Functions of the blood

Blood is made of 4 main componentsPlasmaPlateletsRed Bloods CellsWhite Blood Cells.

Plasma is the pale yellow liquid, that is basically blood, but without the cells, the plasma carries just about everything.Carries the Red and White blood cells and the plateletsCarries digestied food products such as glucose and amino acids drom the gut to the cellsCarries C02 from the body cells to the lungsCarries Urea from the liver to the kidneys where it is excreated as urineCarries hormones which act as the bodies messangersHeat energy.

Platelets are small fragments of cells that help to clot damaged areas.Platelets clump together to form a plug, this is know as blood clotting.Blood clotting help to stop the loss of blood, and also micro organisms entering a wound.A clot is produced when platelets are held to gether by a protein called fibrin and some other proteins called clotting factors.

Red blood cells carry oxygen.Red blood cells transport oxygen to all of the bodies cells, and are adpted to do so.Red blood cells are small and have a biconcave shape, which makes gives thema large surface area for absorbing and releasing oxygen.They contain haemaglobin, which is iron rich and give blood its red colour, in the lungs O2 and haemaglodin react to creat oxyhaemaglobin which is carried to the cells, where the opposite reaction happens and the oxygen is given up to the cells.Red blood cells don't contain a neucleus, this frees up more space to carry more haemaglobin, so helping to carry more O2.

Pathogens.Pathogens are microorganisms that cause disease. certain bacteria and viruses for example.If they are not destroyed quickly, they will reproduce rapidly, your immune system works to destroy these pathogens with the most important component being the white blood cells.There are two types of white blood cell, phagocytes and lymphocytes.

Phagocytes.

Phagocytes.Phagocytes move around detecting foreign things in the body, i.e. pathogens.Phagocytes will engulf a pathogen and digest it.They are referred to as non-specific, as they will engulf anything that is not meant to be there.

LymphocytesPathogens carry unique molecules on their surface called antigens.Lymphocytes will make these pathogens out for destuction by producing an anti body, this anti body locks onto the pathogen.  They are antigen specific, so if the anti body encounter a differen antigen it won't lock on.Anti bodies are then produced rapidly and flow around the body to mark out other similar pathogens.Some lymphocytes stay around in the body as memory cells.  These cells can reproduce very fast if the same antigen enters the body again.  This is why you will be immune to most diseases you have alrady had.  The body is creating a memory of antigens, so it is able to produce anti bodies quickly to fight off re infection.

VacinationIn some cass when a new pathogen enters the body, it takes the lymphocytes a while to produce an anyti body for it to fight of the infection, in this time you can become very ill or even die.Vaccinations were introduced to help reduce this in some diseases, for example polio or measles.Vaccination involves injecting dead or inactive cells into the body.  They still carry antigens, even though they are harmless, the body starts an immune response s it would do normlly and begin to produce antibodies to target the antigen.In the same way after other infections, the body will keep memory cells for that antigen, so it can reproduce the antibodies rapidly to kill of the same type if they ever appear again.so if a live pathogen with the same antigen enters the body, the immune systems response will be rapid enough to destroy it before you become ill.

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