Editing Colon and rectum (section)

=== '''SMA''' ===

*** Arises at level of L1
*** Runs downwards posteriorly to pancreas, with SMV on its right; but then crosses anterior to left renal vein, uncinate process of pancreas, and D3 and enters root of mesentery of small intestine
*** Left side: gives off up to 20 branches to the small intestine
*** Right side: three major branches to the colon
**** '''Middle colic'''
***** Arises from SMA just below the pancreatic head
****** Can arise as a common trunk with right colic artery (see below)
***** Enters the transverse mesocolon and, 5-7cm from the colon, divides into right and left branches, supplying right and left side of transverse colon
***** Can be identified by lifting up the transverse and palpating at the base of the mesentery just to the right of the ligament of Treitz, at the level of the inferior margin of the pancreas
***** Main blood supply to the splenic flexure in about a third of patients
*****
**** '''Right colic'''
***** Most variable of all colic vessels - absent in 50%
***** May be a branch of middle colic or SMA
****** Origin from middle colic (30%) - ascends towards hepatic flexure
****** Origin SMA (20%) - runs transversely
*****
**** '''Ileocolic'''
***** The most constant of these branches
***** Originates from SMA just caudal to D2, about 7cm from SMA origin
***** Last branch to arise from the right side of SMA, whereas the SMA runs more anteriorly and to the left within the mesentery
***** Runs towards the ICJ
***** Gives off ascending, anterior and posterior caecal arteries and the appendiceal artery (which can be double in African communities apparently)
***** Supplies TI, caecum and appendix