Pathophysiology(GIT)*

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Skip lesions: Crohn Dse
-Discontinouse involvement of the intest. mucosa visualized as a "String Sign" on x-ray
Persistent projectile vomiting usually appearing in the 2nd-3rd wk of life: Congenital Hypertrophic Pyloric Stenosis
Difficulty swallowing due to increased tone of the lower esophageal sphincter: Achalasia
-can be caused by destruction of the myenteric plexus in Chagas disease
Right lower quadrant pain, nausea, fever, and an elevated WBC: Acute Appendicitis
Serotinin elaboration causing flushing, diarrhea, bronchospasm, and right heart damage: Carcinoid Syndrome
-carcinoid tumors of the appendix & rectum rarely metastasize
Increased CEA(Carcinoembryonic Antigen): Carcinoma of the colon
-risk factor includes low fiber diet
Barrett esophagus is the only recognized precursor: Esophageal Adenocarcinoma
-Barrett esophagus=squamous to columnar metaplasia(specialized, intestinal type epitheliun)in the distal esophagus
Fatigue,weakness,& iron deficiency anemia in the older males: Carcinoma of the right colon
Presents early as obstruction & crampy dicomfort: Carcinoma of the rectosigmoid colon
Malabsorption that resolves upon withdrawal of wheat gliadins from the diet: Celiac Sprue
-Histologically characterized as flattening of the mucosal villi w/ inflammatory infiltrate
Weakness in the peritoneal wall allowing protrusions of bowel segments: Hernia
Can rupture producing massive hemorrhage into the esophageal lumen: Esophageal Varices
-often assoc. w/ portal hypertension, as in cirrhosis
Cobblestone appearance of the bowel mucosa: Crohn disease
-caused by inflammation & thickening of all 3 layers of the GI wall
Small sac-like outpouchings of the colon through the muscular wall, common in the elderly: Diverticulosis
-most commonly asymptomatic
Signet Ring Cells: Gastric carcinoma, diffuse variant
-extensive infiltration of malignant cells can lead to linitis plastica or "leather bottle stomach"; matastasis bilaterally to the ovaries results in Krukenburg tumors
100% chance of colon cancer by midlife: Familial polyposis syndromes
-caused by autosomal dominant mutations in the APC gene w/ hundreds of adenomatous polyps carpeting the intestines
Pseudomembranes consisting of fobrin, mucin, & inflamatory debris covering the colonic mucosa: Pseudomembranous Colitis
-caused by elaboration of exotoxins by Clostridium difficile
Congenital absence of ganglion cells in the muscular or submucosal layers of the GI wall: Hirschsprung disease(congenital megacolon)
-absence of ganglion cells is in the nondilatedregion of the colon
Telescoping of one intestinal segment into another, usaully in children: Intussusception
Most common & innocuous congenital abnormality in the GI: Meckel diverticulum
-failure of involution of the vitelline duct
Sharply punched out lesions in the stomach or duodenum: Peptic Ulcer
-assoc. w/ NSAID use & Helicobacter pylori
Autosomal dominant disorder w/ multiple benign hamartomatous polyps & melanin pigmentation of the oral mucosa, hands, & genitals: Peutz-Jegher Synd.
