Question

Which of the following substances are expelled during expiration?
A. Water vapor
B. Carbon dioxide
C. Small amounts of oxygen
D. All of the above

Answer 1

Breathing is the process of intake and release of air inside the lungs to facilitate gas exchange. It involves two processes namely, Inhalation is the intake of gases and expiration is the removal of gases.

Complete answer: Inhalation results in contraction of lungs muscle i.e. intercostal muscle and increases in the lung volume expansion of the chest cavity. This increase in volume results in a decrease in the pressure in the thoracic cavity and results in the intake of atmospheric air into the lungs. Now due to the partial pressure of various gases, the diffusion of gases takes place into the blood. During inhalation phrenic muscle that is situated in the diaphragm is contracted, this will also lead to an increase in the thoracic cavity.
Exhalation results in relaxation of lung muscle i.e. intercostal muscle and a decrease in lung volume that also increases the pressure of the thoracic cavity. At the same time, the phrenic muscle gets relaxes which means the diaphragm gets back to its normal position.
When we inhale, the mixture of gases enters the lungs and the volume of the lungs increases it exerts pressure on the diaphragm and rib cage. Exhalation occurs because of the elastic nature of the lungs. In force, full exhalation abdominal muscles are also involved. During forceful exhalation, the abdominal muscle gets contracted to result in the forceful release of air from the body.
So, when we exhale carbon dioxide, water vapor, and a small amount of oxygen is released. The correct answer to the given question is option D. All of these.

Note: The continuous cycle of inhalation and exhalation makes the process of breathing. Exhalation is complementary to inhalation.