Question

Which one of the following is a possibility for most of us in regard to breathing, by making conscious effort?
A. One can breathe out totally without oxygen.
B. One can breathe out air through the Eustachian tube by closing both nose and mouth.
C. One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.
D. The lungs can be made fully empty by forcefully breathing out all air from them.

Answer 1

Breathing and respiration are two distinct but linked physiological processes that aid in the correct functioning of body organs. Breathing is a physical process of exchanging gases, whereas respiration is a chemical activity that creates energy at the cellular level. Respiratory tract along with the passage for air is also the portal for the entry of pathogens.

Complete answer:
Let us check each option with logical reasoning in respect to the mechanics of breathing.
Option: (a) - Normally, the inspired air has around $20.84\%$ oxygen, whereas the expelled air contains approximately $15.7{\text{ }}\%$ oxygen. Even if one holds one's breath, it is impossible to breathe out air completely devoid of oxygen.
So, Option: (a) is incorrect.
Option: (b) - The eustachian tube connects the middle ear to the nasopharynx by a canal. It regulates the pressure in the middle ear, bringing it in line with the outside air pressure. By shutting both the nose and the mouth, no one can breathe out air through the eustachian tubes.
So, Option: (b) is incorrect.
Option: (c) – Yes, without moving the ribs, one may deliberately breathe in and out by moving the diaphragm alone.
So, Option: (c) is correct.
Option: (d) – By forcing all of the air out of your lungs, you will not be able to completely empty them. Even after the most powerful expiration attempt, residual volume remains in the lungs. It is around $1500{\text{ }}ml$ of air.
So, Option: (d) is incorrect.

Therefore, the Correct answer: (c). One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.

Note:
In order to provide oxygen to tissues and remove carbon dioxide from the body, the processes of inspiration (breathing in) and expiration (breathing out) are essential. Inspiration occurs via active contraction of muscles – such as the diaphragm – whereas expiration tends to be passive, unless it is forced. Gaseous exchange occurs by diffusion at the walls of alveoli in the lungs.