Recurs often & is difficult to completely resect bec. of proximity of the facial nerve: Pleomorphic adenoma(mixed tumor of the salivary gland)
-most common salivary tumor
Toxic megacolon is a complication: Ulcerative colitis
-destruction of the neural plexus leading to massive dilation, gangrene, & imminent rupture of colon
Pseudopolyps: Ulcerative Colitis
-regenerating mucosal areas in the ulcerated mucosa & submucosa
Absorption of H2O: Secondary to solute absorption, isosmotic in small intestine & gallbladder(similar to renal proximal tubule)
Secretion of electroytes & H2O by the intestine: Crypts(secretory mech.) & Villi(absorptive mech.); Cl-(primary ion secreted)is transported via Cl channels regulated by cAMP~Na+ passively follows Cl-~H2O follows NaCl to maintain isosmotic condition
Mech. of action of Vibrio cholera(cholera toxin) in causing diarrhea: Cholera toxin binds to luminal memb. receptors(crypt cells)~activates adenylate cyclase(basolateral memb.)~ inc. cAMP~opening of Na channels in luminal memb.~Na & H2O follow Cl(secretory diarrhea)
Digestion & absorption of lipids: In stomach(mixing,lingual lipase digestion, gastric emptying slowing by CCK)~in small intestine(emulsification of lipids by bile acids,pancreatic lipase digestion,solubilization of hydrophobic lipids in micelles by bile acid)~diffusion of F.A,monoglycerides, cholesterol(except glycerol) into the cell~reesterification back to original form~w/ apoprotein form chylomicrons~ transported to lymph vessels
Funct. & innervation of the extrinsic(parasympathetic & sympathetic NS) system on the GI tract: Parasym.:excitatory via the vagus (esophaghus,stomach,pancreas,upperlarge intest.)& pelvic nerve(lower large intest.,rectum,anus); Symp:inhibitory, T8-L2,preganglionic cholinergic synapse in prevertebral ganglia, postganglionic adrenergic synapse in myenteric & submucosal plexus.
Malabsorptive disorder in lipids due to lack of apoprotein B w/c results in inability to transport chylomicrons out of the intestinal cell: Abetalipoproteinemia
Mech. of action of hypersecretion of gastrin & bact. overgrowth in causing malabsorption of lipids: Gastrin hypersecretion(low duodenal pH inactivates pancreatic lipase); Bact. overgrowth(deconjugation of bile acids leading to early absorption in the upper small intestine~depleting the availability of bile acids to aid in lipid absorption
Most common neoplasm of the western world occuring often in 6th-7th decades w/c provide a "model of tumor progression": Adenocarcinoma of colon & rectum
-assoc w/ inc. CEA(useful for following the course of the dse. rather than for diagnosis)
Four mech. in Na+ is absorbed into the intestinal cells,across the luminal memb.,& down its electrical gradient: 1)passive diffusion(colon;inc. by aldosterone) 2)Na-glucose or Na-A.A cotransport(small intestine) 3)Na-Cl cotransport 4)Na-H exchange(small intest.)
-Na+ is transported out of cell via Na-K pump
Absorption & secretion of K+: Absorbed by passive diffusion via paracellular route in the small intestine; secreted in colon
-aldosterone & diarrhea(flow rate dependent mech) inc. K+ secretion
1 of 5 pancreatic protease enzymes (trypsin,chymotrypsin,elastase, carboxypeptidase A,carboxypeptidase B) w/c is 1st activated by enterokinase to its active form, then is used to convert the other 4 enzymes: Trypsinogen to trypsin
-after the enzymes are finished digesting, they degrade each other & are absorbed along w/ the dietary proteins
