The Digestive System

1. The Digestive System Or…What happens to that “Big Mac” once you take a bite!

2. What makes up a “Big Mac”? • The six basic groups of nutrients are: • Water • Carbohydrates • Fats • Proteins • Minerals • Vitamins

3. Water • Water is the most basic nutrient • You die first without it • If you lose 10% of your body water you are in danger of dying –dehydration. • Water makes up 70% or more of your body (depending on your age). • You are dehydrated before you actually experience thirst.

4. Carbohydrates • Made of carbon, hydrogen, and oxygen in the proportion of [CH2O]n. • Nutritional carbs are of plant origin. • Function: provide energy. 1. Simple sugars -Monosaccharides (glucose, fructose, galactose, and mannose) C6H12O6 (isomers)

5. -Dissaccharides (2 monosaccharides combined by dehydration synthesis) Sucrose (glucose + fructose) Lactose (glucose + galactose) Maltose (glucose + glucose) 2. Complex Carbohydrates (polysaccharides) -Starches (amylose, amylopectin, glycogen) -Cellulose -mammals have no cellulase – not digestible = FIBER

6. Isomers: same empirical formula, different structural formula

8. Something to think about!!!

9. Lipids (Fats) • Made of carbon, hydrogen, and oxygen. • Functions: stored energy, cell membranes, insulation and padding, steroid hormones • Calorically dense. 2.54 calories / gram more that carbs or protein • Triglycerides (LDL and HDL), Cholesterol • Basic component is fatty acids • Saturated –each carbon fully hydrated • Unsaturated –some double bonds

12. Generalized triglyceride structure

13. Cholesterol

14. Triglycerides • Cylomicrons • Form of fat absorption from the intestines • More about it later • HDL: High density lipoproteins • Good Cholesterol • Increased by cardiovascular exercise • LDL: Low density lipoproteins • Bad Cholesterol

15. Essential Fatty Acids • Essential: required in the diet for health, not made in adequate amounts by the body to sustain health. • Linoleic acid • Linolenic acid • Aracadonic acid

17. Proteins • Structure: chains of amino acids coded for on DNA -C, H, O, N, and sometimes S. • Functions: structural, enzymatic, antibodies, regulatory (some hormones), energy • Essential Amino Acids: PVT MATT HILL • Non-essential –made by the body. • Complete proteins –have the right combination of essential amino acids • Incomplete proteins have an imbalance of essential amino acids –at least one limiting aa.

18. Meat, milk, eggs, soy.Which is the best protein? • What is protein quality? • How is protein evaluated? • What about vegetarians? • What is the difference between ouevo-lacto and vegan? • What is a complementary protein?

21. Vitamins • Fat Soluble: ADEK • Vitamin A -retinoic acid –eyesight (night vision), epithelial tissue health • Vitamin D –calcitrol –calcium absorption and bone health. Deficiency disease =Rickets • Vitamin E –α-tocopherol –antioxidant in fat soluble tissues. • Vitamin K – part of the clotting cascade. Made by gut bacteria.

22. Water Soluble Vitamins • B vitamins: • B1 =thiamine TPP • B2 =riboflavin FAD -carries hydrogens • B3 =niacin NAD -carries hydrogens • B5 =Pantothenic acid • B6 =Pyridoxine transfers amino acids • B9 = Folic acid • B12 =carboxycobalamine -only one stored! Animal products only

23. Vitamin C • Ascobic acid • Water soluble • Deficiency disease is scurvy • Only required by primates (including humans), guinea pigs, and fruit bats. • Important in the conversion of proline to hydroxyproline to make collegen • Important in immune response. Increase turnover in disease. • Anti-oxidant

24. Minerals • Macro-minerals: required in percentage amounts in the diet –structural: calcium, phosphorus, magnesium -electrolytes: sodium, potassium, chlorine Micro-minerals: trace elements –ppm (1mg/kg) -iron, copper, fluoride, iodine, selenium, manganese

25. Back to the “Big Mac” • What is in a “Big Mac” • Dissect your burger into its nutrients? • Explain the caloric effect of fat in the burger or any food? • Now what happens!!!

