1. DIGESTIVE SYSTEM

2. Digestive System  You need energy to survive  Through the process of digestion, your body breaks the food down into the basic blocks of life, and than rebuilds them by incorporating them into your body.  Your body is constantly breaking food down, and then using the pieces to build, repair, and grow your body.

3. The pyramid of nutrition

4. Food for Energy and Growth  Carbohydrates are obtained primarily from cereals, grains, and breads  on the average, carbohydrates contain 4.1 calories per gram  the body uses carbohydrates for energy  Dietary fats are obtained from oils, margarine, and butter and are abundant in fried foods, meats, and processed snack foods  fats contain 9.3 calories per gram  the body uses fats to construct cell membranes, to insulate nervous tissue, and to provide energy

5. Food for Energy and Growth  Proteins can be obtained from many foods, including poultry, fish, meat, and grains  proteins have 4.1 calories per gram  proteins are used for energy and as building materials for cell structures, enzymes, hemoglobin, hormones, and muscle and bone tissue

6. Animation: Energy for Activity

7. Food for Energy and Growth  In wealthy countries, being significantly overweight is common  this is due to habitual overeating and high-fat diets, in which fats constitute over 35% of the total caloric intake  the standard measure of appropriate body weight is the body mass index (BMI), estimated as your body weight in kg, divided by your height in meters squared

8. Are you overweight? 66% of Americans are overweight with a BMI of 25 or more

9. Food for Energy and Growth  One essential characteristic of food is its fiber content  fiber is the part of plant food that cannot be digested by humans  diets that are low in fiber result in a slower passage of food through the colon  low fiber is thought to be associated with incidences of colon cancer

10. Food for Energy and Growth  Over the course of evolution, many animals have lost their ability to manufacture certain substances they need  many vertebrates are unable to manufacture one or more of the 20 amino acids used to make proteins humans are unable to synthesize eight amino acids, which must be obtained from proteins in food these are called essential amino acids

11. Food for Energy and Growth  In addition to supplying energy, food must also supply essential minerals, such as calcium and phosphorous  some minerals are required in very small amounts and are called trace elements  Essential organic substances that are used in trace amounts are called vitamins  many vitamins are required cofactors for enzymes

12. Digestion 12  Processing of food  Types  Mechanical (physical) Chew Tear Grind Mash Mix  Chemical Catabolic reactions Enzymatic hydrolysis Carbohydrate Protein Lipid

13. Types of Digestive Systems  Heterotrophs are divided into three groups on the basis of their food sources  herbivores eat plants exclusively  carnivores are meat eaters  omnivores eat both plants and animals  Single-celled organisms, as well as sponges, digest their food intracellularly  All other animals digest their food extracellularly, within a digestive cavity

14. Digestion 14  Phases  Ingestion  Movement  Digestion  Absorption  Further digestion

15. Digestive System Organization 15  Gastrointestinal (Gl) tract (Alimentary canal)  Tube within a tube  Direct link/path between organs  Structures Mouth Oral Cavity Pharynx Esophagus Stomach Duedenum Jejenum kIleum Cecum Ascending colon Transverse colon

16. Digestive System Organization Descending colon Sigmoid colon Rectum Anus  Accessory structures  Not in tube path  Organs Teeth Tongue Salivary glands Liver Gall bladder Pancreas 16

17. The Mouth and Teeth  Many vertebrates have teeth, and chewing (mastication) breaks up food into small particles and mixes it with fluid secretions  mammals have heterodont dentition, teeth of different specialized types the general pattern of dentition is modified in different mammals depending on their diet in carnivorous mammals, the canines are prominent, and other teeth are more bladelike and sharp in herbivorous mammals, incisors are well-developed for snipping, canines are reduced or absent, and molars are large and flat, with complex ridges well suited to grinding

18. The Mouth and Teeth  Humans are omnivores and human teeth are specialized for eating both plant and animal material  humans are carnivores in the front of the mouth and herbivores in the back  children have only 20 teeth but these are lost during childhood and replaced by 32 adult teeth

19. Human teeth The tooth is a living organ.

20. Anatomy of the Mouth and Throat 20

21. Human Deciduous and Permanent Teeth 21

22. Dorsal Surface of the Tongue 22

23. The Major Salivary Glands 23

24. Deglutition (swallowing)  Sequence  Voluntary stage Push food to back of mouth  Pharyngeal stage Raise Soft palate Larynx + hyoid Tongue to soft palate  Esophageal stage Contract pharyngeal muscles Open esophagus Start peristalsis 24

25. Deglutition (swallowing)  Control  Nerves Glossopharyngeal Vagus Accessory  Brain stem Deglutition center Medulla oblongata Pons  Disorders Dysphagia Aphagia 25

26. The Esophagus and Stomach  The esophagus is a muscular tube that connects the pharynx to the stomach  the upper third is enveloped in skeletal muscle for voluntary control of swallowing  the lower two-thirds is surrounded by involuntary smooth muscle  rhythmic waves of contractions, called peristalsis, propel food towards the stomach

27. Esophagus 27  Usually collapsed (closed)  3 constrictions  Aortic arch  Left primary bronchus  Diaphragm  Surrounded by  SNS plexus  Blood vessels  Functions  Secrete mucous  Transport food

28. Peristalsis and Segmentation 28

29. Esophagus 29  Sphincters  Upper  Lower  Abnormalities  Achalasia  Atresia  Hernia  Barret’s esophagus  Esophageal varices