Predisposing factors of Adenocarcinoma of the colon & rectum: Adenomatous polyps,inherited mutiple polyposis synd.,long-standing ulcerative colitis,genetic factors,low fiber & high animal fat diet
Funct. & innervation of the intrinsic(enteric nervous system)system: Coordinates & relays inf. from the extrinsic innervation to the GI tract; uses local reflexes to relay inf. w/in the GI tract;controls motility(Myenteric plexus,Auerbach's plexus) & secretion(Submucosal plexus,Meissner's plexus) even in the absence of extrinsic innervation
Four GI hormones released from the endocrine cells in the GI mucosa: Gastrin(G cells), Cholecystokinin(I cells of duedenum & jejunum), Secretin(S cells of duedenum), GIP(duedenum & jejunum)
Effect of your gastric hormones (gastrin,CCK,secretin,GIP): Gastrin(inc. H+ secretion & growth of gastric mucosa),CCK(stimulate gallbladder contraction,relaxation of sphincter of oddi,inc. pancreatic enzyme & HCO3 secretion,inc. exocrine pancreas/gallbladder growth,inhibit gastric emptying),Secretin(inc. pancreatic & biliary HCO3 secretion, dec. gastric H+ secretion),GIP(inc. insulin secretion,dec. gastric secretion)
Stimulus for secretion of the gastric hormones(gastrin,CCK,secretin,GIP): Gastrin(peptides & A.A,distension of the stomach,vagus via GRP,ihibited by H+ in stomach),CCK(peptides & A.A,F.A), Secretin(H+ & F.A in duedenum),GIP(F.A,A.A,oral glucose)
Most potent stimuli for gastrin secretion: Phenylalanine & Tryptophan
Two types of paracrine hormones w/c are released from endocrine cells in the GI mucosa over short distances to act on tardet cells: Somatostatin(secreted in resp. to H+, inhibited by vagal stimulation, inhibits release of all GI hormone)
Histamine(secreted by mast cells,inc. gastric H+ secretion)
Enzyme w/c degrades lactose-glucose & galactose, trehalose-glucose, & sucrose-glucose & fructose: Lactase,trehalase,sucrase
-degradation of disaccharide to monosaccharides
3 types of neurocrine hormones produced in neurons in GI tract w/c move down the axon accross the synaptic cleft to a target cell: Vasoactive intest. peptide(homologous to secretin,relaxes GI smooth muscle, stimulate pancreatic HCO3 secretion, inhibit gastric H+ secretion,mediates pancreatic cholera);GRP-bombesin(stimulates gastrin release); Enkephalins(stimulate GI contraction, inhibit intest. secretion,usefull in opiate tx. of diarrhea)
Difference betw. phasic & tonic contraction in the GI tract: Phasic(occurs in eophagus,gastric antrum,small intest.;contract & relax periodically);Tonic(occur in LES,orad stomach,ileocecal & iinternal sphincter)
The swallowing reflex is coordinated by what area of the brain?: Medulla
Hormone w/c is a mediator for contracions(migrating myoelectric complex) during fasting: Motilin
Type of food product in the stomach w/c may inc. gastic emptying time: High fat diet
-by stimulating release of CCK
GI disorder w/c occurs in periods of stress resulting in constipation(inc. segmentation contractions) or diarrhea(decr. segmentation contractions): Irritable bowel Synd.
GI disorder charact. by absence of the colonic enteric nervouse system resulting in constriction of involved segment,marked dilatation & accumulation of intest. contents proximal to constriction, & constipation: Megacolon(Hirschsprungs's Dse)
Major charact. & fxn. of saliva: Fxn.(starch & triglyceride digestion, lubrication,protection); Charact.(high HCO3&K+,hypotonic,alpha-amylase(ptyalin)for starch digest.,lingual lipase for triglyceride digest.)
