The components of the blood

and their jobs

What is blood made up of?

• Red blood cells • White blood cells • Platelets• Plasma• Breakdown products of digestion, such as glucose,

fatty acids and amino acids• Dissolved mineral salts• Carbon dioxide• Urea• hormones

What is plasma?

• Plasma is the liquid part of the blood which carries everything else.

• Plasma is a straw-yellow coloured liquid

• If everything in plasma was removed, plasma would look like this

What do the different parts of blood look like under a microscope?

Red blood cells

White blood cells

What is the job of red blood cells?

• They have a round, flat disc shape for a large surface area

• They do not have a nucleus• They contain haemoglobin

which combines with oxygen in areas of high concentration to form oxyhaemoglobin

• Oxygen + haemoglobin oxyhaemoglobin

• Red blood cells carry oxygen to the cells of the body for use in respiration

What do white blood cells do?

• White blood cells help the body to fight invading bacteria

• White blood cells will engulf and ingest invading bacteria

Other important jobs of the white blood cells:

• They produce antibodies which can recognise and fight bacteria

• They produce antitoxins which neutralise the toxins (poisons) that bacteria produce, which make us feel ill

What do platelets do?

• Platelets are fragments of cells • The job of platelets is to help blood clot and

form a scab• The platelets are involved in the formation

of fibrin, which is needed for clotting blood• This is useful for stopping bleeding, and for

preventing germs from entering the body through the cut

Summary of the composition of blood

Questions on the blood

• What part of blood carries oxygen to cells?• Why are red blood cells flat disc-shaped?• What is the job of platelets?• What do white blood cells do?• Describe how a white blood cell carries out its

job.• What is the straw-coloured liquid which carries

all the other parts of blood called?

More questions on blood

• Name cell A• Name cell B B

A

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