International surgical boards

2022-06-14 18:49:04 Colon vascular supply

The colon is supplied by both the superior and inferior mesenteric arteries which are branches of the aorta.

The superior mesenteric artery (SMA) arise from the anterior surface of the aorta just below the celiac trunk at the level of the lower part of L1.

SMA branches off the ileocolic artery (abscent in 20% of population) which supplies the terminal ileum and proximal ascending colon, it also gives the right colic and middle colic arteries that supply the distal ascending colon and transverse colon respectively.

The inferior mesenteric artery arise from the aorta at about L3 vertebral level, it gives the left colic artery, several sigmoidal branches, and the superior rectal artery which supplies the proximal rectum.

Each of these arteries communicate via anastomoses through the artery of Drummond, this circle of anastomoses is complete in only 15% to 20% of the population. Open / Comment

2022-06-12 12:52:33 Open / Comment

2022-06-11 12:22:04 The charactaristic triangular appearance of the transverse colon when viewed by colonoscopy. Open / Comment

2022-06-11 12:20:09 Anatomical Landmarks of the colon

The Caecum is the widest part of the colon, its diameter is about 7.5 to 8.5 cm, and it has the thinnest muscle coat, this means its the most vulnerable to perforation and the least vulnerable to obstruction.

The Ascending colon is relatively unremarkable, being fixed in the retroperitoneum, the transverse colon is relatively more mobile, it is tethered by the gastrocolic ligament and by the colonic mesentery, the greater omentum also attaches to the anterior and upper aspects of the transverse colon, these three attachments explains the charactaristic triangular appearance of the transverse colon when viewed from inside by colonoscopy (see figure below)

The splenic flexure marks the transition between the transverse and descending colon, and it is held by the Lienocolic ligament to the spleen, this ligament is sometimes dense and short making mobilisation during colectomy somewhat more difficult, the splenic flexure is also a watershed area between two vascular supplies, namely the superior mesenteric and inferior mesenetric arterial networks, making this region vulnerable to vascular injury, this area is referred to as Griffiths point.

The sigmoid colon is very mobile, and it has the narrowest diameter in the colon making it the most vulnerable part to become obstructed, although its usually positioned in the lower left quadrant; its extreme mobility and redundancy sometimes makes it to lie largely in the lower right quadrant, therefore such diseases like diverticulitis may present with right lower quadrant pain.

The rectosigmoid junction is approximately at the level of the sacral promontory, which is the anterior projection of the first sacral vertebra, for ease of notion, the rectosigmoid junction is the point at which the three tinea coli converge into one continuous outer longitudinal muscle coat of the rectum.

The sigmoid colon marks another vascular watershed area, known as Sudek's point, which marks the area between the inferior mesenteric and internal iliac arteries. Open / Comment

2022-06-07 10:21:03 Bailey & Love's Notes pinned «Announcement The channel will start a thorough discussion about the Colon, Rectum, And Anus.» Open / Comment

2022-06-07 10:17:18 Open / Comment

2022-06-07 10:13:48 Open / Comment

2022-06-07 10:11:33 Open / Comment

2022-06-07 00:00:05 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). Open / Comment

2022-06-06 23:53:37 Announcement

The channel will start a thorough discussion about the Colon, Rectum, And Anus. Open / Comment