01.02 Cardiac Anatomy

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Understanding cardiac anatomy helps to better understand cardiovascular physiology.

Nursing Points


  1. Fun Facts
    1. Electrically independent of the body
      1. SA & AV node self-regulate
    2. Beats 100,000 times/day
    3. Pumps 2,000 gallons/day of blood
    4. Left lung smaller – makes room for heart in mediastinum
    5. Heart begins beating at 4-weeks gestation
    6. Daily energy output enough to drive to moon and back
  2. 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
  3. 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
  4. 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


When we talk about cardiac anatomy, it’s important to get a big picture of not only how blood flows through the heart, but also how it flows through the rest of the body providing oxygen and nutrients to the tissues. You can use the CheatSheets within this Lesson to practice the blood flow through the heart itself. But let’s look at the full systemic circulation together.
Since it’s a continuous system, there’s really no official starting point, but just for grins, let’s start in the Right Atrium. Deoxygenated blood is dumped here when it returns from the body. It then travels through the Tricuspid Valve to the Right Ventricle where it is pumped out through the Pulmonic Valve. It travels through the Pulmonary Artery to the Lungs where it releases CO2 and picks up Oxygen. From the lungs, oxygenated blood returns via the Pulmonary Vein into the Left Atrium. When the atria contract (we call that the atrial kick), blood flows through the Mitral Valve into the Left Ventricle. Then, blood flows out through the Aortic Valve into the Aorta to go to the body. To get to the tissues, blood flows through major arteries like the aorta, to smaller arteries like the renal artery for example. Then, blood flows into smaller vessels called arterioles and then into capillary beds. These capillary beds are where the nutrient exchange happens. Oxygen and nutrients are dropped off and CO2 and waste products are picked up. Now deoxygenated blood flows through tiny vessels called venules, out through veins, then into the major veins known as the Superior and Inferior Vena Cavae. Then…dumps back into the Right Atrium to start the process all over again. So you have this continuous circulation of deoxygenated blood, coming through the heart and lungs to get oxygenated, then going back out into the tissues.

So it goes Heart – Lungs, then Heart – Body, then it goes through the vessels, then into the capillaries for gas & nutrient exchange, then it returns back to the heart to do it all over again.
A couple key things to remember:
Arteries take blood Away from the heart. In all but one instance, they carry oxygenated blood. That is the pulmonary artery, which carries deoxygenated blood to the lungs.
Veins take blood To the heart. The spanish word for to come is Viene, so it’s like the blood coming into the heart. Again, most of the time they carry deoxygenated blood with the exception of the Pulmonary Vein.
The vessels from the heart to the body and back are arteries, arterioles, capillaries, venules, and veins.
Any blockage or damage to any of the vessels large or small can cause a lack of flow or a lack of oxygen delivery to the tissues.

It’s like a network of roads. If you’re a delivery truck driver, you pick up packages from the distribution center, then you drive down major highways, then main roads, then turn into neighborhoods, then up streets and eventually driveways to drop off the packages. Once you’ve done that, you have to come out of the driveway, around the block, out of the neighborhood, back to the main road, to the highway, and back to the distribution center. At any point along the way, if there’s a roadblock or a closure or an accident, you either have to clear the roadblock or find another route, or your package doesn’t get delivered. In this case, the package is oxygen and nutrients! Does your patient have a blood clot? It’s a roadblock, either clear the roadblock, find another route, or nothing gets delivered. So you can see how vital it is that the routes are nice and clear.
Now, listen, in clinical practice, you will never be required to spout out the blood flow through the heart. But having a good foundational understanding of this can help you to better understand what’s happening in your patient when things go wrong. And then you’ll know better how to help them…

And that’s what we want for you guys – to have the tools and confidence you need to care for your patients with excellence. Now go out and be your best self today. Happy Nursing!