With regard to the respiratory system and the process of respiration in man, answer the following questions:

(a) Name the two muscles that help in breathing.

(b) Briefly describe how the above mentioned muscles help in the inspiration of air.

(a) The two muscles that help in breathing are — intercostal muscles and abdominal muscles.

(b) When the intercostal muscles stretch between the ribs, they move outwards and inwards causing them to enlarge the chest cavity.