NURS 8022 Advanced Pathophysiology Exam 4 Study Guide

NURS 8022 Advanced Pathophysiology Exam 4 Study Guide Basics of gastric secretion; what cells secrete what  Gastric juice composition depends on volume & flow rate. Secretion rate lower in AM, higher in PM. Higher K+ in gastric juices.  Inc. gastric emptying – larger volumes of food  Delayed gastric emptying – solids, fats, non-isotonic solutions  Acid – hydrochloric acid (most important acid) o Dissolves food fibers o Bactericide against swallowed organisms o Stimulated by: ACTH, caffeine, Ca2+, gastrin, histamine o Inhibited by: prostaglandins, gastric inhibitory peptide, somatostatin, secretin o Coverts pepsinogen (enzyme) to Pepsin  Pepsin breaks down Protein-forming polypeptides in stomach  ACTH stimulates pepsin  High pH (alkaline duodenum)  inactivates pepsin  Mucus – protective barrier o Prostaglandins & NO = protect mucosal barrier o Inflammation & ulcers caused by: Aspirin & NSAIDs, H. pylori, ethanol, regurgitated bile, ischemia – all break down protective barrier  Intrinsic factor – intestinal absorption of vit B12 in ileum o Combines w/ B12 in stomach o Pernicious anemia = stomach not absorbing B12 well/atrophic gastritis  Hormones – gastrin  Gastroferrin – helps small intestine absorb iron  Gastric pits – duct where glands empty  What cells secrete what: Gastric gland cells Secrete what Parietal cells Hydrochloric acid & intrinsic factor, gastroferrin Chief cells Pepsinogen G cells Gastrin Enterochromaffin-like cells Histamine D cells Somatostatin  A patient presents with heart burn, and you prescribe a histamine blocker. Why would you do this? o Histamine normally stimulates the production of HCl acid  Phases of gastric secretion: 1. Cephalic phase (mouth) a. Secretion process starts here (smell, see, taste, chew, swallow your food) b. Vagus nerve: helps secrete acid, pepsinogen, & gastrin. Pancreas secrete insulin w/ hyperglycemia & stimulates gastric secretion. 2. Gastric phase (stomach) a. Food hits stomach. b. Stomach distends (stimulates Vagus nerve) & proteins are digested  ACTH  secretory effect. Inhibited by atropine. 3. Intestinal phase (intestines) a. Chyme (partially digested food) moves from stomach  duodenum. b. Gastric secretion slows down b/c chyme moves into a more acidic environment  inhibits vagal reflexes  dec. gastric secretion c. Secretin & cholecystokinin  pancreatic secretions & inhibit gastric secretions Basic function of small intestine, and large intestine  Small intestine o Peritoneum – membrane that surrounds abd organs & pelvic cavity  Visceral = organs  Parietal = lines walls of abd cavity  Peritonitis – d/t perf of intestine or after surgery  Peritoneal cavity – space btwn two layers of peritoneum o Mucosal folds (plica) – in small intestine & slows food down so it has time to digest/absorb  Covered by villi – functional unit of intestine (where absorption occurs) o Myenteric plexus & mucosal plexus – where intrinsic motor innervation happens  Parasympathetic – secretion, motility, pain sensation, intestinal reflexes  Sympathetic – stops motility & vasoconstricts o Each villus is made up of absorptive columnar cells (enterocytes) & mucus secreting globlet cells -- secretes enzymes needed for digestion/absorbing nutrients o Villi and microvilli inc. surface area for absorption o Villi shortens by: starvation, vit B12 deficiency, cytotoxic drugs, radiation  dec. absorption  diarrhea & malnutrition  Most water and electrolytes are absorbed where in the GI tract? o Small intestine  Large intestine o Absorbs H2O & electrolytes (no villi) o Segmentation – circular muscles contract & mix chyme – promotes digestion o Ileogastric reflex – stops gastric motility if ileum is distended  The Ileogastric reflex is a normal physiological reflex which is important in Inhibiting gastric motility. o Intestinointestinal reflex – stops intestinal motility when 1 segment is over-distended o Gastroileal reflex – gastric motility inc.  intestinal motility inc.  Starts propulsion in colon during/right after eating when chyme enters from ileum  fecal mass passes rapidly into sigmoid colon & rectum  defecation  Stimulated by gastrin & cholecystokinin; inhibited by epi o Obstruction – probs r/t competence of ileocecal valve  Ogilvie syndrome = acute colonic pseudo-obstruction (nothing is actually obstructing it, it just dilates a lot for no reason)  Mesenteric venous thrombosis – r/t malignancies, R HF, DVT  Acute mesenteric ischemia – dissecting aortic aneurysms, thrombi, emboli  dec. blood flow from arteries that supply large & small intestines  Chronic mesenteric insufficiency – dec. blood flow that causes colicky pain after eating o Colicky pain = sharp, localized GI pain that comes & goes (like spasms) Basics of digestion and absorption; what where  Digestion o Mouth – breaks food down & mixes w/ saliva to start digestion (salivary amylase begins this)  Saliva: controlled by cholinergic parasympathetic fibers that stimulate salivary glands (Ex give Atropine to inhibit salivation). Sympathetic Beta-adrenergic stimulation inc. salivary secretion. pH 7.4 neutralizes bacterial acids to prevent infection. Saliva contains IgA.  Saliva is important in the initial digestion of carbohydrates.  Oropharyngeal = voluntary; esophageal = involuntary o Esophageal sphincters – upper: prevents air into stomach; lower: prevents regurg of food mass into esophagus o What is one of the most important functions of the lower esophageal sphincter?  Prevent reflux of gastric contents into the esophagus.  Inc. sphincter tone = cholinergic vagal stimulation & gastrin  Relax sphincter tone = non-adrenergic, non-cholinergic vagal impulses & progesterone, secretin, & glucagon  Vagus nerve = relaxation during swallowing o Stomach – secretes pepsinogen, gastrin, & hydrochloric acid  mixes w/ food  chyme; intrinsic factor secreted to absorb B12 in small intestine; no nutrients absorbed—only ETOH, aspirin, & NSAIDs o Which of the following substances can be absorbed in the stomach? Alcohol  Lower esophageal sphincter – chyme enters from esophagus to stomach  Pyloric sphincter- chyme leaves stomach into duodenum