Non specific defence against pathogens

What is a chemical and physical defence?

Chemical = chemicals or enzymes destroy pathogens before they enter the blood

Physical = physical barriers that prevent pathogen entering the body

What are the 3 physical defences?

1. Skin —> Oily sebum production prevents pathogen growth

2. Mucous membranes —> Secrete mucus, containing lysosomes and specialised immunological cells called phagocytes that trap microorganisms

3. Explosive reflexes —> Ways to eject or remove pathogens from body

What are the 4 chemical defences?

1. Mucous membranes —> Secrete mucus, containing lysosomes and specialised immunological cells called phagocytes that trap microorganisms

2. Lysosomes —> Found in tears. They are enzymes that break down bacterial cell walls

3. Inflammatory response —> A localised response characterised by redness and heat. Cells in damaged tissue causes the release of histamines and cytokines

4. Blood clots —>

What are histamines and cytokines in the inflammatory response?

Histamines make blood vessels dilate and makes them leaky to form tissue fluid leading to swelling. They also raise temperatures

Cytokines attract white blood cells so that phagocytosis can occur

How blood clots work?

Exposure of platelets in damaged skin or blood cell wall leads to clotting

1. Platelets are exposed to collagen and releases thromboplastin and serotonin

2. Thromboplastin is an enzyme that causes cascade of reactions to clot blood

3. Serotonin causes smooth muscle to contract and narrows blood vessels

4. Clot dries as scabs while blood vessels and skin are being repaired

What are the physical defences in plants?

1. Callose —> When plants get attacked, plants produce a polysaccharide called callose. Layer of polysaccharide forms between cell wall and membrane blocking the plasmodesmata and sieve cells to prevent pathogen travel.

What are the chemical defences in plants?

1. Insecticides —> produces insect killing toxins

2. Insect repellent —> compound that repels insects e.g pine

3. Anti-bacterial compound —> produces compounds killing bacteria

4. Anti-fungus compound —> chemical or enzyme that kills fungus