The Digestive System

1. The Digestive System Lindsey Bily Anatomy & Physiology Austin High School

2. Most of the food that we eat is in a form that CANNOT reach the cells. • Even if it could pass through the intestines, it is too complex for the cells to use. • Food has to modified and broken down so that the nutrients can be absorbed by the cells. What does the Digestive System do?

3. The main organs form a tube that goes through your body and is open at both ends (mouth-anus) • This is called the gastrointestinal (GI) tract. • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Appendix • Liver • Gallbladder • Pancreas Organs of Digestion

4. Made up of 4 layers that have blood vessels and nerves traveling through them. • 1. mucosa: innermost layer and allows for lubrication and easy flow. • 2. submucosa: thicker and made up of connective tissue. Contains the nerves and blood vessels. • 3. muscularis: thick layer of smooth muscle that is innervated. • 4. serosa: connective tissue outer layer that covers the organs. Walls of the GI Tract

5. The mouth is called the “oral cavity” • Lips: skin covers mucous membranes. They are very sensitive and easily irritated (chapped lips). • Cheeks: lined with mucous membrane over the buccinator muscle and fat. Has mucus secreting glands that open by the molars. • Hard Palate: The top anterior part of the mouth made up of bones. • Soft Palate: The top posterior part of the mouth made of muscle and has the uvula hanging down. Forms the partition between the mouth and nasopharynx. • Tongue: skeletal muscle covered with mucous membrane. Helps to ball up food and swallow. The Mouth

6. There are lots of blood vessels under the tongue so some medicines are placed there to dissolve and be absorbed directly into the blood stream. The Mouth

7. Salivary Glands- They secrete about 1 liter of saliva per day! • Parotid Glands: located below the external ear. • Submandibular Glands: under the mandible. You can feel them. • Sublingual Glands: located under the tongue. The Mouth Swollen and inflamed gland salivary gland cyst

8. Teeth allow us to masticate (to chew). • They can cut, tear and grind our food so that it ground into small bits which increases the surface area. • Increased surface area allows more surface for the digestive enzymes to get to. The Teeth

9. Three main parts of a tooth • Crown-exposed part that you see made of enamel which is 97% calcium. • Neck- narrow part that is covered by gum. • Root- fits into the socket of the maxillae and mandible. • Under the enamel is the dentin that contains blood vessels and nerves. • You have 20 baby teeth and then 32 permanent teeth. The Teeth

10. The mass of food that we swallow is made into a round ball called a bolus. • During swallowing, the bolus passes from the mouth, through the pharynx to the esophagus. Pharynx

11. About 25 cm long and goes from the pharynx to the stomach through the diaphragm. • Lies posterior to the trachea • Guarded by 2 sphincters at each end • Upper esophageal sphincter: makes sure you don’t get air in your esophagus. • Lower esophageal sphincter (cardiac sphincter): opening of the esophagus and stomach. Esophagus

12. Hiatal Hernia: The hole where the esophagus passes through the diaphragm may get too big. This causes the esophagus and sometimes the stomach to bulge out. Gastroesophageal reflux disease (GERD): stomach acid comes out of the stomach and into the esophagus. Sometimes caused by a hiatal hernia or due to excess stomach acid. It HURTS!! Esophagus

13. The esophagus dilates to form the stomach. Normally the stomach holds 1-1.5 Liters of food. • Located under the liver and the diaphragm. • When you eat a really large meal, the stomach pushes up on the diaphragm and heart giving you the sensation that it is hard to breathe. The Stomach

14. Flow into and out of the stomach is controlled by 2 sphincters. • Lower esophageal (cardiac) sphincter: between the esophagus and stomach. • Pyloric sphincter: between the end of the stomach into the small intestine. Stomach

15. Stores food until it is partially digested and ready to move to the intestines. • Secretesgastric juice that contains acid and enzymes to help digest food. • Churns the food which breaks it into the small particles and mixes it with the gastric juice. • Secretes intrinsic factor that protects vitamin B12 from being destroyed. • Absorbs some nutrients (some drugs, water, alcohol, and some short chain fatty acids). • Produces hormones gastrin (regulates digestion) and ghrelin (increases appetite). • Destroys some pathogens. Stomach Functions

16. It is 1 inch wide and 20 feet long and fills most of the abdominal cavity! • Has three divisions… • duodenum: part where the stomach attaches. • Jejunum: part where it turns abruptly forward and downward. It is about 8 feet long. • Ileum: The remaining 12 feet. Small Intestine

