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A Level Biology: Mass transport > 7.6 - Blood vessels and their functions > Flashcards

7.6 - Blood vessels and their functions Flashcards

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1
Q

what are the 4 different types of blood vessels

A
  • Arteries
  • Arterioles
  • capillaries
  • Veins
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2
Q

what is the function of the arteries

A

Carry blood away from the heart and into the arterioles

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3
Q

what is the function of the arterioles

A

are smaller arteries that control blood flow from arteries to capillaries

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4
Q

what is the function of the capillaries

A

tiny vessels that link arterioles to veins

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5
Q

what is the function of the veins

A

carry blood from capillaries back to the heart

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6
Q

do all the blood vessels have the same structure

A
  • no
  • however they all have the same basic layered structured from outside inwards
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7
Q

describe the basic layered structure of all the blood vessels

A
  • tough fibrous outer layer: resists pressure changes from within and outside
  • muscle layer: contracts to control the flow of blood
  • elastic layer: helps to maintain blood pressure by stretching and springing back (recoiling)
  • Thin inner lining (endothelium): which is smooth to reduce friction and thin to allow diffusion
  • Lumen: central cavity of the blood vessel through which blood flows
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8
Q

draw a diagram of an artery, vein and capillary. Make sure to include labels of the individual layers

A
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9
Q

why do arteries need to be adapted to their function

A
  • they have to transport blood rapidly under high pressure from the heart to the tissues
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10
Q

what are some of the artery’s adaptations for its functions

A
  • thick muscle layer (compared to veins)
  • thick elastic layer (compared to veins)
  • greater overall thickness of wall
  • no valves
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11
Q

describe how the adaptation of a ‘thick muscle layer’ is related to the artery’s function

A
  • means the smaller arteries can be constricted and dilated in order to control the volume of blood passing through the,
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12
Q

describe how the adaptation of a ‘thick elastic layer’ is related to the artery’s function

A
  • because it’s crucial that blood pressure = high in the arteries so that blood can reach all around the body
  • the elastic wall can be stretched during systole
  • and then spring back during diastole
  • this stretching and recoil action helps to maintain high pressure and smooth pressure surges created by the beating of the heart
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13
Q

describe how the adaptation of a ‘greater overall thickness of wall’ is related to the artery’s function

A

to resist the vessel bursting under pressure

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14
Q

describe how the adaptation of ‘no valves’ is related to the artery’s function

A

(except in the arteries leaving the heart)
- because blood is under constant high pressure due to the heart pumping blood into the arteries
- it doesn’t tend to flow backwards, and there’s no need for a valve to prevent backflow

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15
Q

why do arterioles need to be adapted for their function

A
  • they carry blood under lower pressure than the arteries, from the arteries –> capillaries
  • they also control the flow of blood between the 2
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16
Q

what are some of the Arteriole’s adaptations of the for its functions

A
  • thicker muscular layer (than in the arteries)
  • thinner elastic layer (than in the arteries)
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17
Q

describe how the adaptation of a ‘Thicker muscular layer’ is related to the arteriole’s function

A
  • the contraction of this muscle layer allows the constriction of the lumen of the arteriole
  • this restricts blood flow and so controls the movement of blood into the capillaries that supply tissues with blood
18
Q

describe how the adaptation of a ‘thinner elastic layer’ is related to the arteriole’s function

A

because blood pressure is lower

19
Q

why do the veins need to adapted for their function

A
  • veins need to transport blood slowly, under low pressure
  • from the capillaries in tissues to the heart
20
Q

what are some of the vein’s adaptations for its functions

A
  • thin muscular layer (compared to arteries)
  • thin elastic layer (compared to arteries)
  • overall thickness of the wall is small
  • the are valves at intervals throughout
21
Q

describe how the adaptation of ‘thin muscular layer’ relates to the function of the veins

A
  • because the veins carry blood away from the tissues and therefore their constriction and dilation can’t control the flow of blood to the tissues
22
Q

describe how the adaptation of a ‘thin elastic layer’ relates to the function of the veins

A
  • because the low pressure of blood will not cause them to burst and pressure is too low to cause a recoil action
23
Q

describe how the adaptation of a ‘smaller overall thickness of the wall’ relates to the function of the veins

A
  • there’s no need for a thick wall as the pressure in the veins won’t cause them to burst
  • pressure is too low to create a recoil action
24
Q

describe how the adaptation of a ‘having valves at intervals throughout’ relates to the function of the veins

