Absite: Colorectal Verified Exam Questions and Answers Latest update
2026/2027
Question:
anatomy and physiology: colon function
Answer:
secretes K and reabsorbs Na and water (mostly in R colon and cecum)
Question:
anatomy and physiology: layers
Answer:
4 ... mucosa (columnar epithelium), submucosa, muscularis propria, serosa (in to out)
Question:
anatomy and physiology: describe muscularis mucosa vs muscularis propria
Answer:
musc mucosa = small interwoven inner muscle layer just below mucosa but above basement
membrane ... musc propria = circular layer of muscle
Question:
anatomy and physiology: what part is retroperitoneal?
Answer:
ascending, descending, and sigmoid colon ... peritoneum covers anterior upper and middle 1/3 of the
rectum
Question:
anatomy and physiology: plicae semilunares
Answer:
transverse bands that form haustra
Question:
anatomy and physiology: taenia coli
Answer:
3 bands that run longitudinally along the colon, at rectosigmoid junction the taeniae become broad and
completely encircle the bowel
,Question:
anatomy and physiology: anorectal anatomy with important landmarks
Answer:
distance from anal verge ... 2cm - dentate line .... 4cm - anorectal ring .... 8cm
- end of lower 1/3 .... 12cm - end of middle 1/3 .... 16cm - end of upper 1/3
Question:
anatomy and physiology: vascular supply
Answer:
ascending and 2/3 of transverse colon - SMA (ileocolic, R and middle colic arteries) .... 1/3 transverse,
descending colon, sigmoid colon, upper portion of the rectum - IMA (L colic, sigmoid branches,
superior rectal artery) .... marginal artery - runs along colon margin, connects SMA to IMA (provides
collateral flow) .... arc of Riolan - short firect connection between SMA and IMA .... 80% of blood
flow goes to mucosa and submucosa
Question:
anatomy and physiology: venous drainage
Answer:
follows arterial except IMV, which goes to splenic vein ... splenic vein joins the SMV to form the
portal vein behind the pancreas
Question:
anatomy and physiology: superior rectal artery
Answer:
branch of IMA
Question:
anatomy and physiology: middle rectal artery
Answer:
branch of internal iliac - the lateral stalks during low anterior resection (LAR) or abdominoperineal
resection (APR) contain the middle rectal arteries
Question:
anatomy and physiology: inferior rectal artery
Answer:
branch of internal pudendal (which is a branch of internal iliac)
,Question:
anatomy and physiology: rectal venous drainage
Answer:
superior and middle rectal veins drain into the IMV and eventually the portal vein .... inferior rectal
veins drain into the internal iliac veins and eventually into the caval system
Question:
anatomy and physiology: nodal drainage
Answer:
superior and middle rectum - drain into IMA nodal lymphatics .... lower rectum - drains primarily to
IMA nodes and also to internal iliac nodes .... bowel wall contains mucosal and submucosal
lymphatics
Question:
anatomy and physiology: watershed areas
Answer:
splenic flexure aka Giffith's point - SMA and IMA junction .... rectum aka Sudak's point - superior
rectal and middle rectal junction ...colon more sensitive to ischeia than small bowel 2/2 fewer
collaterals
Question:
anatomy and physiology: part of bowel most sensitive to ischemia
Answer:
colon is more sensitive to ischemia than small bowel 2/2 decreased collaterals
Question:
anatomy and physiology: external vs internal sphincter - muscle, innervation
Answer:
external = puborectalis muscle, continuation of levator ani (striated) muscle, under CNS control via
inferior rectal branch of internal pudendal nerve .... internal = continuation of muscularis (smooth)
muscle, involuntary control, normally contracted
Question:
anatomy and physiology: inner and outer nerve plexi
Answer:
inner = meissner's plexus ... outer = Auerbach's plexus
, Question:
anatomy and physiology: sympathetic vs parasympathetic
Answer:
sympathetic = lumbar and sacral plexi .... parasympathetic = pelvic splanchnic nerves
Question:
anatomy and physiology: distance from anal verge - anal canal, rectum, rectosigmoid junction
Answer:
anal canal 0-5cm .... rectum 5-15cm ... rectosigmoid junction 15- 18cm
Question:
anatomy and physiology: levator ani
Answer:
marks the transition between anal canal and rectum
Question:
anatomy and physiology: crypts of lieberkuhn
Answer:
mucus-secreting goblet cells
Question:
anatomy and physiology: colonic inertia
Answer:
slow transit time, pts may need subtotal colectomy
Question:
anatomy and physiology: main nutrient of colonocytes
Answer:
shortchain fatty acids
Question:
anatomy and physiology: tx of infectious pouchitis
Answer:
flagyl
2026/2027
Question:
anatomy and physiology: colon function
Answer:
secretes K and reabsorbs Na and water (mostly in R colon and cecum)
Question:
anatomy and physiology: layers
Answer:
4 ... mucosa (columnar epithelium), submucosa, muscularis propria, serosa (in to out)
Question:
anatomy and physiology: describe muscularis mucosa vs muscularis propria
Answer:
musc mucosa = small interwoven inner muscle layer just below mucosa but above basement
membrane ... musc propria = circular layer of muscle
Question:
anatomy and physiology: what part is retroperitoneal?
