WHEN you are tired your lungs slow down until you have too little air in them.
When this happens, your body sets off a spasm in your mouth, throat and chest, which forces you to take a deep breath of air. This is called a yawn.
- kidshealth.org; bigsiteofamazingfacts.com; howstuffworks.com
What causes a yawn
WHEN you are tired your lungs slow down until you have too little air in them.
When this happens, your body sets off a spasm in your mouth, throat and chest, which forces you to take a deep breath of air. This is called a yawn.
- kidshealth.org; bigsiteofamazingfacts.com; howstuffworks.com
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