Lung Perfusion: How Oxygen Enters Blood and Carbon Dioxide Leaves

Pulmonary perfusion is the process of delivering deoxygenated blood to the lungs for gas exchange and returning oxygenated blood to the heart. It occurs in four main steps:

1. Pulmonary Arteries

Deoxygenated blood from the right ventricle travels through the pulmonary arteries, branching into arterioles and then capillaries that form a dense network around the alveoli (air sacs).

2. Capillary Exchange

At the capillaries, oxygen diffuses from alveoli into the blood, while carbon dioxide diffuses from blood into alveoli. This passive exchange is driven by concentration gradients.

3. Pulmonary Veins

Oxygenated blood leaves the capillaries via pulmonary veins, which merge and carry blood to the left atrium.

4. Systemic Distribution

The left atrium pumps oxygen-rich blood into systemic circulation to supply tissues and organs.

Ventilation-Perfusion Matching

Efficient gas exchange requires coordination between perfusion (blood flow) and ventilation (airflow). Both processes occur simultaneously to maintain a constant supply of fresh oxygen and removal of carbon dioxide.

Proper perfusion is essential for respiratory and circulatory system function.