Anatomy and Physiology Chapter-16_Digestive-System.pptx

Anatomy and Physiology

1. Chapter 16 Digestive System Lecture Outline Seeley’s ESSENTIALS OF ANATOMY & PHYSIOLOGY Eleventh Edition Cinnamon VanPutte Jennifer Regan Andrew Russo Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.

2. Digestive System Functions Ingestion and mastication – ingestion is the consumption of solid or liquid food. Mastication is chewing. Propulsion and mixing - Propulsion is the movement of food from one end of the digestive tract to the other. Mixing is the movement of food back and forth in the digestive tract to mix it with enzymes and facilitate absorption.

3. Digestive System Functions Digestion and secretion - Digestion is the mechanical and chemical breakdown of large molecules into smaller molecules that can be absorbed. Secretion is the addition of liquids, enzymes, and mucus to the ingested food. Absorption - the movement of molecules out of the digestive tract and into the blood or lymphatic system . Elimination - Elimination is the removal of undigested material, such as fiber from food, plus other waste products from the body as feces.

4. Anatomy of the Digestive System The digestive tract consists of the: oral cavity (mouth) pharynx esophagus stomach small intestines large intestines anus

5. Associated Organs The digestive system includes some associated organs, not directly in the digestive tract, that have ducts that lead into the tract. These associated organs are the: salivary glands liver gallbladder pancreas

6. Layers of Digestive Tract Wall The layers of the tract wall are also termed tunics. Mucosa: innermost layer secretes mucus Submucosa: above mucosa contains blood vessels, nerves, small glands

7. Layers of Digestive Tract Wall Muscularis: above submucosa longitudinal, circular, and oblique muscles Serosa/adventitia: outermost layer If peritoneum is present- serosa If no peritoneum- adventitia

8. Peritoneum and Mesentery Visceral peritoneum - or serosa, is the serous membrane that covers the organs. Parietal peritoneum - is the serous membrane that lines the wall of the abdominal cavity Mesenteries - connective tissue sheets that hold organs in place in the abdominal cavity Lesser omentum - mesentery connecting lesser curvature of stomach to liver and diaphragm Greater omentum - mesentery connecting greater curvature of stomach to transverse colon and posterior body wall

9. Salivary Glands Produce saliva which is a mixture of serous (watery) and mucous fluids: Keeps the oral cavity moist Needed for normal speech Dissolves food particles so they can be tasted Protects against bacteria and neutralizes pH Begins the process of digestion

10. Salivary Glands Salivary Glands: Parotid - serous glands anterior to each ear. Submandibular - found along the inferior border of the mandible; produce more serous than mucous secretions Sublingual - produce primarily mucous and lie below the mucous membrane in the floor of the oral cavity.

11. Salivary Glands Serous (liquid) portion of saliva contains enzymes Mucous portion of saliva contains mucin for lubrication Amylase - digestive enzyme that breaks down carbohydrates Lysozyme - enzymes that are active against bacteria

12. Pharynx Throat Connects the mouth to the esophagus It has three parts: nasopharynx oropharynx laryngopharynx

13. Esophagus Tube that connects the pharynx to the stomach Transports food to the stomach Joins stomach at cardiac opening Heartburn: occurs when gastric juices regurgitate into esophagus caused by caffeine, smoking, or eating or drinking in excess

14. Phases of Swallowing Voluntary phase: bolus (mass of food) formed in mouth and pushed into oropharynx Pharyngeal phase: swallowing reflex initiated when bolus stimulates receptors in oropharynx Esophageal phase: moves food from pharynx to stomach

15. Stomach Located in the abdomen Storage tank for food Can hold up to 2 liters of food Produces mucus, hydrochloric acid, protein digesting enzymes Contains a thick mucus layer that lubricates and protects epithelial cells on stomach wall from acidic pH (3)

16. Regions of the Stomach The esophagus opens into the cardiac part. The fundus is to the left of, and superior to the cardiac part. The body is largest part of the stomach. The body turns to the right, creating a greater curvature and a lesser curvature . The body narrows inferiorly to form the funnel-shaped pyloric part of the stomach.

