Mass Transport in Animals Flashcards
(101 cards)
1
Q
A
The lower the surface area to volume ration and the higher the metabolism of a multicellular organism, the greater the need for a mass transport system.
2
Q
What is mass transport?
A
- Over large distances, efficient movement of substances to and from exchange surfaces is provided by mass transport.
- Mass transport is when all substances move in the same direction at the same speed and is not diffusion as it requires a pressure gradient.
3
Q
What are some key features of mass transport systems?
A
- A suitable medium in which to transport substances. This is usually liquid or water bases as it acts as a solvent.
- A system of tubes/vessels which contain the transport medium and forms a network to distribute to all parts of the organisms (may be open or closed).
- A mechanism for moving the medium within vessels (through pressure differences).
4
Q
What is cardiac output?
A
- The volume of blood pumped by one ventricle of the heart in one minute.
- It is usually measured in dm^3 min^-1 and depends on the heart rate (the rate at which the heart beats) and the stroke volume (volume of blood pumped out at each beat).
5
Q
How do you calculate cardiac output?
A
Cardiac output = heart rate x stroke volume
(dm3 min-1) (bpm) (dm3)
6
Q
What are the different blood vessels?
A
7
Q
Describe the structure of arteries?
A
- Smaller lumen
- Smooth folded endothelium to reduce friction with blood and to allow the artery to stretch.
- Elastic tissue stretches due to high blood pressure when ventricle contracts then recoils when ventricle relaxes. This recoil helps to maintain and smooth blood pressure and therefore helps to maintain and smooth blood flow.
- Thick muscular layer to help the artery wall withstand high blood pressure.
- Tough outer protein layer withstands high blood pressure to stop bursting.
8
Q
Why do arteries have a smaller lumen?
A
9
Q
Why do arteries have a smooth folded endothelium?
A
To reduce friction with blood and to allow the artery to stretch.
10
Q
Wh6 do arteries have elastic tissue?
A
Elastic tissue stretches due to high blood pressure when ventricle contracts then recoils when ventricle relaxes. This recoil helps to maintain and smooth blood pressure and therefore helps to maintain and smooth blood flow.
11
Q
Why do arteries have a thick muscular layer?
A
To help the artery wall withstand high blood pressure.
12
Q
Why do arteries have a thick outer protein layer?
A
Withstands high blood pressure to stop bursting.
13
Q
.
A
14
Q
.
A
15
Q
Why do the aorta (an artery) and pulmonary artery both have semilunar valves?
A
To prevent the back flow of blood into the ventricles.
16
Q
What are arterioles?
A
17
Q
Describe some features of arterioles and compare them to that of arteries.
A
- Control the flow of blood into capillary beds.
- Blood is flowing under lower pressure than arteries.
- These is relatively less elastic tissue and relatively more smooth muscle.
18
Q
Describe the structure of an arteriole in comparison with an artery.
A
Arterioles have the same structure as arteries except for some differences:
- Arterioles are smaller than arteries.
- The muscle layer makes up a higher proportion of the wall of an arterioles.
- The arteriole muscle contracts to constrict the lumen (vasoconstriction) which reduces blood flow to the capillaries.
- The arteriole muscle relaxes to dilate the lumen (vasodilation) to increase blood flow to capillaries.
- The elastic layer makes up a smaller proportion of the wall of an arteriole as blood pressure in an arteriole is lower so elastic stretch and recoil is less important.
19
Q
Why are arterioles smaller than arteries?
A
20
Q
Why does the muscular layer in arterioles make up a higher proportion of the wall than in an artery?
A
21
Q
Why does the arteriole muscle contract?
A
To constrict the lumen (vasoconstriction) which reduces blood flow to the capillaries.
22
Q
Why does the arteriole muscle relax?
A
To dilate the lumen (vasodilation) to increase blood flow to capillaries.
23
Q
Why does the elastic layer make up a smaller proportion of the wall of an arteriole than of an artery?
A
Blood pressure in an arteriole is lower so elastic stretch and recoil is less important.
24
Q
check What are precapillary sphincters?
A
They can open and close to increase blood flow to the skin when you feel hot
25
Describe the structure of veins.
- The muscle layer is relatively thin compared to arteries.
- The elastic layer is relatively thin compared to arteries.
- The overall thickness of the wall is small.
- There are valves at intervals throughout.
- The lumen is wider than that of arteries.
- Also have a smooth endothelium.
26
Why is the muscles layer in veins relatively thin compared to arteries?
Veins carry blood away from tissues and therefore their constriction and dilation can’t control the flow of blood to the tissues.
27
Why is the elastic layer in veins relatively thin compared to arteries?
The low blood pressure within the veins will not cause them to burst and the pressure is too low to create recoil action.
28
Why is the overall thickness of the wall small in veins compared to arteries?
- The pressure is too low to create any risk of bursting.
