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  • Created by: callum
  • Created on: 12-06-11 16:12

What is in blood?

- Plasma fluid, which contains water, dissolved substances such glucose, hormones and waste products.

- Red blood cells bontaining haemoglobin to carry oxygen.

- White blood cells to fight infections, some make antibodies and some engluf and digest microorganisms.

- Platelets, which are fragments of cells that help to clot blood at a wound.

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What are blood types and why are they important?

There are markers called Antigens on the surface of cells. If an antibody recognises a foreign antigen, it joins with it. Antibodies destroy cells in various ways:

If a person receiving a blood transfusion ( the recipient ) has antibodies to the antigens on the donors red blood cells:

- the red blood cells clump together.

- They block blood vesels and the person dies.

so to aviod clotting, the donor and recipients blood type must be matched.

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How do we know which blood type is safe?

Remember the the recipients blood must not contain antibodies to the donors antigens.

blood type        antigens            antibodies     this will clot ?        can recieve blood?

       A                   A                    Anti-B                 B                           A or O

       B                   B                   Anti-A                  A                           B or O

      AB                 AB                  None                None                     AB,A,B,O

       O               Neither         Anti-A and B        A,B,AB                        O

People with type AB are called Universal recipients as they can receive any type.

People with O are called Universal donors as anyone can receive blood type O.

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What is your heart like?

Your Heart pumps blood into arteries. Blood circulates:

heart--->artery--->smaller arteries--->capillaries--->small veins--->veins--->heart

In one circulation the blood flows through the heart twice. This is called the double circulation. We need it so that the blood:

- Gains oxygen and loses carbon dioxide in the circulation through the lungs.

- Loses oxygen and gains waste carbon dioxide as it circulates around the rest of the body.

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Why are capillaries important?

Capillary walls are only one cell thick so:

- blood pressure can force water and dissolved substances from the blood out into the tissue. This forms tissue fluid.

- Substances such as oxygen. carbon dioxide, glucose and urea can diffuse between the blood and the tissues.

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