Quick Answer. The function of the cartilaginous rings of the trachea is to stabilize the trachea and keep it rigid while allowing the trachea to expand and lengthen when the person breathes. If the trachea was not supported in this way, it would simply collapse because of the pressure of the chest.
1 The Pill. The pill is the common name for oral contraception. It's one of the safest, most effective, and popular methods of birth control. The pill is made up of synthetic forms of hormones that naturally occur in a female's body - progestin and estrogen.
Before the pill, the condom was the most common method of birth control. Now people say men won't do this, but that hasn't always been the case. Today, two-thirds of condoms are purchased by women. Maybe men in the very recent past didn't enjoy taking charge of fertility, but they did it anyway.