01.02 Cardiac Anatomy

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Outline

Overview

Understanding cardiac anatomy helps to better understand cardiovascular physiology.

Nursing Points

General

  1. The heart is a pump
  2. Muscular tissue called myocardium
  3. Made up of 4 chambers
  4. Houses 4 valves
  5. Covered in coronary arteries
  6. Cardiac Blood Flow

Nursing Concepts

  1. Anatomy
    1. Location
      1. Between lungs
      2. Mostly left of midline
    2. Size
      1. Approx. size of fist
    3. Layers
      1. Endocardium – inner layer
      2. Myocardium – muscle layer
      3. Epicardium – outermost layer
      4. Pericardium
        1. Sac around heart
        2. Visceral – touches heart tissue (SAME as Epicardium)
        3. Parietal – outer layer of sac
        4. Layer of fluid in between
    4. Four Chambers
      1. Right Atrium
      2. Right Ventricle
      3. Left Atrium
      4. Left Ventricle
    5. Valves (“Toilet Paper My A**”)
      1. Tricuspid (three leaflets)
      2. Pulmonic
      3. Mitral (two leaflets)
      4. Aortic
      5. **Papillary muscles hold valves in place
    6. Vasculature – in order from heart, through tissues, back to heart
      1. Arteries – take blood away from heart
      2. Arterioles – tiny arteries
      3. Capillaries – within tissues
      4. Venules – tiny veins
      5. Veins – carry blood to the heart
  2. Blood Flow
    1. Pulmonary Vein = oxygenated
    2. Pulmonary Artery = deoxygenated
    3. Order of Flow:
      1. IVC/SVC
      2. Right Atrium
      3. Tricuspid Valve
      4. Right Ventricle
      5. Pulmonic Valve
      6. Pulmonary Artery
      7. Lungs
      8. Pulmonary Vein
      9. Left Atrium
      10. Mitral Valve
      11. Left Ventricle
      12. Aortic Valve
      13. Aorta
      14. Body
      15. Back to IVC/SVC
  3. Electrical Basics (see EKG Course)
    1. SA node
      1. In Right atrium
      2. “Packemaker”
      3. 60-100 bpm
    2. AV node
      1. In Septum
      2. Backup “pacemaker”
      3. Delays to allow filling of ventricles
      4. Escape rhythm 40-60 bpm
    3. Bundle of His & Purkinje fibers
      1. In ventricles
      2. Spread signal to whole muscle
      3. Escape rhythm 30-40 bpm
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Transcript

Hey guys, my name is Brad and welcome to nursing.com. And in today’s lesson, what we’re going to be doing is we’re going to discuss the anatomy of the heart. Without further ado. Let’s dive in. 

So, let’s first discuss the function of the heart. What does the heart do, right? The heart is the pump. It is the pump of the body. It’s responsible for pumping all of our freshly oxygenated blood to all of the tissues of our body. And it’s also responsible for pumping deoxygenated blood back up to the lungs to be reoxygenated. I like to think about it like the water pump for our house, right? The water pump for the house is the pump for the house. And it’s responsible for providing fresh water to all of the sinks and toilets and bathtubs in the home. The heart operates much in the same way. It is the pump responsible for providing fresh blood to all of the tissues of the body. 

So, the first thing I’d like to discuss with cardiac anatomy is the myocardium. And the myocardium is the actual muscle of the heart itself, right? Myo being muscle. And cardium referring to the heart. So, as we can see here with this diagram on the right, we have the myocardium, right? This is that thick muscle of the heart, right? This thing is strong enough to pump blood against the gravity, to get blood up and perfuse the tissues of the brain. It’s also responsible for pumping blood to the rest of the body. Now, this myocardium, this heart itself, is actually housed in a protective sack called the pericardium, which is comprised of a parietal pericardium, as well as a visceral pericardium, same thing with the peritoneal cavity, same thing with the lungs. You have a pleural cavity that houses and protects the lungs, same thing with the heart. 

And, so whenever we’re discussing cardiac anatomy, we’re pretty much looking at four chambers and four valves. What I’m going to do here is draw a little, a little heart, if you will. We have a much better visual over here, so be sure to reference that. But we have two atria and two ventricles. And in between the atria and ventricles, we have two atrioventricular valves. Now coming off of this left ventricle, remember anatomically speaking, that’s the left and that’s the right. Coming off of this left ventricle we have a valve that we’re going to pass through and coming off of this right ventricle, we have another valve that we’re going to pass through. And we’re going to discuss that a little bit more in detail over here. So the four chambers of the heart that we have, right, we have two atria – right atria, left atria – as well as a right ventricle and a left ventricle. Make sure you’re referencing our supplemental image over here. 

