Embryology of the Colon, rectum and anus The primitive gut develops at about the 4th week of gestation from the
endoderm The primitive gut is divided into the
foregut, midgut and hindgut, both midgut and hindgut contributes to the colon, rectum and proximal anus.
At the 6th week the midgut herniates out of the abdominal cavity, and returns at the 10th week with a
counterclockwise rotation of about 270 degrees around the superior mesentric artery, and give rise to the small bowel, caecum, ascending colon and proximal transverse colon.
The hindgut gives the distal transverse colon, descending colon, rectum and proximal anus, the distal anus is derived from the
ectoderm and supplied by the
internal pudendal artery. The distal end of the hindgut is called the
Cloaca, at the 6th week the Cloaca is divided by the
Urorectal septum into the rectum dorsally and urogenital sinus ventrally
(see fig above).
