1
Elscores: Aug. 27, 24- 2024/2025
Absite: Colorectal Questions and Answers
anatomy and physiology: colon function
:-- secretes K and reabsorbs Na and water (mostly in R colon and cecum)
anatomy and physiology: layers
:-- 4 ... mucosa (columnar epithelium), submucosa, muscularis propria, serosa (in to out)
anatomy and physiology: describe muscularis mucosa vs muscularis propria
:-- musc mucosa = small interwoven inner muscle layer just below mucosa but above
basement membrane ... musc propria = circular layer of muscle
anatomy and physiology: what part is retroperitoneal?
:-- ascending, descending, and sigmoid colon ... peritoneum covers anterior upper and
middle 1/3 of the rectum
anatomy and physiology: plicae semilunares
:-- transverse bands that form haustra
anatomy and physiology: taenia coli
:-- 3 bands that run longitudinally along the colon, at rectosigmoid junction the taeniae
become broad and completely encircle the bowel
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, 2
Elscores: Aug. 27, 24- 2024/2025
anatomy and physiology: anorectal anatomy with important landmarks
:-- 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
anatomy and physiology: vascular supply
:-- 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
anatomy and physiology: venous drainage
:-- follows arterial except IMV, which goes to splenic vein ... splenic vein joins the SMV
to form the portal vein behind the pancreas
anatomy and physiology: superior rectal artery
:-- branch of IMA
anatomy and physiology: middle rectal artery
:-- branch of internal iliac - the lateral stalks during low anterior resection (LAR) or
abdominoperineal resection (APR) contain the middle rectal arteries
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, 3
Elscores: Aug. 27, 24- 2024/2025
anatomy and physiology: inferior rectal artery
:-- branch of internal pudendal (which is a branch of internal iliac)
anatomy and physiology: rectal venous drainage
:-- 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
anatomy and physiology: nodal drainage
:-- 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
anatomy and physiology: watershed areas
:-- 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
anatomy and physiology: part of bowel most sensitive to ischemia
:-- colon is more sensitive to ischemia than small bowel 2/2 decreased collaterals
anatomy and physiology: external vs internal sphincter - muscle, innervation
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, 4
Elscores: Aug. 27, 24- 2024/2025
:-- 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
anatomy and physiology: inner and outer nerve plexi
:-- inner = meissner's plexus ... outer = Auerbach's plexus
anatomy and physiology: sympathetic vs parasympathetic
:-- sympathetic = lumbar and sacral plexi .... parasympathetic = pelvic splanchnic nerves
anatomy and physiology: distance from anal verge - anal canal, rectum, rectosigmoid junction
:-- anal canal 0-5cm .... rectum 5-15cm ... rectosigmoid junction 15-18cm
anatomy and physiology: levator ani
:-- marks the transition between anal canal and rectum
anatomy and physiology: crypts of lieberkuhn
:-- mucus-secreting goblet cells
anatomy and physiology: colonic inertia
:-- slow transit time, pts may need subtotal colectomy
Exams and Correct Answers |Best Grades | Excellence | Success & Guaranteed Pass
Elscores: Aug. 27, 24- 2024/2025
Absite: Colorectal Questions and Answers
anatomy and physiology: colon function
:-- secretes K and reabsorbs Na and water (mostly in R colon and cecum)
anatomy and physiology: layers
:-- 4 ... mucosa (columnar epithelium), submucosa, muscularis propria, serosa (in to out)
anatomy and physiology: describe muscularis mucosa vs muscularis propria
:-- musc mucosa = small interwoven inner muscle layer just below mucosa but above
basement membrane ... musc propria = circular layer of muscle
anatomy and physiology: what part is retroperitoneal?
:-- ascending, descending, and sigmoid colon ... peritoneum covers anterior upper and
middle 1/3 of the rectum
anatomy and physiology: plicae semilunares
:-- transverse bands that form haustra
anatomy and physiology: taenia coli
:-- 3 bands that run longitudinally along the colon, at rectosigmoid junction the taeniae
become broad and completely encircle the bowel
Exams and Correct Answers |Best Grades | Excellence | Success & Guaranteed Pass
, 2
Elscores: Aug. 27, 24- 2024/2025
anatomy and physiology: anorectal anatomy with important landmarks
:-- 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
anatomy and physiology: vascular supply
:-- 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
anatomy and physiology: venous drainage
:-- follows arterial except IMV, which goes to splenic vein ... splenic vein joins the SMV
to form the portal vein behind the pancreas
anatomy and physiology: superior rectal artery
:-- branch of IMA
anatomy and physiology: middle rectal artery
:-- branch of internal iliac - the lateral stalks during low anterior resection (LAR) or
abdominoperineal resection (APR) contain the middle rectal arteries
Exams and Correct Answers |Best Grades | Excellence | Success & Guaranteed Pass
, 3
Elscores: Aug. 27, 24- 2024/2025
anatomy and physiology: inferior rectal artery
:-- branch of internal pudendal (which is a branch of internal iliac)
anatomy and physiology: rectal venous drainage
:-- 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
anatomy and physiology: nodal drainage
:-- 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
anatomy and physiology: watershed areas
:-- 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
anatomy and physiology: part of bowel most sensitive to ischemia
:-- colon is more sensitive to ischemia than small bowel 2/2 decreased collaterals
anatomy and physiology: external vs internal sphincter - muscle, innervation
Exams and Correct Answers |Best Grades | Excellence | Success & Guaranteed Pass
, 4
Elscores: Aug. 27, 24- 2024/2025
:-- 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
anatomy and physiology: inner and outer nerve plexi
:-- inner = meissner's plexus ... outer = Auerbach's plexus
anatomy and physiology: sympathetic vs parasympathetic
:-- sympathetic = lumbar and sacral plexi .... parasympathetic = pelvic splanchnic nerves
anatomy and physiology: distance from anal verge - anal canal, rectum, rectosigmoid junction
:-- anal canal 0-5cm .... rectum 5-15cm ... rectosigmoid junction 15-18cm
anatomy and physiology: levator ani
:-- marks the transition between anal canal and rectum
anatomy and physiology: crypts of lieberkuhn
:-- mucus-secreting goblet cells
anatomy and physiology: colonic inertia
:-- slow transit time, pts may need subtotal colectomy
Exams and Correct Answers |Best Grades | Excellence | Success & Guaranteed Pass
