Exploring anatomy: the human

An advanced look at the vessels of the posterior abdominal wall

Welcome to this video for exploring anatomy, the human abdomen. This video is going to outline the vessels of the posterior abdominal wall. So let's start off by drawing out the aorta. Now, the aorta enters the abdomen by passing through the diaphragm, through the aortic hiatus at the level of 12th thoracic vertebra. It then runs anterior to the vertebral bodies of the lumbar vertebra. At approximately the level of the fourth lumbar vertebra, it divides into two common iliac . So here we can draw out the two common iliac arteries. And this is approximately at the level of L4. We've got the right common iliac here. And the left common iliac here. For simplification, I'll just mark the right and left sides at the top of the screen. If we stick with the common iliacs for one moment before we actually look at the blood vessels that come away from the abdominal aorta, then both common iliac arteries divide into an external and an internal iliac . So what we have here is the internal iliac artery-- the internal iliac. And here we have the external iliac. The external iliacs are going to supply the lower limb, whilst the internal iliacs supply the pelvis and the perineum. We've drawn them here on the right side. But obviously, we have them on the left side as well. The external iliacs eventually become the femoral arteries that run into the leg. So if we now return to the top of the aorta, then it passes into the abdomen at approximately the 12th thoracic vertebral level. And as I said, it passes through the diaphragm at the aortic hiatus. It then quickly gives off a large branch. And this is the first of the unpaired visceral branches. This is the coeliac trunk. If we then down to approximately L1, we can then find the second of these unpaired visceral branches. And this is the superior mesenteric artery. And this happens at the L1 vertebral level.

Finally, if we move further down the anterior surface of the aorta, we have the inferior mesenteric artery. And this leaves the anterior surface of the aorta at L3. So we have the coeliac trunk, the superior mesenteric artery, and the inferior mesenteric artery. We can then draw on a series of paired visceral branches that supply the viscera within the abdomen. We can draw at the level of L1. We have our two renal arteries. And here we have a renal artery here. It is the right renal artery. And then we have the same on the opposite side. We have a left renal artery. So we have a renal artery here this is our left one. We can then find, if we go in between the superior mesentery artery and the inferior mesenteric artery, we have a pair of blood vessels again that go to supply the gonads. This is the testes in the male and the ovaries in the female. And we have our two gonadal arteries. Here's a left gonadal and here's a right gonadal. And these come off at the L2 vertebral level. We just need to add in some more branches. And these are branches that are going to supply the suprarenal glands. And to do that, we need to put in a small branch that goes up towards the diaphragm. And this is known as the inferior phrenic artery. Again, this comes off at around about the T12 level. And that's our inferior phrenic artery. You have a left one and have inferior phrenic artery on the righthand side as well. And it's important we put these in because the suprarenal glands receive the superior suprarenal artery from these inferior phrenic arteries. So coming from each inferior phrenic artery, we have a superior-- superior suprarenal artery. I won't this draw out the name on this side as I'll overcomplicate it. But coming from the inferior phrenics, we have the superior suprarenal artery. Coming directly from the aorta, we're going to have a middle suprarenal artery. So here we have a middle suprarenal artery. And coming from the renal arteries, we have the inferior suprarenal artery. So here we can see we've got two inferior suprarenal arteries. And then we have the main visceral branches, both paired and unpaired, that come away from the aorta.

You also have a series of parietal branches that go on to supply the body wall. I won't draw these as they'll overcomplicate it. But we have at the level L1, L2, L3, and L4, a series of lumbar arteries. And they go to supply the musculature and the skin of the abdominal wall. So now let's turn to the inferior vena cava, which is also found on the posterior abdominal wall, to the right of the aorta. So if we draw out the inferior vena cava here, we can see again that it is similar in form to the aorta. And it's associated with two common iliac vessels. This time, these are our common iliac . So here we see a right common iliac. And here we see our left common iliac. Let's just add right and left at the top once again. These two comma iliac arteries are both receiving an external iliac and also an internal . So here we can draw out those two iliac veins. The is coming from the lower limb. So here's our external iliac vein and here's our . They're coming from the pelvis and perineum here and coming from the lower limb here. These two converge to form the common iliac. The two comma iliacs converge to form the inferior vena cava. And the inferior vena cava then ascends along the posterior abdominal wall and passes through the diaphragm by the caval opening at level T8. If we just look slightly inferior to the diaphragm, we can see three veins passing into the inferior vena cava. And these three veins are coming from the liver. And they're known as our hepatic veins. We have three of them. We have a right hepatic vein. We have a left hepatic vein. And we have a middle hepatic vein. And what you notice on the inferior vena cava is we don't have coeliac trunks, superior mesenteric artery, or inferior mesenteric artery equivalents. We don't have these unpaired visceral branches. Remember, that these branches-- coeliac trunk, superior mesenteric artery, inferior mesenteric artery-- supply the gastrointestinal tract. And all the venous blood from the GI tract is returned to the IVC by passing through the portal system and then the liver. It's returned to the IVC by the way of these three hepatic veins.

There are some visceral branches that pass into the IVC. And these are from the kidneys. And at a similar level to the renal arteries, we find we have a pair of renal veins. So let's draw out these renal veins here. We can see again, we have a right here and we also have a left renal vein here-- so a right renal vein and a left renal vein. And these are occurring at a similar level, L1, to the renal arteries. If we move slightly further down and then coming off, then draining into the inferior vena cava on this righthand side is the right , draining either the testes or the ovaries. But on the lefthand side, we also have a gonadal vein. But this one is actually draining into the left renal vein. So here we can see we've got our left gonadal vein. Notice how the right one drains into the IVC directly and the left one drains into the left renal vein. Again, there will be various that drain into the IVC, draining blood from the posterior abdominal wall. And there's also going to be a series of suprarenal veins that are draining blood from the suprarenal glands. And they're draining into the IVC, as well. But I won't add these. It will overcomplicate the diagram. So there's the basic layout of the blood vessels on the posterior abdominal wall. [end of transcript]