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Functions of the blood - Coggle Diagram
Functions of the blood
Transport
Blood also transports gases such as oxygen and carbon dioxide between the tissues and the lungs. Red blood cells contain haemoglobin which combines with oxygen to form oxyhaemoglobin. In the tissues, oxygen is released and the darker haemoglobin is reformed.
To increase the space for carrying the maximum amount of haemoglobin, RBCs have no cell nucleus. They also have a special disc shape to help with the exchange of oxygen. On the way back to the lungs, haemoglobin will also carry a small amount of carbon dioxide.
There are two main forms of lipoprotein - high density lipoprotein (HDL) and low density lipoprotein (LDL). While both transport fat to the tissues where it is needed for energy, LDL appears to deposit fat and cholesterol in the walls of the arteries, while HDL appears to prevent or even reverse these harmful deposits. This has led to HDL and LDL sometimes being called 'good' and 'bad' cholesterol.
Blood transports hormones (e.g. insulin and adrenaline) that travel in the blood to target organs where they trigger a response, or initiate a particular process (e.g. fertility or growth).
One of the main functions of blood is to transport elements required for life around the body. Many are transported from the digestive system to the tissues or to storage areas such as the liver. Those that can't dissolve in water (e.g. fats) are carried by lipoproteins.
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Temperature regulation
As mammals, we are endothermic. This means we generate our own internal temperature and maintain it. Life is maintained by millions of chemical reactions that are all affected by heat. We operate best at an internal temperature of 37'c - this is our optimal temperature.
All our chemical reactions are regulated by enzymes which are determined by our genes. These enzymes, like all proteins, become unusable or denatured at high temperatures and chemical reactions slow down at low temperatures. Thus, for life and good health to continue, our optimal temperature must be maintained. Heat is generated in all our cells but especially in tissues such as the muscles. Blood removes this heat and circulates it around the body.
Preventing infection
Viruses, however, pose a different threat. These simple organisms can't live independently and need to hijack cells to survive and reproduce. They change the outside of the infected cell, but T-lymphocytes recognise this and latch onto the cell and destroy it along with the virus. It is this cell destruction that causes many symptoms of viral infections.
Bacteria and parasites will be recognised as threats by cells such as the neutrophils and B-type lymphocytes, which act as antigens to form antibodies. These lock onto specific chemicals in the walls of the bacteria and parasites, immobilising them and making them targets for the monocytes that then kill them and break them down. Special lymphocytes 'remember' these particular pathogens and will respond quickly if there is a re-infection. This is the principle behind vaccines.
Blood clotting
The platelets also help activate the immune response, minimising the threat of a pathogenic invasion.
When exposed to air or foreign material such as glass or plastic, platelets activate a chain reaction known as coagulation that converts the soluble blood protein (fibrinogen) into an insoluble form (fibrin) that forms a net-like structure, trapping both platelets and RBCs to form a clot. Individuals with haemophilia lack one or more of these factors and so have longer clotting times, leading to chronic blood loss.
If, during operations or kidney dialysis, blood is passed outside of the body to machines in tubes, anticoagulants have to be added to stop the blood from clotting.
Women have 4-5 litres and men have 5-6 litres of blood. Losing 2 litres will lead to serious issues or even death. Also, if the skin is broken, pathogens can gain access and blood poisoning or sepsis can quickly cause organ damage.