WAEC - Biology (1993 - No. 8)

During the process of breathing, volume and pressure change occur as a result of the movement of the parts labelled?

I and II

II and IV

III and VII

IV and V

VI and VII

The movement of the rib cage is brought about by the contraction and relaxation of the internal and external intercostal muscles.

When the intercostal muscles contract the rib cage moves up and out (inspiration).

When the intercostal muscles relax, the rib cage moves down and in (expiration).