biology 10.2 - denfence against pathogens

What dis primary non-specific defences do?

Stop organisms from entering the body

What does skin do?

Acts as a physical barrier and produces antimicrobial chemicals and ones that lower the pH to inhibit pathogen growth

What do mucous membranes do?

They protect body openings that are exposed to the environment. Some secrete mucus which traps pathogens and contains antimicrobial enzymes

What does blood clotting do?

Platelets release substances that cause fibrin to be formed when exposed to damaged blood vessels. Fibrin meshes together to trap platelets which causes a blood clot which prevents pathogens entering as well as blood loss

What does inflammation do?

Damaged tissues release molecules which increases blood vessel permeability causing fluid to leak to the surrounding area = swelling and isolates any pathogens that have entered the damaged tissue. The molecules also cause vasodilation (widening) which increases the blood flow so the area will be hot and there will be more white blood cells

What does wound repair do?

The outer layer of skin cells divide and migrate to the edges of the wound the tissue below the wound then contracts so the edges of the wound are brought closer together, then the wound is repaired using collagen fibres = pathogen can’t enter

What do expulsive reflexes do?

When the mucus membranes in the nose are irritated you sneeze, when the respiratory tract is irritated you cough. These are examples of trying to expel foreign objects including pathogens automatically

What does the waxy cuticle do?

It is a physical barrier that stops water collecting in the surface preventing water borne diseases

What do cell walls do?

Act as a physical barrier

What does callose do?

It is a polysaccharide produced by plants that is deposited between cell walls and plasma membranes during times of stress to make it harder for pathogens to enter the cell

What are saponins?

Chemicals produced by plants that destroy the cell membranes of pathogens

What are phytoalexins?

Chemicals produced by plants that inhibit pathogen growth

What do chemicals that are toxic to insects do?

Stop insects that carry diseases infecting plants