Digestive SysteMmmmm

1. Digestive SysteMmmmm

2. Digestion: Mechanical and chemical breakdown of foods so that nutrients can be absorbed by cells Consists of the alimentary canal, leading from the mouth to the anus, and accessory organs whose secretions aid the process of digestion

4. Functions of the digestive system • Ingestion of food • Mechanical breakdown of food particles • Chemical breakdown of food particles • Absorption of nutrients • Elimination of waste

5. The Alimentary Canal • Muscular tube 9 meters long, passes through ventral cavity • Structure of wall similar throughout, vary according to specific function of that area • Layers: tunica mucosa, tunica submucosa, tunica muscularis, tunica serosa

6. Structure of the Wall

7. Alimentary Canal Wall • Tunica Mucosa (innermost layer) • Epithelium attached to connective tissue, protects underlying tissues; secretion and absorption • Tunica Submucosa • Loose connective tissue, houses blood and lymph vessels and nerves; nourishment • Tunica Muscularis • Two layers of smooth muscle, circular and longitudinal; propel food • Tunica Serosa (outermost layer) • Visceral peritoneum, protects underlying tissues, secretes serous fluid for movement

9. Movement of the Alimentary Canal Peristalsis! Mixing Propelling*

10. Which of the following is an accessory organ? • Mouth • Stomach • Esophagus • Liver • My brain • Which is NOT a layer of the alimentary canal wall? • Tunica mucosa • Tunica viscera • Tunica muscularis • Tunica serosa • Tunica submucosa • The submucosal layer is primarily for secretion and absorption? • True • False • Cytoplasmic projections from epithelial cells that enhance surface area are called • Villi • Rugae • Mesentary • Microvilli • Cell hair

11. Alimentary Canal Regions: Mouth • Mouth: first part of the alimentary canal • Functions to receive food and begin mechanical and chemical digestion • Mastication (chewing) • Enzymes

12. Alimentary Canal Regions: Mouth • Tongue • Covered with taste buds within papillae, which also provide friction to move food around • Attached to floor of mouth by frenulum • Tonsils • Lymphatic tissue – fight infections • Palatine, lingual, pharyngeal (adenoids)

13. Alimentary Canal Regions: Mouth • Teeth • Two sets develop in sockets within alveolar processes of the maxillary and mandibular bones • The 20 primary teeth are shed in the order they appeared and 32 permanent teeth replace them • They begin mechanical digestion

14. Alimentary Canal Regions: Mouth • Each tooth is held in its socket by a periodontal ligament

15. Accessory Organs: Salivary Glands • Salivary Glands • Secrete saliva, a substance which has mucus and enzyme components • Enzyme secreted: amylase (carbohydrate digestion) Parotid Submandibular Sublingual

16. Alimentary Canal Regions: Pharynx and Esophagus • Pharynx • Cavity posterior to the mouth • Three regions • Nasopharynx • Oropharynx • Laryngopharynx • Connects to the esophagus • Esophagus • Muscular tube that leads to the stomach • Has esophageal sphincters • Powerful peristalsis!

17. Swallowing Mechanism • Swallowing Reflex • Food forced into pharynx by the tongue • Sensory receptors sense food, which triggers swallowing reflex (medulla and pons) • Peristalsis transports food through the esophagus to the stomach

18. Alimentary Canal Regions: Stomach • Stomach: J-shaped muscular organ that receives and mixes food with digestive juices, and propels food to small intestine • Three sections: Fundus, Body, Pylorus

19. Gastric Secretions • Gastric glands within the mucosa of the stomach open up as gastric pits • Gastric glands generally contain three types of cells • Mucous cell • Chief cell – pepsin (protein digestion) • Parietal cells – HCl • Also secrete intrinsic factor, necessary for vitamin B12 absorption in the small intestine • Regulated by: • The hormone gastrin (increases) • Food entering small intestine (decreases) • Cholecystokinin released from small intestine

21. Gastric Actions • The stomach does very little absorption • Absorbs small amounts of water, salts, alcohol, and lipid-soluble drugs • Mixing and emptying actions • After a meal, mixing actions turn the food into a creamy paste called chyme • The rate at which the stomach empties depends on the fluidity of the chyme and the type of food

22. Sphincter says what? • Esophageal Sphincter • Pyloric Sphincter • Ulcers

23. The parasympathetic nervous system • Promotes digestion • Inhibits digestion • Promotes release of gastrin • A and C only • B and C only • A chief cell secretes HCl into the stomach to aid in digestion • True • False • Carbohydrate digestion begins in the mouth • True • False • eeny meeny miney mo… • Which is NOT a part of the tooth? • Dentin • Enamel • Cementum • Peridontal ligament • Dental conchae

24. Accessory Organs: Pancreas • The pancreas has the exocrine function of secreting pancreatic juice which aids digestion Pancreatic juice made by acinar cells Pancreatic juice drains into pancreatic duct Empties into small intestine via hepatopancreatic sphincter

26. Pancreatic Juice • Contains enzymes that digests proteins, fats, carbohydrates, and nucleic acids • Pancreatic enzymes include: • Pancreatic amylase (carbs) • Pancreatic lipase (lipids) • Trypsin, chymotrypsin, carboxypeptidase (proteins) • Nucleases (nucleic acids) • Regulated by • Endocrine and nervous systems • Secretin (hormone) • Cholecystokinin (released from wall of sm intestine)

