Yawning?

In the lungs there is an organ called the alveoli, or air sacs. Alveoli serves to carry oxygen into the blood and suck up carbon dioxide and then removed.

If the alveoli are not getting fresh air, he will be deflated and the lungs a little hardened. The brain then immediately react to instruct yawning mouth and pulled the air (oxygen).

But certain aspects of yawning remains a mystery. Fetus in the womb, for example, also yawning. However the not yet known whether the fetus is pulled oxygen through his lungs. Yawning also seems to be a symptom of multiple sclerosis with causes unknown.

Another phenomenon that remains a mystery is the male animal, yawning associated with penile erection but not always the animal wants to have sex.