4.3 Circulation

Frage	Antworten
How are substances transported around the body?	By the circulation system (the heart, the blood vessels and the blood)
What is the heart?	An organ that pumps blood around the body. Much of the wall of the heart is made from muscle tissue
How many chambers does the heart have? Give the names of these chambers	The heart has four main chambers Right and left atria Right and left ventricles
What are artificial pacemakers?	Electrical devices used to correct irregularities in the heart rate
How is the natural resting heart rate controlled?	By a group of cells that act as a pacemaker, located in the right atrium
What happens to the heart if you have coronary heart disease?	Layers of fatty material build up inside the coronary arteries, narrowing them This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle Stents are used to keep the coronary arteries open
In some people heart valves may become faulty. What are the two main faults?	The heart valve tissue might stiffen, preventing the valve from opening fully The heart valve might open a leak
What can be used to replace faulty heart valves?	Biological valves - valves from other humans or mammals Mechanical valves
Why might artificial hearts be occasionally used?	To keep patients alive whilst waiting for a heart transplant To allow the heart to rest as an aid to recovery
Explain what happens to blood in the heart	Blood enters the atria of the heart. The atria contract and force blood into the ventricles. The ventricles contract and force blood out of the heart. Valves in the heart ensure that blood flows in the correct direction
How does blood flow from the heart to the organs?	Through arteries Returns through veins
What are the two separate circulations for?	One for the lungs One for all the other organs of the body
Name the blood vessels associated with the heart	Aorta Vena Cava Pulmonary Artery Pulmonary Vein Coronary Arteries
What are the walls of an artery like?	Thick walls containing muscle and elastic fibres
What are the walls of veins like?	Thinner walls and often have valves to prevent back-flow of blood
What are the walls of capillaries like?	Very narrow, thin-walled Substances needed by the cells in body tissues pass out of the blood and substances produced by the cell pass into the blood, through the walls of the capillaries
What is blood?	A tissue consisting of a fluid called plasma, in which the white blood cells, platelets and reed blood cells are suspended
What does blood plasma transport?	Carbon dioxide from the organs to the lungs Soluble products of digestion from the small intestine to other organs Urea from the liver to the kidneys
Explain the structure of red blood cells and what is inside them	No nucleus Packed with a red pigment called haemoglobin
What does haemoglobin do?	Red blood cells transport oxygen from lungs to the organs In the lungs, haemoglobin combines with oxygen to form oxyhemoglobin In other organs, oxyhemoglobin splits up into haemoglobin and oxygen
Do white blood cells have a nucleus?	No
What do white blood cells do?	Form part of the body's defence system against microorganisms
What are platelets?	Small fragments of cells They have no nucleus Help blood clot at the site of a wound
What happens during blood clotting?	A series of enzyme-controlled reactions resulting in the change of fibrinogen to fibrin Forms a network of fibres trapping blood cells and forming a clot
What are antigens?	Proteins on the surface of cells
What happens in an organ transplant?	A diseased organ is replaced with a healthy one from an donor
Why might the recipient's antibodies attack the antigens on the donor organ?	They do not recognise them as part of the recipient's body
What can you do to prevent rejection of the transplanted organ?	A donor organ with a 'tissue type' similar to that of the recipient is used The recipient is treated with drugs that suppress their immune system
What are the advantages of treating organ failure by mechanical devices or transplant?	Better quality of life Better health
What are the disadvantages of treating organ failure by mechanical devices or transplant?	Organ transplants in short supply Some people think it is unethical Increase risk of infection Might not work because the immune system may reject it
What are the four main types of human blood?	O A B OB
Which blood group is the universal donor?	Blood group O
What is the need for blood typing?	Important to match the blood group of the donated blood to the patient for a blood transfusion to be successful Unsuccessful blood transfusions can lead to agglutination
Which antigens are present in which red blood cells?	Antigen A is present in: A and AB Antigen B is present in: B and AB
Which antibodies are present in which red blood cells?	Anti-A antibody is present in: B and O Anti-B antibody is present in: A and O
Which red blood cells are compatible with each other?	A is compatible with A and AB B is compatible with B and AB AB is compatible with AB O is compatible with all of them

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