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Unit 12D applied science complete assignment
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- PEARSON (PEARSON)
Complete unit 12D assignment
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Unit 12DP5:
Non-specific immune system:
The non-specific immune system is made up of physical and chemical barriers.
Physical barriers:
Skin – prevents the entry of bacteria into the body through the skin. The skin
produced an oily substance called sebum. Sebum inhibits the growth of pathogens.
Skin flora – natural healthy bacteria that beat pathogens taking up surface space
instead of pathogens.
Nasal hairs – The inner hairs of the nose act as a physical barrier to infection. The
cells in the nose (goblet cells) produce mucus, which traps pathogens and prevents
them from entering the body.
Cilia – move both the mucus layer and fluid in the layer.
Mucous membrane – trap pathogens on gas exchange surfaces (trachea), contains
lysozymes that destroy bacteria.
Chemical barriers:
Lysozymes/Stomach acid/ Interferons
Fever - increased number of white blood cells present due to infection causing the
hypothalamus in the brain to reset, increasing the temperature of the body.
Blood clotting – thromboplastin and serotonin are released from platelets to help
form a clot to keep out pathogens.
Inflammation –histamines (cause blood vessels to dilate, increasing temperatures
which prevents pathogen reproduction, also increase cell membrane permeability
allowing more tissue fluid to escape causing swelling and pain) and cytokines (Attract
white blood cells to handle pathogens) are released by mast cells
Phagocytosis – components - phagocytes engulf pathogens in vacuole called
phagosomes, phagosomes form phagolysosome by combining with lysosomes,
enzymes present in the phagolysosome break down the pathogens which are then
removed from the phagocyte by exocytosis.
Neutrophils - Neutrophils represent the first line of defence in response to invading
microbes, by phagocytosis of pathogens and/or release of antimicrobial factors
contained in specialised granules.
Monocytes (Macrophages) – specialised phagosomes, antigens from pathogens
broken down bind with the antigens of the macrophage to form a histocompatibility
complex (MHC).
APC – antigens broken down by the macrophages then display the antigens on the
macrophages plasma membrane to form an Antigen-presenting cell.
Specific immune system:
Lymphocytes B cells- B cells are at the centre of the adaptive humoral immune
system and are responsible for mediating the production of antigen-specific
immunoglobulin (Ig) directed against pathogens generally known as antibodies.
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