17. Stomach Muscularis has 3 layers: outer longitudinal middle circular inner oblique to produce churning action Rugae: large folds that allow stomach to stretch Chyme paste-like substance that forms when food begins to be broken down

18. Stomach Pyloric opening : opening between stomach and small intestine Pyloric sphincter : thick, ring of smooth muscle around pyloric opening which regulates movement of food into the small intestine

19. Epithelial Cells in the Stomach Surface mucous cells - produce mucus that coats and protects the stomach Mucous neck cells - produce mucus Parietal cells - produce hydrochloric acid and intrinsic factor Endocrine cells - produce hormones and paracrine molecules Chief cells - produce pepsinogen, a precursor of the protein-digesting enzyme pepsin

20. Secretions of the Stomach Hydrochloric acid Produces a pH of about 2.0 in the stomach. Kills microorganisms, activates pepsin. Pepsin breaks covalent bonds of proteins to form smaller peptide chains Mucus A thick layer, which lubricates the mucosa of the stomach Protects mucosa from acidic chyme and pepsin Intrinsic factor Binds with vitamin B12 making it more readily absorbed by small intestine

21. Movement in Stomach Mixing waves: weak contraction thoroughly mix food to form chyme Peristaltic waves: stronger contraction force chyme toward and through pyloric sphincter Stomach empties every 4 hours after regular meal, and 6 to 8 hours after high fatty meal

22. Small Intestine Measures 6 meters in length Major absorptive organ of the gastrointestinal tract Chyme takes 3 to 5 hours to pass through Contains enzymes to further breakdown food Contains secretions for protection against the acidity of chyme

23. Anatomy of Small Intestine Duodenum: first part 25 cm long contains absorptive cells, goblet cells, granular cells, endocrine cells contains microvilli and many folds contains bile and pancreatic ducts

24. Anatomy of Small Intestine Jejunum: second part 2.5 meters long Primary site of nutrient absorption Ileum: third part 3.5 meters long

25. Mucosa of the Small Intestine The mucosa of the small intestine is simple columnar epithelium with four major cell types. Absorptive cells , which have microvilli, produce digestive enzymes, and absorb digested food Goblet cells , which produce a protective mucus Granular cells , which may help protect the intestinal epithelium from bacteria; and Endocrine cells , which produce regulatory hormones.

26. Secretions of the Small Intestine Secretions of mucus, ions, and water lubricate and protect the intestinal wall from the acidic chyme and digestive enzymes. Peptidases enzymatically breakdown proteins into amino acids for absorption . Disaccharidases enzymatically breakdown disaccharides into monosaccharides for absorption.

27. Movement in the Small Intestine Peristaltic contractions along the length of the intestine cause the chyme to move along the small intestine. Segmental contractions are propagated for only short distances and mix intestinal contents.

28. Liver Anatomy Weighs about 3 lbs. Located in the right upper quadrant of the abdomen under the diaphragm Consists of right, left, caudate, and quadrate lobes Porta: gate where blood vessels, ducts, nerves enter and exit Receives blood from the hepatic artery and hepatic portal vein

29. Liver Ducts Hepatic duct: transports bile out of liver Common hepatic duct: formed from left and right hepatic duct Cystic duct: joins common hepatic duct drains gallbladder Common bile duct: formed from common hepatic duct and cystic duct

30. Functions of the Liver Digestive and excretory functions Stores and processes nutrients Detoxifies harmful chemicals Synthesizes new molecules Secretes 700 milliliters of bile each day Bile: dilutes and neutralizes stomach acid and breaks down fats

31. Pancreas Located posterior to stomach in inferior part of left upper quadrant Head near midline of body Tail extends to left and touches spleen Endocrine tissues have pancreatic islets that produce insulin and glucagon Exocrine tissues produce digestive enzymes that travel through ducts to duodenum

32. Pancreatic Secretions The major protein-digesting enzymes are: Trypsin Chymotrypsin Carboxypeptidase

33. Pancreatic Secretions Pancreatic amylase continues the polysaccharide digestion that began in the oral cavity. The pancreatic enzyme lipase is a lipid-digesting enzyme. The pancreatic nuclease enzymes degrade DNA and RNA to their component ucleotides .

34. Large Intestine Absorbs water from indigestible food and create compact feces Contains cecum, colon, rectum, anal canal Cecum: joins small intestine at ileocecal junction has appendix attached Appendix: 9 cm structure that is often removed

35. Large Intestine Colon: 1.5 meters long contains ascending, transverse, descending, sigmoid regions Rectum: straight tube that begins at sigmoid colon and ends at anal canal

36. Large Intestine Anal canal : last 2 to 3 cm of digestive tract Food takes 18 to 24 hours to pass through large intestine

37. Large Intestine Feces formation is due to absorption of water and salts, secretion of mucus, and action of microorganisms. The colon stores the feces until defecation. Every 8 to 12 hours strong contractions, called mass movements propel the colon contents toward the anus. Movement of feces into the rectum distends the rectal wall and stimulates the defecation reflex .

38. Digestive Process Digestion: Chemical and mechanical breakdown of food Absorption: Most absorption occurs in the duodenum and jejunum, although some occurs in the stomach and ileum Transport: moves food through digestive tract, includes swallowing and peristalsis