Circulatory system-blood

• Red blood cells carry oxygen
• Red blood cells (or erythrocytes) carry oxygen from the lungs to all the cells in the body
• Red blood cells have biconcave disc shape to give it a large surface area for absorbing oxygen
• Red blood cells don't have a nucleus which allow more room to carry oxygen
• Red blood cells contain a red pigment called haemoglobin which contains iron
• In the lungs haemoglobin in RBC binds to oxygen to become oxyhaemoglobin but in body tissues oxyhaemoglobin splits up into haemoglobin and oxygen to release oxygen to the cells
• White blood cells defend against infection
• Phagocytes are white blood cells that can change shape to engulf unwelcome microorganisms this is called phagocytosis
• Lymphocytes are white blood cells that produce antibodies against microorganisms, some also produce antitoxins to neutralise any toxins produced by the microorganisms
• When you have an infection your white blood cell multiply to fight it off so a blood test will show a high white blood cell count
• Platelets help blood clot
• Platelets are small fragments of cells and they have no nucleus
• Unlike red blood cells white blood cells have nucleus
• Platelets help the blood clot at a wound to stop all your blood pouring out and to stop microorganisms getting in
• Lack of platelets can cause excessive bleeding and bruising
• Plasma is the liquid that carries everything in blood
• Plasma carries red and white blood cells, platelets, nutrients like glucose and amino acids, carbon dioxide from the organs to the lungs, urea from the live to the kidneys, hormones, proteins, antibodies and antitoxins produced by white blood cells