17. The lining of the intestine has millions of villi (fingerlike projections). • This increases the surface area in which to absorb nutrients. • Each villus has an arteriole, a venule and a lymph vessel. Small Intestine

18. Diameter of 2.5 inches and a length of 5-6 feet. • Has 3 divisions... • Cecum: first 2-3 inches • Colon: • Ascending colon (goes up) • Transverse colon (goes across) • Descending colon (goes down) • Sigmoid (S Shaped) • Rectum: last 7 or 8 inches • Last inch is the anal canal • Anus is the opening to go outside of the body Large Intestine

19. Vermis means “worm” and forma means “shape”. The appendix is a wormlike tubular structure. • 3-4 inches long • It connects with the cecum of the large intestine. • Believed to be a “breeding ground” for the bacteria that live in your large intestine. Vermiform Appendix

20. Large continuous sheet of membrane that covers most of the organs and holds them loosely in place. Peritoneum

21. Largest gland in the body. • Weighs about 3-4 pounds • Lies right under the diaphragm. • Has 2 lobes (right and left) and is separated by the falciform ligament The Liver

22. Contains lots of tiny cylinders about 2 mm high and 1mm in diameter called hepatic lobules that are made from hepatic cells and have branches of the hepatic vein and hepatic artery going through them. The Liver

23. Blood comes into the hepatic lobules… • From hepatic artery: cells get oxygen • From hepatic portal vein: blood gets “inspected”. • Phagocytic cells eat bacteria, old RBCs, and other foreign particles. • Vitamins, minerals, and nutrients are absorbed by the hepatic cells. • Toxins are absorbed into the hepatic cells and are detoxified (made harmless). The Liver

24. The hepatic duct emerges from the liver and joins the cystic duct from the gallbladder and opens into the duodenum of the small intestine via the common bile duct. • Bile is formed by the liver cells. The Liver-Bile Ducts

25. Detoxifies lots of substances. • Secretes a pint of bile a day. • Metabolizes proteins, fats, and carbs. • Stores iron, vitamins A, B12, and D. • Produces plasma proteins and produces RBCs in the fetus. Liver-Functions

26. Bile is made up of bile salts, bile pigments, and cholesterol. • Bile salts are made from cholesterol by the liver • Aid in absorption of fats. If you don’t have bile, you get really sick after eating a high fat meal. Bile

27. 3-4 inch long sac • Holds 30-50 mL of bile • Lies under the liver • Stores bile and concentrates it. • After you eat, it squirts some of the concentrated bile into the duodenum. • Jaundice is a yellow discoloration of the skin and mucosa. Occurs when the bile cannot get into the duodenum. It then can’t exit the body via feces. Instead it gets absorbed into the blood. Gallbladder

28. Cholecystitis: inflammation of the gallbladder. • Cholelithiasis: gallstone formation. They are solid clumps of mostly cholesterol. Gallbladder Disorders

29. Grayish pink gland about 6-9 inches long. • Has exocrine and endocrine glandular tissue. • Exocrine: secretes digestive enzymes into the duodenum. • Endocrine: secrete insulin and glucagon into the bloodstream. Pancreas

30. Salivary gland diseases can cause a lack of saliva which hinders effective digestion. Cancer or inflammation of the glands can affect levels of immunoglobin A which helps fight off oral infections. • Mumps: caused by a virus (remember your MMR vaccine?) that swells the parotid glands. Usually occurs in children 5-15, but can occur in adults. • A severe infection in adults. Can cause swelling of the joints, pancreas, myocardium, kidneys and testes in men. Mumps virus Digestive Disorders

31. Tooth decay: occurs on the tooth surfaces where food debris, acid-secreting bacteria, and plaque accumulate causing a cavity. If not treated, you can get an infection and loss of teeth. • Gingivitis: inflammation of the gums. Usually caused by poor hygiene (poor flossing or brushing) but also by diabetes, vitamin deficiency, or pregnancy. Digestive Disorders

32. Tooth decay • gingivitis

33. Inflammation of the periodontal ligament that holds the tooth in the jaw. • Usually occurs with untreated gingivitis that spreads into the bony tissue of the jaw. • Leading cause of tooth loss in adults. Periodontis

34. Wide spaces within teeth, overlapping teeth, overbite or underbite. • Contributes to headaches or proper mastication of food. • Corrected by orthodontics Malocclusion

36. Affects more than 60 million Americans • Called heartburn or acid indigestion • Backflow of gastric juices into the esophagus. • Usually symptoms are mild and occur infrequently. • Avoid smoking, caffeine, alcohol, spicy foods, acidic foods, chocolate or losing weight to fix the problem. • Antacids (TUMS) or H2-receptor antagonists (Pepcid, Zantac, or Tagament) Gastroesophageal Reflux Disease (GERD)

