Question

The rib-cage moves downwards and inwards……. In the process:
A) Inhalation
B) Inspiration
C) Expiration
D) All of the above

Answer 1

In physiology, the process of respiration is the movement of oxygen from the external environment to the cells inside tissues, and the transport of carbon dioxide in the opposite direction.

Complete answer:
The physiological meaning of respiration varies from the biochemical definition, which alludes to a metabolic cycle by which a living organism gets energy (as ATP and NADPH) by oxidizing nutrients and delivering by products.

In animals with lungs, physiological respiration includes respiratory patterns of inhaled in and exhaled out breaths. Inhaled breath (taking in) is normally an active movement. The contraction of the diaphragm muscle causes a variation in pressure, which is equivalent to the pressure brought about by elastic, resistive and inertial parts of the respiratory system. Interestingly, exhalation (breathing out) is typically a passive cycle. Breathing in carries air into the lungs where the cycle of gas exchange happens between the air in the alveoli and the blood in the pulmonary capillaries.

Expiration process involves the removal of foul air from lungs. It is a passive process. Expiration starts by the relaxation of outer intercostal muscles while internal intercostal muscles contract. The diaphragm moves up towards the chest to its position. The rib cage moves downwards and inwards bringing about reduced volume of the thoracic cavity. Thus, the intrapulmonary pressure goes over the atmospheric pressure and the air surges out. This is the means by which expiration happens.

Therefore, the correct answer for this question is option C, i.e. Expiration .

Note: Physiologic respiration is important to for cellular respiration and hence life in living organisms, the cycles are distinct: cellular respiration happens in individual cells of the living being, while physiologic respiration concerns the diffusion and transport of metabolites between the organisms and the external environment.