B4.1 The Blood Flashcards
What does the human circulatory system consist of?
Blood
Blood Vessels
The Heart
What is blood?
A unique tissue based on a liquid called plasma, which carries red blood cells, white blood cells, and platelets suspended in it.
Describe the blood plasma (as a transport system).
The blood plasma is a yellow liquid which transports all blood cells (and some other substances) around the body:
Waste carbon dioxide is carried to the lungs
Urea (formed in the kidneys from the breakdown of excess proteins) is carried to the kidneys where it is removed to form urine
The small, soluble products of digestion are carried to cells around the body
Which type of blood cell is most common and what is its purpose?
Red blood cells are present more than any other type of blood cell, and they pick up oxygen from the air in the lungs and carry it to the cells around the body.
How have red blood cells adapted to their job?
They are biconcave discs (disc bushed in on either side), giving them an increased SA:V ratio for diffusion.
They are packed with haemoglobin, a red pigment which binds to oxygen.
They have no nucleus, making more space for haemoglobin.
Describe white blood cells.
They are bigger than red blood cells, but there are fewer of them. They have a nucleus, and form part of the defence system against harmful microorganisms.
What can white blood cells form?
Some form antibodies to fight microorganisms, and some form antitoxins to combat poisons made by the microorganisms. Others engulf and digest invading bacteria and viruses.
What are platelets and what do they do?
Small fragments of cells with no nucleus.
How do platelets help at the site of a wound.
They help the blood to clot at a wound. This is where fibrinogen converts into fibrin, which produces a network of protein fibres. These capture red blood cells and for a jelly like clot to stop blood flowing out of the body.
