SBM Unit 5: Small intestine
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10 terms
Terms | Definitions |
|---|---|
 Small intestine anatomy | Segments: -duodenum: 20 cm -jejunum: 230 cm -ileum: 350 cm |
| Small intestine histology | -Villi: absorptive enterocytes & goblet cells; 3-4x the height of crypts -Crypts: stem cells, Paneth cells, goblet cells, & neuroendocrine cells; much shorter than the villi -Lamina propria: blood vessels, lymphatics, nerves, smooth muscle, collagen, lymphocytes, plasma cells, eosinophils |
| Small intestinal functions | -Villi: digestion & absorption -Crypts: secrete ions, water, & IgA; stem cells for epithelial renewal -Mucous: secreted by goblet cells; for protection of epithelial lining & milieu for uptake of nutrients |
| Peutz-Jeghers syndrome | -autosomal dominant -onset: 20-30s -sx: intestinal polyposis & mucocutaneous melanin pigment spots -hamartomatous polyps: most commonly in jejunum; lobulated/pedunculated with smooth muscle branching & hyperplastic epithelium -complications: hemorrhage, intussusception, malignant change |
| Whipple's disease | -caused by Tropheryma whippelii (gram+ actinomycete) -typically affects middle-aged men -bacteria enter body via small intestine, then disseminate to involve heart, lungs, joints, CNS, etc -sx: malaise, weight loss, malabsorption, diarrhea, arthritis, pleuritis -path: dilated intestine, thickened, rigid; mucosal atrophy with presence of bacteria-filled macrophages in lamina propria (stains with PAS) -tx: antibiotics, excellent response achieved |
| Celiac disease | -autoimmune condition due to destruction associated with anti-gliadin antibodies -epidem: onset at 3 yrs, or btwn 20-40 yrs; highest incidence in N. Europe & UK -pathogenesis: may be due to direct toxicity of gluten byproducts and/or antigliadin-antibody mediated T-cell destruction -sx: steatorrhea, bloating, gassiness, cramps, weight loss, malabsorption -path: blunting of villi, lengthening of crypts, small & crowded enterocytes, intraepithelial lymphocytes, inflammation in lamina propria -dx: antigliadin, antiendomyceal, anti-tissue transglutaminases -complication: 10-15% neoplasia, ulcerative jejunoileitis |
| Crohn's disease | -chronic inflammatory disease of GI tract, most commonly affecting terminal ileum -epidem: common in US, N. Europe/Scandinavia, very common among Jewish people in US -etiology: infx may be involved, immunologic dysfxn (either ab or T-cell mediated) -sx: diarrhea, low-grade fever, LQ pain, anorexia, n/v -path: "skip lesions," aphthous ulcers, linear ulcers, cobblestoning, strictures -histopath: non-casseating granulomas, fissuring ulceration, transmural inflammation, lamina propria inflammation, widening of submucosa & fibrosis, lymphangiectasia, neural hyperplasia -complications: strictures, obstruction, perforation, fistulization, adenocarcinoma, other autoimmune (amyloidosis, ankylosing spondylitis, polyarthritis, PAN) |
| Neuroendocrine cells | -found in mucosa of GI tract, etc -oval/triangular, eosionphilic granular cytoplasm -secrete a variety of peptide hormones/biogenic amines -those in gut are of endodermal origin -cancer: carcinoid |
| Carcinoid | -60-80% midgut: appendix & distal ileum -10-25% hindgut: rectum -10%: stomach, duodenum --appendix & rectum: single, benign --distal ileum: multiple, malignant potential -histo: trabecular/microacinar pattern; small, uniform cells with round nuclei and granular cytoplasm -stains: chromogranin & synaptophysin -syndromes: serotonin-producing, ZES, somatostatinoma syndrome, Cushing's syndrome |
| Appendicitis | -pathogenesis: obstruction -- increased intraluminal pressure & vascular compromise -- bacterial overgrowth & inflammation -sx: RLQ pain, rebound tenderness, n/v, low-grade fever, leukocytosis, left shift of PMNs -swollen/hyperemic gland with fibrin or pus; mucosal ulceration with acute transmural inflammation -complications: perforation, abscess, fistula, diffuse peritonitis, thrombophlebitis |
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