Question

Describe the events that take place in the thorax to cause air to be taken into lungs

Answer 1

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The events that occur during Inspiration are as follows :

1. In normal breathing conditions , the Internal Intercoastal muscles and the Diaphragm contracts .

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \red{ \downarrow}$

2. Internal Intercostal muscles increase the length of thorax in an lateral aspect . Whereas Diaphragm increases the length of thorax in an Supero-Inferior direction.

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \red{ \downarrow}$

3. Both these lead to increase in volume of thorax.

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \red{ \downarrow}$

4. Analogous to Boyle's Law , the pressure on the Thorax decreases .

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \red{ \downarrow}$

5. When the pressure inside the thoracic cavity becomes less than that of the atmospheric pressure , a pressure difference is created.

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \red{ \downarrow}$

This causes air to flow from high pressure region (atmosphere) to low pressure region (thorax).