Double circulation refers to the circulation of blood through two separate pathways: pulmonary circulation and systemic circulation. The heart plays a central role in pumping blood through these pathways. I’ll describe the process of double circulation step by step.

1. Deoxygenated Blood Enters Right Atrium: Deoxygenated blood from the body returns to the right atrium of the heart through the superior and inferior vena cava.

2. Right Atrium Contracts: The right atrium contracts, pushing blood through the tricuspid valve into the right ventricle.

3.Right Ventricle Contracts: The right ventricle contracts, forcing the deoxygenated blood through the pulmonary valve into the pulmonary artery.

4. Pulmonary Circulation: Deoxygenated blood travels through the pulmonary artery to the lungs. In the lungs, carbon dioxide is exchanged for oxygen through the process of pulmonary gas exchange.

5. Oxygenated Blood Returns to Left Atrium: Oxygenated blood returns to the heart through the pulmonary veins, entering the left atrium.

6. Left Atrium Contracts: The left atrium contracts, pushing blood through the bicuspid (mitral) valve into the left ventricle.

7. Left Ventricle Contracts: The left ventricle contracts, sending oxygenated blood through the aortic valve into the aorta.

8. Systemic Circulation: Oxygenated blood is distributed throughout the body through the network of arteries. Oxygen is delivered to tissues, and carbon dioxide is picked up from them.

9. Deoxygenated Blood Returns to Right Atrium: Deoxygenated blood, now carrying carbon dioxide, returns to the right atrium, and the cycle begins again.

Remember, this is a simplified representation, and in a flowchart, each step would be represented by a box with arrows indicating the flow. Additionally, valves play a crucial role in ensuring the one-way flow of blood. Diagram: