Lecture 30Outline of Last Lecture I. The Digestive System: The MouthOutline of Current LectureI. The Digestive System: The Esophagus, Stomach, and IntestinesCurrent Lecture1. Digestive System (Esophagus, Stomach and Intestines)a. Where is the esophagus, and what is its function?i. In the neckii. Carries swallowed food through the neck and the thoracic cavityb. Does its muscular externa contain smooth muscles or skeletal muscles or both?i. Muscular externa contains skeletal muscle in the superior 1/3, smooth and skeletal muscle in the middle 1/3, and smooth muscle in the inferior 1/3c. Describe the stomach’s shape, location, and its five gross regions.i. The stomach is J shapedii. Upper left part of the abdominal cavityiii. Gross regions1. Cardiac part2. Fundus3. Body4. Pyloric atrium5. Pyloric canal6. Pylorus d. What causes stomach ulcers?i. Peptic ulcers result from the acid-tolerant bacterium helicobacter pylori, which infects the stomach and causes inflammation of the stomach walle. What are gastric rugae?i. Folds of the mucosa on the inner surface of the stomach1. Function is to help the stomach expand to hold a large mealf. What type of epithelium lines the inside of the stomach?i. Simple columnar g. What are gastric pits and gastric glands?i. Gastric pits: short cups, lining the stomach’s inner epitheliumii. Gastric glands: extend to lamina propria, h. In the muscularis externa of the stomach, what are the oblique layer and the pyloric sphincter, and what do they do?i. Oblique layer: bends the stomach like a closing jackknife to force the emulsified food into the small intestineii. Pyloric sphincter: stays constricted but leaves a narrow channel between stomach and duodenum, only allowing the most well-mixed and finely emulsifiedfood particles to pass through1. Helps keep the larger chunks of food in the stomach until ready for digestionBIOL_315 1nd Editioni. Name and explain 4 specializations of the small intestine that provide a large surface area for absorbing nutrients.i. Long and coiledii. Folded to increase absorptive area iii. Swaying Villi maximizes the amount of contact between the villi and nutrient soup, allowing more nutrients to be absorbediv. Microvilli increase the surface areaj. Distinguish between villi and microvilli.i. Villi are longer and on the small intestine surfaceii. Microvilli are much smaller and are on the epithelial cellsk. What are absorptive cells in the intestinal epithelium?i. covers intestinal villi ii. nutrients enter l. Which type of nutrient does not enter the blood capillaries, but the lymph capillaries?i. fatm. Describe the function and location of the intestinal crypts of Lieberkuhn.i. Divide rapidly and push upward onto the villi, constantly replacing the intestinal epithelium by differentiating into both absorptive and goblet cellsii. Cells can only resist enzyme destruction for a few days, so must constantly be replacediii. Located in crypts to stay protected from the enzymes n. What is the large intestines main function? i. Absorbs water and ions to compact the feceso. Why, functionally, does the large intestine secrete more mucus and contain more lymphoid tissue than the small intestine?i. To lubricate the passage of feces ii. To fight against bacteria, which there is more of in the large intestinep. Does the large intestine have villi like the small intestine does? Does it have intestinal crypts?i. No.ii. Yes, rectangular tubulesq. Describe the function and location of the appendix.i. Location: base of the appendix where attaches to cecumii. Function: sample bacteria and antigens from the feces and then activate many memory lymphocytes to build up long term immunity r. What causes appendicitis? How can appendicitis lead to peritonitis and death?i. The lumen of appendix is narrow so can get a blockage, leading to a severe bacterial infection ii. An infected appendix can swell and rupture leaking feces into peritoneal cavitys. What is McBurney’s point?i. The point on the skin of the anterior abdominal wall that lies directly anterior to the base of the appendixii. Maximum tenderness is experienced here during appendicitist. What causes hemorrhoids?i. Hemorrhoidal veins become abnormally distended with blood they push into the lumen of the anal