Parasympathetic(CN VII & IX) regulation of salivary secretion: Transport of ACH to muscarinic recptors on acinar & ductal cells~ activation of second messanger(IP3 & inc. intracellular Ca+)
-inhibited by atropin
Sympathetic regulation of salivary secretion: Release of NE to Beta-receptors~avtivation of second messanger(cAMP)
3 major glands w/c produce saliva: Submaxillary,Parotid,Sublingual glands
One of the 4 types of enzymes(endopeptidase,exopeptidase,pepsin, pancreatic protease)w/c degrade proteins for absorption & is only effective in the stomach w/ a pH of 1-3: Pepsin
-secreted as pepsinogen from chief cells & activ. to pepsin by H+
Mech. for gastric H+ secretion in the parietal cells: CO2=H2O--H2CO3--(H+)+HCO3~secretion of H+ via H,K-ATPase into the stomach w/ Cl-,HCO3 absorb into the bloodstream via Cl-HCO3 exchange;omeprazole blocks H+ secretion by inhibiting H,K-ATPase
Mech. of action in metabolic alkalosis caused by vomitting: Gastric H+ never arrives in the small intestine to stimulate pancreatic HCO3 secretion causing art. bld to become alkaline
Stimulation of of gastric H+ secretion via direct pathway: Vagus nerve innervates parietal cells via ACh on muscarinic receptors~ activation of second messsanger (IP3,Ca+)~stimulation of H+ secretion
-inhibited by atropine
Stimulation of gastric H+ secretion via indirect pathway: Vagus nerve innervates G cells~gastrin secretion~activation of neurotransmitter(GRP)~H+ secretion
-vagotomy eliminates both direct & indirect pathways
Stimulation of gastric H+ secretion by Histamine: Released from mast cells~stimulation of H2 receptors on parietal cells~ activation of 2nd mess.(cAMP)~H+ secretion
-Cimitidine inhibit H+ secretion by blocking H2 receptor
Neg. feefback mech. w/c inhibit the secretion of H+: Low ph(<3) in the stomach; Chyme in the doudenum via GIP(due to F.A in the duodenum) & secretin(due to H+ in the duedenum)
Gastrin secreting tumor of the pancrease w/c causes inc. H+ secretion: Zollinger-Ellison Synd.
-inc. H+ has no neg. feedback effect on the pancreatic tumor
Composition & formation of pancreatic secretion: Composition(high HCO3 conc.,isotonic, lipase,amylase,protease,Na & Cl- at low flow rates,Na & HCO3 at high flow rates); Formation(prod. by acinar cells of exocrine pancreas;later modified by ductal cells)
Regulation of pancreatic secretion: Secretin(S cells of duodenum) in response to H+ in duodenum~inc. HCO3 secretion from pancreatic ductal cells; CCK(I cells of duodenum) in response to peptides,A.A,F.A in duodenum~inc. secretion of amylase,lipase,proteases; potentiates secretin secretion of HCO3; ACh(via vagovagal reflex)stimulated by H+,peptide,A.A,F.A in duodenum~ stimulate acinar enzyme secretion; potentiate secretin HCO3 secretion
Pancreatic secretion disorder resulting in a defective Cl- channel w/c results from a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR): Cystic fibrosis
-def. of pancreatic enzymes resulting in malabsorption & steatorrhea
Component in bile w/c is amphipathic helping it aid in the digestion & digestion of lipids by emulsifying & solubilizing them into micelles: Bile salts
Formation of bile: In hepatocytes, primary bile acids(cholic acid,chenodeoxycholic acid) synthesized from cholesterol~in intestine,converted to secondary bile (deoxycholic acid,lithocolic acid) by bact.~conjugated w/ glycine&taurine to form bile salt~added w/ electrolytes & H2O in gallbaladder & concentrated
Mech. in w/c ileal resection results in steatorrhea: Occur due to bile acid not being able to absorbed & recirculated back to the liver depleting the bile acid pool impairing fat reabsorption
Products of Carb.,protein,lipids in w/c they can be absorbed through the small intest.: Carb.(monosccharides:glucose,galactose, fructose), proteins(A.A,dipeptides, tripeptides), lipids(F.A, monoglycerides, cholesterol)
Vascular dse. of the colon w/c is a common cause of unexplained lower bowel bleeding: Angiodysplasia
-tortuous dilatation of small vesels spanning the intestinal mucosa or submucosa often involving the cecum or ascending colon
Inflammatory bowel dse. limited to the large intest. affecting the mucosa & submucosa w/ neutrophil infiltrates in the crypts of Lieberkuhn(crypt abscess) presenting as chronic bloody diarrhea w/ mucus: Ulcerative colitis
-complicated w/ toxic megacolon, perforation & carcinoma
Inflamatory disorder of the colon due to Entamoeba histolytica infection: Amebic colitis
-result in flask shape ulcers
Most common type of intest. adenomatous polyp w/c are small,pedunculated w/c may contain a malignant foci: Tubular Adenomas
-greater % of malignancy w/ larger polyps
An intestinal adenomatous polyp w/ the highest potential for malignancy(>30%): Villous Adenomas
-10% of adenomatous polyps charact. by large #'s of finger-like villi
3 types of Multiple polyposis synd. w/c are assoc w/ greatly inc. risk of malignant transformation: Familial polyposis(almost 100% risk of malignant transformation), Garder Synd.(adenomatous polyps w/ osteomas & soft tissue tumors), Turcot Synd.(adenomatous polyps w/ tumors of CNS)
An autosomal dominant neoplasia charact. by pituitary,thyroid, parathyroid,adrenal cortical, & pancreatic islet cell adenomas or hyperplasia assoc. w/ hypergastrinemia & peptic ulcer: Multiple Endocrine Neoplasia(MEN)Type I(Wermer synd)
Vit. deficiency w/c may result from a gastrectomy: Vit. B12 def.
