 All right, we need to figure out what happens to our blood after it picks up all the nutrients from the digestive system. And I think at some point I mentioned that we were going to have something unique happening here. So take a look at this. Again, reviewing coming from the heart. Here's our diaphragm-ish. Our descending thoracic aorta enters the abdominal cavity and becomes the descending abdominal aorta. And there are a couple of branches of abdominal aorta man that we want to keep track of. And the first one is the celiac artery. And actually, I'm going to list them all out for you and you tell me what they all have in common. Remember, I could have drawn out abdominal aorta man again. And I didn't. This time I just said, okay, here is my descending, descending abdominal aorta. It's on its way down. And look, we can even do this thing and go ahead and have it branching out. We're going to do the whole thing. I could throw in the renal arteries coming off of there. But the important thing that I want you to keep track of isn't all that other stuff. I want you to remember that we're just looking at it again. But why do you think I have celiac, superior mesenteric, and inferior mesenteric as my parts here? Because these guys all feed stomach, small intestine, and large intestine. All of them feed into the stomach, the small intestine, and the large intestine. And now, wouldn't you expect that we're going to feed in, give good fresh blood to all the cells in the small intestine and the stomach and the large intestine, and then pick up their crap blood and take it back to the heart and call it good? Except it's crap blood and it's worse than crap blood. It's not only been deoxygenated by the cells of the digestive system, but it's carrying this, I mean, possibly sketchy blood from the lumen of the digestive system, of the tube. Because who knows what you just ate or drank accidentally or on purpose? Who knows what that was? And so we need some kind of system to allow us to actually filter that. There, all of these arteries pass through the stomach, small intestine, large intestine, and then they feed into a single vein and it's called the hepatic portal vein. It's an interesting thing. Hepatic makes you think liver. Portal, a portal system. I don't know if you know this yet, but a portal system is two capillary beds in sequence. Most capillaries, remember, that's where gas exchange occurs. That's where nutrient exchange occurs. If we're going to expect to absorb anything in the small intestine, in our digestive tract, we're going to expect to get anything into our bloodstream. We're going to have to go through an exchange process. And if we want to feed oxygen to our cells in the digestive tract, we're going to have to go through some sort of exchange process. So the blood is going to get dirty. Dirty blood is now passing out of there. However, it's very nutrient rich because all of these cells, not only did they use a lot of oxygen and energy themselves but they absorbed a whole lot of stuff from the environment, from what you ate. So all of that nutrient-rich energy and oxygen-poor blood is going to travel to my friend. Who do you think? Who's going to go through all that and make sure that it's okay? That's the liver. Now it's interesting because the liver is going to need its own supply of fresh oxygenated blood, right? Because it can't do anything unless it's getting its own blood. And in fact, the ciliac artery has a branch of fresh good blood that's going to go directly to the liver. And that is going to bring the liver fresh. It's going to take care of the liver's needs. The hepatic portal vein is also going to the liver. Mixing nutrient-rich oxygen-poor blood with good, clean, healthy blood inside the liver. And we're going to get this purple mess, which I don't think I have a purple pen. I'm going to make a purple pen. What? And all that mixing happens inside of here while the liver does its thing and cleans the blood and filters it. Now where is the liver going to send the blood after it's done? Who do you think it's going to send it to? It's going to send it via the hepatic vein into the inferior vena cava. Oh, how's that for a connection? This is inferior vena cava. Where's my hepatic artery? I want this to be the hepatic artery. Do you think it is? I hope so. The hepatic vein takes the old blood. It's been filtered, has a lot of nutrients in it, and sends it to the inferior vena cava where it goes up to the lungs to get new oxygen, back to the left side of the heart and out to the body where it will deliver all those great nutrients that it picked up to the body. How cool is that? In this review, why is it called a portal system? What's the scoop with that? We have a capillary bed here and a capillary bed here. And the fact that there are two capillary beds in sequence is the definition of a portal system. It's weird. Why would you do that? Why would you filter out all your stuff due to gas exchange in a capillary bed and then go into another capillary bed? There's no benefit of that because you've already emptied out all the stuff in your blood. The unique thing is that this capillary bed actually puts nutrients into the blood. And so now we just have to make sure that those nutrients are good for you. Is that cool? That's really, really one of my favorite things. Should we do the lower limb? I'm in. Okay, I guess I will.