The Circulatory System Flashcards
1
Q
What type of circulatory system do mammals have
A
A closed, double circulatory system
2
Q
What does having a closed, double circulatory system mean
A
Blood is confined to vessels and passes twice through the heart for each complete circuit of the body.
3
Q
Why do mammals have a double circulatory system
A
- When blood passes through the lungs, its pressure is reduced.
- If it were to pass immediately to the rest of the body its low pressure would make circulation very slow.
- Blood is therefore returned to the heart to increase its pressure before being circulated to the tissues and as a result, substances are delivered quickly to the body.
- This is necessary as mammals have a high body temperature and therefore high rate of metabolism.
4
Q
What are the four types of blood vessels found ion the circulatory system
A
Arteries, Arterioles, Veins and capillaries.
5
Q
Which side of the heart pumps oxygenated blood
A
The left side of the heart
6
Q
Which side of the heart pumps deoxygenated blood
A
The right side
7
Q
Does the left side of the heart pump oxygenated or deoxygenated blood
A
Oxygenated blood
8
Q
Does the right side of the heart pump oxygenated or deoxygenated blood
A
Deoxygenated blood.
9
Q
Describe the two chambers found on each side of the heart
A
- The atria which are thin walled and elastic and stretches as they collect blood.
- The ventricles which have a much thicker muscular wall as they have to contract strongly to pump blood some distance, either to the lungs or the rest of the body.
10
Q
Explain why the heart is made up of two separate pumps (so forms double circulatory system)
A
- Blood has to pass through tiny capillaries in the lungs in order to present a large surface area for the exchange of gases.
- When this occurs, there is a very large drop in pressure and so the blood flow to the rest of the body would be very slow (If it didn’t return to the heart).
- Therefore the blood returns to the heart to increase its pressure before being distributed to the rest of the body.
11
Q
Which atrioventricular valve is the bicuspid valve
A
The left atrioventricular valve.
12
Q
Which atrioventricular valve is the tricuspid valve
A
The right atrioventricular valve.
13
Q
What do arteries do
A
Pump blood away from the heart
14
Q
What do veins do
A
Carry blood back into the heart.
15
Q
What are the four blood vessels connected to each chamber of the heart
A
Aorta, Vena Cava, Pulmonary artery, Pulmonary vein.
16
Q
Which chamber of the heart is the aorta connected to
A
The left ventricle
17
Q
Which chamber of the heart is the vena cava connected to
A
The right atrium
18
Q
Which chamber of the heart is the pulmonary artery connected to
A
The right ventricle
19
Q
Which chamber of the heart is the pulmonary vein connected to
A
The left atrium
20
Q
Describe the function of the aorta
A
- The aorta is connected to the left ventricle
- It carries blood to all parts of the body except the lungs.
21
Q
Describe the function of the vena cava
A
- The vena cava is connected to the right atrium.
- It carries deoxygenated blood back from the body tissues to the heart.
22
Q
Describe the function of the pulmonary artery
A
- The pulmonary artery is connected to the right ventricle.
- It carries deoxygenated blood back to the lungs where its oxygen is replenished and carbon dioxide removed.
23
Q
Describe the function of the pulmonary vein.
A
-The pulmonary vein is connected to the left atrium.
- It brings oxygenated blood from the lungs back to the heart.
24
Q
What are the semi-lunar valves
A
- The semi-lunar valves are found in the aorta and pulmonary artery.
- They prevent the back flow of blood into the ventricles.
25
Describe the function of the coronary arteries
- The coronary arteries supply the heart muscle with oxygen.
- They branch off the aorta shortly after it leaves the heart.
26
What is a myocardial infarction and what causes it
- A heart attack
- Caused by a blockage of the coronary arteries.
- This results in the heart not being supplied with blood and therefore oxygen.
27
What are the three stages in the cardiac cycle
1) Diastole
2) Atrial systole
3) Ventricular systole
28
Approximately how many times does the cardiac cycle repeat in humans when at rest
70 times a minute
29
Describe the diastole stage of the cardiac cycle
- Diastole is relaxation of the heart.
- The blood returns to the heart through the vena cava (from body) and pulmonary vein (from lungs).
- As the atria fill, the pressure in them rises.
- When this pressure exceeds that in the ventricles, the atrioventricular valves open, allowing blood to pass into the ventricles.
- The passage of blood here is aided by gravity.
- The muscular walls of both the atria and ventricles are relaxed.
- The relaxation of the ventricle walls causes them to recoil and reduces the pressure within the ventricle.
- This causes the pressure to be lower than that in the aorta and pulmonary artery, and so the semi-lunar valves in the aorta and pulmonary artery close.