30. The Esophagus and Stomach  The movement of food from the esophagus into the stomach is controlled by a ring of circular smooth muscle, called a sphincter  contraction of the sphincter prevents food in the stomach from moving back into the esophagus  in humans, stomach contents can be brought back out during vomiting  the relaxing of the sphincter may lead to acid reflux, which is when stomach acid moves into the esophagus this produces a burning sensation known as heartburn

31. The Esophagus and Stomach  The stomach is a saclike portion of the digestive tract  the stomach contains an extra layer of smooth muscle for churning food  gastric juice is released by gastric glands in the lining of the stomach parietal cells secrete hydrochloric acid (HCl) chief cells secrete pepsinogen pepsinogen requires a low pH to be activated into pepsin, a protease that begins the digestion of proteins

32. Stomach 32  Usually “J” shaped  Left side, anterior to the spleen  Mucous membrane  G cells – make gastrin  Goblet cells – make mucous  Gastric pit – Oxyntic gland – Parietal cells – Make HCl  Chief cells – Zymogenic cells Pepsin Gastric lipase

33. Anatomy of the Stomach 33

34. Stomach  3 muscle layers  Oblique  Circular  Longitudinal  Regions  Cardiac sphincter  Fundus  Antrum (pylorus)  Pyloric sphincter  Vascular  Inner surface thrown into folds – Rugae  Contains enzymes that work best at pH 1-2 34

35. Stomach  Functions  Mix food  Reservoir  Start digestion of Protein Nucleic acids Fats  Activates some enzymes  Destroy some bacteria  Makes intrinsic factor – B 12 absorption  Destroys some bacteria  Absorbs Alcohol Water Lipophilic acid B 12 35

36. The Small and Large Intestines  The small intestine is the true digestive vat of the body  only relatively small portions of chyme are introduced into the small intestine at one time this allows time for acid to be neutralized and enzymes to act  in the small intestine, carbohydrates, protein, and lipids are broken down and absorbed into the bloodstream

37. Small Intestine  Absorbs  80% ingested water  Electrolytes  Vitamins  Minerals  Carbonates Active/facilitated transport Monosaccharides  Proteins Di-/tripeptides Amino acids  Lipids Monoglycerides Fatty acids Micelles Chylomicrons 37

38. The Small and Large Intestines  While some enzymes necessary for digestion are secreted by the cells of the intestinal wall, most are made in the pancreas  the pancreas is an exocrine gland, meaning it secretes through ducts  the pancreas sends it products via a duct that empties into the first part of the small intestine, the duodenum

39. The Small and Large Intestines  Much of the food energy the vertebrate body harvests is obtained from fats  fat digestion involves bile salts that are secreted into the duodenum by the liver  bile salts act like detergents and combine with drops of fat to form microscopic droplets this process is known as emulsification this increases the surface area for the enzyme lipase to work on in order to breakdown the fat

40. Small Intestine  Secretes digestive enzymes  Peptidases Amino- Di- Tri-  Sucrases  Maltase  Lactase  Saccharidases Di- Tri-  Lipase  Nucleases 40

41. Small Intestine  Control  Requires pancreatic enzymes & bile to complete digestion 41

42. Large Intestine 42  Extends from ileocecal valve to anus  Regions  Cecum – Appendix  Colon Ascending Transverse Descending  Rectum  Anal canal

43. Anatomy of the Large Intestine 43

44. Large Intestine 44  Histology  No villi  No permanent circular folds  Smooth muscle Taeniae coli Haustra  Epiploic appendages  Otherwise like rest of Gl tract

45. Large Intestine 45  Functions  Mechanical digestion Haustral churning Peristalsis Reflexes Gastroileal Gastrocolic  Chemical digestion – Bacterial digestion Ferment carbohydrates Protein/amino acid breakdown – Absorbs More water Vitamins – B – K – Concentrate/eliminate wastes

46. Feces Formation and Defecation  Chyme dehydrated to form feces  Feces composition  Water  Inorganic salts  Epithelial cells  Bacteria  Byproducts of digestion  Defecation  Peristalsis pushes feces into rectum  Rectal walls stretch  Control  Parasympathetic  Voluntary 46

47. Liver 47  Location  R. Hypochondrium  Epigastric region  4 Lobes  Left  Quadrate  Caudate  Right  Each lobe has lobules – Contains hepatocytes – Surround sinusoids – Feed into central vein

48. Liver  Functions  Makes bile Detergent – emulsifies fats Release promoted by: Vagus n. CCK Secretin Contains Water Bile salts Bile pigments Electrolytes Cholesterol Lecithin 48

49. Liver  Detoxifies/removes Drugs Alcohol  Stores Gycolgen Vitamins (A, D, E, K) Fe and other minerals Cholesterol  Activates vitamin D  Fetal RBC production  Phagocytosis  Metabolizes absorbed food molecules Carbohydrates Proteins Lipids 49

50. Liver  Dual blood supply  Hepatic portal vein Direct input from small intestine  Hepatic artery/vein Direct links to heart 50

51. Animation: Impact of Alcohol

52. Final Assignment  Keeping a food diary for 3 full week (21 days)  Track all food and beverage consumption  Use websites to track calories  Fitwatch.com  Use measuring cups/spoons  If you work-out; track your calorie outtake  Due via email in table format by FINALS WEEK  Worth: 200 points