GI Anatomy, Histology, Hepatitis Serology, Genetics, Imaging Signs, Key Lab Patterns

A comprehensive set of flashcards covering key topics in GI anatomy, histology, hepatitis serology, genetics, imaging signs, and laboratory patterns.

What are the 3 branches of the celiac trunk?

Left gastric artery, splenic artery, common hepatic artery.

What does the SMA supply?

Superior mesenteric artery supplies the MIDGUT: distal duodenum → proximal 2/3 of transverse colon.

What does the IMA supply?

Inferior mesenteric artery supplies the HINDGUT: distal 1/3 transverse colon → rectum.

What are the two GI watershed zones?

1. Splenic flexure (border between SMA and IMA territory); 2. Rectosigmoid junction (border between IMA and internal iliac territory).

What is the ligament of Treitz?

Suspensory ligament of the duodenum marking the duodenojejunal junction, dividing upper GI from lower GI.

What organs are intraperitoneal?

Stomach, spleen, jejunum, ileum, cecum, appendix, transverse colon, sigmoid colon, liver, gallbladder.

What organs are retroperitoneal?

Suprarenal glands, Aorta/IVC, Duodenum (2nd-4th parts), Pancreas, Ureters, Colon (ascending + descending), Kidneys, Esophagus, Rectum.

How does fat get absorbed in the GI tract?

Fat-soluble vitamins + long-chain fatty acids → absorbed into lacteals → cisterna chyli → thoracic duct → left subclavian vein.

What does water-soluble nutrient absorption in the GI tract involve?

Water-soluble nutrients + short/medium chain fatty acids → portal vein → liver.

What is McBurney's point?

1/3 of the way from the right ASIS to the umbilicus; point of maximum tenderness in acute appendicitis.

What is the difference between the parotid duct and submandibular duct?

Parotid (Stensen's duct) opens opposite the upper 2nd molar; Submandibular (Wharton's duct) opens at the floor of the mouth.

What are the four layers of the GI wall?

1. MUCOSA; 2. SUBMUCOSA; 3. MUSCULARIS PROPRIA; 4. SEROSA or ADVENTITIA.

What is the function of Auerbach's plexus?

Controls motility (peristalsis) between inner circular and outer longitudinal muscle of the muscularis propria.

What is the function of Meissner's plexus?

Controls secretion and blood flow in the submucosa.

What unique feature does the esophagus have histologically?

Lined by stratified squamous epithelium (non-keratinized) and only has adventitia.

What cells are found in the stomach?

Parietal cells (HCl + intrinsic factor), Chief cells (pepsinogen), G cells (gastrin), D cells (somatostatin), ECL cells (histamine), Mucous neck cells.

What distinguishes the jejunum from the ileum histologically?

Jejunum has taller villi, most prominent plicae circulares, and highest absorptive capacity; ileum has Peyer's patches.

What is absent in colon histology?

No villi and no plicae circulares, but many goblet cells are present.

What are the histologic features of Crohn's disease?

Transmural inflammation, non-caseating granulomas, skip lesions, fissures.

What are the histologic features of ulcerative colitis?

Mucosal and submucosal inflammation, crypt abscesses (neutrophils in crypts), and pseudopolyps.

What are the key features of HAV?

Transmission: fecal-oral; Genome: +ssRNA; Chronicity: NEVER becomes chronic.

What does HBV serology indicate during the acute phase?

HBsAg+, IgM anti-HBc+, HBeAg+.

What is the HBV window period?

Brief phase where HBsAg disappears but anti-HBs has not yet appeared; only IgM anti-HBc is positive.

What is a key risk factor associated with HCV?

80% of HCV infections become chronic; highest among hepatitis viruses.

What does HDV require for replication?

HBsAg, thus it only infects HBsAg-positive individuals.

What is the key danger of HEV?

20-30% mortality in pregnant women during the 3rd trimester.

What are some extrahepatic manifestations of HBV?

Polyarteritis nodosa, Membranous nephropathy, Serum sickness-like prodrome.

What gene is mutated in hemochromatosis?

HFE gene (C282Y most common), leading to iron overload.

What are the findings in Wilson's disease?

Liver disease, neuropsychiatric symptoms, Kayser-Fleischer rings, and Fanconi syndrome.

What distinguishes hereditary hemochromatosis from Wilson's disease?

Hemochromatosis: iron overload + elevated ferritin; Wilson's: copper overload + low ceruloplasmin.

What is Gardner syndrome?

Variant of FAP with extracolonic features like osteomas and soft tissue tumors.

What is Turcot syndrome associated with?

Colorectal polyposis and CNS tumors, either FAP-associated or Lynch-associated.

What triad is associated with MEN1?

Parathyroid, Pituitary, Pancreatic islet cell tumors.

What is the key association of Peutz-Jeghers syndrome?

Hamartomatous polyps and mucocutaneous melanin pigmentation.

What does the double bubble sign indicate?

Duodenal atresia; seen as air in stomach and proximal duodenum.

What does the coffee bean sign represent?

Diagnosis of sigmoid volvulus based on X-ray appearance.

What does the bird beak sign indicate?

Achalasia, visualized on barium swallow.

What does the string sign suggest?

Crohn's disease, indicating a narrow lumen in the terminal ileum.

What does lead pipe colon indicate on barium enema?

Chronic ulcerative colitis.

What is the thumbprinting sign indicative of?

Ischemic colitis due to scalloped indentations in the colon.

What does the apple core lesion signify?

Colorectal adenocarcinoma.

What does beads on a string suggest?

Primary sclerosing cholangitis (PSC) seen on MRCP.

What does a corkscrew esophagus suggest?

Diffuse esophageal spasm (DES) on barium swallow.

What is the halo sign on CT indicative of?

Invasive aspergillosis, visible as ground-glass opacity.

What does the presence of daughter cysts on imaging indicate?

Echinococcus (hydatid cyst disease) with internal cysts.

What is the significance of a ring-enhancing brain lesion?

Neurocysticercosis, associated with Taenia solium eggs.

What does an AST:ALT ratio >2:1 indicate?

Alcoholic hepatitis.

What does an elevated ALP with elevated transaminases suggest?

Cholestatic pattern due to bile duct obstruction.

What does elevated ferritin + transferrin saturation >45% indicate?

Hemochromatosis.

What does low ceruloplasmin and elevated urine copper indicate?

Wilson's disease.

What does an elevated 5-HIAA in urine diagnose?

Carcinoid syndrome.

What indicates PMN >250 cells in ascitic fluid?

Spontaneous bacterial peritonitis (SBP).