chapter 36: colorectal Flashcards
Colon secretes ____ and reabsorbs _____
colon secretes K and reabsorbs Na and water (mostly in right colon and cecum)
4 layers of the colon
mucosa (columnar epithelium) -> submucosa -> muscularis propria -> serosa
colonic layer: small interwoven inner muscle layer just below mucosa but above basement membrane
muscularis mucosa
colonic layer: circular layer of muscle
muscularis propria
retroperitoneal portions of colon
ascending, descending and sigmoid colon are all retroperitoneal
- peritoneum covers anterior upper and middle 1/3 of the rectum
transverse bands that form haustra
plicae semiliunares
3 bands that run longitudinally along colon. at rectosigmoid junction, these become broad and completely encircle the bowel
taenia coli
cm: dentate line from anal verge
2cm
cm: anal transition zone from anal verge
4 cm
vasculature: ascending and 2/3 of transverse colon
SMA (ileocolic, right and middle colic arteries)
vasculature: 1/3 transverse, descending colon, sigmoid colon, and upper portion of the rectum
IMA (left colic, sigmoid branches, superior rectal artery)
vascular: runs along colon margin, connecting SMA to IMA (provides collateral flow)
marginal artery
artery: short direct connection between SMA and IMA
Arc of Riolan
how is vascular supply distributed in the colon?
80% of blood flow goes to mucosa and submucosa
venous drainage of colon?
follows arterial except IMV, which goes to the splenic vein
what forms the portal vein?
splenic vein joins the SMV to form the portal vein behind the pancreas
what does superior rectal artery branch off of?
superior rectal artery - branch of IMA
what is the middle rectal artery a branch of?
branch of internal iliac
what contains the middle rectal arteries during low anterior resection [LAR] or abdominoperineal resection [APR]?
the lateral stalks
what is the inferior rectal artery a branch of?
branch of internal pudendal (which is a branch of the internal iliac).
where do superior and middle rectal veins drain?
superior and middle rectal veins drain into the IMV and eventually the portal vein.
where do inferior rectal veins drain?
inferior rectal veins drain into the internal iliac veins and eventually the caval system
major blood supply of the colon
SMA and IMA
drain to IMA nodal lymphatics
superior and middle rectum