How do Microbes Enter Our Body?
You have learnt that microbes exist virtually everywhere, and hence our body is constantly exposed to them. They gain access to our body through the natural openings like our mouth, nose, urinary and reproductive passages (Fig). This can happen while we breathe contaminated air, drink impure water or eat infected or spoiled food; They reach our lips when we touch them with gemcarrying fingers or finger nails, when we drink from glasses or cups which have not been washed well or even while wiping the mouth with dirty and used towels. We can get infected from other persons by contact while shaking hands, or otherwise touching their body. Germs can enter our body through urinary and reproductive passages during sexual activity.
Our eyes get germs from infected air or dust. Each of these natural openings leads to a tube which reaches other organs. Thus germs get into our body and infect our organs. The tubes are lined with soft mucous membranes which can resist penetration only when a person is ih a state of gd health. In case of common cold, the mucous membrane itself is attacked, and gens sit and multiply on it. Gems are invisible invaders and it is not easy to check their entry. The major physical barrier to their entry is our skin. As mentioned earlier, a large number of them live on our skin and most of them are harmless. Some germs do cause boils and pimples, invade roots of hair and set up local infection. If the infection is not controlled it may spread deeper under the skin. If the skin is cut or scraped off by injury. bacteria get under the skin. and the wound becomes septic. Insects are also carriers of many disease germs. The blood-sucking insects on biting, puncture the skin, and thus introduce germs into the body. For example, the female mosquito Anopheles injects germs of malaria; worms of filaria are also camed by a kind of mosquitoes. Similarly, plague and sleeping sickness are caused by bites of fleas and a fly called the tse-tse, respectively. Many worms, such as hookworm can penetrate through the skin and enter the blood stream. Eggs of pinworm enter through the mouth by contaminated fingers or infected food or water. As'you know, the bite by a mad dog is almost always fatal. This is because the dog cames germs causing rabies. Dirty and infected syringes used for injections can also cause disease.