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This quiz contains 12 questions from a mix of 1 subtopics.

Platelets and blood clotting


When a blood vessel is damaged (e.g. if you cut yourself), you lose blood, and there is an increased risk of infection.

Platelets cause the blood cells to clump together, forming blood clots. 


Blood clots help in two main ways:

  1. Stoping blood loss - the blood clot seals the opening in the blood vessel, preventing further blood loss.
  2. Forming a physical barrier - the blood clot preventins pathogens from entering the wound, reducing the chance of infection.

Blood clotting process:

  1. Platelets release an enzyme upon exposure to air or damaged cells.
  2. The enzyme converts soluble fibrinogen in blood plasma to insoluble fibrin.
  3. Fibrin is sticky and forms long threads, creating a net.
  4. The net traps red blood cells, forming a blood clot.
  5. Phagocytes are attracted to the damaged site and engulf pathogens.
  6. The blood clot hardens, forming a scab that protects the wound as the skin heals underneath.
Illustration showing red blood cells.

What is the role of red blood cells?

To clot the blood when a blood vessel breaks 

To carry oxygen from the lungs to the tissues 

To carry substances and cells around the body

To defend against pathogens 

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Red blood cells are packed full of a large proteins called , which bind to oxygen. 

haemoglobin

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How are red blood cells adapted for their function?

(Select all that apply)

They have spherical shape to fit in more haemoglobin 

They have no nucleus to fit in more haemoglobin 

They have a nucleus so they can divide by mitosis 

They have a biconcave shape to increase their surface area

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2

What is the role of white blood cells?

To carry oxygen from the lungs to the tissues 

To clot the blood when a blood vessel breaks 

To carry substances and cells around the body

To defend against pathogens 

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is the process by which a white blood cell binds to, and then engulfs a pathogen, in order to destroy it. 

Phagocytosis

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Illustration showing antibodies with antigen-binding sites highlighted.

How do antibodies help defend against pathogens? 

They bind to pathogens and help immune cells destroy them

They activate our immune system 

They stop pathogens from entering the body 

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Do white blood cells have a nucleus? 

Yes

No

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1

What is the role of platelets?

To carry oxygen from the lungs to the tissues 

To clot the blood when a blood vessel breaks 

To carry substances and cells around the body

To defend against pathogens 

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Give two reasons why it is so important that our blood clots when we are cut.

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2

Do platelets have a nucleus? 

Yes

No

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The blood plasma is a yellowish liquid that makes up 55% of the bloods volume. Its role is to carry large structures like red blood cells, white blood cells, and platelets, as well as smaller dissolved substances.


Name as many of these smaller dissolved substances as you can. 

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4