Digestion :Final Day

1. Digestion :Final Day

2. Part I. Review Let’s Be Specific About Enzymes

3. Carbohydrates Mouth: Amylase( present in saliva) digests starch to oligosaccharides. Has pH optima of 6.75 -7.0 Sm. Intestines: Pancreatic amylase; oligosaccharides to dissacharide (maltose) Brush border enzymes: (dextrinase and glucoamylase): hydrolyze dissacchrides to monosaccharides. (these enzymes are secreted from the duodenal mucosum)

4. Proteins • Digestion starts in Stomach with PEPSIN ( optimum pH 1.5-2.5) Polypeptides reduced to oligopeptides • Small Intestine with Pancreatic enzymes TRYPSIN and CHRYMOTRYPSIN into smaller peptides ( 2 or 3 amino acids) • Brush border enzymes (aminopeptidase and dipeptidase finalize digestion to amino acid monomers

5. About Lipid Digestion • Begins and is Finished in the Small Intestines. • Enzyme? Just say Lipase for Triglycerides • Triglycerides that are not digested, combine w/ cholesterol and phospholids to form chylomicrons “milky fat” ; These are too large to enter capillaries and enter the lacteal. They form milly portion of lymph. • Eventually this extra fatty lymph will empty into blood stream via thoracic duct. • LIPOPROTEIN LIPASE will digest to fatty acids and glycerol or new chylomicrons are used to transport cholesterol back to liver.

6. Nucleic Acid Digestion • For Both DNA and RNA. • To nucleotide monomers • In the Small Intestine only. • By pancreatic enzyme and Brush Border (nucleosidases and phosphatases)

7. Some Terms To Review • Microscopic Anatomy: • A villus in Small Intestine is covered with two kinds of epithelial cells; Absorptive and Goblet. • Goblet: Secrets mucus • Absorptive; It is for absorption; This is your BRUSH BORDER CELL

8. Part III. Regulation of Digestion: Hormones

9. Vomiting (Emesis) Induced by excess stretching of the stomach (says your text) However, many cues may prompt this act such as bacterial toxins, excessive alcohol and certain drugs or mixtures or drugs. Before vomiting a person typically is pale and feel nauseas. The emetic center of medulla initiates contractions of the abdominal wall, and the cadiac sphinster relaxes thereby ejecting chyme.

10. Which Hormones Regulate the Pancreas?

11. Hormonal Control of Secretion • Cholecystokinin released from duodenum in response to arrival of acid and fat • causes contraction of gallbladder, secretion of pancreatic enzymes, relaxation of hepatopancreatic sphincter • Secretin released from duodenum in response to acidic chyme • stimulates all ducts to secrete more bicarbonate • Gastrin from stomach and duodenum weakly stimulates gallbladder contraction and pancreatic enzyme secretion

13. Stimulation of the Release of Pancreatic Juice • Vagus nerve • Local hormones • Secretin • Cholecystokinin Figure 14.16

18. Part I. About The Cells (Things We May Have Missed)

19. Revisiting the Colon • Although water absorption from undigested food is one of its functions, it is not the colon’s primary function.

20. What are the Crypts of Lieberkuhn? • You observed these in the appendix. But they are found throughout the GI tract ; i.e. between villi the pits, if the lead to a gland..its considered COL. • COLs secrete juice or mucus or enzymes. • Deep in the crypts are specialized cells called PANETH CELLS….release Lysozyme, an antibacterial enzyme. • Crypts DECREASE as you go down the GI tract.

21. All the Crypts ARE LYBYS

22. What About Goblet Number? • Its as we originally said : Goblets INCREASE in number as we go down the GI tract. There are NONE in the stomach (But what about the much needed mucus for all that acidity? The neck cells take care of that) some in the intestine, and plenty in the large intestines.

23. Liver, Gallbladder and Pancreas • All release important secretions into small intestine to continue digestion

24. Gross Anatomy of Liver • 3 lb. organ located inferior to the diaphragm • 4 lobes - right, left, quadrate and caudate • falciform ligament separates left and right • round ligament, remnant of umbilical vein • Gallbladder adheres to ventral surface between right and quadrate lobes

25. Inferior Surface of Liver

26. Microscopic Anatomy of Liver • Tiny cylinders called hepatic lobules (2mm by 1mm) • Central vein surrounded by sheets of hepatocyte cells separated by sinusoids lined with fenestrated epithelium • Blood filtered by hepatocytes on way to central vein

27. The Liver • Largest Gland in the Body • Has SEVERAL metabolic functions • Only DIGESTIVE Function is SYNTHESIS AND SECRETION OF BILE

28. Important Anatomical Feature To Remember about Liver Concerning Bile • Hepatopancreatic Sphincter or also called Sphincter of Oddi; This regulates passage of bile and pancreatci juice into the duodenum .

29. Part IV. Selected Diseases of the Digestive Tract

30. Peptic Ulcer • A peptic ulcer, also known as PUD or peptic ulcer disease is an ulcer of an area of the gastrointestinal tract that is usually acidic and thus extremely painful.. • Ulcer results from excessive acid production or inadequate alkaline mucus that protects epithelium. As much as 80% of ulcers are associated with Helicobacter pylori, a spirochete that can live in acidic environments and this guy erodes the epithelium. The lamina propria is destroyed by gastric juices. H.pylori can live in stomach or duodenum (so either gastric or duodenunal ulcer). • H.pylori can cause stomach cancer. • Cure: Tetracycline or amoxicillin

31. GALLSTONES

32. Why Do We Get Gallstones? • Cholesterol is a fat--- bile, a watery solution. Fats insoluble in watery solutions. In order to make cholesterol dissolve in bile, the liver also secretes two detergents-bile acids and lecithin-into the bile. These detergents dissolve the fatty cholesterol so that it can be carried by bile through the ducts. • If liver secretes too much cholesterol for the lecithin it secretes, some will not dissolve. Similarly, if liver does not secrete enough bile acids and lecithin, some cholesterol does not dissolve. Likewise, the undissolved cholesterol clumps together --gallstone.

33. Many times these are not to painful; they remain unnoticed and are flushed down the bile duct and eliminated. However in some people a situation called CHOLECYSTITIS results (SEE NEXT SLIDE) Gallstones

34. Cholecystitis • The gallstones enter and jam the cystic or Bile duct. • This is painful! • Gallbladder becomes swallen and inflamed. • Jaundice can arise. • Surgery Necessary • If gallbadder is also removed do to damage it is called CHOLECYSTECTOMY.

35. Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrotic scar tissue as well as regenerative nodules, leading to progressive loss of liver function. Basically, your hepatacytes don’t function anymore because they are scar tissue. Cirrhosis is most commonly caused by alcoholism and hepatitis C . Alcholism due to “overworking” as in detoxing and in hepatitis the cells are inflamed-- which kills them. Hepatic Cirrhosis

36. Stomach Cancer • Stomach cancer represents roughly 2% (25,500 cases) of all new cancer cases yearly in the United States, but it is much more common in Korea, Japan, Great Britain, South America, and Iceland. It is associated with high salt in the diet, smoking, and low intake of fruits and vegetables. Infection with the bacterium H. pylori is the main risk factor in about 80% or more of gastric cancers. It is more common in men. • Treatment/Cure: This cancer responds best to surgery. Doesn’t respond well to chemo. You Can live without your stomach. However, you will not get your intrinsic factor SO patient needs vitamin B-12 shots. Also, modify diet..eat less, smaller meals.