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Analyse the effectiveness of the body's response to different hazards in the external environment

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Task Two: Analyse the effectiveness of the bodies protective mechanisms in response to different hazards in the external environment. In task one I reviewed the ways the body had to protect itself. In this task I will look at how effective these defences are in providing protection. Everyday our bodies come into contact with hazards that are capable of causing disease or injury yet most of the time we are not affected, this is because of the body's defences. The integumentory system consisting of the skin and accessory structures such as hair, nails and a variety of glands is the largest organ system in the body. The skin is important as it is the first organ we see and can often reflect events occurring in other parts of the body for example cyanosis, a bluish colour due to decreased blood oxygen content is an indictation of impaired circulatory function or respiratory function also when red blood cells wear out, they are broken down and part of them are excreted by the liver as bile figments into the intestine, jaundice, a yellowish skin colour occurs when there are excess bile figments in the blood. If the liver is damaged by disease such as viral hepatitis, bile pigments are not excreted and accumulate in the blood. Rashes and lesions in the skin can be symptomatic of problems elsewhere in the body, for example, scarlet fever results from a bacterial infection in the throat. The bacteria release a toxin into the blood that causes a pink-red rash. Allergic reactions can also occur, the release of histamine into the tissues produces swelling and reddening which can indicate an allergy to ingested foods or drugs such as penicillin. The condition of the skin, hair and nails is also affected by nutritional status. In vitamin A deficiency the skin produces excess keratin and assumes a characteristic sandpaper texture, whereas in iron deficiency anaemia the nails lose there normal contour and become flat or concave. ...read more.


In regeneration the new cells are the same type as those that were destroyed and normal function is usually restored. In replacement a new type of tissue develops that eventually causes scar production and the loss of some tissue function. The dominant process depends on the tissues involved and the nature of the wound. Cells can be classified into three groups; labile, stable and permanent according to their regenerative ability. Labile cells, for example, the skin, mucous membrane and hemopocetic and lymphoid tissues continue to divide throughout life. Damage to these cells can be repaired by regeneration. Stable cells, for example, in connective tissue and glands including the liver, pancreas and endocrine glands do not activity replicate after growth ceases, but they do retain the ability to divide if necessary and are capable of regeneration. Permanent cells cannot replicate and if killed they are replaced by a different type of cell. Neurons are put into this category although they have some ability to recover from damage if the cell body of the neuron is not destroyed if this is destroyed it cannot regenerate. Muscle cells also have little ability to regenerate although they can repair themselves. Repair of the skin is a good example of wound repair. If the edges of the wound are close together the wound heals by a process called primary union. If the edges are not close together or if there has been a large loss of tissue a process called secondary union occurs. In primary union the wound fills with blood and a clot forms which bond the edges of the wound together and the surface of the clot dries to form a scab, which seals the wound to help prevent infection. An inflammatory response also includes vaso-dilation increasing blood cells and other substances to the area, Blood vessels permeability increases resulting in odema, also fibrin and blood cells move into the wounded tissues because of this. ...read more.


Diseases that cause proliferation of lymphocytes for example, leukaemia's and myelomas can result in an abundance of lymphocytes that do not function properly. The immune system may also be suppressed by drugs to prevent graft rejection. Congential immunodeficiency's may involve inadequate B and T cell formation or both. Severe combined immunodeficiency disease (SCID) involves both B and T cells were they fail to differentiate, unless the sufferer is kept in a sterile environment or is given a bone marrow transplant death from infection occurs. As discussed previously in task 1, transplants can cause problems. There are a cluster of genes in humans called the human lymphocyte antigen (HLA) genes which are responsible for the antigenic labelling of tissues. These genes control the production of HLA's which are inserted onto the surface of cells. The immune system recognisees self from foreign antigens because self cells are marked with HLA's, so a rejection of transplanted tissue is caused by the rejection of foreign HLA's. To reduce rejection a tissue match is performed and only tissues with similar HLA's to the recipient have a chance of being accepted to prevent rejection. Much research is on going into how the immune system responses new knowledge could create therapies to selectively augment or diminish immune responses against particular antigens and may also result in selective desensitisation to treat allergy or asthma or control transplant rejection. There is a promising new approach to treating cancer patients this is trying to generate an immune response to the cancer by vaccinating the sufferer with their own cancer cells. Usually cancer cells are ignored by the immune system because they are seen as 'self', however there us now evidence that the tumour may carry antigens that are not present on other cells and if this is the case it may be possible to force the immune system to mount a response. However this research is still in a early stage and requires more in depth work before it is able to cure cancer. ...read more.

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