Human body have the capability to fight against diseases. This system of the body can be denoted and body's defense system. This defense system in actual is called as immunity.

Our body is always exposed to different kinds of disease causing germs or pathogens. They can enter our body by different means like directly through the skin, through mucous membranes of eyes, nose, urinary or genital tracts, through food or water intake, through the air we breathe in etc. Our body's immune system prevents all these kind of invasions.

The defense system of our body works at two levels :

Local Defense System and Immune System

A. Local defense system : It is a kind of barrier system which deal with the germs at there first entry point. This system is consist of different parts.

Protective mechanical barriers : This include skin, hair, mucus etc.

Skin : It is the outer tough covering made up of a protein keratin and it is almost impermeable to germs.Our body remain exposed to different microorganisms, which can invade our body through scratch and cut in the skin. By cleaning our body with water and soap we can removes the germs.

Hair : Presence of hair in different part of the body prevents the entry of germs in the body.

Mucus : Mucus is a slimy substance which is secreted by different type of cells in our body. Mucus secreted in the nasal passage and the wind pipe, traps many bacteria and prevents their entry into the body tissues.

Mucus also helps in lubrication of epithelial walls of different part of the body.

Coughing, sneezing and vomiting are the methods of throwing out of germs from the body. If any germ particle enters respiratory and digestive system then they are thrown out either by coughing , sneezing and vomiting.

The other system of our body that help us to protect body from germs are the secretions like saliva, sweat, tears, nasal secretions and hydrochloric acid(HCl).

Saliva, sweat, tears and nasal secretions contain germ killing substances.

Hydrochloric acid on the other hand is secreted by the stomach kills germs that gain entry along with the food.

These are called as germ killing secretions.

Germ fighting white blood cells (WBC's) : White blood cells are present in the our blood. White blood cells are of different types. They fight germs either by phagocytosis or by producing antibodies against the foreign particles.