- It allows them to be flattened easily, aiding the flow of blood within them.
29
Why do veins have valves at intervals throughout?
To ensure that blood does not flow backwards, which it might otherwise do as the pressure is so low. As body muscles contract, veins are compressed, pressurising the blood within them. The valves ensure this pressure directs the blood towards the heart.
30
Why are the lumens of veins wider than that of arteries?
Allows veins to carry a larger volume of blood.
31
Why do veins also have a smooth endothelium?
To reduce friction with the blood.
32
.
33
***check*** What is the function of capillaries?
Capillaries allow the exchange of substances between blood and the surrounding tissues.
34
Describe the structure of capillaries.
- Endothelium is one cell thick
- Endothelium cells are flattened.
- Narrow lumen
- Small diameter
- Pores between endothelial cells
35
Why is the endothelium one cell thick in capillaries?
***So*** diffusion pathway is short.
36
Why are the endothelium cells flattened in capillaries?
***So*** diffusion pathway is short.
37
Why do capillaries have a narrow lumen?
- Increases friction and therefore reduced rate of good flow ***so*** there is more time for diffusion.
- Red blood cells are in close contact with the endothelium (pass through in single file) ***so*** diffusion oat heat for oxygen is short.
38
Why do capillaries have a small diameter?
***So*** large surface area to volume ratio.
39
Why do capillaries have pores between endothelial cells?
Allow water and certain dissolved substances to leak out of blood and form tissue fluid.
40
Why do capillaries have pores between endothelial cells?
Allow water and certain dissolved substances to leak out of blood and form tissue fluid.
41
.
42
What are networks of capillaries in tissues called?
Capillary beds
43
.
44
.
45
.
46
.
47
.
48
.
49
.
50
.
51
What is the heart wall made of?
Myocardin
52
What are myogenic cells?
They can beat spontaneously without the need of any nerves to stimulate it.
53
What are the four chambers of the heart?
- Left atrium
- Right atrium
- Left ventricle
- Right ventricle
54
What is the septum?
The wall separating the right and left sides of the heart (after birth, the blood from the right and left sides so not mix).
55
What side of the heart pumps deoxygenated blood?
Right
56
What side of the heart pumps oxygenated blood?
Left
57
Why does the left ventricle have a thicker, more muscular wall than the right ventricle?
The left needs to contract powerfully to pump blood all the way around the body whereas the right side only needs to get blood to the nearby lungs.
58
Why do the ventricles have thicker walls than the atria?
The ventricles need to push blood out of the heart whereas the atria just need to push blood a short distance into the ventricles.
59
What are the different valves in the heart called?
- Atrioventricular
- Semilunar
60
What are the two atrioventricular valves called?
- Bicuspid valve
- Tricuspid valve
61
What side of the heart is the bicuspid valve on?
Left
62
What side of the heart is the tricuspid valve on?
***Ri***ght
63
What is the role of atrioventricular valves?
They link the atria to the ventricles and prevent the back flow of blood from ventricles into the atria when the ventricles contract.
64
Which side of the heart are the semi-lunar valves found?
Both the left and the right
65
What is the role of the semi-lunar valves?
They link the ventricles to the pulmonary artery and aorta and prevent the back flow of blood from the arteries back into the ventricles after the ventricles contract.
66
.
67
.
68
.
69
What is the cardiac cycle?
The time taken for one complete heartbeat.
70
Describe the importance of pressure gradients on the transport of blood.
- Blood circulation by the heart relies on pressure gradients.
- Blood always moves down a pressure gradient (high to low pressure).
71
When is high pressure within a chamber of the heart achieved?
1. The chamber fills with blood.
2. The muscles of the chamber wall contract.
72
What causes valves to open and close?
The differences in pressure between compartments.
73
What are the three stages of the cardiac cycle?
- Atria contract, ventricles relax (Atrial systole)
- Atria relax, ventricles contract (Ventricular systole)
- Atria relax, ventricles relax (Diastole)
74
What happens during atrial systole?
- The ventricles are relaxed.
- The atria contract, decreasing the volume of the chambers and increasing the pressure inside the chambers pushing the blood into the ventricles.
- The atrioventricular valves are open.
- The semi-lunar valves are closed.
75
Are the atrioventricular valves open or closed during atrial systole?
Open
76
Are the semi-lunar valves open or closed during atrial systole?
Closed
77
What happens during ventricular systole?
- Atria relax.
- Ventricles contracts (decreasing their volumes), increasing their pressure.
- The pressure becomes higher in the ventricles than in the atria so the atrioventricular valves shut to prevent back-flow.
- The pressure becomes higher in the ventricles than in the aorta / pulmonary artery so the semi-lunar valves open and blood is forced out into these arteries.
78
Are the atrioventricular valves open or closed during ventricular systole?
Closed
79
Are the semi-lunar valves open or closed during ventricular systole?
