06.02 The Heart

In this lesson we're going to take a look at the heart and the general structure and function of it.

The first thing that we need to look at is that we need to look at the functions of the heart.The hearts primary function is to act as a muscular pump, and circulate blood throughout the entire body

So let's take a look at the hearts location.

Inside the chest, there's an area just to the left of midline, and it's essentially a cavity. And it's called the mediastinum. It's an actual space between the right and left lung lobes. it extends from the sternum all the way to the vertebral column and it goes basically from the top side of the trachea all the way down to the xiphoid process.

Now looking at the location of the heart, the base is actually in the second intercostal space, again just to the left of midline. When I say intercostal, I'm talking about the space in between the Ribs. The apex of the heart is located at the fifth intercostal space, right along the midclavicular line. When I say midclavicular line, you can see the clavicle right here. I want you to divide it in half, and go straight down until the get to the space in between the fourth and fifth ribs. That's where the apex of the heart is.
In terms of structure, the heart is a big giant muscle.

The heart is made up of three different layers, the endocardium, The myocardium, and epicardium. Let's look at these more in-depth.There's a great lesson on cardiac muscle tissue and muscle contractility, so I encourage you to check those out

When we’re talking about the endocardium, we're talking about the innermost wall of the heart.

It's composed of simple squamous Endothelium, and it is smooth. And the reason it smooth is because it helps prevent clotting. The other thing is that it has a serous membrane along the inside.

The myocardium, is the thick middle layer. It is essentially known as the heart muscle and it has the main squeeze every time the heart contracts.

The epicardium, is the most outer layer of the heart. It's covered by something called the visceral pericardium, and it actually releases fluid to the outside of the heart.

That leads me to my next point, which is the pericardial Sac. Now imagining that the outside of the heart continues to produce fluid inside the chest, well it's got to go somewhere right. Well around the heart is something called the pericardial sac and it's responsibility is to reduce friction between the beating heart and other tissues. Imagine your beating heart every time it beats rubbing up against other tissues. This also helps to reduce some of the shock anytime that that any sort of impact comes in and hits the chest.

The pericardial sac actually has a little bit of a fluid in it called the pericardial fluid. And this pericardial fluid is found in the space between the visceral and parietal pericardium. The parietal pericardium is the outermost layer of the pericardium. So you have any epicardium which is an outside wall of the heart, or commonly known as the visceral pericardium, and then you have the parietal pericardium which is the outside layer. Now let's get to the bulk of the heart.

The heart is divided up into four chambers. You have two on top, and two on bottom. The two on top or call the atria, or Atrium which is singular. And then you have each ventricle. The heart is also divided into a right and a left side.

Starting with the atria, these are your upper chambers. You have a right side in the left side, and they are connected to each ventricle. So the right atria is connected to the right ventricle and the left atrium is connected to the left ventricle. The atria are separated by something called the interatrial septum. So now that we've got something that separates the atria, we have to have something that separates the ventricles right?

Well each atria and each ventricle are separated by something called valves. These valves act like doorways that allow blood to go from one chamber, the door was open, and then the blood goes into another. In the right side of the heart you have something called the tricuspid valve. In the left side you have something called the bicuspid or mitral valve. Most people call it the mitral valve, but you also need to know that is called bicuspid. Another reason that the tricuspid valve is called tricuspid, is because it has three flaps. The bicuspid valve on the other hand only has two.

So how does blood get from the body to the atria? Wall on the right side, blood is delivered to the right atrium from the superior and inferior vena cava. On the left side, you have the left atrium which receives blood from the four pulmonary veins. There are two on each side.

Now the ventricles are the lower chambers of the heart. You have a right and left ventricle, and they force blood out of the heart to wherever they're going. The right ventricle forces blood out of the heart into the lungs, and then the left ventricle forces blood out of the heart into the rest of the body. The important thing to know here is at the left ventricle is the power house for the pump.

Similar to the separation between the atria and the ventricles, there are valves that separate the ventricles to the outside of the heart. These are called semilunar valves. On the right side, coming from the right ventricle to the lungs it's called the pulmonic valve. On the left side, going from the left ventricle to the aorta, it's called the aortic valve. So what we're talking about blood flow we have blood that goes from the right ventricle, and it exits via the pulmonary artery to the lungs and it's going to go through that pulmonic valve.

On the left side is going to exit via the aorta going through the aortic valve.




Okay so let's recap.

We were talking about the heart, you have to remember that the heart is a pump. It's one primary responsibility is to circulate blood throughout the body.

The heart consists of four chambers, two atria and two ventricles. There's two on the right and two on the left of each side. The atria are on top, and the ventricles are on the bottom.

All of the chambers are separated by valves. The tricuspid in the mitral separate the atria from the ventricles. And the similar valves separate the ventricles from the outside of the heart.

The heart is located just to the left of midline with the base starting at the second intercostal space, and the apex of the heart going to the 5th intercostal space, right along that midclavicular line.

We're talking about structure the heart, the heart consists of three layers. There's the endocardium, which is the Innermost layer, you have The myocardium which is the thick middle layer of the heart, and then you have the epicardium which creates the visceral pericardium.


That's it for the lesson on the heart. Be sure to check out all the other resources attached to this lesson. Now go out and be your best self today, and as always happy nursing