Alveolar sac

Alveolar sac is the terminal part of the respiratory system where gas exchange occurs. It is a structure found in the lungs, and is a part of the alveolar duct system. Each alveolar sac is made up of multiple alveoli, which are small, balloon-like structures where the exchange of oxygen and carbon dioxide takes place.

Structure

The alveolar sac is a cluster of many individual alveoli, which are connected to the bronchioles through the alveolar ducts. Each alveolus is surrounded by a network of small blood vessels, or capillaries. These capillaries carry deoxygenated blood from the body to the lungs, where it picks up oxygen and releases carbon dioxide.

Function

The primary function of the alveolar sac is to facilitate gas exchange. When we inhale, air fills the alveoli in the alveolar sacs. The oxygen in the air diffuses across the thin walls of the alveoli and capillaries into the blood. At the same time, carbon dioxide, a waste product of cellular respiration, diffuses from the blood into the alveoli. This carbon dioxide is then exhaled from the body.

Clinical significance

Damage to the alveolar sacs can lead to a number of respiratory diseases. For example, in emphysema, the walls of the alveoli are destroyed, reducing the surface area available for gas exchange. This leads to shortness of breath and other symptoms. In pneumonia, the alveoli may fill with fluid or pus, impairing gas exchange.

See also

• Respiratory system
• Alveoli
• Lung
• Bronchioles
• Emphysema
• Pneumonia