Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we're going to be looking at the heart valves. And in order to do so, we’re going to be exploring mainly this image that you see now on the screen and, to show you what is happening here, I have another image of the heart here. So, this is an anterior view of the heart and, on this image on the right side – what we did is just made a cut here where we can then expose the different valves of the heart from a superior view – so we’re looking at it from a superior view – and this portion here is the anterior part or the front of the heart while this part here is the posterior or the back portion of the heart. So, we’re basically looking at this here, as we’re looking at the top portion if we made a cut and looking now from the superior view or cranial view.
The first point that I would like to make that you can clearly see here on this image is that there are 4 main valves in the heart. So, 2 atrioventricular valves which are known as the mitral valve and the tricuspid valve. And you can see here, this is the mitral valve and the tricuspid valve. There are also 2 semilunar valves. They are found in the arteries. These are then the aortic valve and the pulmonary valve. Now, notice here that this is the aortic valve in the aorta and the pulmonary valve found on the pulmonary trunk.
Now, let’s explore these structures in a little bit more detail, and right now we’re looking at the mitral valve or the left atrioventricular valve highlighted in green. We just made here a cut on the left ventricle of the heart and we can then expose here the left atrioventricular valve or the mitral valve. We can also call this valve as the bicuspid valve because, as the name indicates, bi- meaning duo, flap cuspid, cusp. So dual flap valve that you find in your heart that lies between the left atrium and the left ventricle. And as you can see, this is the left ventricle as I mentioned, and the left atrium should be around here.
In terms of role, the role of the left atrioventricular valve that you see now highlighted in green from this superior view, the role of the mitral valve will be to then during diastole, a normally function mitral valve will be opening as a result of increased pressure from the left atrium as it fills with blood. As atrial pressure increases above that of the left ventricle, then the mitral valve will be opening as you see now on the screen.
Now, opening will then be facilitating the passive flow of blood into the left ventricle. Diastole ends with the atrial contraction which ejects the final 20% of blood that is transferred from the left atrium to the left ventricle. The mitral valve will be then closing at the end of the atrial contraction to then prevent a reversal of blood flow. Now, the mitral valve has 2 flaps, bicuspid valve, and the one that we’re highlighting right now is known as the anterior cusp of the mitral valve.
Now, the anterior cusp is the ventral and larger one of the 2 cusps that forms then the mitral valve. It originates ventromedially at the left fibrous ring – this portion here – which we will talk about a little bit later, then attaches at the septal aspect of the left atrioventricular orifice via the heartstrings.
Posteriorly, we’re going to be highlighting now the posterior cusp of the mitral valve. Now, the second cusp of the mitral valve is placed dorsally and smaller than the anterior cusp that originates dorsolaterally from the left fibrous ring, as you can see here, this rim, and attaches to the mural aspect of the atrioventricular orifice via the heartstrings.
One structure that I’m going to be highlighting now is the fibrous ring that I just talked about – so this is the fibrous ring of the mitral valve – which is also known as the left annulus fibrosus of the mitral valve and surrounds the left atrioventricular orifice that consists mostly of collagen. It is part of the framework that separates the atrium from the ventricle and is point of attachment for then the mitral valve.
We’re going to move now to this valve that you see here, the tricuspid valve or also known as the right atrioventricular valve. Now, the tricuspid valve is on the right dorsal side of the heart between the right atrium and the right ventricle. The normal tricuspid valve usually has 3 leaflets as you can see here, or 3 flaps, and 3 papillary muscles. They are connected to the papillary muscles by the chordae tendineae which lie in the right ventricle.
If I move onto this image here to the anterior view of the heart where we cut open the right ventricle, you can see the tricuspid valve highlighted in green. To say that this valve is connected to the papillary muscles – these muscles here – through the structures which are known as the chordae tendineae lying then in the right ventricle. The tricuspid valve also has a function and the main function is to prevent the backflow of blood into the right atrium – you can see here, we just cut open the right atrium and you see the tricuspid valve highlighted.
Now, we’re going to look at the different cusps of the tricuspid valve. First one that we have here highlighted in green is known as the anterior cusp of the tricuspid valve. Now, the anterior cusp is the largest and most ventrally-positioned cusp. It originates at the right fibrous ring, so, also you find here a fibrous ring on the tricuspid valve and the right fibrous ring will be then serving as an origin point for the anterior cusp. And then it will be attaching at the right atrioventricular orifice to the respective papillary muscle via then the heartstrings or the chordae tendineae.
We’re going to be highlighting now this posterior cusp, which is then the posterior cusp of the tricuspid valve. Now, this cup is medium-sized and is the most dorsally placed of the 3 leaflets of the right atrioventricular valve. And like the anterior cusp, it’s going to be originating also from that ring, the fibrous ring, specifically the right fibrous ring, and then attaches at the right atrioventricular orifice to the respective papillary muscle via then the heartstrings.
Next, we’re going to be highlighting this structure which is then the septal cusp of the tricuspid valve. Besides the right fibrous ring, the septal cusp has an additional origin point at the interventricular septum and, like the other cusps, it is connected to the chordae tendineae running towards the papillary muscles.
