Composition of blood

Blood transports materials and heat around the body, and helps to protect against disease. It contains:

  • plasma
  • red blood cells
  • white blood cells
  • platelets

Plasma is a straw-coloured liquid that makes up just over half the volume of blood.

Pie chart showing blood composition: 55% is plasma, and 45% is red blood cells, white blood cells and platelets that float within the plasma.Systemic circulation between the heart and other organs

This table explains the functions of various blood components.

PlasmaTransporting carbon dioxide, digested food, urea, hormones and heat
Red blood cellsTransporting oxygen
White blood cellsIngesting pathogens and producing antibodies
PlateletsInvolved in blood clotting