Rectal Artery

00:00 Staying on the example of the rectal artery, I said the inferior mesenteric artery comes here and divides into left colic, sigmoid, and superior rectal.

00:15 Your veins will follow the arteries, so you have a superior rectal vein going back.

00:22 Then it forms the inferior mesenteric vein.

00:24 This is part of portal circulation or systemic circulation? Portal, because it's going into the inferior vena cava.

00:31 Sorry, not inferior. It's going into the portal circulation because it’ll finally go into the portal vein, correct? Now, I said superior rectal artery supply, it comes off the inferior mesenteric.

00:45 Where does the middle rectal and the inferior rectal come from? Very good. Middle rectal comes with the internal iliac and the inferior rectal also comes through the internal iliac but from the internal pudendal. That's fine.

01:01 If you look back, what happens to the veins? The veins will have to drain back through the middle rectal vein, inferior rectal vein into the internal iliac vein into the inferior vena cava which is a systemic circulation.

01:21 So, the inferior rectal artery drains into the inferior rectal vein.

01:26 So, it drains along with the rectal artery.

01:28 That’s correct. Superior rectal artery, it's coming off the abdominal aorta.

01:36 Then, it is anastomosing with the middle rectal artery and the inferior rectal artery which is coming off the internal iliac.

01:54 Got it? If you look at it in reverse, that means the venous drainage, so the superior rectal vein will drain into the portal circulation.

02:11 Your middle rectal vein and the inferior rectal vein will drain into the systemic circulation because it's draining back into the inferior vena cava.

02:20 When you have portosystemic anastomosis or a bleed, these channels open up.

02:26 That's when you get a portosystemic anastomosis leading to hemorrhoids or leading to melena or leading to any form of rectal bleed.

02:35 The same thing happens in the esophagus.

02:38 Esophagus, the anastomosis is between the left gastric vein which is a portal circulation and the azygos vein which is a systemic circulation.

02:48 Think about the azygos vein, what does the azygos vein do? The azygos vein drains back directly into the heart.

02:56 What does the gastric vein do? Gastric vein essentially goes back into the splenic veins because of portal vein.

03:10 What's happening around the umbilicus? What veins? Inferior? Well, it's called superficial epigastric veins which is the systemic circulation anastomosing with the veins in the falciform ligament or the paraumbilical veins.

03:32 These are three common sites of portosystemic anastomosis, lower end of the esophagus, rectum, umbilicus.

03:41 Uncommon sites are the bare area of liver and the retroperitoneum.

03:46 There are five sites for portosystemic anastomosis.

03:49 One, two, three, four and the fifth is retroperitoneum.

03:56 Retroperitoneum is an anastomosis between the colic veins and the lumbar veins.

04:00 You don't have to know that much in detail.

04:05 The easiest way to remember the portosystemic anastomosis is think the arterial circulation and work it around with the venous.

04:14 Then this comes down further.

04:21 At this point, it is bifurcating into common iliacs.

04:25 That is a lower border of L4 vertebra, also called the translumbar plane or the intertubercular plane.

04:39 That is what we are seeing here Imagine that’s the aorta, common iliac, internal iliac is going in and the external iliac is coming and becoming the common femoral.

04:58 What happens to the internal iliac artery? Internal iliac is going into the pelvis.

05:09 What happens after that? What does it divide? What does it supply? Two. Two is fine. Anterior, posterior? It's okay. Good. Yes.

05:28 The easiest way to remember, because as I said, we just can't memorize the whole thing.

05:32 The easiest way to remember, it goes into the pelvis, and then it divides into an anterior branch and a posterior branch.

05:38 Anterior supplies everything in the pelvis and posterior supplies the gluteal region and the lumbar region.

05:43 That's a way to remember it.

05:45 If you think about the names of the internal iliac's anterior branch, you have internal pudendal, vesical, uterine arteries.

05:56 Then whatever is supplying the bladder, it's all coming from the anterior division of internal iliac.

06:05 You also have the inferior gluteal artery.

06:08 That is also from the anterior division.

06:13 Posterior division has got superior gluteal artery and the iliolumbar arteries.

06:25 They’re like the interiliac question because many people know about the external iliac.

06:31 Not many people think about the internal iliac.

06:33 Maybe we don't read about internal iliac.

06:35 You just assume interiliac goes there.

06:37 But then they'll ask you a little bit more specific.

06:41 Internal pudendal is an important branch of the anterior division of internal iliac from which you have the inferior rectal artery.

06:56 I know that since we are going towards the end of the day, there's a lot of information coming through now.

07:02 Take your time to assimilate this bit of information About the portosystemic anastomosis and the iliacs because next thing we are going to discuss is about the stomas.

07:15 So, you need to make sure that you understand the blood vessel supply.

07:18 The superior rectal artery comes up off the aortic artery.

07:23 No. Superior, okay.

07:27 You have the inferior mesenteric comes off, gives three branches.

07:31 And one of those is the superior? Correct.

07:33 So, left colic, sigmoid, superior rectal.

07:36 The middle rectal and the inferior rectal are further down.