11.30.11+-+Gastrointestinal+System+II+-+Stomach+Through+Anal+Canal

11.30.11 - Gastrointestinal System II - Stomach Through Anal Canal


 * 1. Describe the structure and function for the following gastrointestinal organs.**

Stomach Adventitia in retroperitonial ascending and descending parts || None || Intestinal glands || absorptive cells, goblet cells ||  || 6 days ||
 * Organ || Mucosal Layer || Submucosal Layer || Muscularis Layer || Adventitia/Serosa || Villi || Glands || Cell Types || Functions || Cell Renewal ||
 * Oral Cavity || some keratinized, some non-keratinized stratified squamous epithelium || N/A || N/A || N/A || None || 3 exocrine salivary (mucous and serous) glands (submandibular, sublingual, and parotid) ||  || Begin CHO digestion with salivary amylase; ||   ||
 * Tongue || Dorsal surface: keratinized stratified squamous epithelium. Ventral surface: non-K stratified squamous epithelium. Lamina propria w/ minor salivary glands (mucous and serous) || None || 4 intrinsic muscles: superior and inferior longitudinal, vertical, and transverse ||  || None || Minor exocrine salivary (mucous and serous) Von Ebner glands at base of trench surrounding vallate papilla ||   || Taste, mixing food, swallowing, phonation ||   ||
 * Esophagus || Non-K stratified squamous epithelium w/ lamina propria and longitudinal smooth muscle layer. W/in the lamina propria near the stomach are mucous secreting esophageal cardiac glands. ||  || prox 1/3 skeletal, middle 1/3 mixed, distal 1/3 smooth muscle || thoracic = adventitia, abdominal = serosa (peritoneum) || None || esophageal cardiac glands near stomach - mucous secreting ||   || transports food to stomach || 2-3 days ||
 * Stomach || Simple columnar, gastric pits in epithelium. Cardiac, gastric, and pyloric glands in lamina propria. ||  || Inner oblique; middle circular, outer longitudinal || Serosa || None || Cardiac, gastric, and pyloric glands in lamina propria. || parietal, chief, APUD, stem, mucous neck || low pH, mix food and fluids to form chyme. || 4-7 days ||
 * Duodenum || simple columnar epithelium covers villous surface and lines crypts. lamina propria forms CT core of each villus and surrounds intestinal glands. ||  || Inner circumferential, outer longitudinal || Serosa for intraperitoneal segments. Retroperitoneal covered by adventitia || Yes || mucous glands of Brunner in lamina propria and submucosa. intestinal glands (crypts of Leiberkuhn) || intestinal absorptive cell, goblet cells, paneth cell, APUD cell || final digestion and absorption of nutrients. || 3-6 days ||
 * Jejunum || simple columnar epithelium covers villous surface and lines crypts. lamina propria forms CT core of each villus and surrounds intestinal glands. ||  || inner circumferential, outer longitudinal || Serosa || Yes || no Brunner's glands. But yes on Intestinal glands (crypts of Leiberkuhn) || intestinal absorptive cell, goblet cells, paneth cell, APUD cell || final digestion and absorption of nutrients. || 3-6 days ||
 * Ileum || simple columnar epithelium covers villous surface and lines crypts. lamina propria forms CT core of each villus and surrounds intestinal glands. || Peyer's patches || inner circumferential, outer longitudinal || Serosa || Yes || no Brunner's glands. But yes on Intestinal glands (crypts of Leiberkuhn) || intestinal absorptive cell, goblet cells, paneth cell, APUD cell || final digestion and absorption of nutrients. || 3-6 days ||
 * Colon || simple columnar epithelium, lamina propria with intestinal glands. plicae semilunaris || solitary lymphoid nodules || inner circumferential, outer longitudinal thickened in 2-3 areas to form taeniae coli. || Serosa for transverse and sigmoid;
 * Appendix || simple columnar epithelium, lamina propria with intestinal glands. plicae semilunaris || numerous lymphoid follicles in LP and submucosa || no taeniae coli || Serosa || None || None || absorptive cells, goblet cells || Endocrine and immune function || 6 days ||
 * Anal Canal || simple columnar epithelium with goblet cells proximally, last 1" is lined with non keratinized stratified squamous epithelium that converts to keratinized at anal verge || large rectal veins || inner circular smooth muscle thickened to form internal sphincter. no taenae coli ||  || None ||   || non-keratinized stratified squamous epithelium || water absorption, forming fecal mass, production of mucus ||   ||


