Alveolus

An alveolus (plural: alveoli) is a small air sac in the lungs where the exchange of oxygen and carbon dioxide takes place. Alveoli are crucial components of the respiratory system and are located at the end of the bronchioles in the lungs. They are surrounded by a network of capillaries that facilitate the gas exchange process.

Structure

Alveoli are tiny, balloon-like structures with thin walls composed of a single layer of epithelial cells. These cells are of two types: Type I alveolar cells and Type II alveolar cells. Type I cells are involved in the gas exchange process, while Type II cells secrete surfactant, a substance that reduces surface tension and prevents the alveoli from collapsing.

Function

The primary function of alveoli is to enable the exchange of gases between the air and the blood. Oxygen from the inhaled air diffuses through the walls of the alveoli and enters the blood in the capillaries. Simultaneously, carbon dioxide from the blood diffuses into the alveoli to be exhaled. This process is essential for maintaining the body's homeostasis.

Gas Exchange Process

The gas exchange process in the alveoli is driven by diffusion, which is the movement of molecules from an area of higher concentration to an area of lower concentration. Oxygen, which is in higher concentration in the alveoli, diffuses into the blood, while carbon dioxide, which is in higher concentration in the blood, diffuses into the alveoli.

Related Conditions

Several medical conditions can affect the alveoli, including:

• Pneumonia: An infection that inflames the air sacs in one or both lungs.
• Emphysema: A condition where the alveoli are damaged, leading to breathing difficulties.
• Pulmonary edema: A condition characterized by excess fluid in the alveoli.
• Acute respiratory distress syndrome (ARDS): A severe condition where the alveoli fill with fluid, leading to respiratory failure.

See Also

• Lung
• Respiratory system
• Bronchiole
• Capillary
• Surfactant
• Gas exchange