The cardiovascular system

Date

JULY 28, 2019

 

Hello, today we're going to talk briefly about the anatomy of the heart. Before we continue, let's just remember that:

  • Blue represents deoxygenated blood;
  • Red represents oxygenated blood.

 

This is an anterior view of the heart. We'll be looking at superficial anatomy.

 

The superior vena cava and inferior vena cava bring deoxygenated blood from the right side of the heart to the right atrium and then to the right ventricle.

 

The right ventricle pumps this deoxygenated blood to the pulmonary trunk, then to the left pulmonary artery and on to the right pulmonary artery.

 

The left and right pulmonary arteries carry this blood to the lungs, where it returns to the heart on the left side of the heart via the left and right pulmonary veins.

 

The left atrium receives oxygenated blood, which is then routed to the left ventricle, then from the left ventricle through the aorta.

 

The upper part of the aorta, here known as the aortic arch, blood can then flow upwards or downwards through the descending aorta behind the heart.

 

There's a ligament connecting the aortic arch with the pulmonary trunk, an ocean of arterial ligament which is a vestige of the patent ductus arteriosus.

 

You can also see the apex of the heart.

 

Let's look at the posterior view.

 

The superior vena cava and inferior vena cava bring deoxygenated blood to the right side of the heart, to the right atrium, and then to the right ventricle.

 

The right ventricle then pumps blood into the pulmonary trunk, from where it branches off to the left and right via the pulmonary arteries.

 

Blood flows into the lungs and then returns to the left side of the heart.

 

From the left, via the right and left pulmonary veins, blood enters the left atrium.

 

From the left atrium, blood flows to the left ventricle, which then pumps this oxygenated blood into the aorta.

 

Here we can see the aortic arch, which can then pump blood up the body or down via the descending aorta.

 

So now, here's a cross-section of the anterior view. Let's take a look at what's going on inside.

 

Right away, you can see that there are four chambers in the heart, and these are the atria and ventricles.

 

To recap again, you can see the superior vein and inferior vena cava, which carry blood from the right side of the heart to the right atrium.

 

From the right atrium, blood flows into the right ventricle through a valve called the tricuspid valve.

 

Blood in the right ventricle flows into the pulmonary trunk through another valve, the pulmonary valve.

 

From the pulmonary trunk, blood flows to the lungs. From the lungs, blood returns to the left side of the heart through the pulmonary veins, into the left atrium.

 

From the left atrium, blood flows into the left ventricle via the mitral valve.

 

The left ventricle pumps this blood into the aorta via the aortic valve, then the blood flows up or down the body via the descending aorta.

 

Once again, we can see the apex of the heart.

 

Now that we know how blood flows through the heart, let's take a closer look:

  • The flow of blood from the heart to the body's tissues;
  • The flow of blood from the heart to the lungs.

 

These are known respectively as :

  • Systemic circulation;
  • Pulmonary circulation.

 

So, here you'll find :

  • The heart;
  • The lower part of your body;
  • Upper body;
  • The right lung;
  • The left lung.

 

So, once your tissues around your body use oxygenated blood, it will therefore return deoxygenated to the right side of the heart.

 

The upper blood will return to the heart via the superior vena cava, and the lower blood from the body will return to the right side of the heart via the inferior vena cava.

 

Deoxygenated blood enters the right atrium and travels to the right ventricle.

 

Deoxygenated blood is pumped through the pulmonary trunk and into the lungs via the right and left pulmonary arteries.

 

This deoxygenated blood undergoes gas exchange in the lungs (shown in orange). What happens here is that carbon dioxide is released and the lungs reoxygenate the blood with oxygen.

 

The carbon dioxide is eliminated, the lungs reoxygenate the blood and the oxygenated blood returns in red from the left side of the heart to the left atrium.

 

Blood then flows from the left atrium to the left ventricle, and from the left ventricle to the aorta.

 

The top of the aorta carries oxygenated blood to the upper part of the body, and the bottom of the aorta carries oxygenated blood to the lower part of the body.

 

Once again, this oxygen is delivered to the tissues, and once again, gas exchange takes place (shown in orange).

 

Oxygen is discharged onto the body's tissues and, as a by-product, carbon dioxide is released into the bloodstream.

 

Deoxygenated blood returns to the right side of the heart.

 

Oxygen is still discharged to the tissues and, as a by-product, carbon dioxide is released.

 

Deoxygenated blood is returned to the right side of the heart.

 

This cycle goes on and on.

 

This diagram represents both pulmonary and systemic circulation.

 

Let's look at something clinical on a chest X-ray. Let's look at what each part of the X-ray represents.

 

Here's a normal chest X-ray.

 

You can see:

  • The right lung;
  • The left lung;
  • Superior vena cava;
  • Inferior vena cava;
  • Inferior vena cava;
  • Right atrium;
  • Right ventricle;
  • Pulmonary trunk;
  • Left atrium;
  • Left ventricle;
  • Aorta.

 

There are some important angles to remember when looking at a chest X-ray. These are :

  • Right cardio-phrenic angles;
  • Left cardio-phrenic angles;
  • Right costo-phrenic angles
  • Left costo-phrenic angles.

 

These zones are important because their attenuation will represent a pleural effusion.

 

Other important landmarks to remember are :

  • The right clavicle;
  • The left clavicle;
  • The tracheal shadow.

 

The tracheal shadow is really important, as the deviation of the triple shadow to the left or right can signify what's known as a “tension pneumothorax”.

 

This diagram therefore represents a normal chest X-ray.

 

It's important to remember some of these areas because you can compare them to an abnormal chest X-ray.

 

Graphic credit: Armando Hasudungan

 

Alexandre Grenier - Founder and Owner

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