 * 2. Describe the structure and function of constituent cells of the gastric glands.**

//Parietal (Oxyntic) Cells// //Chief (Zygomatic) Cell// //Enteroendocrine (APUD) Cell// //Stem Cells//- not covered //Mucous Neck Cells//-not covered
 * structure: large, polygonal acidophilic concentrated in the neck of the gastric glands. Contain 1-2 round nuclei, many mitochondria, intracellular canaliculus lined with microvilli. At rest, cytoplasm exhibits smooth membrane tubulovesicles and small intercellular canaliculus with few microvilli. During secretion, fewer tubulovesicles and intracellular canaliculus becomes large adn expansive with more microvilli.
 * function: Secrete H+ and Cl- with stimulation from vagal cholinergic (parasympathetic) fibers, gastrin from APUD cells, and histoamine from mast cells. Also produce intrinsic factor, which induces ileum to absorb vitamin B12, important for RBC maturation (prevents pernicious anemia).
 * structure: pyramidal-shaped mostly in the bases of gastric glands. Abundant basophilic rER in basal cell cytoplasm. Apical secretory zymogen granules stain acidophilic.
 * function: produce and store pepsinogen, which is converted into proteolytic enzyme, pepsin. Also produces lipase, an enzyme that initiates breakdown of dietary lipids
 * structure: small ovoid cells in the base of gastric glands. Contain secretory granules.
 * function: release products across basal membrane where they cross the basal lamina and enter nearby capillaries. Produce many different types of amines, peptides, or protein hormones that control GI tract secretion and motility.


 * 3. Describe structure and function of cells forming intestinal crypts and villi.**

__Cells forming the villi__

//Intestinal Absorptive Cell (enterocyte)// //Goblet Cell//
 * structure: columnar in shape with basal, oval nucleus. numerous microvilli crown apical surface, creating a striated border. SER, RER, and mitochondria are in the apical cytoplasm. Junctional complexes join adjacent columnar cells
 * function
 * dietary carbohydrates -Salivary amylase and pancreatic enzymes digest CHO into disaccharides. intestinal absorptive cells produce disaccharidases that hydrolyze disaccharides into monosaccharides. These are actively transported into intestinal absorptive cell and released into the lamina propria where they enter blood capilaries
 * dietary protein - After gastric pepsin and pancreatic enzymes digest protein into polypeptides and then dipeptides, intestinal absorptive cells make dipeptidases that hydrolyze dipeptides into amino acids. These are actively transported into the intestinal absorptive cella nd released into the lamina propria to blood capillaries.
 * dieartary lipid - After lipid is emulsified by bile and cleaved into glycerol, fatty acids, and monoglycerides by pancreatic lipases, intestinal absorptive cell absorbs the products. triglycerides are re-synthesized in the SER and released into the basolateral intercellular space as chylomicrons. Long chain fatty acids enter lacteals, short chain fatty acids enter blood capillaries
 * structure: help form villus epithelium. Cup shaped cells with large mucin granules in apical cytoplasm. Triangular shaped nucleus in narrow base. More numerous distally.
 * function: secrete mucus for lubrication and protection of mucosa

__Cells forming the crypts__

//Paneth Cell// //APUD Cell// //stem cells// //immature absorptive cells// //goblet cells//
 * structure: pyramidal shaped cells in gland base. RER in basal cytoplasm, acidophilic secretory granules in apical.
 * function: contain lysozyme, enzyme that lyses bacterial cell walls
 * structure:lie in gland base
 * function: release hormones and amine compounds such as secretin and cholecystokinin to help control secretion and motility


 * 4. Describe the absorption and processing of CHO, protein and lipid products by the absorptive cell of the small intestine.**

See above intestinal absorptive cells.


 * 5. Describe cell renewal rates for stomach, small intestine and large intestine.**

Stomach: 4-7 days Small Intestine: 3-6 days Large Intestine: 6 days


 * 6. Define the term GALT.**

Gut-Associated Lymphoid Tissue. Condensed into follicles. Called Peyer's Patches in the Ileum.