul><ul><ul><li>Cells use cholesterol to make various compounds, including bile and Vitamin D </li></ul></ul><ul><ul><li>Elevated blood cholesterol levels are associated with an increased risk of cardiovascular disease </li></ul></ul><ul><li>Studies suggest that trans fatty acids (trans fats) are more harmful than saturated fatty acids </li></ul><ul><ul><li>Found in commercially packaged foods, such as cookies and crackers; in commercially fried foods, such as French fries </li></ul></ul>31-
  39. 39. 31-
  40. 40. 31.14 Proteins are nutrients that supply building blocks for cells <ul><li>Dietary proteins are digested to amino acids, which cells use to synthesize hundreds of cellular proteins </li></ul><ul><ul><li>Of the 20 amino acids, nine are essential amino acids and must be present in diet </li></ul></ul><ul><ul><ul><li>Eggs, milk, meat, poultry, and most animal-derived foods contain all nine essential amino acids </li></ul></ul></ul><ul><li>Plant-derived foods generally do not have as much protein as those from animals </li></ul><ul><ul><li>Each type of plant food generally lacks one or more of the essential amino acids </li></ul></ul><ul><ul><li>A balanced vegetarian diet is quite possible by adding supplements and other foods made from processed soybeans </li></ul></ul><ul><ul><ul><li>Example : tofu or soymilk </li></ul></ul></ul><ul><li>Protein should not supply the bulk of dietary calories </li></ul><ul><ul><li>Average American eats twice as much protein as necessary </li></ul></ul><ul><ul><li>High-protein diets can also increase calcium loss in the urine and encourage the formation of kidney stones </li></ul></ul>31-
  41. 41. 31.15 Minerals have various roles in the body <ul><li>Need about 20 different minerals for numerous physiological functions </li></ul><ul><ul><li>Regulation of biochemical reactions, maintenance of fluid balance, and incorporation into certain structures and compounds </li></ul></ul><ul><li>Occasionally, individuals do not receive enough iron, calcium, magnesium, or zinc in their diets </li></ul><ul><ul><li>Adult females need more iron in the diet than males if they are menstruating each month </li></ul></ul><ul><ul><li>Many people take calcium supplements, as directed by a physician, to counteract osteoporosis , a degenerative bone disease </li></ul></ul><ul><li>One mineral that people consume too much of is sodium </li></ul><ul><ul><li>Recommended amount of sodium intake per day is 2,400 mg, while the average American takes in 4,000–4,700 mg each day </li></ul></ul>31-
  42. 42. 31-
  43. 43. 31.16 Vitamins help regulate metabolism <ul><li>Vitamins are organic compounds that regulate various metabolic activities </li></ul><ul><ul><li>No scientific evidence vitamins are “wonder drugs” </li></ul></ul><ul><ul><li>Vitamins C, E, and A are termed antioxidants and defend body against free radicals </li></ul></ul><ul><li>Vitamin deficiencies can lead to disorders, and even death, in humans </li></ul><ul><ul><li>Although many foods in the U.S. are enriched, or fortified with vitamins, some individuals are at risk for vitamin deficiencies </li></ul></ul><ul><ul><li>Include the elderly, young children, alcoholics, and low income people </li></ul></ul>31-
  44. 44. 31-
  45. 45. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 31.17 Nutritional labels allow evaluation of a food’s content 31-
  46. 46. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 31.18 Certain disorders are associated with obesity <ul><li>Consuming too many calories contributes to body fat, which increases a person’s risk of obesity and associated illnesses </li></ul><ul><ul><li>Diabetes type 2 and cardiovascular disease are often seen in obese people </li></ul></ul><ul><li>Diabetes Type 2 </li></ul><ul><ul><li>People are usually obese and display insulin resistance </li></ul></ul><ul><ul><li>When the blood glucose level rises rapidly, the pancreas produces an overload of insulin to bring the level under control </li></ul></ul><ul><ul><li>Chronically high insulin levels apparently lead to insulin resistance, increased fat deposition, and a high blood fatty acid level </li></ul></ul><ul><li>Cardiovascular Disease </li></ul><ul><ul><li>Often due to arteries blocked by plaque from saturated fats and cholesterol </li></ul></ul><ul><ul><li>Cholesterol is carried in the blood by two types of lipoproteins: low-density lipoprotein (LDL) and high-density lipoprotein (HDL) </li></ul></ul><ul><ul><li>Consuming saturated fats, including trans fats, raises LDL cholesterol levels, while eating unsaturated fats lowers LDL cholesterol levels </li></ul></ul>31-
  47. 47. Figure 31.18A Exercising for good health 31-
  48. 48. Figure 31.18B Foods high in trans fats 31-
  49. 49. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 31.19 Eating disorders appear to have a psychological component <ul><li>Anorexia nervosa - severe psychological disorder characterized by an irrational fear of getting fat </li></ul><ul><ul><li>Results in the refusal to eat enough food to maintain a healthy body weight </li></ul></ul><ul><li>Bulimia nervosa - binge-eats, and then purges to avoid gaining weight </li></ul><ul><ul><li>The binge-purge cyclic behavior can occur several times a day </li></ul></ul><ul><ul><li>People with bulimia nervosa can be difficult to identify because their body weights are often normal and they tend to conceal their binging and purging </li></ul></ul><ul><li>Many obese people suffer from binge eating disorder </li></ul><ul><ul><li>Characterized by episodes of overeating not followed by purging </li></ul></ul><ul><ul><li>Stress, anxiety, anger, and depression can trigger food binges </li></ul></ul><ul><li>Muscle dysmorphia - Preoccupation with diet, body-building activities, and body form </li></ul><ul><ul><li>A person with this condition thinks his or her body is underdeveloped when actually it is extremely well developed </li></ul></ul>31-
  50. 50. Figure 31.19A Anorexia nervosa patients think they are fat, even though they are thin 31-
  51. 51. Figure 31.19B Bulimia nervosa is characterized by occasional binge eating followed by purging 31-
  52. 52. Figure 31.19C Muscle dysmorphia is also characterized by a distorted body image 31-
  53. 53. Connecting the Concepts: Chapter 31 <ul><li>Assigning any organ to a particular body system seems arbitrary </li></ul><ul><ul><li>For example, the stomach and small intestine contribute to the endocrine system by producing hormones </li></ul></ul><ul><li>The liver has so many functions that it really belongs to many systems of the body </li></ul><ul><ul><li>Belongs to the cardiovascular system because it produces plasma proteins and to the urinary system because it produces urea, as well as to the digestive system because it produces bile </li></ul></ul><ul><ul><li>Also detoxifies blood by removing and metabolizing poisonous substances </li></ul></ul><ul><li>Three systems (digestive, respiratory, and urinary) refresh the blood directly because they communicate with the external environment </li></ul><ul><li>The digestive tract digests food to nutrient molecules that enter the blood </li></ul>31-