30
Describe the atrial systole stage of the cardiac cycle
- Atrial systole is contraction of the atria.
- This contraction of the atrial walls, along with the recoil of the relaxed ventricle walls, forces the remaining blood into the ventricles from the atria.
- This is because the volume of the atria decrease, causing the pressure to increase and so blood is forced into the ventricles.
- Throughout this stage, the muscle of the ventricle walls remains relaxed.
31
Describe the ventricular systole stage of the cardiac cycle
- After a short delay (following atrial systole) to allow the ventricles to fill with blood, the ventricles contract.
- This increases the pressure within them which forces the atrioventricular valves to close and prevent the back flow of blood.
- With the AV valves closed, the pressure in the ventricles rises further.
- Once it exceeds that in the aorta and pulmonary artery, the semi-lunar valves open and blood is forced from the ventricles into these vessels.
32
Describe how the structure of the ventricles relates to their function
- The ventricles have thick muscular walls which means that they contract forcefully.
- This creates the high pressure necessary to pump blood around the body.
- The thick wall of the left ventricle has to pump blood to the extremities of the body while the relatively thinner wall of the right ventricle pumps blood to the lungs.
33
Describe the status of the cardiac valves during atrial systole
Atrioventricular valves: Open
Semi-lunar valves: Closed
34
Describe the status of the cardiac valves during ventricular systole
Atrioventricular valves: Closed
Semi-lunar valves: Open
35
Describe the status of the cardiac valves during diastole
Atrioventricular valves: Open
Semi-lunar valves: Closed
36
Summarise how valves in the cardiovascular system work
They open whenever the difference in blood pressure either side of them favours the movement of blood in the required direction.
37
What are the three key types of valve in the cardiovascular system
1) Atrioventricular valves
2) Semi-lunar valves
3) Pocket valves
38
Describe the function of the atrioventricular valves
- The atrioventricular valves are found between the atrial and ventricles.
- The left AV valve is bicuspid.
- The right AV valve is tricuspid
- They prevent the backflow of blood when contraction of the ventricles means that ventricular pressure exceeds atrial pressure.
- Closure of these valves ensures that, when the ventricles contract, blood within them moves to the aorta and pulmonary artery rather than back to the atria.
39
Describe the function of the semi-lunar valves
- The semi-lunar valves are found in the aorta and pulmonary artery.
- They prevent the backflow of blood into the ventricles when the pressure in these vessels exceeds that in the ventricles.
- This arises when the elastic walls of the vessels recoil, increasing the pressure within them, and when the ventricle walls relax, reducing the pressure in the ventricles.
40
Describe the function of the pocket valves
- The pocket valves are found in the veins that make up the venous system.
- These ensure that when the veins are squeezed (eg. When skeletal muscles contract), blood flows back to the heart rather than away from it.
41
Describe the basic structure of all of the valves in the circulatory system and how they work.
- They are made up of a number of flaps of tough, but flexible, fibrous tissue that are cusp shaped.
- When pressure is greater on the convex side of these cusps, rather than on the concave side, they move apart to let blood pass between the cusps.
- When pressure is greater on the concave side, rather than convex, blood collects in the ‘bowl’ of these cusps. This pushes them together to form a tight fit that prevents the passage of blood.
42
What is cardiac output
Cardiac output is the volume of blood pumped by one ventricle of the heart in one minute. It is usually measured in dm^3min^-1
43
What two factors does cardiac output depend on
- the heart rate (how fast heart beats)
- The stroke volume (volume of blood pumped out at each beat)
44
What is the equation for cardiac output
Cardiac output= heart rate x stroke volume
45
Which stage of the cardiac cycle do graphs showing the pressure changes in the heart start with
Atrial systole, then ventricular systole, then diastole
46
How should you structure an exam question asking you to describe the cardiac cycle
- contraction/relaxation of chambers.
- change in volumes
- change in pressures
- impact on valves
- blood flow
47
What are the four different types of blood vessel
- Arteries
- Arterioles
- Veins
- Capillaries
48
Briefly describe what arteries do
Carry blood away from the heart and into arterioles.
49
Describe briefly what arterioles do
Arterioles are smaller arteries that control blood flow from arteries to capillaries.
50
Describe briefly what capillaries do
Capillaries are tiny vessels that link arterioles to veins.
51
Describe briefly what veins do
Carry blood from capillaries back to the heart.
52
Which blood vessels all have the same basic layered structure
Arteries, arterioles and veins
53
Describe from outwards to inwards, the basic layers and their functions that arteries, arterioles and veins share.
1) Tough fibrous outer layer: this resists pressure changes from both inside and outside.
