health and disease

health and disease pages 160-163

  • Created by: Atlanta
  • Created on: 12-04-12 15:49


health can be defined as your physical, mental and social welbeing. 

If you are in good health, you are:

  • free from disease
  • able to carry out all the normal physical and mental tasks expected in society
  • well fed, with a balanced diet
  • usually happy, positive outlook 
  • suitably housed with proper sanitation
  • well intergrated in society
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disease can be defined as a departure from good health.

  • a disease is a malfunction of the body or mind which causes symptoms
  • these symptoms may be physical, mental or social
  • diseases can be grouped according to their causes
  • diseases caused bu living organisms are called infectious diseases
  • the symptoms of these are usually physical but may effect mental or social health
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a parasite is an organism that lives on/in another living thing (its host), causing harm to it's host.

  • cause harm by taking nutrition from the host 
  • may live all or part of their life in/on the host
  • parasites that live on the host are called external parasites e.g headlice
  • parasites that live in the host are internal parasites e.g. tapeworms
  • parasites may live unoticed on the host, which benefits the parasite so that the host doesnt try to remove it
  • parasites may cause damage which allows other organisms to invade the host and cause a secondary disease.
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A pathogen is an organism that causes disease.

  • human body is an ideal habitat for micro-organisms
  • pathogens live by taking nutrients from the host and they cause damage in the process
  • damage can be considerable
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transmission of malaria

  • Malari is caused by plasmodium; plasmodium falciparum is the most widespread. 
  • Malari is spread by vector (an organism that carries a disease-causing organism from one host to another). 
  • the female anopheles mosquito carries the plasmodium from person to person when it withdraws their blood. 
  • the paracites live in the red blood cells of the human host and feed on the haemoglobin.
  • the malarial parasite can also be transmitted by careless and unhygienic medical practices, unscreened blood transfusions, use of unsterile needles and it can also be passed through the placenta into a unborn child.
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transmission of malaria (2)

the parasites are transmitted by the following cycle:

  • if the host already has malaria, the mosquito will **** the parasite gametes into its stomach
  • the gametes fuse and the zygotes develop in the mosquitos stomach
  • infective stages are formed aand these move to the mosquitos salivary glands
  • the saliva contains the infective stage of the parasite
  • in the human host, the infective stages enter the liver, where they multiply before passing into the blood again.
  • in the blood they enter red blood cells, where the gametes are produced.
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transmission of HIV/AIDS

HIV/AIDS is caused by the Human Immunodeficiency Virus. The virus may enter the body but remain inactive (known as being HIV positive). When active the virus destroys T helper cells in the immune system, that usually help prevent infection.  if destroyed resistance to infection is reduced. 

HIV can be transmitted by:

  • exchange of body fluids - like blood to blood contact
  • unprotected sex
  • unscreened blood transfusions 
  • unsterile surgical equipment
  • sharing needles
  • across the placenta in pregnancy
  • from mum to baby during breast feeding
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transmission of tuberculosis

TB is caused by 2 species of bacterium: Mycobacterium tuberculosis and M.Bovis. TB is usually found in the lungs and it is transmitted by droplet infection. 

  • the tiny droplets of liquid are released when an infected person coughs, sneezes, laughs or talks. 
  • you can become infected when you inhale these droplets-luckily it isnt that easy to contract
  • usually takes close contact with an infected person over a prolonged period of time to contract the disease.
  • conditions that help the spread of TB are: over crowding-many people sleeping and living in one house together, poor ventilation, poor health- especially if a person has HIV/AIDS they are more likely to catch T, poor diet, homelessness, living or working with people who have migrated from areas where TB is common. 
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