-instrinsic factor(released from parietal cells) is needed for vit.B12 absorption in the ileum; leads to pernicious anemia
Vit. produced in the kidney needed for absorption of Ca+ in the small intestine: Vit.D(1,25 dihydroxycholecalciferol)
-Vit.D def. or chronic renal failure results in inadequate Ca+ absorption~ rickets(children) & osteomalacia(adults)
Absorption of Iron: Absorbed as heme iron or free Fe+ in small intestine~heme is degraded to release free Fe+~free Fe+ binds to apoferritin & transported into bld. circulation~binds to transferrin w/c transport free Fe+ to storage sites(liver)~transported to bonemarrow for hemoglobin synthesis
Severe gingival infl. occuring in immune compromised px. due to symbiotic bact. infection (Fusobacterium & Borrelia vincentii): Acute necrotizing ulcerative gingivitis(trench mouth,Vincent infection, fusospirochetosis)
Most common benign epithelial tumor of the oral mucosa(tongue,lips,gingivae, buccal mucosa): Papilloma
Most common odontogenic tumor; a hamartoma derived from odontogenic epithelium & odontoblastic tissue: Odontoma
Malignant tummor,commonly squamous cell carcinoma, w/c involves the tongue 50% of cases & is assoc. w/ tobacco & alcohol abuse: Oral cancer
An autoimmune dse. of the salivary gland characterized by keratoconjuctivitis sicca,xerostomia, assoc. w/ a connective tissue dse.(rheumatoid arthritis): Sjögren Synd.
-assoc. w/ inc. incidence of malignant lymphoma
Most common variant of tracheoesophageal fistula w/c leads to copious salivation assoc. w/ choking, coughing, & cyanosis during food intake: Lower portion of esophagus communicates w/ trachea near the tracheal bifurcation;uppeer esophagus ends in a blind pouch
-assoc w/ polyhydramnios
3 locations for an esophageal diverticula(pulsion-false or traction-true): Above the upper esophageal sphincter(Zenker diverticulum); midpoint of the esophagus; above the lower esophageal sphincter(Epiphrenic diverticulum)
3 important causes of upper GI hemorrhage: Esophageal varices(dilated submucosal veins due to portal HPN), bleeding peptic ulcer,Mallory-Weiss Synd.(bleeding from esophagogastric laceration due to severe retching
A columnar metaplasia of esophageal squamous epithelium due to long standing gastroesophageal reflux: Barret Esophagus
-precursor of esophageal adenocarcinoma
A chronic inflammatory condition of unknown etiology affecting the distal ileocecum,small intest.,or colon often people in there 2nd-3rd decade of life: Crohn dse
-can lead to carcinoma of the small intest. or colon(although more common in ulcerative colitis
Morphology of Crohn dse.: Transmural involvement,thickening of involve segment,linear ulceration, cobblestone appearance,skip lesions, noncaseating granulomas,submucosal fibrosis
Clinical manifestation of Crohn dse: Abd. pain,diarrhea,malabsorption,fever, obstruction due to fibrous stricture, fistulas betw. loops of intestine & betw. the intest.,bladder,vagina,skin
Malabsorption synd. most commonly affecting the small intest. w/ arthralgia,cardiac,neurologic sympt. showing PAS-positive macrophages in intest. mucosa: Whipple Dse.
