Digestion and Absorption

1. Digestion and Absorption

2. Digestion • the breaking down of food into nutrients to use or to pass • necessary step in order for the body to absorb the nutrients • BUT. . . . . .

3. Digestion Obstacles • breath, eat, drink through our mouth

4. Obstacles • food has to pass through the diaphragm: a muscle separating the thoracic cavity from the abdominal cavity

5. Obstacles • material should be kept moving forward, slow and steady

6. Obstacles • food must be lubricated

7. Obstacles • every particle of food has to accessible to the digestive enzymes: need enough water • must be able to excrete leftover residue without wasting water

8. Obstacles • enzymes are designed to digest carbs, fats, and protein • our digestive system is made up of carbs, fats and proteins • CONTROL over excreting the waste

9. Digestive Tract Anatomy Salivary glands Pharynx Mouth Epiglottis Trachea (to lungs) Upper esophageal sphincter Lower esophageal sphincter Esophagus Stomach Liver Gall bladder Pancreas Pyloric sphincter Pancreatic duct Bile duct Small intestine (duodenum, jejunum, ileum) Ileocecal valve Large intestine (colon) Appendix Rectum Anus

10. Anatomy • gastrointestinal tract (GI tract) • mouth, esophagus, stomach, small intestine, large intestine, rectum, anus • much passes without being absorbed or digested

11. Mouth • digestion begins here • food is crushed an mixed with fluid for ease of swallowing • fluids help dissolve food and allows for taste

12. Mouth • tongue moves food around to enhance chewing and swallowing • tongue is mostly responsible for taste

13. In the mouth, the lips, teeth and tongue help prepare the bolus (food mass) for further stages of swallowing. • Access between the nasal cavity and mouth closes as the bolus moves into the pharynx (throat).

14. The bolus is propelled toward and into the esophagus as the esophagus entrance opens and the epiglottis helps guard against access to the lungs. The airway reopens and the esophagus entrance closes as muscle contractions move the bolus toward the stomach

15. esophagus to stomach • upper esophageal sphincter opens during swallowing • bolus slides through to stomach • lower esophageal sphincter (entrance to stomach) closes • stomach keeps bolus adding digestive juices and grinding: resulting in chyme • chyme is slowly released through pyloric sphincter to small intestine

16. small intestine • travels through duodenum, jejunum, ileum • most digestion takes place here

17. large intestine (colon) • another sphincter controls entrance into the large intestine • withdraws water from the chyme • leaves a semi-solid waste • strong muscles of rectum and anal canal holds the waste back • rectal muscles relax and 2 sphincters of the anus open

18. Muscular Action of Digestion • activity that most times you are entirely unaware of happening • peristalsis • muscular contractions of GI tract that moves contents along • often referred to as a wave like contraction

19. stomach action • thickest walls and strongest muscles of the GI tract • circular, diagonal, longitudinal • churn the chyme with the gastric juices to totally liquefy it

20. segmentation • circular muscles of intestine • mix the chyme • allow for close contact with intestinal wall for absorption

21. sphincter contractions • control the movement of contents through the digestive tract • prevents contents from backing up to other organs • reflux of stomach into esophagus • intestinal contents into stomach esophagus stomach

22. Review of Digestive Process

23. Digestion Secretions • necessary for the breakdown and absorption of food • 5 organs produce digestive secretions • salivary glands • stomach • pancreas • liver • small intestines

24. Saliva • provides enough moisture to moisten food for ease in swallowing • contains water, salts, mucus and enzymes • initiates the digestion of carbohydrates • protects teeth and lining of mouth and esophagus

25. Gastric Juices • water, enzymes and hydrochloric acid • protein digestion • prevents bacterial growth, including those that are on food • protection from gastric juices is from mucus secreted from the stomach wall

26. Pancreatic Juices • are delivered into the duodenum from the pancreas • enzymes act on 3 energy nutrients: carbs, protein, fat • contains sodium bicarbonate, neutralizes the acid in chyme

27. Bile • produced by the liver • stored in the gallbladder • flows into the duodenum • bile is an emulsifier • puts fats into suspension in water for ease in enzyme breakdown

29. Intestinal Protection • thriving bacteria population • infectious bacteria don’t have a chance to populate

30. Final Stage • carbs, fat and protein have been disassembled and ready for absorption • vitamins, minerals and water don’t need to be broken down • undigested material continues through the GI tract, form a semi-solid material and is passed from the body

31. Absorption • once digested, absorption needs to take place • most takes place in small intestine • small intestine • 10 feet long • area = to tennis court • engulfs and absorbs nutrients • blood carries nutrients to live and other parts of body

32. Small Intestine Anatomy • inner surface • wrinkled and folded • each fold has 1,000’s of projections • villa • made up of 100’s of cells, each covered with hairs: microvilli • constantly wave, squirm, and wiggle • traps nutrient molecules

33. Small Intestine Villi Stomach Folds with villi on them Small intestine Circular muscles Longitudinal muscles

34. Lymphatic vessel (lacteal) Capillaries A villus Goblet cells Crypts Artery Vein Lymphatic vessel

35. Microvilli

36. Villi Cells • recognize and absorb nutrients the body needs • the microvilli have enzymes and “pumps” • can handle all types and any combinations of food

37. Absorption of Nutrients Outside cell Carrier loads nutrient on outside of cell . . . Carrier loads nutrient on outside of cell . . . Cell membrane Energy Energy . . . and then releases it on inside of cell. . . . and then releases it on inside of cell. Inside cell SIMPLE DIFFUSION FACILITATED DIFFUSION ACTIVE TRANSPORT Absorption of nutrients into intestinal cells typically occurs by simple diffusion or active transport.

38. Specialization • ready early, absorbed near the top • sugars, white bread, bananas • slower to digest, absorbed farther down • whole grain bread, fats, protein

39. Transport of Nutrients • either the bloodstream or lymphatic system • water soluble and small fats go the bloodstream and to liver • fat-soluble and larger fats are assembled by intestinal cells into chylomicrons • released into lymphatic system

40. Vascular System blood leaving the digestive system is routed to the liver Head and upper body Lungs Pulmonary vein Pulmonary artery Aorta = Arteries = Capillaries = Veins = Lymph vessels Left side Right side Heart Hepatic artery Hepatic vein Liver Portal vein Digestive tract blood leaving the liver is routed to the heart liver gets first rights to nutrients: major metabolic organ Lymph Entire body

41. Lymphatic System • one way system for fluid around tissue to enter the blood

42. Regulation of Digestion & Absorption • governed by hormones and nerves • regulation is a feedback mechanism • certain conditions demand responses 1. food enters the system 2. hormone gastrin is released 3. gastrin stimulates acid 4. acid turns off gastrin stomach pH is maintained at 1.5 – 1.7

43. good digestion and absorption of nutrients demand good health: sleep, activity, state of mind, as well as diet