Blood is a mixture of fluid and solid matter.

  • Plasma is the liquid part of our blood. It makes up about 50 – 60 % of it. Plasma consists mostly of water, but many other substances are in it. It contains dissolved food, chemicals that control our growth and do other jobs, proteins, minerals and waste products.

  • Red blood cells look like flat, round discs. They contain haemoglobin, a protein that carries oxygen to the body and gives blood its red colour. Each drop of blood has about 300 million of these red cells.

  • White blood cells, also called leukocytes, fight infections and harmful substances that invade the body. Most of these cells are round and colourless. They have different sizes and shapes. White blood cells are not as numerous as red ones. For every 700 red blood cells, there is only one white blood cell.

  • Platelets are tiny bodies that are much smaller than red blood cells. They stick to the edges of a cut and form blood clots to stop bleeding. The blood of a normal adult has about 2 trillion platelets.

Blood components 

Image (altered) : Alan Sved, CC BY-SA 4.0, via Wikimedia Commons


 

Words

  • adult = grown up person
  • bleed = to lose blood if you are hurt
  • blood clot = a thick solid mass of blood
  • consist = to be made up of
  • dissolve = to mix with a liquid and become part of it
  • edge = the outside part of something
  • fluid = liquid, watery substance
  • growth = the speed at which we become taller
  • harmful = dangerous
  • invade = here: enter
  • mixture = combination
  • numerous = many
  • oxygen = a gas that is in the air and which we need to breathe
  • protein = a substance that is in food like meet, eggs and beans and which your body needs to grow and stay strong
  • shape = form; what something looks like
  • solid matter = something that is hard
  • stick = hang on to
  • substances = material
  • tiny = very small
  • trillion = a number with 12 zeros