Alveoli: Gas Exchange

Alveoli are tiny air sacs at the end of bronchioles, often described as having a cauliflower shape, where vital gas exchange occurs.

Oxygen and carbon dioxide diffuse across one-cell-thick membranes between the alveoli and blood capillaries; oxygen binds to hemoglobin in red blood cells while CO2 exits the body.

Continuous breathing and blood flow ensure a concentration gradient is maintained, allowing for the constant and efficient transfer of respiratory gases.

The lungs achieve efficient gas exchange through a large surface area, a short diffusion pathway (one-cell thickness), moist lining to dissolve gases, extensive capillary networks, and consistent ventilation.

To maximize marks on assessments, explain that efficiency is driven by the large surface area, short diffusion pathways from thin surfaces, and the dense capillary network.