27. What is digestion? • Digestion is the sum of the mechanical and chemical processes that convert food elements into small enough particle to be absorbed into the body. • There are 2 basic aspects of digestion: • Chemical Processes –enzymatic • Physical process –mechanical like chewing and mixing

28. Mouth: Processes Mechanical digestion: Prehension: food gathering –lips, hands, etc. • Mastication: chewing, breaks food into smaller pieces (greater surface area) to facilitate enzyme breakdown. • Ensalivation: coats food particles with saliva to facilitate swallowing -lubrication Chemical digestion • Salivary amylase: breaks down starch (amylose) into dextrins (6 carbon sugars).

29. Teeth • Dental Formula • Set up like a fraction = ½ of the mouth • Numerator = the top of the jaw • Denominator = bottom jaw • Numbers are given in the following order • Incisors/canines/premolars/ molars • Human permanent teeth = • 2123/2123 X 2

30. Permanent teeth

32. Do all animals have the same teeth?

33. Swallowing • Food is swallowed • Moves through the pharynx • Past the epiglottis What is the purpose? • Enters esophagus • Moves by peristalic movement (wave-like movement)

34. Stomach: gastric phase

35. Gastric Activities • Mixing movements • Gastric secretions: pH=2-3 • Pepsinogen • HCl • mucous • Hormone release: (gastrin and intrinsic factor) • Absorption alcohol and water

36. Secretions • Chief cells -secrete pepsinogen • Parietal cells –secrete HCl • HCl converts pepsinogen to pepsin

37. Functions of the Stomach • 1. Break down of proteins into peptides • 2. Absorption of water –especially if dehydration exists. • 3. Absorption of alcohol • 4. Absorption of acidic drugs (due to pH) • 5. Secretion of “rennin” in babies causes milk proteins to form “curds” for digestion.

38. Intestinal Digestion

39. Small Intestine • Parts: No distinct bounderies. • Duodenum -first 25 cm (10 inches) -primary area of digestion and absorption • Jejunum • Continued digestion and absorption • Ileum mostly water • Ileocecal junction: where SI joins the cecum and LI

40. Intestinal lining

41. Intestinal “juices” ACTION ORIGIN • Sodium bicarbonate -neuralizes pH pancreas • Mucous – -protection Brunner’s glands goblet cells. • Chyme has a pH of____7_________.

42. Enzymes (all enzymes are proteins –coded for on DNA) • ENZYMEACTION ORIGIN • Peptidase 1 breaks down proteins • Dissaccharidases convert dissacharides SI to monosaccharides • Lipase breaks down triglicerices SI & P • Enterokinase breaks down proteins SI • Amylase Breaks down amylose SI & P • Chyme passes through the ileocecalvalveinto the Large Intestine

43. LARGE INTESTINE • Cecum -in some animals (rabbits and horses) is very large and provides a fermentation vat. • Vermiform appendix – function is a lymph node • Ascending colon • Transverse colon • Descending colon • Sigmoid colon • Rectum • Anus has 2 sphincters.

44. Lots of distance –little function • The digestive function of the large intestine is absorption. • Onlymucous is secreted • Absorption of water. • Intestinal bacteria make: vitamin K, some amino acids.

45. LI problems • Diverticula: balloon like projections that form in the large intestine due to strain and weakness of the intestinal wall. • Diverticulitis= inflammation of the diverticula • painful

48. Digestion of Fat: • Bile emulsifies fat: O (droplets) + Bile  o ooooo • Emulsify means: the mixture of immiscible liquids (like oil and water). • Lipase attaches to the glycerol of the triglyceride and breaks off the fatty acids 1 and 3. Glycerol is absorbed into the blood Fatty acids pass through mucosal cells are combined with protein as cylomicrons the lymph system.

49. Chylomicron –transport of fat coated with protein from intestines in lymphatics to thoracic duct. -Dumped into the vena cava. -Can go directly to muscle and adipose tissue or to the liver to be reprocessed. • LDL and HDL made by liver and transport of fat in blood. HDL –happy cholesterol.

50. LIVER • Largest gland in the body. • Many important functions: • Carbohydrate metabolism • -maintains blood glucose level • -converts excess glucose to glycogen for storage. • -gluconeogenesis- breaks down glycogen to glucose when blood sugar is low.