The Digestive System

1. The Digestive System

2. Features of the Generalized Vertebrate Gut

3. Oral Cavity - Origin 1. Origin Heterostomes - most of the invertebrate phyla Mouth originates from the blastopore 2. Deuterostomes - not formed early, but breaks through later in development; anus originates from the blastopore

4. Teeth 1. Origin - dermal denticles 2. Structure • Enamel - hardest substance in the body, occurs above the gum line • Cementum - continuation of enamel below the gum line • Dentin-matrix • Pulp-living portion of tooth Enamel Dentin Pulp Cementum Blood vessels and nerves

5. Glands of the mouth • Salivary glands secrete saliva • mucin - lubricant • salivary amylase - converts starch to glucose

6. Esophagus 1. Length-short in fish, longer in tetrapods to bypass lungs 2. Muscles Upper end- striated Lower 2/3 - smooth 3. Modifications of the esophagus - crop in birds for storing food

7. Stomach 1. Occurrence • Present in invertebrates with complete digestive tract • Absent in most lower chordates, even fish 2. Regions

8. Functions of the stomach • Little absorbtion by stomach - water and alcohol • secretes • HCl - very acid pH • mucin - lubricant • pepsin - digests proteins to shorter peptides • gastrin - hormone which regulates HCl secretion

9. Specialized stomachs • Muscular gizzard of ground birds • 4 chambers of grazing mammals - ruminants rumen is specialized for storing food to be chewed later

10. Small Intestine • Primary site of digestion • Digested food absorbed here - absorbtion • Enzymes • peptidases - peptides to amino acids • lactase - lactose (milk sugar) to simple sugars • maltase - maltose to glucose • sucrase - sucrose to simple sugars

11. Absorbtion in the Small Intestine

12. Pancreas - enzymes for digestion • lipase - fats to triglycerides • trypsin - proteins to shorter peptides • nucleases - DNA & RNA • secretin - hormone which stimulates buffering of HCl

13. Caecum • large sac at junction of small and large intestines • contains symbiotic bacteria that digest cellulose • our appendix is a rudimentary caecum

14. Colon • no digestion • reabsorbs H20 and ions • contains bacteria that synthesize Vitamin K • Fermentation of gases by bacteria

15. Liver A. Development - outpocket of the gut - tube that remains is the common bile duct B. Digestive function - produces bile that emulsifies fats • Bile is stored in the gall bladder for secretion into the small intestine

16. Other function of the liver C. Other functions - • stores glycogen • stores fats - cholesterol • filters and stores toxic materials • destroys red blood cells

17. Circulation and the Liver

18. Pancreas A. Origin - outpocket of the gut B. Functions 1. Exocrine - produces digestive enzymes 2. Endocrine - produces insulin that regulates blood glucose levels

19. The fate of food

20. NUTRITION • Nutrient - specific substance that must be taken into the body in sufficient quantities to meet the body’s needs • Essential Nutrient - required preformed; body cannot make it or cannot make enough to meet needs • Nonessential nutrient - body can make IF raw materials are available • Body needs BOTH to function

21. Nutrient Classes • Water (H2O) • Carbohydrate (CHO) • Protein (Pro) • Lipid (Fat)

22. Amount of energy?? • calorie - energy needed to raise 1 gm of H2O 1 degree Centigrade • Kilocalorie (kcal) - 1000 calories; energy needed to raise 1 liter of H2O 1 deg. C • Direct Calorimetry - measuring the heat (energy) • Indirect Calorimetry - measuring the CO2 & O2 and “deriving” the energy

23. Energy from Nutrients

24. Phytochemicals (plant) • Only few of 10,000’s studied • associated with • decrease CVD & cancer risk • decrease infections • increase immune function • examples - flavonoids; carotenoids (> 600); isoflavones; plant sterols

25. Best to get from food NOT supplements • ** soy; tomatoes, garlic, onions, legumes, green tea; cruciferous vegetables, red wine, grapes • I.e., EAT MORE AND WIDER VARIETY OF FRUITS & VEGETABLES

26. Water & Micronutrients • Functions • Intake Sources • Losses • Dehydration • Balance • Maintaining Hydration

27. Water Functions • Regulates body temperature • cools body temperature AND evens heat throughout body • Environment for cells & chemical reactions • Transport (blood) • blood pressure fxn of volume of H2O • secondary lubrication of joints • takes part in chemical reactions

28. Body Water (45 liters) INTERCELLULAR BLOOD/LYMPH (3) (12) INTRACELLULAR (30)

29. Sources of Water • Fluids - 550 - 1500 ml • Foods - 700 - 1000 ml • Metabolic H2O - 200 - 300 ml • Total 1450 - 2800 ml

