alvèols

Alvèols are microscopic structures found in the lungs of vertebrates, playing a crucial role in the process of respiration. These tiny sac-like cavities are the primary sites where gas exchange occurs between the air and the bloodstream. Each alveolus is surrounded by a network of capillaries, allowing oxygen to diffuse from the inhaled air into the blood and carbon dioxide to diffuse from the blood into the alveoli to be exhaled.

The human lung contains approximately 150 to 600 million alveoli, collectively forming a vast surface area—roughly the size of a tennis court—enhancing the efficiency of gas exchange. The walls of the alveoli are composed of two types of cells: Type I alveolar cells, which are thin and facilitate rapid diffusion, and Type II alveolar cells, which produce surfactant, a substance that reduces surface tension and prevents the alveoli from collapsing.

Alveoli are part of the respiratory bronchioles, which branch off from the bronchioles within the lungs. Their structure ensures that oxygen-rich air reaches the deepest parts of the lungs, maximizing oxygen absorption and carbon dioxide removal. Damage or disease affecting the alveoli, such as emphysema or pulmonary fibrosis, can impair respiratory function by reducing their surface area or elasticity.

The efficient design of alveoli is essential for maintaining homeostasis, ensuring that oxygen is delivered to tissues and metabolic waste products are expelled from the body. Their delicate nature highlights the importance of protecting lung health through measures like avoiding smoking, reducing air pollution exposure, and maintaining overall respiratory wellness.