What’s in Blood

Blood is a liquid called plasma, with red cells, white cells and platelets floating in it. You have nearly 5 litres of it in your body – enough to fill 9 milk bottles or 2 ½ 2 litre drink bottles.

Plasma Plasma is a yellowish liquid. It is mostly water, with different things dissolved in it such as: Glucose and other nutrients from digested food Hormones Carbon dioxide and other waste from cells

Red Cells Red cells are the body’s oxygen carriers. They contain a red substance called haemoglobin which combines with oxygen easily. It gives the cells their red colour. They are made in red marrow in some bones (mainly the ribs, femur, humerus and femur) There are around 5 million cells in each drop of blood.

White Cells They defend your body against infection. They are larger than red cells and have a nucleus. There are several different kinds of white cell, all doing different jobs. Other white cells make antibodies. These are chemicals that destroy germs. Different germs need different antibodies. They are made in your red bone marrow, lymph nodes and spleen. There are fewer white than red cells. When you are ill more white blood cells are produced.

Platelets They are fragments from special cells made in red bone marrow. They stick to each other easily. They stop your body losing blood by forming a clot. (example). When you cut your hand platelets stick to the surface of the wound and each other. They then produce a substance that grows tiny fibres (a clot forms). The clot hardens and forms a scab.