IMAT 2011 Q57 [Ventilation]

In the process of ventilation the following occur:

  1. Pressure in thorax increases
  2. Volume of thorax increases
  3. Diaphragm goes down
  4. Ribcage goes down

Which of these occur during inhalation?

A. 1 and 2 only

B. 2 and 3 only

C. 3 and 4 only

D. 1 and 3 only

E. 2 and 4 only

The question states a few events that occur during ventilation, which is the process of both inhalation and exhalation.

Which of these occur during inhalation.

We must know that during inhalation, to allow air to flow into the lungs, we must have “negative pressure” compared to the outside, inside our lungs. What does it mean? In order to let air inside out pressure, the diaphragm must go down, and this rib cage goes up, making the volume of our thorax and chest cavity larger than usual, the larger volume is decreasing the pressure inside our lungs, forcing air from the outside to come into our lungs to equalize the sudden change in pressure. The pressure changes because we increased the thorax volume while keeping the content of the gases similar and as we know,


So which one of the following 4 answers fits this action?

Pressure in thorax increases – Pressure means Force applying over an area, the more particles hitting the inside wall of a “container” the more significant the pressure will be, and particles are more likely to hit the thorax when we exhale, not inhale.

The volume of the thorax increases – to inhale we must make the thorax larger, so the volume of the thorax increases.

Diaphragm goes down – Yes! Definitely, as we said earlier, the volume of the thorax must be larger than usual in order to make a negative pressure, the diaphragm goes down in order to increase the volume of the chest cavity.

ribcage goes down – If the ribcage goes down, the volume of the chest cavity decreases, we definitely don’t want it to happen during an inhalation.

The answer must be B

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