The Digestive System

1. The Digestive System

2. Digestive System is approximately 8 meters long

4. Human digestive system

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

6. Digestion • Phases • Ingestion • Movement • Digestion • Absorption • Further digestion • After chewing and swallowing, it takes 5 to 10 seconds for food to pass down the esophagus to the stomach, where it spends 2 to 6 hours being partially digested. • Final digestion and nutrient absorption occur in the small intestine over a period of 5 to 6 hours. • In 12 to 24 hours, any undigested material passes through the large intestine, and feces are expelled through the anus.

7. Digestive System Organization • Gastrointestinal (Gl) tract or 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

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

9. Anatomy of the Mouth and Throat

10. Human Deciduous and Permanent Teeth

11. Dorsal Surface of the Tongue

12. The Major Salivary Glands

13. Alimentary canal • Mouth- physical and chemical breakdown. • Mastication-the act of chewing • Saliva contains enzyme amylase to break down carbohydrates

14. Pharynx- contains opening to trachea as well. Epiglottis covers opening of trachea. • Esophagus-muscular tube dorsal to trachea • Relies on a rhythmic wave-like motion called peristalsis

15. Peristalsis and Segmentation series of involuntary wave-like muscle contractions which move food along the digestive tract

16. Anatomy of the Stomach

17. 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 Stomach

18. 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 Stomach

19. Extends from pyloric sphincter  ileocecal valve Regions Duodenum Jejenum Ileum Movements Segmentation Peristalsis Small Intestine

20. Small intestine • The walls of the small intestine are lined with millions of microvilli. This is the site of nutrient absorption. • Small intestines also produce many digestive enzymes to break large polymers completely down into monomers. • Chyme- the thin liquid mush that is your food being passed through the intestines

21. Small Intestine • Intestinal glands – Intestinal enzymes • Duodenal glands – Alkaline mucous • Paneth cells – Lysozyme • Microvilli • Lacteals • Plicacircularis • Smooth muscle • Lymphatic tissue – GALT • Vascular

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

23. Structure of the Villi in the Small Intestine

24. Villi and microvilli

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

26. Requires pancreatic enzymes & bile to complete digestion Small Intestine

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

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

29. 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 Liver

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

31. Gall bladder- stores and concentrates bile • Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion. • Pancreas- produces insulin, pancreatic juices amylase and lipase. • Pancreatic juice digests all major nutrient types.

32. The Duodenum and Related Organs

33. The Organs and Positions in the Abdominal Cavity

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

35. Anatomy of the Large Intestine

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

37. Large Intestine • 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

38. You’ve got company! • Living in the large intestine is a community of helpful bacteria • Escherichiacoli (E. coli) • produce vitamins • vitamin K; B vitamins • generate gases • by-product of bacterial metabolism • methane, hydrogen sulfide

39. 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 Feces Formation and Defecation

40. Structures of the Alimentary Canal

41. Digestion and pH

42. Hormones and digestion • Many hormones produced by the digestive system itself are responsible for appetite and digestion. • Gastrin in the stomach, produced when food is present, signals release of acid. • Secretin signals the release of sodium bicarbonate by the pancreas. • Ghrelin and Leptin, recently discovered, control appetite. Changes in these hormones cause overeating, because people with too little of these hormones don’t realize they’re full.

43. Does a colon need cleaned? • Products like these raise worry in people who believe their colon is “dirty.” These are laxatives that are unnecessary, or even harmful. • “Cleansing” products can disrupt bowel function and do not cure any real illnesses. A diet high in fiber is a healthier option.