How the body maintains good health.

27th September 2004

Angela Carpenter

How the body maintains good health

The body is very clever at protecting it’s self from micro-organisms such as bacteria and viruses there are three main ways of doing this, these are called innate immunity. Once micro-organisms are in the body there are several ways the body can react to maintain good health.

The first line of defence is the skin and eyes. The epidermis of the skin is very reluctant to puncture and this makes it a very effective organ in protecting the body. If the skin is broken, then the blood clots quickly to seal the puncture. If the skin is punctured then small blood vessels will be cut. The white blood cells contain platelets which are vital to blood clotting. The first reaction would be for the skin to swell which will narrow the blood vessels to slow the flow of the blood, when platelets come into contact with damage skin they stick to the edges and then eventually to each other forming a plug. This will be enough for a small cut, but if the cut is larger then the plug needs more support, it gets this by turning the soluble fibrinogen into insoluble strands of fibrin which tangle together around the platelet plug thus reinforcing it. The blood cells become trapped and close any remaining gaps, eventually the blood stops and a scab is formed protecting the body from any bacteria. New skin grows underneath the scab and when it is ready the scab will shrink and fall off.

The eyes produce a chemical called muramidase that is evident in our tears; this kills most bacteria before it enters the body. Bacteria thrive in moist, warm, and pH neutral places, this is why the skin is kept at a constant pH level of 6, which is slightly acidic, to stop any bacteria from thriving.

The respiratory system is also used to protect the body. Its entire respiratory tract; the nasal passage, the trachea and the lungs are lined with mucus and cilia which catch dust and bacteria to stop it from reaching the lungs.

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The digestive system produces hydrochloric acid which kills any micro-organisms that enter via contaminated food or dirty water.

Once micro-organisms have entered the body they reproduce very quickly until symptoms appear. The microbes will be recognised by the immune system as foreign and our defence system will start to attack them. The white blood cells are one of the main defences against antigens. They move freely around the body and when they find a microbe that ‘does not belong there’ they surround it and swallow the microbe, this is called phagocytosis. White blood cells are often destroyed themselves in the process or this clean-up operation.

Each different antigen needs it own antibody to destroy it. The body can not keep every type of antibody it has ever needed floating around the body, just in case it is needed. The body needs a way to produce these antibodies if and when we need them this is where the lymph nodes come in, they are simulated by our body when an antigen is present and produce white cells. Antibodies are released into the blood stream and when it comes into contact with the antigen it has been produced to connect with it can do one of three things. Firstly, the antigen/antibody complex could just breakdown destroying the antigen with it. Secondly, the complex could mean that it is now recognised by the white cells and phagocytosis is now possible, or finally the antibodies cause the antigens to agglutinate into clusters which again cam be attacked by the white cells.

Reference:

Notes, from Isabella in class dated 24 September 2004.