Open
80
What happens during diastole?
- The ventricles and atria relax.
- The pressure in the pulmonary artery / aorta is greater than the pressure in the ventricles so the semi-lunar valves close to prevent back-flow into the ventricles.
- Blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and pulmonary vein. This starts to increase the pressure of the atria.
- As the ventricles continue to relax, their pressure falls below the pressure of the atria and so the atrioventricular valves open allowing blood to flow passively into the ventricles.
- The atria then contract, causing the whole process to begin again.
81
Are the atrioventricular valves open or closed during diastole?
Open
82
Are the semi-lunar valves open or closed during diastole?
Closed
83
Why is it important that one valve always shuts before the other one opens?
84
What arteries supply the cardiac muscle with oxygen?
Coronary arteries
85
What happens when the coronary arteries become completely blocked?
- The muscle cells supplied by the blocked vessels are deprived of glucose and oxygen so can’t respire is they die.
- This causes a myocardial infarction (more commonly known as a heart attack).
86
Define atherosclerosis.
Plaques form in the coronary arteries, reducing blood flow.
87
Describe atheroma formation.
- If damage occurs to the endothelium in the wall of an artery, white blood cells and lipids from the blood clump together under the lining to form fatty streaks.
- Over time, more white blood cells, lipids and connective tissue builds up and harden to form a fibrous plaque called an atheroma.
- This plaque will partially block the lumen of the artery restricting blood flow which leads blood pressure to increase.
88
What is an aneurysm?
A ballon-like swelling of the artery.
89
Describe how an aneurysm occurs.
- It starts with the formation of atheromas which damage and weaken arteries as well as narrowing the lumen which leads to an increase in blood pressure.
- When blood travels through weakened arteries at a high pressure it may push the inner layers of the artery though the outer elastic layer to form an aneurysm.
- This aneurysm may burst, causing a haemorrhage (bleeding).
90
What is caused when an aneurysm bursts?
Haemorrhage (bleeding)
91
Define thrombosis.
The formation of a blood clot.
92
How does thrombosis occur?
- It starts with the formation of atheromas which can rupture the endothelium of an artery.
- This damages the artery wall and leaves a rough surface.
- Platelets and fibrin (a protein) accumulate at the site if damage and form a blood clot (a thrombus).
- This blood clot can cause a complete blockage of the artery or it can become dislodged and block a blood vessel elsewhere is the body. Debris from the rupture can also cause another blood clot to form further down the artery.
93
What can a heart attack cause?
- Damage and death to the heart muscle.
- If larger areas of the heart muscle are affected them complete heart failure can occur, which is often fatal.
94
What are the symptoms of a heart attack?
- Pain in the chest and upper body
- Shortness of breath
- Sweating
95
What are some risk factors for cardiovascular disease?
- Smoking
- High blood cholesterol
- Diabetes
- Diet and obesity
- High blood pressure
96
How does smoking increase the risk of cardiovascular disease?
- Cigarette smoke contains nicotine and carbon monoxide which both increase the risk of cardiovascular disease and myocardial infarction:
- Nicotine increases the risk of high blood pressure
- Carbon monoxide combines with haemoglobin which reduced the amount of oxygen transported in the blood so reduced the ammonia of oxygen available to tissues. If the heart muscle doesn’t receive enough oxygen it can lead to a heart attack.
- Smoking also decreases the amount of antioxidants in the blood which are important for protecting cells from damage. Fewer antioxidants means cell damage in the coronary artery walls is more likely which can lead to atheroma formation.
97
How does high blood cholesterol increase the risk of cardiovascular disease?
- Cholesterol is one of the main constituents of the fatty deposits that form atheromas.
- Atheromas can lead to increased blood pressure and blood clots. This could block blood flow to the coronary arteries which could cause a myocardial infarction.
98
How does diabetes increase the risk of cardiovascular disease?
- Both type 1 and type 2 diabetes significantly increase the risk of cardiovascular disease:
- The high blood glucose concentration lowers the water potential of the blood which causes more water to move into the blood vessels by osmosis meaning there is a larger volume of blood within the circulatory system causing blood pressure to increase.
99
How does obesity increase the risk of cardiovascular disease?
Obesity contributes directly to other cardiovascular risk factors including type 2 diabetes, high blood pressure and high cholesterol.
100
How does poor diet increase the risk of cardiovascular disease?
- A diet high in saturated fat is associated with high blood cholesterol levels.
- A diet high in salt increased the risk of high blood pressure.
101
How does high blood pressure increase the risk of cardiovascular disease?
- High blood pressure increased the risk of damage to the artery walls.
- Damaged walls have an increased risk of atheroma formation, causing a further increase in blood pressure.
- Atheromas can also cause blood clots to form.
- A blood clot could block blood flow to the heart muscle, possibly resulting in myocardial infarction.
