The mechanism of coughing

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How do we cough? What happens in you throat and lungs?

This action reminds one of a pressure cooker blowing off steam...

A pulmonologist explains what happens in your throat and lungs.

Sensing something is wrong
Both the upper and lower airways are lined by slow-reacting and fast-reacting receptors that can respond to a number of different types of stimuli, ranging from dust to irritant gases as well as excess mucus.

Once the receptors are triggered, a signal is sent via the vagus nerve, setting up a reflex with the signal being transmitted to your brainstem and consciousness making you aware that you need to clear these noxious particles or gases.

Preparing for the cough
In a matter of milliseconds, the cough centre situated in the medulla makes your consciousness aware of the fact that you need to cough. It sends an impulse back down to the diaphragm and intercostal rib muscles, preparing them for the cough action.

The first action is that the diaphragm "drops" to suck air into the chest, filling the thoracic cavity. After this, the glottis or "voice box" closes to prevent any air from leaving the chest.

Finally, the actual cough
Thereafter the cough centre triggers the diaphragm and intercostal muscles to contract, making the thoracic cavity smaller and building up pressure inside the chest; then the closed glottis opens, allowing the high pressure air to suddenly escape from the chest through the airways, hopefully taking with it any irritating particles, foreign bodies or phlegm that triggered the entire reflex to start with.

Air leaving the chest can reach speeds of up to 200 km/h and even faster in the event of a sneeze!

- (Dr Greg Symons, pulmonologist)

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