Welcome to the heart screencast. I'll cover the location, anatomy, blood flow, and histology over the course of these few slides. So first off, notice that there's two separate circuits, really, two separate sides to the heart. There's the right side over here in blue with the right atrium on top and the right ventricle below, and that's going to pump blood out to the lungs and back, and you call that the pulmonary circuit. and that's where the blood gets oxygenated.
On the left side, in the right here in our picture, but left side of the heart, left atrium, left ventricle, that's part of the systemic circuit which is going to pump blood out to the body, other body tissues and back where it drops off oxygen. This image, these images show the pericardial cavity which is the cavity that's closest to the heart. So if you look here at this image of this hand punching this balloon type thing here, see that the hand is touching one part of that rubber of that balloon, but then that balloon continues around here to form kind of an outer layer as well with an air space in between. Well, inside of your body, you've got a pericardial cavity, which doesn't have air in it. It's got fluid, pericardial fluid, which acts as kind of a lubricant and a supporter for that, for the heart.
In the right image, you see a few layers that you have to know. The endocardium, which is simple squamous epithelium. The myocardium, which is cardiac muscle. And then you'll see these layers of that pericardium, right?
These two layers that I'm putting my lines on right now are the two layers of the balloon, like over here. So these two things are these two things. Blue stuff is the fluid that fills it, and then the outer bit here is a dense irregular connective tissue layer called the fibrous pericardium, which acts as the overall capsule containing the rest of it.
All right, let's look at some of the features here on the inside and outside of the heart. Oracles act as sort of reservoirs. You can see one kind of creeping in right there.
There would have been another one here, but it was removed when the front piece of that heart came off. The atria are on top and the ventricles are down here. This right side is the pulmonary circuit receiving blood from the body, pumping it out to the lungs. And then the left side is the systemic circuit receiving blood from the lungs and pumping it out to the body. Now we get to some of the more specific structures inside of the heart.
So this is the right atrium which has just received blood from the superior vena cava and then the inferior vena cava which would be down here. The blood's going to go through this tricuspid valve right there. That's the right atrioventricular or tricuspid valve between the right atrium and right ventricle.
There are some structures that I'd like to point out right here. See these little guys? These little guys?
line looking things right there, that's what you call chordae tendineae. So chordae tendineae are these little ropes and then these little bumps that you see down here, those are called papillary muscles and they kind of connect from the heart wall to the valves. And it looks like they'd pull them down almost, looks like you'd pull them open that way.
But that's not the case. You don't pull open the valves. What you do is just try to prevent them from going backwards.
So you don't want the blood to flow back into the atria when these ventricles contract, right? When the ventricles contract, blood pressure is going to go up, and you want the blood in those cases to leave through this aorta and leave through this pulmonary trunk. The valve integrity is maintained by having cables that prevent that valve from flapping back the other way.
Bicuspid valve is on the left. And the left side of the heart is stronger. And if you ask a kid to show you how strong they are, they'll show you their biceps. So bicuspid is the strong side of the heart.
The interventricular septum is this structure right there. And the interatrial septum is right here. So they're pretty continuous, you know.
They keep the left and the right side separate. And one more feature that... I feel I need to mention here and you can barely see is hiding right in there.
And you saw it in the photo and in the video. But that is the fossa ovalis, which is a remnant of your fetal circulation. You used to have a hole between the left and right sides of your left and right atrium so that you could mix oxygenated and deoxygenated blood together. That's not something we want to do when we have lungs that work and breathe air. Oh, the semilunar valves, almost missed those.
Semilunar valves are located at the exits of the ventricles. This is the aortic semilunar valve. The pulmonary semilunar valve is not shown here, but we'll see kind of an impression of it next. Alright, blood flow.
You see a kind of a nice list over there on the right, but I'd also like to add to that. So, it says, number one, blood enters the right atrium. So, there's not really a first step.
There's not a natural first place to start, but most everybody picks this just because you've got to start somewhere. So, you may as well start where the blood first gets back to the heart from the rest of the body. the blood will flow from the right atrium into the right ventricle and it goes through this tricuspid valve right there. Here we see the chordae tendineae again and the papillary muscles attached to them.
Then when the ventricle or ventricles contract, and this is simultaneous, so don't think that it goes right side first then left side. They go at the same time. Both ventricles contract at the same time, but we're just following it one at a time.
When the ventricles contract, the blood that was in the right ventricle exits through this guy, and there's that pulmonary semilunar valve right there, into the pulmonary trunk, which splits into pulmonary arteries. And you'll notice that those arteries are blue because they're deoxygenated blood inside, going to the lungs to become oxygenated. Once that occurs, that blood's going to come back, all red and oxygenated through these pulmonary veins and these are veins that are bringing blood back to the heart. In this case it's oxygenated blood.
In the blood goes to the left atrium through the bicuspid valve into the left ventricle and then out. Now in this case the aortic semilunar valve is kind of hidden somewhere. It would be behind this guy maybe in there somewhere. Anyway out to the aorta and to the various blood vessels that will distribute it to the body and once your body's used up the oxygen it comes back to the heart and you start all over again. Here are those vessels.
There are two vena cavea. That's plural so there's a superior one and an inferior one. This is the superior one and you can flip over you can see the inferior one right there.
The pulmonary veins return blood from the lungs to the heart and that's, you can barely see them right here, that's these red forked guys right there. Excuse me. Leaving the heart, you have the aorta, which is the big obvious red one right there.
That takes blood from the left ventricle out to the body. And if you're going to take blood from the heart to the lungs, you go via the pulmonary trunk, which is... Not seen very well in this picture, but there it is right there. So it's been cut off. So this pulmonary trunk leaves from the right side of the heart, the right ventricle, and goes out, breaking into pulmonary veins.
I'm sorry. Take that back. Breaking into pulmonary arteries, not veins. Veins are the red ones.
Actually, this is my second recording of this. First one, I made the same mistake and just had to start over. I'm not going to do that again.
All right, last but not least, histology. So you can see a couple of noticeable features here. The nuclei of these cells are these dark sort of black structures here.
And then you'll notice that you'll see this little stuff right there like that. Well, that cardiac muscle striated, and you can see the clear stripes there, and that's from those actin and myosin filaments that you learned about in ANP1. And...
You see large structures like this, big lines, and these guys are called intercalated discs. Intercalated discs are both chemical and physical connectors between the heart muscle cells. They act to let cytoplasm go back and forth and electrical signals be transferred from one to the next.
The structures that allow that are called gap junctions. The structures that are involved in those intercalated discs that actually staple the heart cells together are called desmosomes. They're kind of like rivets or staples.
That's it. Watch your videos and look at the photos and study up.