Inferior Mesenteric Artery

00:01 Now let's have a look at the inferior mesenteric artery.

00:05 The inferior mesenteric artery, again, if we zoom into have a look at the abdominal aorta is going to come off the abdominal aorta around about the third lumbar vertebral level.

00:16 And here we can see it's mostly going to supply the hindgut.

00:19 So that's part from the distal third of the transverse colon up to the splenic flexure, descending colon, sigmoid colon, and then part of the rectum.

00:29 We can see here we have the left colic artery, which is going to give an ascending branch that goes up and becomes associated with the marginal artery.

00:37 We'll see again in a moment.

00:39 Ascending branch coming from the left colic, we also have a descending branch, and that's going to unite with the sigmoid artery that's going to supply the sigmoid part of the colon.

00:49 We can see again, have we have more poorly formed but still some arterial arcades in this region.

00:56 The final terminal branch of the inferior mesenteric artery is that one that's passing down to the rectum, and this is the superior rectal artery.

01:05 As its name suggests, we may have inferior or even middle versions of this artery.

01:11 Let's go back to the marginal artery.

01:13 We saw it associated with the superior mesenteric artery.

01:17 And now we can see the ascending branch of the left colic running up to help supply that transition between the midgut and the hindgut.

01:26 And also we can see those vasa recta coming off all of them those straight arteries to supply the substance of the large intestine itself.

01:35 So this is that important transition between the midgut and the hindgut.

01:39 Here we have the superior mesenteric artery giving rise to the middle colic, is giving rise to the marginal artery that's now running around the transverse colon.

01:48 It's going to unite form an anastomosis with the ascending branch of the left colic artery, which is coming from the inferior mesenteric.

01:57 And here we have that anastomosis between the superior and inferior mesenteric arteries.

02:03 It typically happens around the splenic flexure.

02:06 That's typically the area where this transition, these anastomosis occur.

02:11 So now let's have a look down at the rectum and we spoke about the superior rectal artery going to supply the rectum.

02:18 Here we have the superior rectal artery coming from the inferior mesenteric artery.

02:23 We also have the middle rectal artery, and we have an inferior rectal artery.

02:28 These two arteries supply the middle and the inferior aspect of the rectum.

02:33 And they come from arteries, which we haven't really touched on before.

02:36 But for completion, the middle rectal arteries coming from the internal iliac.

02:41 The internal iliac is formed from the bifurcation of the common iliac.

02:45 And remember, the common iliac was the bifurcation of the aorta as it entered into the pelvis.

02:52 Coming off the internal pudendal artery is the inferior rectal artery and this supplies the lower portion of the rectum.

02:59 The internal pudendal artery is a branch again coming from the internal iliac artery.

03:05 The internal pudendal artery goes on to supply other structures which we can discuss another time.

03:12 So here we have that overview again from the inferior mesenteric artery.

03:17 Gives rise to the left colic.

03:18 We can anastomosed with the middle colic artery from coming from the superior mesenteric artery.

03:25 And the connection between the left colic and the middle colic is that marginal artery.

03:30 The left colic also gives rise to sigmoid arteries and the superior rectal artery that go and supply the rectum.

03:37 The sigmoid arteries goes to supply the sigmoid colon.

03:40 Importantly, the superior rectal artery will anastomosed with both the middle rectal and the inferior rectal to supply the rectum.