Answer:
ascending, descending, and sigmoid colon ... peritoneum covers anterior upper and middle 1/3 of the
rectum
Question:
anatomy and physiology: plicae semilunares
Answer:
transverse bands that form haustra
Question:
anatomy and physiology: taenia coli
Answer:
3 bands that run longitudinally along the colon, at rectosigmoid junction the taeniae become broad and
completely encircle the bowel
,Question:
anatomy and physiology: anorectal anatomy with important landmarks
Answer:
distance from anal verge ... 2cm - dentate line .... 4cm - anorectal ring .... 8cm
- end of lower 1/3 .... 12cm - end of middle 1/3 .... 16cm - end of upper 1/3
Question:
anatomy and physiology: vascular supply
Answer:
ascending and 2/3 of transverse colon - SMA (ileocolic, R and middle colic arteries) .... 1/3 transverse,
descending colon, sigmoid colon, upper portion of the rectum - IMA (L colic, sigmoid branches,
superior rectal artery) .... marginal artery - runs along colon margin, connects SMA to IMA (provides
collateral flow) .... arc of Riolan - short firect connection between SMA and IMA .... 80% of blood
flow goes to mucosa and submucosa
Question:
anatomy and physiology: venous drainage
Answer:
follows arterial except IMV, which goes to splenic vein ... splenic vein joins the SMV to form the
portal vein behind the pancreas
Question:
anatomy and physiology: superior rectal artery
Answer:
branch of IMA
Question:
anatomy and physiology: middle rectal artery
Answer:
branch of internal iliac - the lateral stalks during low anterior resection (LAR) or abdominoperineal
resection (APR) contain the middle rectal arteries
Question:
anatomy and physiology: inferior rectal artery
Answer:
branch of internal pudendal (which is a branch of internal iliac)
,Question:
anatomy and physiology: rectal venous drainage
Answer:
superior and middle rectal veins drain into the IMV and eventually the portal vein .... inferior rectal
veins drain into the internal iliac veins and eventually into the caval system
Question:
anatomy and physiology: nodal drainage
Answer:
superior and middle rectum - drain into IMA nodal lymphatics .... lower rectum - drains primarily to
IMA nodes and also to internal iliac nodes .... bowel wall contains mucosal and submucosal
lymphatics
Question:
anatomy and physiology: watershed areas
Answer:
splenic flexure aka Giffith's point - SMA and IMA junction .... rectum aka Sudak's point - superior
rectal and middle rectal junction ...colon more sensitive to ischeia than small bowel 2/2 fewer
collaterals
Question:
anatomy and physiology: part of bowel most sensitive to ischemia
Answer:
colon is more sensitive to ischemia than small bowel 2/2 decreased collaterals
Question:
anatomy and physiology: external vs internal sphincter - muscle, innervation
Answer:
external = puborectalis muscle, continuation of levator ani (striated) muscle, under CNS control via
inferior rectal branch of internal pudendal nerve .... internal = continuation of muscularis (smooth)
muscle, involuntary control, normally contracted
Question:
anatomy and physiology: inner and outer nerve plexi
Answer:
inner = meissner's plexus ... outer = Auerbach's plexus
, Question:
anatomy and physiology: sympathetic vs parasympathetic
Answer:
sympathetic = lumbar and sacral plexi .... parasympathetic = pelvic splanchnic nerves
Question:
anatomy and physiology: distance from anal verge - anal canal, rectum, rectosigmoid junction
Answer:
anal canal 0-5cm .... rectum 5-15cm ... rectosigmoid junction 15- 18cm
Question:
anatomy and physiology: levator ani
Answer:
marks the transition between anal canal and rectum
Question:
anatomy and physiology: crypts of lieberkuhn
Answer:
mucus-secreting goblet cells
Question:
anatomy and physiology: colonic inertia
Answer:
slow transit time, pts may need subtotal colectomy
Question:
anatomy and physiology: main nutrient of colonocytes
Answer:
shortchain fatty acids
Question:
anatomy and physiology: tx of infectious pouchitis
Answer:
flagyl