A
  • ensures that blood doesn’t flow backwards, which it might otherwise do because the blood pressure is so low
  • when body muscles contract, veins are compressed, pressurising the blood within them
  • the valves ensure that this pressure directs the blood in 1 direction only (to the heart)
25
Q

why do capillaries need to adapted for its function

A
  • they need to exchange metabolic materials such as oxygen, carbon dioxide and glucose between the blood and the cells of the body
  • blood flow is slow
26
Q

what are some of the adaptations of the capillaries for its functions

A
  • the walls consist mostly of the lining layer
  • they are numerous and highly branched
  • narrow diameter
  • lumen in narrow
  • spaces between the lining (endothelial) cells
27
Q

describe how the adaptation of a ‘wall consisting mostly of the lining layer’ is related to the capillary’s functions

A
  • makes them extremely thin, creates a short diffusion pathway
  • allowing for rapid diffusion of materials between the blood and the cells
28
Q

describe how the adaptation of ‘numerous and highly branched’ is related to the capillary’s functions

A

provides a large SA for exchange

29
Q

describe how the adaptation of ‘narrow diameter’ is related to the capillary’s function

A
  • to permeate tissues, which means that no cells is far from a capillary and there is a short diffusion pathway
30
Q

describe how the adaptation of ‘narrow lumen’ is related to the capillary’s function

A
  • so red blood cells are squeezed flat against the side of the capillary
  • bringing them even closer to the cells that they supply oxygen to
  • reducing the diffusion distance
31
Q

describe how the adaptation of ‘spaces between the lining (endothelial) cells’ is related to the capillary’s function

A

it allows white blood cells to escape in order to deal with infections within tissues

32
Q

what are all the molecules that tissue fluid contains, why does it contain them?

A

it is a watery liquid that contains:
- glucose
- amino acids
- fatty acids
- ions in solution
- oxygen
—-> to supply tissues with these substances

33
Q

what is tissue fluid formed from

A

formed from blood plasma

34
Q

describe how tissue fluid is pushed out the capillaries

A
  • How much liquid leaves the plasma to form tissue fluid depends on two opposing forces:
    1) When blood is at the arterial end of a capillary, the hydrostatic pressure is great enough to push molecules out of the capillary
    2) Proteins remain in the blood; the increased protein content creates a water potential between the capillary and the tissue fluid
  • However, overall movement of water is out from the capillaries into the tissue fluid
  • At the venous end of the capillary, less fluid is pushed out of the capillary as pressure within the capillary is reduced
  • The water potential gradient between the capillary and the tissue fluid remains the same as at the arterial end, so water begins to flow back into the capillary from the tissue fluid
  • Overall, more fluid leaves the capillary than returns, leaving tissue fluid behind to bathe cells
35
Q

describe the result of the pressure pushing tissue fluid out the capillaries

A
  • the pressure is only enough to force small molecules out of the capillaries, leaving all cells and proteins in the blood because these are too large to cross the membranes
  • this type of filtration under pressure is called ultrafiltration
36
Q

what happens once tissue fluid has exchanged metabolic materials with the cells it bathes

A
  • it’s returned to the circulatory system
  • most tissue fluid returns to the blood plasma directly via the capillaries
37
Q

describe the process by how tissue fluid returns to the blood plasma via the capillaries

A
  • the loss of tissue fluid from the capillaries reduces the hydrostatic pressure inside them
  • as a result, by the time the blood has reached the venous end of the capillary network its hydrostatic pressure is usually lower than that of the tissue fluid outside it
  • therefore tissue fluid is forced back into the capillaries by this gradient
  • in addition, the plasma has lost water and still contains proteins. It therefore has a lower water potential than the tissue fluid
  • As a result, water leaves the tissue by osmosis down a water potential gradient
38
Q

does all tissue fluid get returned to the capillaries

A
  • no
  • the remainder is carried back via the lymph capillaries in the form of lymph
39
Q

describe the lymph capillaries

A
  • The lymph capillaries are separate from the circulatory system
  • They have closed ends and large pores that allow large molecules to pass through
  • The lymph eventually reenters the bloodstream through lymph capillaries —> veins located close to the heart
40
Q

describe how contents of lymph are formed

A
  • Larger molecules that are not able to pass through the capillary wall enter the lymphatic system as lymph
  • Small valves in the vessel walls are the entry point to the lymphatic system
  • The liquid moves along the larger vessels of this system by compression caused by body movement. Any backflow is prevented by valves
41
Q

Why is it important that any plasma proteins that have escaped from the blood are returned to the blood via the lymph capillaries

A

If plasma proteins were not removed from tissue fluid they could lower the water potential (of the tissue fluid) and prevent the reabsorption of water into the blood in the capillaries

42
Q

If blood pressure is high (hypertension) then what does this mean for the pressure at the arterial end

A
  • the pressure at the arterial end is even greater
  • This pushes more fluid out of the capillary and fluid begins to accumulate around the tissues. This is called oedema

A Level Biology: Mass transport (10 decks)

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