Health and disease

• Health: is a state of physical, mental and social wellbeing, not just the absence of disease
• Disease: is the departure from good health caused by the malfunction of the mind and body

Parasite

• an organism that lives in or on another living thing, causing harm to its host
• they obtain their nutrients from the host
• they may cause damage that can allow other organisms to invade the host and cause secondary infections

Pathogens

• an organism that causes disease
• they invade the body
• they multiply in the tissues or inside cells and cause disease
• they obtain their nutrients from the host but they cause damage in the process

Malaria

• caused by a parasite called Plasmodium
• the vector for this parasite is the female Anopheles mosquito
• the female Anopheles mosquito carries Plasmodium from an infected person to an uninfected person 
• malarial parasite live in the red blood cells and feed on haemoglobin

malaria can be transmitted when:

• the mosquito bites an uninfected person and injects saliva
• the saliva contain infective stages of the parasite
• the infective stages enters the person's liver where they multiply
• it is then passed into the blood
• once inside the blood, it enters the red blood cells
• gametes are produced

malaria can also be transmitted by: 

• careless and unhygienic medical practices
• from a mother to an unborn child through the placenta

HIV/AIDS

• caused by Human Immunodeficiency Virus
• enters the body and remains inactive, this is known as being HIV positive
• Once active, it destroys the T helper cells in the immune system, therefore the person's ability to resist infections is reduced
• the person may contract a range of opportunistic infections
• a person with HIV never actually dies of HIV, it is the effects of these opportunistic infections that kills them
• AIDS: Acquired Immuno Deficiency Syndrome

HIV/AIDS can be transmitted from person to person in a number of ways:

• unprotected sexual intercourse
• unsterilised surgical equipments
• exchange of body fluid such as blood-to-blood contact
• from mother to child across the placenta, during childbirth or during breastfeeding
• unscreened blood transfusions
• using hypodermic needles

Tuberculosis(TB)

• caused by Mycobacterium tuberculosis and Mycobacterium bovis
• can affect many parts of the body but usually found in the lungs

TB can be transmitted by:

• when an infected person coughs, sneezes, laughs or talks
• airborne: when droplets in the air are inhaled

TB can be contracted by:

• homelessness
• poor ventilation
• overcrowding
• poor diet and health

The immune response

• Immune response: the specific response to pathogens which involves the actions of the lymphocytes and the production of antibodies
• Antibodies: protein molecules that can identify and neutralise antigens
• Antigens: molecules that stimulate an immune response

Primary defences

• Skin: epidermis, layer of dead skin cells that acts as an effective barrier against pathogens
• Mucous membrane: pathogens are collected in the mucus which is then moved to the top of the trachea by the Cilia and it is swallowed and killed by the acidity in the stomach
• Ear: the ear canal i lined with wax 
• Eyes: antibodies in tear fluid
• maintenance of…