Question

6. What are the levels of the respiratory system, starting with the trachea as the ‘first level.’ Make the last level the smallest unit of the lungs. What major process/function happens at the smallest level?

Answer 1

The levels of respiratory tree are called Weibel is generations. It has 23 generations with Trachea being generation'0' and alveoli, smallest unit of lungs, being generation'23'.

The smallest unit of lungs is alveoli. Alveoli is involved in alveolar ventilation.

During inspiration, the air is received from the conducting airways and the other components of respiratory airways. The air reached (350 ml) is not equal to tidal volume (500ml). This amount of air is utilised in the diffusion process with the pulmonary capillaries. Oxygen is given to the capillaries and CO2 is taken from the capillaries. This occurs through a membrane called respiratory membrane.

Now during the process of expiration, the CO2 containing alveoli due to elastic recoil returns the air back to the conducting airways and CO2 is exhaled.

So alveoli is involved in ventilation and Transport of gases.

It also contains alveolar macrophages which play an important role in defence system.

It has some cells called Type II pneumocytes which produce surfactant which reduces the surface tension.