The human body is an extremely complicated machine. It is also susceptible to a lot of diseases caused by disease causing germs known as pathogens. They include bacteria, viruses, fungi and a lot of other microbial organisms. Diseases can also result from a lot of other reasons that may include chemicals, body’s internal mechanisms and genetic causes. But mostly the human body has its own defense mechanism to fight most of these diseases.

The defense mechanism of the human body can be broadly classified into a number of lines. The first line of defense or the outside defense system is a combination of physical and chemical barriers that play a vital role in thwarting infection from external sources. This first line of defense include the skin, mucus, cilia, acid present in the stomach, tears, the WBC or White Blood Cells also known as neutrophils, urine, and some friendly bacteria among others.

The Skin
It is also the largest organ of the human body. The pathogens are resisted by the skin from infecting or entering the human body. This is also a waterproof barrier that not only protects excess water from flowing in; it also prevents us from dehydration as well. The skin also acts as the first line of defense against chemicals, pollution, infection and toxins. The sensors on the skin also act as an informant about the immediate changes in temperature, pressure, humidity etc. in and around the immediate environment.

Mucus, Saliva & Tears
The three most important openings in the human body, they eyes, nose and mouth can act as entry point for a host of pathogens and other disease causing agents.

Mucus present in lining of the nasal cavity and wind pipe, as well as the food pipe traps particles, microbes and prevent them from causing any damage or infection.

The tears always protect the eyes from pathogenic infection and also protect them from getting dehydrated.

Saliva in the buccal or oral cavity also traps and in many cases dissolves the cell wall of bacteria. This prevents the bacteria from causing infection or diseases.

Pathogens that are trapped in the mucus are either ejected from the body by various methods or swallowed.

Stomach Acid
The stomach has a very strong acid. This acid not only helps in digesting food, but it also acts as a first line of defense for the body by killing the bacteria and parasites that are swallowed. Pathogens that are swallowed with food are also destroyed by the acid in the stomach.

Urine and Sweat
The kidney filters the blood and flushes out toxic chemicals from the body. They also flush out many pathogens as well.

Sweat is another form of flushing out toxins from the body. They also help in killing or flushing pathogens from the skin also.

Cilia/Hairs
The nasal lining is full of hairs that filter out lot of particles, and particulate manner that can cause diseases. The wind pipe is also lines with very fine hair known as cilia. These cilia moves away trapped particles and mucus away from the lungs and keep the internal organs clean. The particles include bacteria, dust, pollens, and so on.

WBC (White Blood Cells)
WBC or White blood cells are a blood component that finds, kills and ingest pathogens that has somehow gained entrance in the body. They are the most important defense mechanism inside the body. They are also known as neutrophils.

Beneficial Bacteria
There are lots of beneficial bacterial colonies in the human body. They can reside in oral cavity, gut, skin and bowels also. They live in a symbiotic relationship with humans and are known to destroy most of the pathogens on their way to infection and causing diseases.

Conclusion
The body has its own defense mechanism, in case the first line of defense fails somehow. But the first line of defense works round the clock to keep the body healthy and working. But the best and most important line of defense that can be actually be considered as the first line of defense is our common sense. It is time tested knowledge that prevention is better than cure, so it is extremely important to use that common sense and take care of our general health and avoid any situation that might be harmful for us.

About The Author: Alia is a writer/blogger. She loves writing travelling and reading books. She contributes to Gamification