Question

Breathing, an important step of the respiratory system, is a two-part process involving- inhalation and exhalation. During the process of breathing, the thorax region shows some changes. Identify the statement/s from below that is/are related to the exhalation process.
$I.$ External intercostal muscles contract
$II.$ Pressure in the lungs increases
$III.$ Diaphragm contracts
$IV.$ The volume of the thorax decreases

• A. $II$ and $IV$ only
• B. $I, \, II$ and $III$ only
• C. $I, \, II, \, III$ and $IV$
• D. $II$ and $III$ only

Answer 1

Answer: (A)

Breathing is the process of taking the atmospheric air in and giving out the spent air or used air. It has two parts inspiration (taking the air in) and expiration (giving out the used air). During the exhalation process, air is given out due to the pressure gradient developed by relaxation of the diaphragm and the external intercostal muscles which were contracted during inhalation. This causes reduction in thorax volume (statement IV) and increasing the pressure (statement II) inside compared to outside atmospheric pressure. This causes the used air in lungs to move out of the thorax. Statements I and III are changes occurring during inhalation process of breathing.