So this tutorial is on the Inferior Mesenteric Artery. This follows on from the previous tutorial I did on the superior mesenteric artery.   The inferior mesenteric artery is this artery right at the bottom here. This comes off anteriorly on the abdominal aorta and slightly to the left.   Above it, you've got the superior mesenteric artery and you've got the celiac axis, which supply the other gut structures.

The inferior mesenteric artery originates on the aorta at roughly the level of lumbar vertebra L3.   Remember the aorta bifurcates at L4, so just a little bit above this, you've got the inferior mesenteric artery.

 

The inferior mesenteric artery vascularizes the hind gut structures. I'll just switch to a diagram to illustrate some of its branches.

 

We’re looking here at a diagram which shows the abdominal aorta and you can see the inferior mesenteric artery coming off here. This vessel on the right is the superior mesenteric artery and you can see it vascularizing the ascending colon, the transverse colon and parts of the small intestine here.

 

The inferior mesenteric artery has three main branches. The first branch is this one here that comes off of the top. It's the left colic artery. You can see it splits, divides into this ascending branch and descending branch.   The ascending branch ascends to anastomose with the right branch of the middle colic artery.   The ascending branch vascularizes part of the descending colon. It then goes intraperitoneal into the transverse mesocolon and vascularizes the distal third of the transverse colon.

 

The descending branch descends along the descending colon and sends of branches to supply the descending colon. It anastomoses with the next branch down.

 

Just below the left colic artery, you've got several vessels which come off the inferior mesenteric artery. These are the sigmoidal arteries and you've got quite a few of these. These form these arcades. They vascularize the distal part of the descending colon. And as the name suggests, the sigmoid colon as well.

 

These vessels enters the sigmoid mesocolon to supply the sigmoid colon and the lowest parts of the descending colon.

 

The last branch we've got is the superior rectal artery.   This is the terminal branch of the inferior mesenteric artery. It supplies the distal part of the sigmoid colon and as the name suggests, it supplies the proximal rectum.

 

I'll just switch over to the 3D model and show you the course that the superior rectal artery takes.   We’re looking here at a model with a skeleton and also the arteries.   I haven't got the veins in this model.

 

The inferior mesenteric artery can be seen at the level of lumbar vertebra L3. You've got the left colic artery coming off first. And then you've got these various sigmoidal arteries.

 

And then distally, you've got this terminal branch. This is the superior rectal artery. It crosses over the common ileac vessels. The veins aren't in this model, but the inferior vena cava and their common ileac vein would be seen here.   The superior rectal artery actually crosses over these vessels and it enters the pelvic cavity.

 

I've just brought in the viscera. I'm going to rotate around to the back. You can see this is the superior rectal artery coming over the end of the colon and towards the rectum. And you can see that it splits into these two branches and it descends down the sides of the rectum.   You could see that here.

 

I've just brought back in the skeleton and if I zoom in a little bit further, you can see this is the superior rectal artery and you can see that it divides here. This is the level of S3, so you can see the body of S3 lies at the level where the superior rectal artery splits into its two divisions.

 

That’s the inferior mesenteric artery. It comes off lumbar vertebra level L3 and it's got three main branches. It's got the left colic artery, which has an ascending and descending branch. The ascending branch is sent retroperitoneally and it supplies the descending colon. It then enters into the transverse mesocolon to supply the distal third of the transverse colon.

 

The descending branch goes inferiorly and supplies the lower part of the descending colon and it anastomosis with the sigmoid arteries.

 

The sigmoid arteries, there's quite a few of these, which come off below the left colic artery. These supply the sigmoid colon obviously and right the distal part of the descending colon.

 

And then finally, we've got the superior rectal artery which supplies the distal sigmoid colon and the proximal rectum. It has two branches.   It splits at the level of this body of S3 and it crosses from the abdominal cavity into the pelvic cavity.

 

That’s the inferior mesenteric artery.