non specific animal and plant defence Flashcards
state and explain 4 PHYSICAL plant defences against pathogens
- waxy cuticle= physical barrier against pathogen entry + stops water collecting on the leaf reducing infection between plants in water
- cell walls= physical barrier against pathogens that make it past waxy cuticle
- produce polysaccharide - callose= deposited between cell walls and plasma membranes, making it harder for pathogens to enter cells, is deposited at the plasmodesmata so limits spread of viruses between cells
- lignin= waterproof substance which thickens cell walls
State and explain 5 CHEMICAL plant defences against pathogens
- produce antimicrobial chemicals= kill pathogens or inhibit their growth
- produce chemicals that are toxic to insects= e.g cyanide. reduces amount of insect-feeding on plants
- phytoalexins are produced in response to contact with a pathogen or parasite= fungicidal, specific to particular attacking organisms, inhibiting their growth
- Insectides= often alkaloid substances that are toxic to insects
- tylose= blockage in xylem vessels to stop pathogens being carried in water breaking through plant
What are non specific defence mechanisms for animals against pathogens?
mechanisms against any pathogen, so doesn’t need to recognise its antigen shape
What is the purpose of the first line of defence for the non specific responses?
To prevent pathogens from entering the body
What is the purpose of the second line of defence for the non specific responses?
To deal with pathogens which have accessed the blood supply and tissues- to stop them from reproducing or entering cells
What is the purpose of the third line of defence for the specific responses?
To recognise pathogens and make antibodies against them so that the pathogen will be destroyed. Also so that future exposure to the same pathogen will be dealt with quickly and illness prevented.
explain the skin as a non specific defence in animals
- forms a continuous, physical barrier which prevents pathogens from reaching the tissues
- outer layer of cells are not alive= prevents being used as host cells
- outer layer constantly being sloughed off and replaced= difficult for pathogens to establish a reproducing colony
- production of sebum= has antimicrobial properties
- commensals= live on our skin and occupy the ecological niche that the skin may provide
explain mucous membranes as a non specific defence in animals
- found in areas not covered by skin e.g lining of airways and digestive track
- mucus makes it more difficult for the pathogens to make contact with the cells underneath it
explain tears as a non specific defence in animals
- Tears are produced by the tear glands and wash over the surface of the eye before being drained away through the tear duct
- has a flushing effect which keeps the surface of the eye clean
- tears contain lysozyme= enzyme which can destroy many bacteria
explain stomach acid as a non specific defence in animals
- The hydrochloric acid in the stomach kills pathogens that are ingested in food or drink
- any pathogens that are breathed in stick to the mucus which is swept up by the ciliated epithelium cells lining the airways to the back of the throat then swallowed, are also killed by the stomach acid
explain blood clotting as a non specific defence in animals
Blood clotting
- When there is a breech in the skin caused by trauma it is important that the wound is sealed as quickly as possible
- this prevents excessive blood loss and opportunistic pathogens from gaining access to the tissues underneath the skin
Explain the process of the clotting cascade
- blood clot is formed from many strands of the insoluble protein fibrin, which acts as a mesh to catch red blood cells forming a temporary seal to plug the wound
- The inactive, soluble precursor of fibrin is fibrinogen, which circulates in the blood instead of fibrin which would form blood clots at any time.
- It converts to fibrin in the presence of the enzyme thrombin and calcium ions
- thrombin has to be made from its inactivated enzyme precursor, prothrombin in the presence of thromboplastin and calcium ions
- Thromboplastin is released by platelets when they are activated, denting damage has been done to the blood vessel wall
- Once wound has been sealed, epidermis cells undergo mitosis to permanently cover the wound. As the skin heals the blood clot dries out to form a scab, and once skin has healed underneath, the scab will fall off
explain expulsion reflexes as a non specific defence in animals
- various physiological processes which can expel pathogens from the body
- include coughing, sneezing, vomiting, diarrhoea
- if pathogens are removed from the breathing or digestive systems, then it will not be able to access the blood system and travel to other parts of the body
explain inflammation as a non specific defence in animals
redness
heat
swelling
pain
Explain how this inflammatory response is created by the body.
- type of white blood cell called a mast cell contains lots of vesicles of histamine
- when there is tissue damage the mast cells release their histamine
- when they detect antigens and release histamine, the histamine binds to histamine receptors in the smooth muscle of blood vessel walls, causing it to relax= vasodilation. Lumen of blood vessel is increased so more blood flows here, causing redness and heat
- heat as an anti-microbial effect as it slows down the rate at which pathogens can reproduce
histamine causes capillaries to become more permeable, so more tissue fluid is made and swelling is caused - swelling causes pain as nerve endings are pressurised by the increased pressure of the extra tissue fluid
- mast cells also release cytokines which attract phagocytes to the area to destroy the pathogens