-visualization of Tropherma whippelii bacilli on electron microscopy
Common types of malabsorption synd.: Celiac Dse(gluten sensitivity),Tropical sprue(infectious origin),Whipple Dse(PAS-positive macrophage in intest.mucosa),Disaccharidase def.(lactase def. most common), Abetalipoproteinemia(def.apoprotein B), Intestinal lymphangiectasia(protein loss~hypoproteinemia & edema)
Common malignant tumors of the small intest.: Adenocarcinoma(common primary tumor), Carcinoid(most common in the appendix), Lymphoma(present in malabsorption)
2 most common affected areas in ischemic bowel dse. resulting in mucosal,mural,transmural infarction often caused by atherosclerotic occlusion of atleast 2 major mesenteric vesels: Splenic flexure & rectosigmoid junction
-both lie in watershed areas(poor vascularized regions)
In carcinoma of the esophagus(adenocarcinoma & squamous cell),w/c type occurs most frequently in the upper middle 3rd of the esophagus?: Squamous cell
-as compared to lower 3rd(adenocarcinoma) w/c may also arise from barret esophagus;diffuse by local extension(trachea,bronchi,aorta)
Dse. of the stomach caused by hypertrophy of pylorus resulting in a palpable mass,gastric outlet obstruction(resulting in projectile vomitting at 1st 2weeks of life): Congenital pyloric stenosis
-common in boys;corrected by surgery
An acute gastric ulcer assoc. w/ severe burns: Curling ulcer
-as compared to Cushing ulcer(assoc. w/ brain surgery)
Most common form of chronic gastritis assoc. w/ inc.gastric acid prod., gastric & duodenal ulcer,carcinoma of the stomach & gastric lymphoma of the mucosa-assoc. lymphoid tissue(MALT)type: Helicobacter pylori-assoc. gastritis
Dse. of the stomach characterized by hypertrophy of the gastric rugae & loss of plasma proteins from the altered mucosa: Ménétrier dse(giant hypertrophic gastritis)
Etiopathogenic mech. of gastric peptic ulcer are: 1)H.pylori-mediated ulcer(bact. ureas & proteases break down epthelial protection in gastric mucosa); 2)Inc. H+ permeability resulting of back diffusion of H+ leading to injury; 3)Bile-induced gastritis leading to gastric ulceration
Malignant tumor of the stomach w/c occours often in males in there 50's, have bld. grp.A & are suspected of H.pylori inf., high nitrosamine diet,excessive salt & low fruit-veg. diet: Carcinoma of the stomach
-predisposed by achlorhydria & chronic gastritis
Characteristics of carcinoma of the stomach: Almost always adenocarcinoma;often involves the distal stomach;aggessive spread to adjacent organs & lymphatic metastasis(Virchow node-involvement of supraclavicular lymphnode;Krukenberg tumor-bilateral involvement of the ovaries,charact. by signet-ring cells)
Morphologic variant in carcinoma of the stomach assoc w/ H.pylori infxn. resulting in ulcers w/ irregular necrotic base & firm,raised margins: Intestinal type
-differentiated from peptic ulcer based on shape of ulcer;manifest as polypoid(fungating)carcinoma
Morphologic variant of carcinoma of the stomach not assoc. w/ H.pylori, charact. by thickened, rigid stomach wall, caused by diffuse infiltration of tumor cells w/ accompanying extensive fibrosis: Infiltrating or Diffuse carcinoma(linitis plastica,leather-bottle stomach)
Most common appendiceal neoplasm: Carcinoid

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