Blood Flow in the Heart

Sequence of Blood Flow

1. Initial Entry into the Heart

   • Blood enters the right atrium from the superior and inferior vena cavae.

2. From Right Atrium to Right Ventricle

   • Blood in the right atrium flows through the right atrioventricular (AV) valve, also known as the tricuspid valve, into the right ventricle.

3. Right Ventricle Contraction

   • Contraction of the right ventricle forces the pulmonary semilunar valve open.

4. Pulmonary Valve to Pulmonary Arteries

   • Blood flows through the pulmonary valve into the pulmonary trunk.

5. Gas Exchange in the Lungs

   • Blood is distributed by the right and left pulmonary arteries to the lungs.
   • In the lungs, blood unloads carbon dioxide (CO2) and loads oxygen (O2).

6. Return to the Heart from Lungs

   • Oxygenated blood returns from the lungs via the pulmonary veins to the left atrium.

7. From Left Atrium to Left Ventricle

   • Blood in the left atrium flows through the left AV valve, also known as the mitral valve, into the left ventricle.

8. Left Ventricle Contraction

   • Contraction of the left ventricle forces the aortic semilunar valve open (happens simultaneously with the contraction in Step 3).

9. Aorta and Systemic Distribution

   • Blood flows through the aortic valve into the ascending aorta.
   • Blood in the aorta is distributed to every organ in the body, where it unloads oxygen and loads carbon dioxide.

10. Return to Heart

• Deoxygenated blood returns to the heart via the venae cavae, completing the circulation cycle.