Where is ventilation and perfusion greatest in the normal healthy lung of an awake individual?

In a normal, healthy lung of an awake individual, ventilation and perfusion are greatest in the dependent regions of the lungs. The dependent regions refer to the areas of the lung that are lower when a person is upright, typically the bases of the lungs.

When a person is in an upright position, gravity affects both the distribution of blood flow and airflow in the lungs. Blood flow, or perfusion, is influenced by gravity; thus, it is higher in the lower parts of the lungs where blood vessels are more filled due to gravitational pull. This allows for optimal exchange of gases because these regions receive the most blood flow.

Similarly, ventilation tends to be greater in the lower parts of the lungs as well, but it is important to note that while perfusion is more gravity-dependent, ventilation also benefits from the characteristics of lung mechanics. The lower regions can expand adequately during inhalation, allowing for effective air movement into those areas.

Overall, the combination of increased blood flow and adequate air movement in the dependent areas supports efficient gas exchange, which is essential for overall respiratory function. Hence, declaring that both ventilation and perfusion are greatest in the dependent regions aligns with physiological understanding of lung function in an upright position.