Announcements No Class on November 23 rd Want some Independent Study Credits? SEE ME!

1. Announcements No Class on November 23rd Want some Independent Study Credits? SEE ME!

2. Specialized Cells for STOMACH Secretion Enteroendocrine cells: small - more common in gland base - pale, vesicles don’t fix well - may not reach lumen, but sample lumenal contents with microvilli -release variety of hormones into blood

3. Enteroendocrine cells

4. Specialized Cells of the Small Intestine Enterocytes (intestinal absorptive cells) Paneth cells- secrete antimicrobial substances Enteroendocrine cells- release hormones M cells- dome cells cap lymphatic nodules Goblet cells- mucous secreting

5. Enterocytes (intestinal absorptive cells) Tall columnar cells Microvilli=>striated border Epithelial specializations -Terminal web - Tight junctions Secrete Digestive Enzymes

6. Paneth Cells • - base of intestinal glands • large • intense acidophilic granules • phagocytose bacteria • secrete lysozyme- digests • bacterial cell wall

7. Epithelial Renewal in Stomach and Small Intestine

8. Celiac Disease (Sprue) • an inherited, autoimmune disease • lining of the small intestine damaged by eating gluten and other proteins found in wheat, barley, rye, and possibly oats. • exact cause unknown • flattening of intestinal villi • http://www.nlm.nih.gov/medlineplus/ency/article/000233.htm

9. Normal Intestine Celiac Disease www.aafp.org/afp/20071215/afp20071215p1795-u3.jpg

10. Large Intestine Simple columnar epithelium Absorption of water and electrolytes Columnar absorptive cells Crypts of Lieberkuhn Goblet cells www.kumc.edu/.../histoweb/gitract/gi21.htm

11. Ulcerative Colitis • An inflammatory bowel disease that affects the lining of the large intestine (colon) and rectum. • Symptoms include: • - Abdominal pain and cramping and sounds • - Blood and pus in the stools • - Diarrhea • Treatments: • - Diet and nutrition • - Manage stress • - Medications • - Surgery • Histology: Presence of crypt abscesses in which the crypt epithelium breaks down and the lumen fills with cells. The lamina propria is infiltrated with leukocytes.

15. Secretion / Digestion / Absorption • Requires coordination of secretion and motility with ingestion • NERVOUS AND HORMONAL SIGNALS

16. Secretion / Digestion / Absorption • Requires coordination of secretion with ingestion • Must coordinate the: • Release of saliva • Release of digestive enzymes • Release of HCl • Release of bile from gall bladder • Motility of gastrointestinal tract

17. Secretion / Digestion / Absorption What signals might trigger release of hormones and digestive enzymes?

18. Gastrin secretion: release from stomach enteroendocrine cells (G cells) is stimulated by 1) peptides and amino acids in stomach lumen 2) distention of stomach wall 3) sensory inputs --> neural innervation (GRP) - Parietal cells have gastrin receptors GASTRIN RELEASE HCl RELEASE PEPSIN ACTIVATION PROTEIN DIGESTION Enterochromaffin-like cell=ECL Cell

19. Regulation Parietal CellHCl secretion HCl produced by parietal cell Gastrin produced by G cell Gastrin stimulates Parietal Cells http://www.uwgi.org/gut/stomach_03.asp

20. Choleocystokinin (CCK): hormone released from enteroendocrine cells of small intestine is stimulated by presence of H+, amino acids, and fatty acids - Pancreatic cells have CCK receptors**(may act through neurons innervating the pancreas in humans) CCK RELEASE (INTESTINAL ENDOENDOCRINE CELLS) PANCREATIC DIGESTIVE ENZYME RELEASE DIGESTION OF CARBOHYDRATES, PROTEINS, LIPIDS IN SMALL INTESTINE

21. PANCREAS

22. PANCREAS: Endocrine / Exocrine Gland http://www.uwgi.org/gut/stomach_03.asp

23. PANCREAS: Exocrine Gland http://www.uwgi.org/gut/stomach_03.asp

24. PANCREAS: Exocrine Gland http://www.med-ed.virginia.edu/public/CourseSitesDocs/CellandTissueStructure/handouts/unrestricted/original/MMHndt_Liver.html

25. PANCREAS: Exocrine Gland

26. PANCREAS: Exocrine Gland

27. Choleocystokinin (CCK) -Gall Bladder smooth muscle cells have CCK receptors CCK RELEASE (INTESTINAL ENDOENDOCRINE CELLS) GALL BLADDER CONTRACTION RELEASE OF BILE INTO LUMEN OF SMALL INESTINE FACILITATED DIGESTION OF LIPIDS

28. GALL BLADDER

29. GALL BLADDER - lumen lined by simple columnar epithelium - microvilli, tight junctions, mitochondria - smooth muscle - concentrates bile (Na+ actively pumped out of lumen in exchange for H+, water follows) - stores bile until release

30. Pancreas: Endocrine Gland

32. PANCREAS: Endocrine Gland Islet of Langerhans: most numerous tail of pancreas, 2% volume

33. Pancreas: Endocrine Function  Cells: secretion of insulin in response to high blood glucose, causes uptake and storage of glucose into liver and skeletal muscle; diabetes mellitus Type I and II  Cells: secretion of glucagon in response to low blood glucose, causes synthesis of glucose and breakdown of glycogen in liver  Cells: secretion of somatostatin; inhibits insulin and glucagon release

34. Pancreas: Islets of Langerhans Blood Supply: Fenestrated capillaries Cascading Perfusion: portal-like  and  cells on periphery  cells centrally Acini of exocrine pancreas Insulin: stimulates exocrine secretion Glucagon & somatostatin: inhibits exocrine

35. Normal Islets of Langerhans Blood flow through Fenestrated Capillaries Exocrine acinar cells A &D cells B cells Insulin (B): stimulates exocrine secretion Glucagon (A) & somatostatin (D): inhibits exocrine secretion

36. Normal Islets of Langerhans Diabetes Mellitus Type 2 Congo red stain reveals amyloid deposits in and around capillaries and between cells. There is almost complete loss of islet cell detail. Amylin, or Islet Amyloid Polypeptide (IAPP) is secreted by b cells.

37. SAMPLE QUESTION! In patients with Zollinger-Ellison syndrome, a small tumor (gastrinoma) in the small intestine results in an increased production of the hormone, gastrin. Briefly describe gastrin function and predict a symptom of this disease including the cells that normally produce gastrin and its target cell.