30. Carbohydrates • Introduction to CHO • Terminology • Simple/sugars • Complex/Starch • Digestion • Metabolism Overview

31. Carbohydrates.... • First link in the food chain • Photosynthesis - plants store some of sun’s energy (0.1%) in chemical bonds of CHO • CO2 + H2O -----> CHO • ALL PLANT foods have CHO • Only significant animal sources of CHO are milk and some milk products • Energy source for man - 8% Eskimos; >70% some non-industrialized countries

32. CHO Functions • Energy - all cells use • Some cells (RBC, brain) can use only CHO until starvation sets in • Needed for effective burning of fat • Spares protein from use for energy • Fiber, alternative forms of CHO, provides a number of benefits

33. CHO Terminology • Saccharide = building block • Simple CHO = “sugars” • (1-3 saccharides) • mono (1), di (2), tri (3) • Complex CHO = Starch or Amylose • (many saccharides) - poly • Complex CHO = Fiber • Different bonding than starches

34. Monosaccharides • Glucose (Glu) - most abundant CHO; part of table sugar; “blood” sugar • Fructose (Fru) - found in fruit & honey; part of table sugar • Galactose (Gal) - part of milk sugar; generally not found free in nature

35. Disaccharides • Sucrose = Glu + Fru • Table sugar • Maltose = Glu + Glu • product of amylase digestion; beer; sprouts • Lactose = Glu + Gal • Milk sugar

36. Polysaccharides • multiple glucose (usually) units bound together • Starch/Amylose = many Glu • Storage form of energy in plants • Fiber - # different kinds; some are multiple Glu units but different chemical bonding from Amylose • examples - cellulose; pectin

37. Fiber (cont.) - often the structural CHO in plants • ONLY FOUND IN PLANTS • Glycogen = storage form of CHO in animals (many Glu units) • very highly branched to aid release

38. Major Hormones of Digestion • Insulin - made in pancreas; lowersblood glu; increasesallenergy stores • Glucagon- made in pancreas; raises blood glu; decreases adipose fat & liver glycogen stores • Epinephrine (adrenaline) - made in adrenal glands; raisesblood glu; decreases all energy stores

39. CHO Health Issues • Fiber • Abnormal CHO Metabolism • Lactose Intolerance • Hypoglycemia • Diabetes Mellitus • Type 1 diabetesResults from the body's failure to produce insulin, the hormone that "unlocks" the cells of the body, allowing glucose to enter and fuel them. It is estimated that 5-10% of Americans who are diagnosed with diabetes have type 1 diabetes. • Type 2 diabetesResults from insulin resistance (a condition in which the body fails to properly use insulin), combined with relative insulin deficiency. Most Americans who are diagnosed with diabetes have type 2 diabetes. • Gestational diabetesGestational diabetes affects about 4% of all pregnant women - about 135,000 cases in the United States each year. • Pre-diabetesPre-diabetes is a condition that occurs when a person's blood glucose levels are higher than normal but not high enough for a diagnosis of type 2 diabetes. There are 41 million Americans who have pre-diabetes, in addition to the 20.8 million with diabetes. • Syndrome X – • insulin resistance (the inability to properly deal with dietary carbohydrates and sugars), abnormal blood fats (such as elevated cholesterol and triglycerides), overweight, and high blood pressure.

40. Sources of Sugar

41. Take 12 oz H2O • add 10 tsp sugar • drink • ~ 160 empty calories, i.e., • A soda

42. Proteins • Structure • Digestion • Absorption • Roles in Body • Tissue maintenance & Growth • Regulation & Control • Energy

43. Distribution of Body Proteins

44. Protein Structure • Made up of carbon, oxygen, hydrogen & nitrogen (C, O, H, N) • Amino acids (aa) are building blocks • 9 essential • 11 nonessential (can be made from other aa or carbon skelton (“glucose”) if N available • AA differ by side chain (R group)

45. Regulation & Control Functions • Enzymes • Hormones (some) • Antibodies; immune system • Transport • Acid-base balance (buffers in blood) • Fluid & electrolyte balance

46. Protein Sources (US)

47. Protein in Foods

48. Lipids • Classes • Triglycerides (TG) • Phospholipids (PL) • Sterols • Class Functions • Terminology • Digestion • Transport - Lipoproteins

49. Lipid Classes • Triglycerides • made of 3 fatty acids (fa) & 1 glycerol • fa 4-22 Carbons long; mostly 16-20 • 95% of dietary lipids (fats & oils) • Phospholipids • 1 fa replaced by a phosphate group • Sterols • complex ringed structures; noncaloric • ex. cholesterol & Vit D

50. TG Functions • Concentrated energy (diet and main storage form) • Provides essential fatty acids (linoleic; linolenic) • Carrier of Fat Soluble Vits (A,D,E,K) • Body Insulation & padding around organs • Cell membranes • Adds flavor & texture to foods • Contributes to satiety