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Human Physiology Defence Against Infectious Diseases Notes

This is a sample of our (approximately) 4 page long Human Physiology Defence Against Infectious Diseases notes, which we sell as part of the Human Physiology Notes collection, a Grade 7 package written at The British International School, Ho Chi Minh in 2013 that contains (approximately) 32 pages of notes across 6 different documents.

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HUMAN PHYSIOLOGY Defense against infectious diseases

6.3.1Define pathogen (1)

A pathogen is an organism that can cause disease

Bacteria, viruses, fungi and other parasitic multicellular organisms

6.3.2 Explain why antibiotics are effective against bacteria but not against viruses (3) Antibiotics block specific metabolic pathways found in bacteria to prevent pathogenic growth Viruses reproduce using the host cell metabolic pathways that are not affected by antibiotics

Viruses do not have metabolic pathways like bacteria and therefore antibiotics do not work on viruses.

Viruses can only be treated by their specific anti-microbial agent and antibiotics should never be prescribed for viral infections (such as flu).

6.3.3 Outline the role of skin and mucous membranes in defense against pathogens (2) Skin:

Epidermis (tough outer layer)

Physical barrier: keratinized layers of skin discourage pathogenic growth


Lower layer produce new cells which replace those lost from the surface

Produce fatty acids and oil that prevent pathogenic growth (sebaceous glands secrete sebum)

Mucus Membrane:

Respiratory system: lining of the trachea, bronchi and bronchioles

Cilia hair like extensions move the mucus out of the respiratory system upward to the epiglottis to prevent infection

Here the mixture of mucus and microorganisms are swallowed down into the acid of the stomach.

Mucus contains lysosomes which help to kill bacteria

6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues (2) Source: Blood and body tissues Action: Ingest and destroy pathogens (Bacteria and viruses) through phagocytosis

A phagocyte comes in contact with pathogen cells - does not recognize the glycoprotein structure on its cell war

Pathogen ingested through endocytosis - the engulfed vesicles join together to form a pathogen vacuole (phagosome)

Pathogen vacuole binds with lysosome containing digestive enzymes which kill and digest microbes

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