The inner surface of the larynx is lined by:

Ventrally and laterally,the thoracic chamber is formed by

The upper respiratory system in human beings includes all of the following parts $EXCEPT$ . . . . . . .

The nasal cavity is divided by a central septum and contains several bony projections called:

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

In birds,the sound is produced by which of the following?