 Please keep in mind that separating the systemic and pulmonary systems is sort of arbitrary because they are completely connected to each other and the blood that came from the body has to go to the lungs and the blood that comes from the lungs has to go to the body. So there's like this cycle that whether you decide to include a structure with a systemic system or the pulmonary system, hopefully it will be clear here in a second how we're going to do that. Okay, so let's start with the right atrium because what do we know about the blood that enters the right atrium? First of all, we know that it's dirty blood. And look at what's happening. In the first picture that we drew, we actually drew just one arrow. Here we come from the body. But we have an upper body and a lower body. And that means that you actually have, this vessel has two parts. It's almost like this vessel kind of bulged out and formed the atrium, the right atrium. So it's kind of a whether you depict these vessels coming into the atrium in two different places or joining together to come into the atrium. It's almost like these two vessels became the atrium. So who are they? Well, this is the inferior, what? Vena cava. The inferior vena cava brings dirty blood from the lower extremities to the right atrium. So who's this? So nice. This is superior vena cava bringing dirty blood from the upper extremities, including your lovely head. Systemic because it's coming from the body. However, what happens to this blood? Passes from the right atrium into the right ventricle. And from the right ventricle, we go somewhere that we're not allowed to go to before talking systemic circulation. Oh, can't go there. So we won't go there. We'll pretend like it doesn't exist. If we're only talking systemic system, then the next place we have to end up is in the left atrium. But it's true, we went to the lungs first. So we're about to do pulmonary circulation in a second. Inferior vena cava comes, takes the blood to the lungs, brings the blood back into the left atrium. The blood passes into the left ventricle. And then passes up the ascending aorta. And this is it right here. I'm going to have to make a little star and put it over here. That's the ascending aorta. And the aorta has parts. So sure it has parts. All right, I'm going to make my other part look like this instead of a star. And then I'm making you a key down here. This is the ascending aorta, which turns into the aortic arch. Thank you. I can totally handle aortic arch because it's an arch. It looks like an arch. The ascending aorta becomes the descending aorta. And it actually has, oh dear, whatever that sign is, that's my next one. But of course, it's an upside down on its side A. That thing is my descending aorta. And we'll actually separate that out because it's the thoracic, the descending thoracic aorta when it's in the thoracic cavity. And it's the abdominal aorta when it is in the abdominal cavity. So that works pretty clear. But we might flesh that out a little bit more. Okay, guess what? That's it. From the descending or from the aorta that's down thoracic or abdominal, we're going to go to the body. We're going to go to some sort of capillary system. We're going to get dumped back eventually through a bunch of veins into the inferior vena cava and we're going to start all over again. We missed half of our calling and so we have to do the pulmonary circulation next.