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.
Globally less than 10% of those using birth control are using the condom. Rates of condom use are higher in the developed world. In United Kingdom the condom is the second most common method of birth control (22%) while in the United States it is the third most common (15%). About six to nine billion are sold a year.