Module 4 : Section 1 - Defence Against Pathogens Flashcards
How do pathogens cause disease
By entering an organism
What do animals have that to prevent pathogens entering an organism
A range of primary, non-specific defences
What do Primary, non-specific defences refer to
- Skin
- Mucous Membranes
- Blood Clotting
- Inflammation
- Wound Repair
- Expulsive Reflexes
How is skin a primary, non specific defence
- acts as a physical barrier (prevent pathogens from entering the body)
- acts as a chemical barrier (produces antimicrobial chemicals and lowers pH stunting growth of pathogens)
How are mucous membranes a primary, non specific defence
- protect body openings that are exposed to the environment (mouth, nostrils, ears, genitals, anus)
- some membranes secrete mucus a sticky substance that traps pathogens and contains antimicrobial enzymes
How is blood clotting a primary, non specific defence
- a blood clot is a mesh of protein (fibrin) fibres
- blood clot plug wounds to prevent pathogen entry and blood loss
- formed by a series of chemical reactions that take place when platelets are exposed to damaged blood vessels
How is inflammation a primary, non specific defence
- signs of inflammation are swelling, pain, heat and redness
- triggered by tissue damage
- damaged tissue releases molecules which increase permeability of the blood vessels
- so they start to leak fluid into surrounding area
- causes swelling and helps to isolate any pathogens
- the molecules cause vasodilation which increases blood flow to the affected area
- this makes the area hot and brings White blood cells to the area to fight any pathogens present
How is wound repair a primary, non specific defence
- the skin is able to repair itself if an injury happens an reform the barrier against pathogen entry
- surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound
- the tissue below the wound then contracts to bring the edges of the wound closer together.
- It is repaired using collagen fibres - too many collagen fibres and you’ll end up with a scar
How is Expulsive reflexes a primary, non specific defence
- this refers to coughing and sneezing
- a sneeze happens when the mucous membranes in the nostrils are irritated but things such as dust or dirt
- a cough stems from irritation in the respiratory tract
- both are an attempt to expel foreign objects, including pathogens from the body
- they happen automatically
Plants have….
- Physical defences
- Chemical defences
against pathogens
What are the physical defences against pathogens for plants
- waxy cuticle
- cell walls
- callose
How does a waxy cuticle provide a defence against pathogens for plants
- provides a physical barrier against pathogen entry
- stops water collecting on the leaf, which could reduce the risk of infection that are transferred between plants in water
How does a cell wall provide a defence against pathogens for plants
- plant cells themselves are surrounded by cell walls
- these form a physical barrier against pathogens that make it past the waxy cuticle
How does callose provide a defence against pathogens for plants
- callose is a polysaccharide
- callose gets deposited between plant cell walls and plasma membranes during times of stress e.g. pathogen invasion
- callose deposition may make it harder for pathogens to enter cells
- callose deposition at the plasmodesmata may limit the spread of viruses between cells
What chemical defences do plants have against pathogens
- production of antimicrobial chemicals
- chemicals that are toxic to insects
