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How does a plant or animal respond to infection? - Coggle Diagram
How does a plant or animal respond to infection?
Organisation Levels of the body's Defences
First line of defence
Physical Barriers
Skin
: Consists of outer epidermis, dermis, hypodermis. Good blood supply = access for WBCs, RBCs, platelets. Epidermis is covered in keratin (waterproof protein = extra barrier). Upper epidermis = barrier of dead skin cells.
Mucous membrane
: Line body cavities. Features—cilia (to remove particles), secrete protective substances (mucus traps and flushes away foreign substances)
Tight junctions
: Line blood vessels to prevent diffusion of pathogens.
Peristalsis
: Alimentary canal (mouth to anus) contracts, moving food and preventing bacteria from reproducing.
Vomiting
, diarrhoea, increased urination: expel harmful substances and pathogens.
Chemical Barriers
Lysozyme
- An enzyme which breaks down the cell walls of bacteria, killing them and helping to fight infection. Found in; tears, saliva and mucus. Digestive enzymes in the stomach are also important
Acidic Secretions
- They contain degradative enzymes like lysozyme. They contain degradative enzymes like lysozyme. Body secretions also chemically screen out pathogens by being very acidic (they have a low pH). Acidic secretions are produced in the vagina, ear canal,stomach and skin.
Second line of defence
Inflammation
: A chemical response that helps wound repair and leads to pathogen destruction. The five cardinal signs of the inflammatory response: dolor (pain), calor (heat), rubor (redness), tumor (swelling), function laesa (loss of function)
Phagocytes
: The process by which phagocytes change shape and completely enclose a foreign particle, releasing enzymes to destroy it. the main types of phagocytes: neutrophils, monocytes/macrophages, dendritic cells, natural killer cells.
Responses by Plants Against Pathogens
Plant defences
Passive defences
Physical barriers
Chemical barriers
Active defences
Rapid active responses
Delayed active responses
Pathogen recognition
Plant response (e.g. Banskia)
Polygalacturonase inhibitor proteins inhibit the activity of pathogens in penetrating cell wall
Chemical compounds ward off fungus and reduce growth
Enzymes are produced to break down toxins released by fungus
Chemical receptors activate active defence—hydrogen peroxide is released to kill fungus, cell wall is reinforced to seal off fungus.
Example of plant disease
Host: Tomato Plant
Pathogen:Tomato Spotted Wilt Virus
Disease: Tomato Spotted Wilt
Example of plant disease
Host: Ipomoea costata (Potato Plant).
Pathogen: Phytophthora Infestans (Fungi).
Disease: Late Blight (or Potato Blight).
Complement Activation
The
complement
system is a group of proteins that assist other defence mechanisms in destroying phagocytes to become more active, attract phagocytes to the site of infection or destroy the membranes of the invading pathogen.
An
Antigen
is any molecule that the body recognises as foreign and that triggers an immune response
Mast cell
-
Characteristics
: blood vessel dilation, release of heparin and histamines, recruitment of neutrophils and macrophages, also involved in allergic reactions.
Location
- Connective tissues and mucous membranes.
Macrophage
-
Charcteristics
: Phagocytosis of pathogens and cancer cells, antigen-presenting cell.
Location
- Migrates from blood vessels into tissues.
Neutrophil
-
Characteristics
: Most common white blood cell at site of trauma or infection, release toxins that kill or inhabit bacteria and fungi, results other immune cells to the site of infection.
Location
- Migrates from blood vessels into tissues.