Large Intestine Flashcards
Describe the purpose of the large intestine (4)
Produces vitamins
Removes last bit of water
Temporary store until defication
Produces fatty acids from fermentation of fibre.
Describe the peritoneal arrangement around the large intestine. (3)
Ascending and descending colon are retroperitoneal
Transverse and sigmoid colons have their own mesenteries.
Rectum is in thirds: intraperitoneal, retorperitoneal, extraperitoneal.
Describe the blood supply to the large intestine. (9)
Midgut artery: SMA: caecum - ileo-colic, ascending colon - R colic, transverse colon - middle colic.
Hindgut artery: IMA: descending colon - L colic, rectum - superior rectal artery.
Venous drainage: midgut - SMV, hindgut - IMV. Rectum - superior rectal vein.
Explain the differences between the small and large intestines. (6)
Length - 6ft vs 20ft
Diameter - 6cm vs 3cm
Has crypts not villi
External longitudinal muscle is incomplete in the large intestine - teniae coli are longitudinal bands that form haustra.
Describe how the last little bit of water is absorbed out of the colon. (1)
ENaC.
Describe inflammatory bowel disease. (3)
Idiopathic inflammation that affects gut function. 2 types: Crohn’s disease and ulcerative colitis.
Explain the differences between ulcerative colitis and Crohn’s disease regarding where the disease manifests. (4)
CD: can affect anywhere in the gut, often terminal ileum, “skip lesions” and transmural (thickness of bowel wall).
UC: always starts in the rectum but can progress to be in all the colon (pancolitis). Only mucosal inflammation.
Explain the differences between ulcerative colitis and Crohn’s disease regarding presentation. (10)
CD: RLQ pain, mild anaemia, perianal lesions, weight loss, smoker.
UC: very frequent bloody stools, weight loss, diffuse pain, no perianal disease, non smoker (smoking protective).
Explain the differences between ulcerative colitis and Crohn’s disease regarding macroscopic pathology. (7)
CD: skip lesions, mucosal oedema, ulcers thickening of wall, cobblestone appearance, fistulae
UC: pseudopolyps, loss of haustra.
Explain the differences between ulcerative colitis and Crohn’s disease regarding microscopic pathology. (4)
CD: granuloma formation from epithelioid macrophages.
UC: chronic inflammatory infiltrate, crypt abscesses, reduced number of goblet cells.
Explain the differences between ulcerative colitis and Crohn’s disease regarding investigations. (6)
CD: bloods for anaemia, barium enema for strictures, colonoscopy has cobblestone appearance and skip lesions.
UC: can’t image because it’s all mucosal. Can see loss of haustra (lead pipe colon). Bloods for anaemia and serum markers.
Explain the differences between ulcerative colitis and Crohn’s disease regarding surgical management. (2)
CD: surgery can’t remove all of it, repeated surgery.
UC: curative collectomy.
Location?
CD: anywhere in the GI tract
UC: rectum/colon
Rectal involvement
UC only
Gross bleeding
Common in UC, rare in CD.
