Blood Flow Through the Heart

The Right Side of the Heart: Pumping Blood to the Lungs

The right side of the heart is responsible for receiving deoxygenated blood from the body and sending it to the lungs to be oxygenated. This process involves six main steps:

1. Superior and Inferior Vena Cava
   The journey begins with the superior and inferior vena cava, the large veins that carry deoxygenated blood from the upper and lower body, respectively, to the right atrium.

2. Right Atrium
   The deoxygenated blood enters the right atrium, the first chamber of the heart. From here, the blood flows into the right ventricle during diastole, the phase when the heart relaxes and fills with blood.

3. Tricuspid Valve
   As blood moves from the right atrium to the right ventricle, it passes through the tricuspid valve, a one-way valve that prevents backflow.

4. Right Ventricle
   The right ventricle is the second chamber on the right side. During systole, the phase when the heart contracts, the right ventricle pumps blood forward.

5. Pulmonary Valve
   Blood exits the right ventricle through the pulmonary valve, which ensures that blood flows in the correct direction.

6. Main Pulmonary Artery
   Finally, the deoxygenated blood is carried by the main pulmonary artery to the lungs, where it will be oxygenated. This artery branches into the right and left pulmonary arteries, which deliver blood to the lungs.

The right side of the heart’s primary function is to pump deoxygenated blood to the lungs. A simple way to remember this is that the right side pumps blood right to the lungs.

The Left Side of the Heart: Pumping Oxygenated Blood to the Body

Once the blood has been oxygenated in the lungs, it returns to the heart, where the left side takes over. The left side also follows six steps, mirroring the pattern of the right side:

1. Pulmonary Veins
   Oxygenated blood from the lungs travels through the pulmonary veins to the left atrium.

2. Left Atrium
   The left atrium receives the oxygenated blood and, during diastole, sends it to the left ventricle.

3. Mitral Valve
   Blood flows from the left atrium to the left ventricle through the mitral valve, another one-way valve.

4. Left Ventricle
   The left ventricle is the heart’s most muscular chamber. During systole, it contracts forcefully to pump oxygenated blood into the aorta.

5. Aortic Valve
   Blood exits the left ventricle through the aortic valve, which prevents backflow into the heart.

6. Aorta
   The aorta, the body’s largest artery, carries oxygenated blood from the left ventricle to the rest of the body.

The left side of the heart’s main job is to pump oxygenated blood to the body. A helpful way to remember this is that the left side pumps blood that has left the lungs.

Visualizing the Process

To better understand the flow of blood through the heart, let’s visualize it using a two-by-two table:

Right Side Left Side

1. Superior & Inferior Vena Cava 1. Pulmonary Veins

2. Right Atrium 2. Left Atrium

3. Tricuspid Valve 3. Mitral Valve

4. Right Ventricle 4. Left Ventricle

5. Pulmonary Valve 5. Aortic Valve

6. Main Pulmonary Artery 6. Aorta

This table highlights the symmetry between the two sides of the heart. Both sides follow a similar pattern: blood vessels → atrium → valve → ventricle → valve → blood vessel.

Bringing It All Together

To summarize, the heart’s 12-step process ensures that deoxygenated blood is sent to the lungs for oxygenation and that oxygenated blood is delivered to the body. Here’s a quick recap:

1. Right Side:

   • Deoxygenated blood enters through the superior and inferior vena cava.

   • It flows through the right atrium, tricuspid valve, right ventricle, pulmonary valve, and main pulmonary artery to reach the lungs.

2. Left Side:

   • Oxygenated blood returns via the pulmonary veins.

   • It flows through the left atrium, mitral valve, left ventricle, aortic valve, and aorta to be distributed throughout the body.