Anatomy, Thorax, Heart and Pericardial Cavity - StatPearls - NCBI Bookshelf
The epicardium is the layer of muscle found covering the external surfaces of the heart. It is directly fused with the myocardium internally and is in contact with the serous layer of the pericardium. It is sometimes. epicardium (tunica adventitia) myocardium (tunica media) endocardium (tunica intima). You also need to know about Purkinje fibres, which lie in the endocardium. of the heart (mesothelium) is also the visceral layer of the serous pericardium. Oct 27, On each side of the heart, the pericardium acts as the medial border of the pleural space. Perfusion of the myocardium and epicardium is dependent on . and the source, a link is provided to the Creative Commons license.
And one of the interesting things about the membranous part, in particular, is that a lot of babies are born with holes in that membranous part.
So when I say a lot, I don't mean the majority of babies, by any means. But one of the most common defects, if there is going to be a defect, would be that you would actually have a communication between these two so that blood could actually, again, flow from a place that it's not supposed to go, the left ventricle, into a place it shouldn't be going, the right ventricle. So blood can actually flow through those holes, and that is a problem. That is called a VSD. And actually, you might hear that term at some point.
So I just wanted to point out where that happens. And while I'm writing VSD, you can take a stab at guessing what it might stand for. Ventricular, and S is septal. Again, septal just means wall. And D is defect. So a VSD is most common in that membranous part, more so than that muscular part.
Now, let's move on again to one final thing I want to point out, which is I want to zoom in on the walls. So here in a gray box I'm going to kind of highlight what's going on this wall and how many layers there are in this wall. Let me draw out a little rectangle to correspond to that little rectangle I drew on the heart itself.
So there are three layers to the heart muscle. And actually, I'm going to go through all three layers. And we'll start from the inside and work our way out. So on the inside, you have what's called the endocardium.
And I'm actually going to draw the endocardium all the way around here. It goes all the way around the valves, so now you already learned that the valves now have endocardium. It goes around the ventricle and, as I showed you in the beginning, also around the atrium. And it goes all the way up and covers both the right and left side. The endocardium is very, very similar in many ways to the inner lining of the blood vessels, actually. So it's a really thin layer. It's not a very thick layer.
It's the layer that all the red blood cells are kind of bumping up against. So when the red blood cells are entering the chambers of the heart, the part that they're going to see is going to be the endocardium. So this is what it looks like, and this is that green layer all the way around that I've drawn now. So if I was to draw it kind of in a blown-up version, it might look like this.
And it's a few cell layers thick. And like I said, on the inside you have some red blood cells bumping along. So maybe this is one red blood cell, and this is maybe another one.
And they would bump into that endocardium. Now, if you go a little bit deeper to the endocardium, what do you get to next? Well, next you get to myocardium. And that would be, let's say, the biggest chunk of our wall.
And that would look something like this. And that myocardium you can kind of appreciate without even having me point it out, because it's the most common part of this entire thing. So this is our myocardium, and let me go back and actually label the endocardium as well.
And on the other side-- and actually, just notice that the words are all pretty similar.
And actually, while I'm on myocardium, let me just point out one more thing. The myocardium is where all of the contractile muscle is going to be, so that's where a lot of the work is being done. And that's also where a lot of the energy is being used up. So when the heart needs oxygen, it's usually the myocardium, because that's the part that's doing all of the work.
Pericardial arteries supply blood to the dorsal portion of the pericardium. Sets heart in mediastinum and limits its motion Protects it from infections coming from other organs such as lungs Prevents excessive dilation of the heart in cases of acute volume overload Lubricates the heart Clinical significance[ edit ] Inflammation of the pericardium is called pericarditis.
Histology Guide | Circulatory System
This condition typically causes chest pain that spreads to the back that is worsened by lying flat. In patients suffering with pericarditis, a pericardial friction rub can often be heard when listening to the heart with a stethoscope. Pericarditis is often caused by a viral infection glandular fevercytomegalovirusor coxsackievirusor more rarely with a bacterial infection, but may also occur following a myocardial infarction. Pericarditis is usually a short-lived condition that can be successfully treated with painkillersanti-inflammatoriesand colchicine.
In some cases, pericarditis can become a long-term condition causing scarring of the pericardium which restricts the heart's movement, known as constrictive pericarditis. Constrictive pericarditis is sometimes treated by surgically removing the pericardium in a procedure called a pericardiectomy. Pericardial effusions often occur secondary to pericarditis, kidney failure, or tumours and frequently do not cause any symptoms. However, large effusions or effusions that accumulate rapidly can compress the heart in a condition known as cardiac tamponadecausing breathlessness and potentially fatal low blood pressure.
- Layers of the heart
The pericardium is a two-layered connective tissue sac that encloses the heart. The fibrous pericardium is the outer layer, and the serous pericardium is the inner layer. The space between the two layers is the pericardial cavity, that contains serous fluid. This facilitates the pumping action of the heart.
Background detail about heart contraction: First, impulses are generated by the sinoatrial node SAwhich is found in the wall of the superior vena cava. It is a small mass of specialised cardiac muscle fibres and associated connective tissue, and is supplied by nerve fibres from the autonomic nervous system. Excitation of the SA node sets of a wave of depolarisation around the atria via gap junctions between the muscle fibres.