Question

17. How does movement of the rib cage change air pressure in the chest cavity?

When the rib cage rises, an increase in air pressure in the chest cavity causes air to rush into the lungs.
When the rib cage relaxes, an increase in air pressure in the chest cavity causes air to rush into the lungs.
When the rib cage rises, a decrease in air pressure in the chest cavity causes air to rush into the lungs.
When the rib cage relaxes, a decrease in air pressure in the chest cavity causes air to rush out of the lungs.

Answer 1

The correct answer would be the third option.

The intercostal muscles present between ribs contract to pull them outward and upward.

In addition, the diaphragm also contracts and gets thin.

Both these movements increase the cavity size due to which pressure inside the lungs decreases as compared to the atmospheric pressure.

Consequently, the air is pulled inside the lungs as it travels from high pressure to low pressure.

Answer 2

The movement of the rib cage changes air pressure in the chest cavity because when the rib cage raises, a decrease in air pressure in the chest cavity causes air to rush out into the lungs.