Immunity=the means by which the body protects itself against infection
There are 2 defense mechanisms of the human body:
It is important to know that about 10 million different lymphocytes already exist in the body. They are NOT produced in response to an infection. The huge number of lymphocytes means that there is a high probability that one of these lymphocytes will have a protein on its surface that is complementary to the pathogens antigen. There is a time delay between exposure of the pathogen and the body's defenses destroying the pathogen as lymphocytes with the complementary proteins have to be built up to an efficient level in destroying the pathogen.
Phagocytosis= non-specific cellular process where phagocytes engulf and destroy pathogens (which are too large to be diffused or actively transported through cell-surface membranes).
Step by Step:
Antigen-presentation= phagocytes and other antigen-presenting cells alert more WBC by presenting the pathogens antigens on their cell surface membrane. This ensures the antigens can be detected easily by receptors.
Note: during phagocytosis, histamine is released which results the following:
There are 2 defense mechanisms of the human body:
- Non-specific=DON'T distinguish between pathogens, respond to all pathogens in the SAME WAY, IMMEDIATE response (e.g Barrier to entry of pathogens, phagocytosis)
- Specific=DO distinguish between different pathogens, SLOW response, involves lymphocyte WBC (e.g Cell-mediated involving T cells, Humoral involving B cells)
It is important to know that about 10 million different lymphocytes already exist in the body. They are NOT produced in response to an infection. The huge number of lymphocytes means that there is a high probability that one of these lymphocytes will have a protein on its surface that is complementary to the pathogens antigen. There is a time delay between exposure of the pathogen and the body's defenses destroying the pathogen as lymphocytes with the complementary proteins have to be built up to an efficient level in destroying the pathogen.
Phagocytosis= non-specific cellular process where phagocytes engulf and destroy pathogens (which are too large to be diffused or actively transported through cell-surface membranes).
Step by Step:
- Love is in the air- Phagocyte ATTRACTED to the pathogen by chemo-attractants
- Stuck like glue- Phagocyte BINDS to pathogen
- Dinner time- Phagocyte ENGULFS pathogen to form a PHAGOSOME (vesicle enclosing pathogen)
- Migration- Lysosomes MOVE towards the phagosome
- New name-Lysosome FUSES with the phagosome to form a PHAGOLYSOSOME
- Total breakdown- Pathogen DIGESTED by lytic enzymes released by the lysosomes
- What a user!-Phagocyte cytoplasm ABSORBS the useful products of the breakdown. The other products are EXPELLED
Antigen-presentation= phagocytes and other antigen-presenting cells alert more WBC by presenting the pathogens antigens on their cell surface membrane. This ensures the antigens can be detected easily by receptors.
Note: during phagocytosis, histamine is released which results the following:
- dilation of blood vessels --> speeds up phagocyte delivery to infection site
- causes inflammation at infection site
- swollen area --> pus containing dead pathogens and phagocytes
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