28. Accessory Organs: Liver • The liver is the second largest organ in your body! • The liver functions in metabolic activities, storage of nutrients, filtration of blood, and chemical digestion • Performs over 500 jobs, and makes over 1000 essential enzymes!! • Divided into left and right lobes, which consist of lobules containing hepatic cells radiating from a central vein

29. Accessory Organs: Liver • Hepatic sinusoids lined with Kupffer cells – phagocytic cells responsible for cleaning up debris, bacteria, and old erythrocytes Bile is produced by hepatocytes, drains into bile ducts and used for digestion of fats

30. Liver Functions • Metabolic activities: • Synthesis, breakdown, or conversion of carbohydrates, lipids, and proteins • Detoxification (eg. ammonia  urea) • Stores: • Glycogen, vitamins A, D, B12, iron, and copper • Filters the blood, removing damaged RBCs, foreign substances, toxins • Secretes bile for digestion

31. Bile Composition • Bile is a yellow-green liquid that hepatic cells secrete • Contains water, bile salts, bile pigments, cholesterol, and electrolytes • Bile pigment bilirubin is from breakdown of heme (hemoglobin) • Only bile salts involved in digestion Stored in gall bladder Release controlled by cholecystekinin (released by cells of sm intestine wall) Bile salts emulsify fats and make them easier to digest and absorb

32. Alimentary Canal Regions: Small Intestine • Receives secretions from pancreas and liver • Completes digestion of chyme • Absorbs the products of digestion • Transports the remaining residue to the large intestine MAJOR SITE OF ABSORPTION!! 90% food fuel and water Consists of duodenum, jejunum, and ilium Attached to posterior abdominal wall by double layered peritoneum called mesentary

33. Structure of Small Intestinal Wall • Lined with villi • Increase surface area, help in mixing actions • Each villus has a core of connective tissue containing blood vessels and a lymphatic capillary called a lacteal

34. Villi and Microvilli

35. Regulation of Small Intestine Secretions • Mechanical and chemical stimulation from chyme stimulates goblet cells to secrete mucous • Distention (stretching) of intestinal wall stimulates parasympathetic reflexes that stimulate secretions from the small intestine • Cholecystekinin • Movements: • Peristalsis • Segmentation

36. Alimentary Canal Regions: Large Intestine • The large intestine absorbs water and forms and stores feces • Ascending Colon, Transverse Colon, Descending Colon, Sigmoid Colon, Rectum Doesn’t digest or absorb nutrients Secretes mucous and absorbs water and electrolytes Diarrhea – often due to infections/irritants; leads to malabsorption or increased motility Contains important intestinal flora which synthesize vitamins

37. Which does the small intestine do? • Peristalsis • Segmentation • Chemical digestion • A and C only • All of the above • Cholecystekinin • Inhibits bile release into small intestine • Is released from the small intestine • Prevents pancreatic juice release • Stimulates increased digestion in the stomach • Has way too many syllables • Acinar cells produce pancreatic enzymes • True • False • The liver is involved in • Metabolism • Storage • Bile production • Detoxification • All of the above

38. Nutrition and Nutrients

39. Original Version (1994):Shows suggested amounts of each food type for a healthy and rounded diet…but what is a “serving”? What about different ages and activity levels?

40. New Design (2005): Emphasis on physical activity, easier to understand, relative proportion of each food type, personalized for age, sex, activity level (see mypyramid.gov)

42. Diabetic Food Pyramid: Groups foods based on their protein and carbohydrate content (eg. potatoes and beans in the “grains” box, cheese in the “meats” box)

43. Healthy Living Food Pyramid

44. Nutrition and Nutrients • Nutrition: Process by which the body takes up and uses nutrients • Nutrients: Food/chemicals that we need to live and grow • Essential nutrients: nutrients our cells cannot synthesize; must take in from the outside (eg. food) • Macronutrients, vitamins, minerals

45. Carbohydrates • Sugars and starches used for energy • Ultimately want glucose (simple sugar) for use in cellular respiration Get 38 ATP per glucose in aerobic respiration All carbs are absorbed as monosaccarides. Only macronutrient that is not essential to the diet A lot of controversy regarding carbs in today’s society!

46. Carbs to Blame? • Changes in the western diet linked to obesity and inflammatory bowel diseases • Evolution hasn’t had time to catch up to the industrial and agricultural revolutions! IBD: Rising prevalence in Western culture, virtually non-existent in cultures maintaining primitive diets Childhood Obesity (tripled since 1980)

47. Lipids • Includes fats, phospholipids, and steroids • Used for energy and energy storage, cell membranes, hormones Fats serve as compact energy storage Need to eat fats to absorb fat-soluble vitamins (A,D,E,K) Saturated vs unsaturated Hydrogenated and trans fats Unsaturated – plant origin Saturated – animal origin Cholesterol – only in animal fats HDL vs LDL

48. Proteins • Polymers of amino acids • MANY functions (enzymes, antibodies, hormones, clotting factors, etc) • Amino acids can also be a source of energy if necessary • Absorbed in the duodenum and jejunum Complete vs incomplete proteins Food combining to get all essential AAs

49. Vitamins • Organic compounds necessary for normal metabolism • Often co-factors or activators for enzymes • Not produced in adequate amounts by cell • Need to ingest • Fat soluble (A, D, E, K) and water soluble (C, B-vitamins) Vitamin A

50. Minerals • Derived from the soil and used in metabolism • Concentrated in bones and teeth • Calcium and phosphorus most common (75% by weight of minerals in our body) • Other minor minerals: potassium, sulfur, chlorine, magnesium