Final answer:
Alveoli are arranged in grape-like clusters to maximize the surface area for gas exchange within the lungs, allowing for rapid diffusion of oxygen and carbon dioxide between the blood and the lungs.
Step-by-step explanation:
The alveoli are arranged in grape-like clusters to maximize the surface area available for gas exchange in the lungs. This structural organization allows about 300 million alveoli in each lung to facilitate the efficient diffusion of oxygen into the blood and the removal of carbon dioxide from it.
The alveoli are small sacs, around 200 to 300 microns in diameter, surrounded by capillaries that are also one-cell thick. This close proximity and the vast number of alveoli greatly increase the surface area to approximately 75 m², which is roughly the size of a tennis court.
This extensive surface area, combined with the thin walls of the alveoli and capillaries, ensures that gases can diffuse rapidly across the cells, making the process of gas exchange highly efficient.
Furthermore, the alveoli are connected by alveolar pores, allowing for equal air pressure throughout the lung and further supporting effective gas exchange.
The alveoli and their clusters, known as alveolar sacs, are at the end of the respiratory tree, which starts with the trachea and subdivides into bronchioles, ending with the alveolar ducts to which these sacs are attached.
The elasticity of the alveolar walls also permits the alveoli to stretch during inhalation, which significantly increases their surface area available for gas exchange.