Blood

• The four components of blood are plasma, red blood cells, white blood cells, and platelets.
• 55% of blood is plasma and 45% is red/white blood cells and platelets.
• Plasma is the fluid part of the blood and contains 90% water.
• Red blood cells transport oxygen from the lungs to tissues. It contains the pigment hemoglobin. They are formed in bone marrow and on average last 120 days.
• Red blood cells have a concave shape and have no nucleus or mitochondria.
• Anaemia is caused by a lack of hemoglobin in our red blood cells as a result of a lack of iron in our diet.
• White blood cells protect the body from disease. Monocytes last for 6-9 days while lymphocytes last for days. These are also formed in the bone marrow.
• Platelets are small cell fragments produced in bone marrow from large cells breaking down. They consist of cytoplasm surrounded by a membrane with no nucleus.
• Platelets are involved in blood clotting. Haemophilia is a genetic condition where the blood does not clot properly.
• The blood defends the body against diease, distributes heat, transports material e.g food and hormones and provides pressure