Heart Valve

00:01 Well, as I mentioned earlier, the heart has got the valve in it. And those valves stop the backflow of blood during contraction of the ventricles, and also contraction of the atrial components when blood passes from the atrium into the ventricle, and then the ventricle into blood vessels. When you look at the histology of the heart valve, it’s a little bit confusing unless you know the sorts of sides, the surfaces on which this heart valve are associated with.

00:42 Heart valves either separate the atria from the ventricle or the ventricle from blood vessels like the aorta or the pulmonary trunk. So sometimes, on the surface of the heart valve, you might have an atrial surface and a ventricular surface, if you’re looking at the valve between the atrium and the ventricle. Sometimes, there could be a blood vessel surface and a ventricular surface depending on whether or not you’re looking at a heart valve that separates the blood vessel from the ventricle. So bearing that in mind, when you look at the heart valve, you can identify some histological components, all be it, they’re rather distorted here because the heart valves are often very hard to fix properly and examine under a microscope.

01:39 But there is a central core to the heart valve. That central core is called the fibrosa.

01:47 It’s the strong component of the heart valve that joins on with the fibrous skeleton component of the heart that I've mentioned earlier. And then on top, on the surface, that’s adjacent to either the atrium or either the blood vessel, you have a thin layer called the spongiosum.

02:08 The spongiosum or spongiosa, as it’s often referred to, is a very thin layer. It’s elastic, and that helps to dampen the force of vibrations on the heart valve caused by the continual closing of the heart valve during the heartbeat. And finally, the layer below is called the ventricularis. This is the layer of tissue that’s adjacent to the ventricle space. And that’s dense connective tissue as well, and it becomes continuous with the chordae tendineae, structures that extend from the heart valves between the atria and ventricles that attach to little papillary muscles inside the ventricle and stop the valves from opening in the wrong direction during contraction of the ventricle.