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Function of the blood

Blood is the transport system within the body. It transports oxygen, carbon dioxide, nutrients, hormones, enzymes and electrolytes. There are about 9 pints of blood in the human body. However, small increases to this can be achieved through training. Blood is made up of four different components:

  • Red blood cells
  • White blood cells
  • Plasma
  • Platelets

Red blood cells

Red blood cells are sometimes referred to as erythrocytes and are manufactured within the bone marrow. They make up around 99% of the blood cells in the body and are red in colour as they contain a red-coloured protein known as haemoglobin. Haemoglobin combines readily with oxygen to form a compound called oxyhaemoglobin through which oxygen is transported to the tissue cells.

White blood cells

White blood cells are sometimes referred to as leucocytes. They are colourless and much fewer in number. The white blood cells are manufactured within the bone marrow, the lymph nodes and the spleen. There are several kinds of white blood cells, some fight and destroy bacteria, some are involved in tissue repair, whilst some actually produce chemicals to protect against infection.

Plasma

Plasma is a straw coloured liquid in which dissolved salts, hormones, fats and sugar are carried. It accounts for approximately 55% of the total blood volume.

Platelets

Platelets are parts of cells that help to produce clotting when a blood vessel is damaged. They become sticky when in contact with the air to form the initial stage of repair to damaged tissue.