what happens in the body when you yawn, n what causes yawning??

Answer 1

Yawn is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from lack of stimulation
causes of yawning
An indication of tiredness, stress, over-work, lack of directed attention or boredom.
An action indicating psychological decompression after a state of high alert.
A means of expressing powerful emotions like anger, apathy, apprehension, remorse or tedium.

what happens in the body:
yawning is similar to stretching. Stretching, like yawning, increases blood pressure and heart rate while also flexing many muscles and joints. It is also theorized that yawning helps redistribute an oil-like substance which coats the lungs and aids breathing. Some have observed that if one tries to stifle or prevent a yawn by clenching one's jaws shut, the yawn is unsatisfying. As such, the stretching of jaw and face muscles seems to be necessary for a satisfactory yawn.

yawning occurs to stabilize pressure on either side of the ear drums. The deep intake of air can sometimes cause a popping sound that only the yawner can hear; this is the pressure on the inner ear stabilizing. This commonly occurs in environments where pressure is changing relatively rapidly, such as inside an airplane and when travelling up and down hills, which cause the eardrums to be bent instead of flat.

Answer 2

We just need more oxygen.