Digestive System

1. Digestive System

3. The process by which complex chemicals in food are broken down into simpler chemicals that can be used by the body. What is Digestion?

4. Has 6 Parts: • Ingestion • Mechanical Processing • Digestion • Secretion • Absorption • Excretion The Digestive System

5. Food enters the digestive tract • AKA buccal cavity • Functions: • Sensory analysis • Mechanical processing • Lubrication • Limited digestion of carbohydrates and lipids Mouth/Oral Cavity

7. Lined by the oral mucosa • Tongue and the roof of the mouth have stronger cells to withstand abrasion from food • Includes: • Tongue • Salivary glands • Teeth Oral Cavity

8. Tongue • Manipulates material in the mouth and assists in chewing • Sensory analysis • ligual lipase-starts lipid digestion Oral Cavity (cont.)

10. Salivary Glands-secrete 0.5-1.5 liters of saliva each day • Paratoid salivary glands(25%) • Produce salivary amylase-breaks down starches • Sublingual salivary glands(5%) • Produce mucous that acts as a lubricant • Submandibular salivary glands(70%) • Produces lubricant, salivary amylase and mucins Oral Cavity (Cont.)

11. Teeth • Mastication (chewing) • Incisors • Front teeth-cutting or clipping (scissors) • Cuspids • Canines-tearing or slashing • Bicuspids/molars • Premolars-crush/mash Oral Cavity (cont.)

12. Passage of solid food, liquid, and air • Bolus-small oval mass of digestive contents • Pharyngeal constrictor muscles push bolus along • Palatopharyngeal and Stylopharyngeal Muscles elevate the larynx Pharynx

14. Transport solid and liquid food to the stomach • Passes through the esophageal hiatus-an opening in the diaphragm • Peristalsis: waves of muscle contractions that move the bolus through the digestive tract. Esophagus

16. Shaped like a J-lesser curvature is on the medial surface, greater curvature is on the lateral surface • 4 Regions: • Cardia • Fundus • Body • Pylorus Stomach

18. Cardia-first 3 cm. • Contains mucus to coat the connection to the esophagus and protect the esophagus from stomach acids • Fundus • Contacts the diaphragm 4 Regions of the Stomach

19. Body • Largest region of the stomach • Mixes ingested food with acids and enzymes-most acids and enzymes are produced in the body and fundus by Gastric Glands • Pylorus • Sharp curve of the J • Pyloric sphincter regulates the release of chyme • Pyloric canal empties into the duodenum Regions of the Stomach

20. Rugae-folds in the stomach-flatten when stomach is full • 4 functions: • Storage • Mechanical breakdown of food • Production of acids and enzymes to break down chemical bonds in food • Production of intrinsic factor-B12 Functions of the Stomach

21. Movement • Gastroenteric reflex-stimulates movement • Gastroileal reflex-relaxes ileocecal valve • Intestinal villi-fingerlike projections in the inner membrane of the small intestine • Covered by microvilli • Increases the surface area for absorption by 600 Small Intestine

24. 90% of nutrient absorption happens in the small intestine • Average length: 6 meters • 3 sections: • Duodenum • Jejunum • Illeum Small Intestine

25. Cecum-collects, stores, and begins to compact food • Colon- • Haustra-pouches that allow for expansion • Taeniae coli-smooth muscle-runs along outer surfaces of the colon • Fatty appendices-teardrop shaped fat along the outer surface Large Intestine-Colon

27. Reabsorption of water • 1500ml enters the large intestine-200ml is ejected • Absorbs bile salts and vitamins Function of the Large Intestine

28. 4 sections: • Ascending Colon • Transverse Colon • Descending Colon • Sigmoid Colon Colon

29. Smallest portion-25cm • Closest to the stomach • Receives chyme and digestive secretions from pancreas and liver • Mixing bowl Duodenum

30. Middle section-2.5 meters • Most chemical digestion and nutrient absorption happens here Jejunum

31. Last segment-largest-3.5 meters • Ends at the illeocecal valve-controls the flow of food into the cecum (beginning of the large intestine) Illeum

32. Begins at the upper border of the cecum • Right side of the peritoneal cavity to the inferior surface of the liver • Ends at the right colic flexure, AKA hepatic flexure Ascending Colon

33. Crosses from right to left along the abdomen • Travels from the right colic flexure to the left colic flexure (splenic) Transverse Colon

34. Descending Colon: Travels down the left side from the left colic flexure to the sigmoid flexure • Sigmoid Colon: S shaped • Empties into the rectum Descending and Sigmoid Colon

35. Last 15 cm of the digestive tract • Temporary storage of feces • Anal Canal is the last portion of the rectum Rectum

36. Liver • Pancreas • Gall Bladder Accessory Organs

37. Second largest organ in the body (skin is largest) • Left lobe and right lobe are separated by the falciform ligament • Porta Hepatis-convergence of hepatic portal vein, hepatic artery and common bile duct Liver

39. 3 main functions: • Metabolic regulation • Regulates nutrients, glucose levels, cholesterol, and amino acids in the blood. Also removes wastes and breaks down drugs • Hematological regulation • Phagocytosis, removes hormones, antibodies, toxins • Bile production Function of the Liver

41. Green organ • Small, hollow organ that stores and concentrates bile before it is released into the small intestine • Bile enters from the liver through the cystic duct and is released through the common bile duct when CCK is released (because chyme enters the duodenum) • Gallstones form when bile becomes TOO concentrated in the gallbladder Gallbladder

42. Posterior to the stomach • Long pinkish-grey organ • Head of the pancreas lies in the loop of the duodenum • Body-extends toward the spleen • Tail- short and rounded • Lumpy and lobular and wrapped in a thin connective tissue Pancreas

44. Pancreatic alpha-amylase • Breaks down some starches • Pancreatic lipase • Breaks down complex lipids • Nucleases • Break down nucleic acids • Proteolytic enzymes • Breaks apart proteins Functions of the Pancreas

45. Carbohydrate Metabolism • Lipid Metabolism • Protein Metabolism Digestion/Metabolism

46. Starches (bread, cereal, rice, etc.) and fruit • 2 part Digestion • Carbohydrases are released in the salivary glands and pancreas • Salivary amylase continues working for 1-2 hours after food is swallowed • Brush border(in the small intestine) enzymes • Maltase-breaks maltose • Sucrase-breaks down sucrose • Lactase-Breaks down lactose Carbohydrate Metabolism

47. Lingual Lipase-from the tongue-begins lipid digestion • Pancreatic Lipase-breaks down triglycerides with the help of bile salts Lipid Metabolism

48. Complex and time consuming • Mastication begins the process • Strong acids in the stomach break down connective tissue or cell walls • Pepsin-breaks down polypeptides • Peptidase-breaks down peptide chains into amino acids which can be absorbed Protein Metabolism

49. Vitamin A • Significance: synthesis of visual pigment, supports immune system, promotes growth • Source: leafy green vegetables, yellow vegetables • Deficiency: night blindness, retarded growth • Vitamin D • Sig: normal bone growth, calcium absorption • Source: sunlight • Deficiency: rickets, skeletal deterioration Fat Soluble Vitamins

50. Vitamin E • Sig: Prevents breakdown of vitamin A and fatty acids • Source: meat, milk, veggies • def.: anemia • Vitamin K • Sig: liver synthesis; clotting factors • Source: vegetables • Def.: bleeding disorders Fat Soluble Vitamins