Pericardium

00:01 When you open up the chest cavity, you're probably imagining that you're going to see the heart sitting right there, just like you've probably seen it in pictures.

00:09 But that's not the case.

00:11 That's because the hearts actually protected by something that's not talked about very much, called the pericardium.

00:18 And that's actually what you'll see when you open up the chest before you actually see the heart itself.

00:24 So it's hidden from our view here by a tough connective tissue sheath called the fibrous pericardium.

00:32 Providing a nice sort of protective sac around the heart.

00:37 And this fibrous pericardium, as you can see here, is also where the left and right phrenic nerves travel through the mediastinum on their way to innervate the diaphragm.

00:49 We're going to have to remove this fibrous pericardium to actually see the heart.

00:56 And of course, the location of these phrenic nerves probably tell you that they're what are going to innervate the pericardium.

01:04 So instead, let's look at the blood supply.

01:07 The blood supply coming off of these branches of the internal thoracic artery called the pericardial phrenic arteries.

01:16 Very appropriately named because not only are they supplying the pericardium, but they're on their way down to the diaphragm as well.

01:26 And similarly, we have pericardial phrenic veins.

01:29 And they're draining back up to the internal thoracic veins.

01:35 The pericardium, though, is more than just a tough fibrous outer layer though.

01:39 In order to understand the finer details of the pericardium, we're gonna have to zoom in at the edge of the pericardium to get a better idea here.

01:49 The outer part, the tough fibrous pericardium, that's for protection, and it's going to protect the heart underneath it, which is mostly muscle called myocardium.

01:59 There are different layers, but the majority of it is this muscle called myocardium.

02:04 Sitting on top of that myocardium though, is actually another layer of pericardium, a serous pericardium and it's called the visceral layer of the serous pericardium.

02:16 It doubles back on itself to form an outer layer called the parietal layer of serous pericardium that's attached to the deep surface of the fibrous pericardium.

02:29 And we're fibrous tells you something about its nature that it's a tough protective layer. Serous also does.

02:35 Because serous kind of in this sense means watery.

02:38 And the parietal and visceral layers of the serous pericardium are making a watery substance called pericardial fluid.

02:47 It's probably sounds very similar to pleural fluid.

02:51 Because it is. It's something that is going to help decrease friction between the visceral and parietal layers of the serous pericardium as the heart is constantly beating from beat to beat.