Like other vessels, our heart is composed of three distinct layers: the epicardium, the myocardium, and the endocardium. Each of these layers have a different role for heart contraction. In this article, we are going to dissect each layer, and to understand the pathology that can happen within each of these layers.
The epicardium is used primarily for energy storage. In a human heart as illustrated above, you can see that there are a lot of fat surrounding the heart. The layer in which the fat sits on is the epicardial layer, hence the fat is call the epicardial fat. This fat not only serves as an energy source, it also helps to protect the heart form injury by acting like a cushion pad. Interestingly, our heart actually runs on fat under normal condition! However, when it is in trouble (such as during an heart attack), the heart switches its energy supply from fat to carbohydrates and glucose! Weird! Unfortunately, we do not know why that is and it is currently a very controversial and hot topic in research at many universities!
Facts: Did you know that mice that are born with an excessive use of carbohydrates or glucose in the heart is less prone to developing congestive heart disease?
Next, the myocardium. This is where the action of the heart occurs. It is generally very thick and full of muscle fibers. As you can imagine, this is the place where contraction occurs. Our heart is run by calcium to produce contraction patterns. Therefore this layer is extremely well-perfused by the coronary vessels of the heart. Our blood has an abundance of calcium ion that ultimately getting uptake by the cardiomyocytes (the heart cells) via a structure call a T-tubule. This T-tubule is basically the freeway of our heart that connects the blood supply (trucks full of christmas presents) to each individual contractile cell (kids who are waiting for Santa Claus). As you can imagine, if the blood supply gets cut off such as in congestive heart failure, our heart muscle cells do not get enough calcium ion and nutrients, they start to die off! In other words, if our kids don't get their christmas present, they are going to make the parents very miserable and they start to break things around the house!
Facts: people who have big heart (hypertrophic or super muscular heart) is often indicative of diseases such as congestive heart failure, swelling of the lung (pulmonary edema), or liver failure.
Lastly, the endocardium is the innermost layer of our heart. It is responsible for releasing various hormones, cytokines (signaling molecules), and provide protection to the important inner structures of the heart. This is a 1 cell layer thick wall that can increase or decrease how leaky some of the vessels are within the heart. It has been shown that it forms a barrier to prevent toxins from building up inside the heart. It is also often the first site of getting infection from bacteria traveling through the blood!
No comments:
Post a Comment