[BLANK_AUDIO] Okay so that's the first set of valves. And I want to just now think about something that Stef said which was the ventricles contract. The AB valves will close and then blood will pass into these big vessels that leave the left and the right atrium. Right? Blood will pass into the pulmonary trunk from the right ventricle and into the aorta from the left ventricle. Right? Well, the opening into those large blood vessels is also guarded by valves. And we call the valves that are positioned at the opening into those large vessels semilunar valves. The semilunar valves are being depicted on this model. You can see that we have one at the entry into the pulmonary trunk, and we call it the pulmonary. Pulmonary semi lunar valve. Sometimes it's simply called the pulmonic valve. At the opening, into the aorta it's a little bit more difficult to see the semi lunar valve. But you can see it tucked behind the mitral valve. You see it? that. Semilunar valve is called the aortic semilunar valve or simply the aortic valve. Okay? They get their name as semilunar valves, because the cusps of the valve actually have a half moon shape when the cusps are closed. Right? >> Mm-hm. Now, what happens is when these cusps are closed, they kind of fall into the center pulmonary trunk, or fall into the center of the aorta. And that prevents blood from flowing backward. From the blood vessel into the ventricle. [SOUND] >> But what do you think makes those valves open? [SOUND] >> Is it the same sort of pressure concept? That we talked about before? >> Exactly, yes. So when the ventricles are contracting, we know they're going to eject blood into these large ventricles or into these large vessels, right? And so when the ventricles contract and pressure increases at the point that ventricular pressure is. Is higher than pressure in these big blood vessels. The semi lunar valves open, right? And then, again, going back to our idea. The idea of atria contract, ventricles contract. And things relax. During that relaxation at some point ventricular pressure fall below the pressure in these big blood vessels. And what will happen? >> They'll close. >> The semilunar valves will close. Exactly. Okay. Now it's, it's a little bit more complicated because if you think about it what's happening is during this [SOUND] [SOUND] relax. When we're relaxed, which valves are open and which valves are closed? Who wants to take a guess? So during that relaxation time. Mia. >> Do the semilunar valves close, and the mitral, and tricuspid open? >> Exactly. So they, they will be in that state. During that period, when, everything in the heart wall is. Relaxed. The AV valves will be open. And the semi lunar valves will be closed. And during that time, blood is going to be coming back into the Atria through these big blood vessels that we talked about right? So blood will come back to the right atria through which vessels? The superior vena cava, the inferior vena cava, and the coronary sinus. >> Right, and so that blood's coming back into the right atrium because pressure's low in the right atrium. Pressure's also low in the right ventricle, and so the tricuspid valve is open. And the blood is just going to flow through the right atria into the right ventricle, right? On the other side of the heart, things are equally relaxed. And blood is coming back to the left atrium through which vessels? >> The pulmonary veins? >> The pulmonary veins, which are carrying that oxygenated blood back from the lungs, right? And the mitral valve is. It's open because the pressure is low in all the chambers. And so blood is flowing just flowing freely from the left atrium through the mitro valve which is open into the left ventricle, right? During that period when everything's relaxed though we do not want blood flowing backward. Through these vessels. Right? So, the semilunar valves are closed. Fabulous. Okay. So, now, the next thing that happens, everything was relaxed, now, we have this contraction of the atria. That causes pressure to be a little bit higher in the atria, but. Nothing really has changed in terms of valve status because of that, right? But then the atria relax and the ventricles contract, and so now tell me, when the ventricles contract what's the first valve change you ex. Expect to see. Nat. >> The atrial ventricular valves will close? >> Yes, exactly. So during the first part of ventricular contraction, pressure in the ventricles will become higher than pressure in the atria, and that will cause the av valves. To swing shut. Right? OK. And then pressure continues to climb as the ventricles continue to contract, and eventually pressure in the ventricles will be higher than pressure out here in these big blood vessels, and what will happen Mina? >> The semilunar valves will open. >> Yes, and then we will start to do that thing the heart was meant to do. [UNKNOWN] eject blood, right? >> Mm-hm. >> Into either the pulmonary or the systemic circulation. Okay, and so then the ventricular contraction will stop and the ventricle will begin to relax and what do you expect to happen first, Andre? >> We'll have some [INAUDIBLE]. [INAUDIBLE] >> Exactly. The semi lunar valves will close. The ventricles will continue to relax. And then, what will happen? Steph? >> The tricuspid and [INAUDIBLE] valves will open [UNKNOWN]. >> Excellent. And so, it will all start all over again. Because when those two AV valves. Open but will be able to be passed from the atria into the ventricles, right? It's kind of cool. Now, you haven't thought about this before. But when those valves close, [SOUND] they swing shut and they cause vibrations to occur in the blood that's passing through. For the heart. And those vibrations get carried to the body's surface and you can actually, if you listen with a stethoscope, you can actually hear sounds caused by those vibrations. And we refer to those sounds as either sound one or sound two. When the AV valve swings shut, it creates sound one. When the semilunar valves shut, it creates sound two. So, have you wondered what's going on when you're sitting in your physicians office or you know, some primary care specialist listening to your heart. You guys know cause you've been practicing it right? Yeah they, they can actually listen to hearts sounds at the body surface. And those heart sounds are simply indicating that valves have closed. This week in the simalab we're going to be practicing listening to heart sounds. That would be pretty cool. Any questions? Okay.
