Give biological reason for the following:

Throat infection can lead to ear infections

Eustachian tube:

1. It is a narrow tube that serves as a connection between the middle ear and the throat.
2. As eustachian tube remain closed most of the time, it opens only during the swallowing and yawning.
3. When it is open it lets in or out the air from the middle ear to equalize the pressure on the sides of the ear drum.
4. So, at that time bacteria can enter the ear and cause spread of the infection to the ear also.