Inside the lungs there are millionsof air sacs called alveoli, which increase the surface area forexchange of gases. The thin walls of alveoli are richly suppliedwith blood capillaries to carry blood for gas exchange. CO2diffuses out from the blood into the air and the blood takes upfresh oxygen from the air.

Lung Structure for Gas Exchange
The lungs in human beings are designed in a specific way to maximize the area for the exchange of gases, allowing for efficient oxygen intake and carbon dioxide release.

Bronchial Tree
- The lungs are divided into lobes, which are further divided into smaller segments called bronchopulmonary segments.
- The bronchial tree consists of bronchi, bronchioles, and alveoli, which are responsible for the exchange of gases.

Alveoli
- Alveoli are tiny air sacs at the end of bronchioles where gas exchange occurs.
- The walls of the alveoli are thin and surrounded by a network of capillaries, increasing the surface area available for gas exchange.

Capillary Network
- The capillaries surrounding the alveoli have thin walls that allow for diffusion of gases.
- The close proximity of the alveoli and capillaries maximizes the efficiency of gas exchange.

Surfactant
- Surfactant is a substance produced by the alveoli that reduces surface tension, preventing the alveoli from collapsing and facilitating gas exchange.

Diaphragm
- The diaphragm is a dome-shaped muscle beneath the lungs that contracts and relaxes to facilitate breathing.
- When the diaphragm contracts, the chest cavity expands, allowing for air to be drawn into the lungs.
In conclusion, the intricate design of the lungs, with their bronchial tree, alveoli, capillary network, surfactant, and diaphragm, maximizes the area available for the exchange of gases, ensuring efficient oxygen uptake and carbon dioxide release in human beings.