Self-Defense requires knowledge of the human anatomy.  The human body has many vunerable and vital strike areas that can be exploited during a self-defense encounter and with knowledge, self-defense techniques can be used against attackers who are bigger and stronger.

The vital areas of the head and neck are the eyes, ears, nose, throat and base of the skull.  Eyes can be punched, poked or gouged.  Ears can be slapped and when both ears are slapped simultaneously, the drums can be damaged.  The nose can be struck most effectively with the palm heel of the hand.  In fact, all striking techniques are most effective when directed at a vital or sensitive area.  The throat can be penetrated in the frontal soft area protecting the trachea and the back of the neck is susceptible to a knife-hand chop.

The torso has vulnerable points at the solar plexus, floating ribs and kidney area.  These three areas are the main targets of the basic kicking techniques.  In addition, these areas can be attacked with the fist, elbow and knee.  All of the striking techniques seek to "knock the wind out of the opponent." In other words, leave the opponent in a breathless, injured and disoriented position.

The lower abdomen, groin and side of the knee are easily accessible lower body targets.  Kicks to these low areas are safe and powerful.  You can kick a big person in the groin or side of the knee, and keep your balance. It will be difficult for the attacker to grab you or your leg, and if you kick correctly, the attacker shouldn't even be able to stand.

The entire human body also has pressure points known as acupressure or acupuncture points.  These points can be touched with healing pain reduction effects or they can be pressed with a pain inducing intent.  The acupressure points have been located and used for many hundreds of years by Orientals for healing and self-defense purposes.  The best way to learn how to manipulate pressure points is under the guidance of an expert instructor even though there are books that illustrate the location of pressure points and some basic concepts on how to manipulate them.

In conclusion, for self-defense purposes do not look at an attacker and see his size, his muscles, his strengths.  View the attacker as a composite of vulnerable areas.  See not the fortress but the holes in the walls.