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Circulatory System - Blood - Coggle Diagram
Circulatory System - Blood
The composition of blood
Blood transports materials and distributes heat around the body. It also helps to protect against disease. Blood contains plasma, which is a liquid that the other components of blood are suspended in.
Plasma is a straw-coloured liquid that makes up just over half the volume of blood.
Plasma
Transporting dissolved carbon dioxide, digested food molecules, urea and hormones; distributing heat
Red blood cells
Transporting oxygen
White blood cells
Ingesting pathogens and producing antibodies
Platelets
Involved in blood clotting
Red blood cells
Red blood cells (also called erythrocytes) transport the oxygen required for aerobic respiration in body cells.
They must be able to absorb oxygen in the lungs, pass through narrow blood capillaries, and release this oxygen to respiring cells.
Red blood cells have several adaptations that enable them to carry out this function:
They contain the proteinhaemoglobin, which gives them their red colour
Haemoglobin can combine reversibly with oxygen. This is important - it means that it can combine with oxygen as blood passes through the lungs, and release the oxygen when it reaches the cells.
They have no nucleus so they can contain more haemoglobin.
They are small and flexible so that they can fit through narrow blood capillaries.
They have a biconcave shape - they are the shape of a disc that is curved inwards on both sides - to maximise their surface area for oxygen absorption.
They are thin, so there is only a short distance for the oxygen to diffuse to reach the centre of the cell.
White blood cells
Phagocytes
About 70 per cent of white blood cells are phagocytes. Phagocytes engulf and destroy unwanted microorganisms that enter the blood, by the process of phagocytosis.
Lymphocytes
Lymphocytes make up about 25 per cent of white blood cells. Lymphocytes produce soluble proteins called antibodies when a foreign body such as a microorganism enters the body.
Antibodies neutralise pathogens in a number of ways:
they bind to pathogens and damage or destroy them
they coat pathogens, clumping them together so that they are easily ingested by phagocytes
they bind to the pathogens and release chemical signals to attract more phagocytes
Lymphocytes may also release antitoxins that stick to the toxins that the microorganism makes, which stops it damaging the body.
Platelets
Platelets are cell fragments produced by giant cells in the bone marrow.
Platelets stop bleeding in two main ways:
they have proteins on their surface that enable them to stick to breaks in a blood vessel and clump together
they secrete proteins that result in a series of chemical reactions that make blood clot, which plugs a wound