Unit 2: Physiology & Health - Key Area 5/6: The Structure and Function of Arteries, Capillaries and Veins/The Structure and Function of the Heart Flashcards
Where is the pathway of blood circulation in the heart?
Blood leaves the heart in arteries, then flows through capillaries before returning to the heart in veins.
In what condition is blood when it leaves the heart?
When blood leaves the heart it is under high pressure (having been pumped out of the heart).
What happens to blood pressure when it flows away from the heart and through the circulatory system?
As the blood flows away from the heart and through the circulatory system there is a decrease in blood pressure.
Where do arteries carry blood to?
Away from the heart, to the rest of the body.
What is the structure of an artery like?
Endothelium lines the central lumen and is surrounded by layers of tissue. Arteries have an outer layer of tissue containing elastic fibres and a middle layer containing smooth muscle with more elastic fibres.
What do the elastic fibres in arteries mean for the artery and what are they needed for?
The elastic fibres mean that arteries have elastic walls which can stretch and recoil to accommodate the surge of blood after each contraction of the heart.
What can the smooth muscle in arteries do and what does this cause?
The smooth muscle can contract causing vasoconstriction or relax causing vasodilation to control blood flow.
How do the the central lumen of arteries compare to that of veins and why is this?
Arteries have a narrower central lumen than veins due to the thicker layer of muscle in arteries.
What do arteries divide into?
Arteries divide into arterioles.
Do arteries contain valves?
No.
What do capillaries allow to happen?
Capillaries allow exchange of substances with diffusion through their very thin walls.
What do veins do?
Veins carry blood back to the heart.
What is the structure of a vein like?
Veins have an outer layer of tissue containing elastic fibres and a much thinner muscular wall than arteries. Their central lumen is wider than in arteries. Veins contain valves that prevent the backflow of blood.
What are the smaller vessels that come together to form veins called?
Venules
Where is the lumen in an artery and vein?
The very centre of the artery and vein.
Where is the endothelium in an artery and vein?
The endothelium is the layer that surrounds the central lumen in an artery and vein.
Where is the muscle tissue in an artery and vein?
The muscle tissue is the middle layer of the artery and vein that surrounds the endothelium and is in between the connective tissue and endothelium.
Where is the connective tissue in an artery and vein?
The connective tissue is the outer layer of a vein and artery.
What do valves in veins do?
Prevent the back flow of blood.
What is one of the major structural differences between veins and arteries?
Veins contain valves but arteries do not.
Why do arteries not need valves but veins do?
The blood flow is under so much pressure leaving the heart that it can only flow in one direction only. Whereas in veins the blood is under very low pressure, so to prevent the back flow of blood valves are needed in veins.
What is the difference in blood arriving at the arteriole end of a capillary bed compared to the blood in the capillaries?
Blood arriving at the arteriole end of a capillary bed is at a higher pressure than blood in the capillaries.
As the blood is at a higher pressure at the arteriole end of the capillary bed what happens to the blood?
The blood is forced into the narrow capillaries, it undergoes pressure filtration.
What happens when blood undergoes pressure filtration?
Much of the plasma (liquid part of the blood) is squeezed out through the thin walls - this liquid is called tissue fluid.
What is the only difference between plasma and tissue fluid?
The only difference between plasma and tissue fluid is that plasma contains plasma proteins whereas tissue fluid does not.
Why does plasma contain plasma proteins but tissue fluid doesn’t?
The protein is too large to be filtered through the capillary walls.
What role does tissue fluid have?
Tissue fluid supplies respiring cells with glucose oxygen and other substances. Carbon dioxide and other metabolic waste diffuse out of the cells and into the tissue fluid to be excreted.
What happens to most of the tissue fluid?
It returns to the blood.
What happens to tissue fluid which does not return to the blood?
The fluid that does not return to the blood (excess tissue fluid) is absorbed by small lymphatic vessels and the fluid is now referred to as lymph.
What do the lymphatic vessels do with lymph?
The lymphatic vessels return the lymph to the circulatory system.
What is the inner lining of blood vessels called?
The endothelium.
Why do arteries need more elastic fibres than veins?
Arteries constrict and dilate more than veins, to accumulate surges of high blood pressure.
Describe vasoconstriction?
The artery wall contracts to make the size of the lumen smaller so less blood can flow through so blood pressure increases.
Describe vasodilation?
The artery muscle increases in size so that the size of the lumen increases and more blood can flow through.
What is the heart?
A muscular pump consisting of 4 chambers and various associated blood vessels.
Through what vein does deoxygenated blood arrive at the heart?
The vena cava.
Where does deoxygenated blood that has arrived at the heart from the vena cava go ?
The deoxygenated blood that has arrived at the heart through the vena cava moves into the right atrium and down into the right ventricle.
How does deoxygenated blood that is in the right ventricle get pumped out and where does this go?
When the heart contracts blood is pushed into the pulmonary artery which carries it to the lungs to be oxygenated.
