keuhkorakkulot

Keuhkorakkulot, also known as alveoli, are tiny, thin-walled air sacs found in the lungs of mammals and birds. They are the primary sites of gas exchange within the respiratory system. These microscopic structures are clustered together like bunches of grapes at the end of the bronchioles, the smallest airways in the lungs. Each lung contains millions of alveoli, providing a vast surface area for efficient oxygen and carbon dioxide transfer.

The wall of each alveolus is only one cell thick, allowing for rapid diffusion of gases. Surrounding the alveoli is a dense network of capillaries, tiny blood vessels. Oxygen from inhaled air passes through the alveolar and capillary walls into the bloodstream, where it binds to hemoglobin in red blood cells and is transported to the body's tissues. Simultaneously, carbon dioxide, a waste product of cellular respiration, diffuses from the blood into the alveoli to be exhaled.

The inner surface of the alveoli is covered with a thin layer of fluid containing a substance called surfactant. Surfactant reduces surface tension, preventing the alveoli from collapsing during exhalation and making it easier to inflate them during inhalation. Damage to or inflammation of the alveoli, such as in pneumonia or emphysema, can significantly impair the lungs' ability to perform gas exchange, leading to respiratory distress.