Also worth highlighting here, the right fibrous ring that we just talked about or the fibrous ring of the tricuspid valve. Now, this ring is going to be surrounding the right atrioventricular orifice and consists mostly of collagen. This fibrous ring is part of the framework that separates the atrium from the ventricle and is then the attachment point for the tricuspid valve.
We’re going to start talking about the semilunar valves and right now we’re looking at the aortic valve. Now, the aortic valve has normally 3 leaflets that lies between the left ventricle and the aorta. In terms of the role associated to the aortic valve and notice here that I just cut open the left ventricle and you can see here then the aortic valve which opens to then this structure here which is the aorta. When it comes to the role of the aortic valve during ventricular systole, pressure arises in the left ventricle. When pressure in your left ventricle rises above pressure in the aorta, the aortic valve will be opening allowing then blood to exit the left ventricle into the aorta, and then to the rest of your body. So, when ventricular systole ends, pressure in the left ventricle rapidly drops, but when pressure in the left ventricle decreases, the aortic pressure forces the aortic valve to then close. And knowing that, we’re going to move on and talk about the different cusps of the aortic valve.
We’re now highlighting the right semilunar cusp of the aortic valve. This is one of the 3 cusps that regulate blood flow from the left ventricle into the aorta and prevents then the blood from flowing backwards during diastole. Now this right semilunar cusp will be then overlying the origin of the right coronary artery which you can see here – so this is the right coronary artery and the origin or the opening here.
Next, we’re going to be opening here the aortic valve and highlighting the left semilunar cusp of the aortic valve. Also one of the 3 semilunar cusps of the aortic valve, the left semilunar cusp lies in the left posterior position in the adult heart and overlies then the origin of the left coronary artery as you can also see here, the left coronary artery and you see a little bit of the opening here.
Next, we’re going to be highlighting a bit more posteriorly then the posterior semilunar cusp of the aortic valve and this cusp lies in the right posterior position in the adult heart and does not overlie the origin of either coronary arteries.
We’re going to move on and talk about the next semilunar valve. This one is the pulmonary valve. The pulmonary valve is positioned at the transition from the conus arteriosus and the pulmonary trunk. This valve prevents the blood from flowing back into the right ventricle during diastole. Now, just to highlight here that the valve has 3 cusps, and as we move here onto this image, you can also see here the 3 cusps and now we’re just cutting open here the right ventricle. We’re exposing the right ventricle. Notice here the conus arteriosus and then the pulmonary trunk, just here highlighted then the pulmonary valve. Now, the pulmonary valve will be opening in ventricular systole when the right ventricle pumps blood into the pulmonary arteries, which you can see a little bit here. So the pulmonary trunk and then the 2 pulmonary arteries. Closure of the pulmonary valve contributes to then the second heart sound.
Let’s have a closer look to the different cusps of the pulmonary valve. We’re now looking at the anterior semilunar cusp of the pulmonary valve. Now, together with the other 2 cusps of the pulmonary valve, this one will be functioning to then seal the heart valve when closed and then preventing back flow of blood.
Next highlighted here, you’ll see then the right semilunar cusp. And the right semilunar cusp of the pulmonary valve is located on the right portion of the pulmonary valve. You also have a, then, left semilunar cusp which is then located on the equivalent left side.
Now, that we talked and covered about the different structures, different valves, I want to just talk about a few structures that you find on these images so you can have a better idea of what you’re seeing throughout these images. And, for now, we’re going to be highlighting one structure that I mentioned before which is then the right coronary artery.
Now, the right coronary artery is an artery originating above the right cusp of the aortic valve as you can see on this image and it travels down the right atrioventricular groove towards the crux of the heart. Now, it branches into the posterior descending artery in 85% of the cases, and the right marginal artery. In addition, this artery will be then supplying blood to the right ventricle and the right coronary artery also supplies 25% to 35% of the left ventricle.
The next structure worth highlighting here on this image is known as the circumflex branch of the left coronary artery. As you can see on this image, it follows the left part of the coronary sulcus running first to the left and then to the right reaching nearly as far as the posterior longitudinal sulcus. You’re going to also see here a little bit on this view here, anterior view of the heart. See a little bit of the circumflex branch of the left coronary artery highlighted in green coming from this artery here which is the left coronary artery.
Going back to this image we’re now highlighting a very important structure, the coronary sinus. Now, the coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart muscle. The coronary sinus will be delivering deoxygenated blood to the right atrium as do the superior vena cava and also the inferior vena cava. You can also see here the coronary sinus on this image of the posterior view of the heart where you can also see here the superior vena cava and the inferior vena cava. You notice how they are all connected to the right atrium. To be more clear, we’re looking at the posteroinferior view of the heart.
The next structure I would like to highlight here – this triangle – which is known as the right fibrous trigone. Now, the right fibrous trigone is a thickening of the inferior part of the fibrous heart skeleton. This structure mechanically and electrically separates the atria and ventricles of the heart. It is pierced by the bundle of His. This is the only electrical connection between atrium and ventricle which makes it a very important structure.
There’s also another triangle here that I’m highlighting which is known as the left fibrous trigone, and the left fibrous trigone is part of the heart skeleton. It is located between the left side of the left atrioventricular ring and the aortic ring. And, like the right fibrous trigone, it mechanically and electrically separates atria and ventricles of the heart.