Also, now the four valves that our blood is going to flow through. It’s important to understand the way in which blood flows through the heart and through the rest of the body, right? So deoxygenated blood is going to be carried by our inferior and superior vena cava. And this is going to carry all of our deoxygenated blood returning from all the tissues of our body, back up to be deposited in our right atrium. Blood is going to be passed from our right atria down into our right ventricle via the tricuspid valve. Now, once in the right ventricle, blood is going to be ejected out through one of our two semilunar valves. This is the pulmonic semilunar valve. So as the right ventricle squeezes and ejects blood is going to pass through that pulmonic semilunar valve and go up into the lungs to be oxygenated carried via the pulmonary arteries.  Fun fact, this is the only time in the body where deoxygenated blood is carried by an artery. Blood goes up to the lungs, it gets nice and reoxygenated.  Fresh oxygenated blood, then returning back into that left atrium via the pulmonary veins. Again, the only time that veins carry oxygenated blood in the body, in that pulmonary vasculature. Blood then passes from our left atrium into our left ventricle via our bicuspid valve, also known as the mitral valve. These two terms are used interchangeably. Now, once the blood is in that left ventricle and the left ventricle contracts, blood then is ejected through our second semilunar valve, our aortic semilunar valve, but then goes into our aorta and to go to the rest of the tissues of our body and provide freshly oxygenated blood. 

Now, one other thing to note here with the cardiac anatomy, that was kind of the cardiac flow, but one of the things to note with the cardiac anatomy is we actually have these little things down here. Not really visualized that well in this image, but they’re papillary muscles and connected to these papillary muscles are these little web-like tethers called chordae tendineae And the entire idea of this chordae tendineae is as this right ventricle and as this left ventricle contract, blood is supposed to be ejected through our pulmonic and our aortic semilunar valves and our tricuspid and bicuspid valves close preventing blood from being retrograde, pushed into a backup into our atria. These chordae tendineae act as tethers preventing that valve from prolapsing, from retrograde flow prolapsing back into the atria. And instead of blood being pumped backwards through the heart, this actually allows full valve closure so that blood can be pumped out forward. 

And finally, I thought it was important to mention the coronary vasculature, the actual heart vessels themselves. In nursing school, you’re not likely to be tested on all of these intricate vessels that feed into the heart itself. And no, this image over here on the right is not completely inclusive of all of the coronary vasculature, but I thought it was important to propose this concept to you. We know that the heart is a pump. We know that the heart is responsible for pumping freshly oxygenated blood to all of the tissues of the body, but let’s not forget also that the heart is responsible for pumping blood to itself, right? All of these nice, fine, spider-like coronary vessels that cover and web up over top of the heart, they also pump freshly oxygenated blood to the pump itself. Remember, should the pump cease to receive freshly oxygenated blood, the pump ceases to pump. So, as it’s equally, if not more important, that the heart receives nice blood, nice blood flow, equally as important as its job of pumping blood to the rest of the body. 

And so to summarize some of our key points regarding cardiac anatomy, remember the heart is a pump. It is made of that nice myocardium, myo – muscle, cardium – heart, that is strong enough to pump blood against gravity, to our brain, as well as to all the rest of the tissues of our body. The heart is a pump. It’s comprised of four chambers: left atrium, right atrium, left ventricle and right ventricle. And also recalling that there are four valves, two atrioventricular valves, the tricuspid valve, which passes blood from the right atrium to the right ventricle, as well as the bicuspid valve also known as the mitral valve pumping blood from the left atrium to the left ventricle. And then there are two semilunar valves as well. The pulmonic semilunar valve, which allows passage of blood from the right ventricle up to the lungs to be oxygenated. And then the aortic semilunar valve, which allows passage of blood from the left ventricle up to the aorta, and then to the rest of the body. Also recalling the cardiac blood flow, the way in which blood flows throughout the body, throughout the heart and throughout that pulmonary vasculature. And then also recalling that there are that spiderweb-like arrangements of coronary vessels that actually feed blood to the pump itself.

 I hope that this video will help. I hope that you enjoyed it. Go out there and be your best selves today, guys. And as always, happy nursing.

 

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