The diagram given alongside shows the "Human Respiratory System". Study the same and answer the following questions :

(i) Label the guidelines 1 to 4.

(ii) Define the structure shown as part 2.

(iii) Name the basic structural and functional unit of part 3.

(iv) Write one specific structural feature of the inner lining of part 1.

(v) What is the muscular sheet on which part 3 rests ?

(i) The guidelines 1 to 4 show:

1. Trachea
2. Larynx
3. Lung
4. Bronchus

(ii) At the entrance of the trachea, there is a voice box called larynx. It contains two ligamentous folds called 'vocal cords'. Air expelled forcibly through the vocal cords vibrates them, to produce sound.

(iii) Alveoli is the basic structural and functional unit of part 3, i.e., lungs.

(iv) The inner linings of the trachea, bronchi and bronchioles have ciliated epithelium. The continuous movement of the cilia pushes out the unwanted particles that may be present in the inhaled air.

(v) Diaphragm is the muscular sheet upon which the lungs rest.