2) Muscle layer: This can contract and so control the flow of blood.
3) Elastic layer: This helps to maintain blood pressure by recoiling.
4) Thin inner lining (endothelium): It is smooth which reduces friction and it it is thin to allow for diffusion.
5) Lumen: this is not actually a layer but the central cavity of the blood vessel through which the blood flows.
54
How do the structure of the blood vessels differ despite having the same layers
The relative proportions of each layer differ according to the vessels function.
55
Describe the key features of an arteries structure
- The muscle layer is thick (compared to veins)
- The elastic layer is relatively thick (compared to veins)
- The overall thickness of the wall is great.
- There are no valves.
56
Explain how having a thick muscle layer compared to veins relates to an arteries function
It means that smaller arteries can be constricted and dilated in order to control the volume of blood passing through them.
57
Explain how having a relatively thick elastic layer compared to veins relates to an arteries function
- This is because it is important that blood pressure in arteries remains high so that blood can reach all extremities of the body.
- The elastic wall is stretched at each beat of the heart (systole).
- It then springs back when the heart relaxes (diastole).
- This stretching and recoil action helps to maintain high pressure and smooth pressure surges created by the beating of the heart.
58
Explain how having a thick wall relates to an arteries function
This resists the vessel bursting under pressure.
59
Explain how having no valves relates to an arteries function
Because blood is under constant high pressure due to the heart pumping it in the arteries so no back flow occurs.
60
What is the exception to arteries having no valves
The arteries that take blood from/leave the heart have valves.
61
Describe the structure of an arteriole and how this relates to its function
- The muscle layer is relatively thicker than it arteries. The contraction of this muscle layer allows the constriction of the lumen of the arteriole. This restricts the flow of blood and so controls its movement into the capillaries that supply the tissues with blood.
- The elastic layer is relatively thinner than in arteries because blood pressure is lower.
62
Describe the function of an artery
To transport blood rapidly under high pressure from the heart to the tissues.
63
Describe the function of an arteriole
Arterioles carry blood, under lower pressure than arteries, from arteries to capillaries.
64
Describe the function of veins
Veins transport blood slowly, under low pressure, from the capillaries in tissues to the heart.
65
List the key features of a veins structure
- The muscle layer is relatively thin
- The elastic layer is relatively thin
- The overall thickness of the wall is small.
- There are valves at intervals throughout.
66
Explain how having a relatively thin muscle layer relates to a veins function
The muscle layer is relatively thin (compared to arteries) because veins carry blood away from tissues and therefore their constriction and dilation cannot control the flow of blood to the tissues.
67
Explain how having a relatively thin elastic layer (compared to arteries) relates to the function of veins.
This is because the low pressure of blood within the veins will not cause them to burst and pressure is too low to create a recoil action.
68
Explain how having a thin wall relates to the function of a vein
There is no need for a thick wall as the pressure within veins is too low to create any risk of bursting. It also allows them to be flattened easily which aids the flow of blood within them.
69
Explain how having valves at regular intervals throughout them relates to the function of veins.
- valves ensure that blood does not flow backwards, which it may otherwise do as the pressure is so low.
- When body muscles contract, veins are compressed and the blood within them is pressurised.
- Valves ensure that this pressure directs the blood in one direction only: towards the heart.
70
Describe the function of capillaries
- The function of capillaries is to exchange metabolic materials such as oxygen, carbon dioxide and glucose between blood and cells of the body.
- The flow of blood is much slower to allow more time for the exchange of materials.
71
Describe the key features of the structure of capillaries
- Their walls consist mostly of the lining layer
- They are numerous and highly branched
- They have a narrow diameter
- Their lumen is very narrow
- There are spaces between the lining (endothelial cells)
72
Explain how capillary walls consisting mainly of the lining layer relates to their function
- Consisting of only the lining layer makes the capillary walls very thin, so the distance over which diffusion takes place is short.
- This allows for rapid diffusion of materials between the blood and the cells.
73
Describe how capillaries being numerous and highly branches relates to their function
It provides a large surface area for exchange.
74
Describe how having a narrow diameter relates to a capillaries function
It allows them to permeate tissues, which means that no cell is far from a capillary and there is a short diffusion pathway.
75
Describe how having a narrow lumen relates to a capillaries function
- The lumen is so narrow that red blood cells are squeezed flat against the side of a capillary.
- This means brings them even close to the cells to which they supply oxygen.
- This again reduced the diffusion distance.
76
Explain how having spaces between the lining (endothelial) cells relates to a capillaries function
These spaces allow white blood cells to escape in order to deal with infections within tissues.
77
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