37. Severe cases can cause asthma attacks, severe chest pain, bleeding or erosive esophagitis. • Proton pump inhibitor drugs decrease the production of stomach acid (Nexium, Prilosec, Prevacid) • Barrett’s esophagus is a precancerous condition when GERD is left untreated. GERD

38. Craterlike wound or sore caused by tissue destruction. • 1 in 10 Americans will have a gastric or duodenal ulcer in their lifetime. • Cause burning pain and may result in hemorrhage, perforation, widespread inflammation, or scarring. • Most are caused by an infection of the bacteria H. pylori. • The bacteria burrows in the mucosa lining and impairs the body to produce mucus. • Can also be caused by long term use of NSAIDs (aspirin and ibuprofen). They interfere with the prostaglandin function of regulating the mucus lining of the GI Tract. Ulcers

39. Pylorospasm: common in infants. The pyloric sphincter doesn’t relax to let food out of the stomach, so the patient vomits all of the food. • Pyloric stenosis: narrowing of the pyloric sphincter. Pyloric Sphincter Disorders

40. Inflammation of the mucus lining of the appendix. • Can rupture if not treated or removed in time. This can be fatal as the infection is released throughout the body. Appendicitis

41. The purpose of the digestive system is to bring nutrients into the body so they are available to the cells. • Ingestion: food taken in • Digestion: complex nutrients broken down into smaller nutrients • Motility: movement through the GI tract • Secretion: digestive enzymes are secreted • Absorption: nutrients move into the body from the GI tract • Elimination: materials not absorbed must be excreted. Digestive Physiology

42. Includes all movement of food through the GI tract. • Mastication: chewing. Particle size is reduced. • Deglutition: swallowing • Peristalsis: the smooth muscles of the GI tract produce a wavelike ripple of movement to propel the food forward through the tract. • Segmentation: Forward and back movement in one region to break apart the food. peristalsis Segmentation  Mechanical Digestion

43. It takes anywhere from 2-6 hours for food to empty the stomach after a meal. • Food is churned and mixed with gastric juices to form a milky substance called chyme. • This slowly is squirted into the duodenum. • It takes about 5 hours to travel through the small intestine. Food Movement

44. The food undergoes hydrolysis reactions (combines with water) to split into smaller compounds. • Digestive enzymes are organic catalysts that speed up the breakdown of food. Most of the organs in the system secrete some kind of enzyme. Chemical Digestion

45. Carbs are made up of saccharides • Polysaccharides- starch and glycogen • Disaccharides- sucrose, lactose, maltose • Monosaccharides- glucose, fructose, galactose • Amylases are enzymes that break apart polysaccharides into disaccharides. (salivary amylase and pancreatic amylase) • Maltase, sucrase, and lactase break down the disaccharides into monosaccharides. Carbohydrate Digestion

46. Proteins are made up of long folded amino acid chains. • Proteases break apart these chains by hydrolysis. Examples: pepsin- in the gastric juice trypsin and chymotrypsin- in pancreatic juice peptidases- in the intestine Protein Digestion

47. Fats are insoluble (don’t dissolve) in water. • They have to be EMULSIFIED first. They are broken down into tiny droplets. • Bile and lecithin are formed in the liver and are emulsifiers. • Lipases are enzymes that then can break down the fats into smaller particles. • Lipases are found in pancreatic juice Fat digestion

48. Mostly water that helps to liquefy the food • Contains salivary amylase to break down polysaccharides. • Also contains lipase but really doesn’t have enough time to do any digestion of fats. • Contains NaHCO3 which makes it slightly basic. Amylase works best is a higher pH. • Contains mucus so the food can slide through the GI tract easier Saliva

49. Contains water and mucus just like saliva, but also… • Chief cells in the stomach secrete pepsinogen. This is an inactive form of pepsin (digests proteins). It is activated by HCl. • Parietal cells produce the HCl in the stomach. • Parietal cells also produce intrinsic factor which protects Vitamin B12 from being “eaten” by the acid and enzymes. Gastric epithelium. Red large cells are gastric cells, the yellow are mucus secreting cells. Gastric Juice

50. Pancreatic juice is mostly water but has lots of different enzymes • trypsin- a protease • Chymotrypsin-a protease • Various lipases • Various nucleases (digest RNA and DNA) • Amylase • The pancreas secretes bicarbonate to neutralize the acidic pH of the chyme as it comes from the stomach. Pancreatic Juice