 Trust it! Everybody, Dr. Rowe. In this video, I'm going to walk you through two images and show you some of the key external features of the heart. I'm not going to cover everything here. You're going to need to spend some time just looking at these images and make sure you know everything. Some of these will be covered in separate videos. I'll do a separate video where I cover the internal structures and the path of blood through the heart. And we'll also cover the major blood vessels in a third video. So the first thing you need to know about the heart is it's a four chambered heart, which means we have two atria. The right and left atrium you can see there, and then we have two ventricles. So the atria are called the receiving chambers. They receive blood either from your systemic circulation coming back from the superior or inferior vena cava. That's what the right atrium does, or receiving blood back from the pulmonary veins that are carrying oxygenated blood back from the lungs. So that's the primary job of the atria. Now they do contract and help fill the ventricles, but they only do about 20% of the work. The left ventricles are going to be the two big powerhouses, the pumps. The right ventricle here is going to pump blood to and from the lungs. The left ventricle is going to pump blood to and from the rest of your circulation, which is why the left ventricle is much thicker. It's about 300% thicker, about three times thicker, much more powerful pump. The left ventricle has to pump blood from the top of your head to the tips of your toes. The right ventricle has to pump blood just to and from your lungs. So those are the four chambers. When you look at the atria, you are going to see what are called the oracle. So oracle means ears. On top of the two atria, there's going to be these pouches that can expand as they receive blood. Those are going to be called the oracles. All right. So those are your four main chambers of the heart. Coronary blood vessels. So you can see here, I won't ask you to know them by name, but just remember that coronary arteries are what carry oxygen-rich blood to feed the muscles of the heart. And the cardiac veins are going to be what carries the blood back, just like we have arteries carrying blood to all your body tissues and veins carrying them back. The coronary arteries and cardiac veins will do that. Oh, let's see here. Some of the key blood vessels I've already mentioned, the superior vena cava there, that's going to receive blood from above the heart and carry it back to the right atrium. The inferior vena cava on the bottom is going to receive all the blood back from the rest of your body. We have the pulmonary trunk. So the pulmonary trunk is going to carry blood to the lungs so it can drop off carbon dioxide and pick up oxygen. That pulmonary trunk is going to branch and form your pulmonary arteries. Remember what makes these unique is you may have learned that arteries carry oxygen-rich blood and veins carry de-oxygenated blood, but in this case it's not true. So the only true definition of an artery is that it carries blood away from the heart. So the pulmonary arteries will carry blood to the lungs where like I just mentioned they can drop off CO2, pick up oxygen, and they will come back and enter those four pulmonary veins that you can see. All right, the most important artery that we have in our body is right there at the top of the screen. That's going to be your aorta. So it's going to take all the blood that's pumped out of the left ventricle and it's going to start and carry it through your entire circulatory system, which is 60 to 100,000 miles of blood vessels depending on size. All right, as I scan through here, let's see the ligament martyriosum, not a huge deal, but when you were in your mother's womb that was actually a blood vessel that connected the pulmonary trunk and the aorta. And if that doesn't properly close up and turn into a ligament, that can be a heart defect. What else? The apex. So it's kind of odd, but the apex of the heart is on the bottom. The base of the heart would be on the top. So usually when you think of the base, think of the bottom of something, but the heart is kind of upside down. So the base is on the top and the apex is on the bottom. Now let's go ahead and look at the back. I think we covered all the major ones, but again you can see that on the back you're going to see more of the left side of the heart, whereas more of the right side of the heart is going to be on the front. I believe I covered all these. But again, make sure you spend some time going through this. I'll cover these in other videos too, but these are going to be all the key features on the outside of the heart. Anything else you can see here? Yeah, one more thing. You'll see the coronary signage. You couldn't see that on the front. That's going to be where all these cardiac veins drain the blood that's going to return into the right atrium and then go pick up oxygen and then come feed the heart again. So your heart has its own circulatory system. It needs quite a bit because it's such a powerful, effective pump and it never takes a break. So somewhere around 7% of your cardiac output is going to go to just feeding the heart itself so that it can help you feed the rest of your body with oxygen-rich blood. OK, so those are the key external features of the heart. I hope this helps. Have a wonderful day. Be blessed.