It prevents the entry of food into the larynx.

Which one of the following has the smallest diameter?

Identify the component of the respiratory system which displays the features given below and choose the correct option:
$I.$ Double layered
$II.$ Fluid contained in it reduces the friction on the lung surface
$III.$ Its outer layer is in contact with the thoracic wall
$IV.$ Its inner layer is in contact with the lungs

The bronchioles do not collapse even when they are empty. What is the reason for this?

In mammals,the tracheal cartilaginous rings are

During the act of swallowing,which of the following structures prevents the food bolus from entering the glottis?