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Biology AS > 8.2 Blood vessels > Flashcards

8.2 Blood vessels Flashcards

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1
Q

What are the 5 components of an artery, starting from the outside working inwards?

A

1) tough collagenous outer layer
2) muscle layer
3) elastic layer
4) endothelium
5) lumen

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2
Q

What are elastic fibres? How do they help blood vessels function?

A

Composed of elastin, can stretch and recoil to provide blood vessel walls with flexibility

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3
Q

What does smooth muscle do in blood vessels?

A

Contracts or relaxes, which alters the size of the lumen (channel within the blood vessel)

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4
Q

What does collagen provide blood vessels with?

A

Structural support to maintain the shape and volume of the vessel.

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5
Q

In which direction do arteries carry blood?

A

Away from the heart to the tissues of the body

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6
Q

Do arteries carry oxygenated or deoxygenated blood?

A

Oxygenated blood

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7
Q

Are there any exceptions where arteries carry deoxygenated blood?

A

Yes;

  • pulmonary artery carrying deoxygenated blood from the heart to the lungs
  • umbilical artery during pregnancy carrying deoxygenated blood from the fetus to the placenta
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8
Q

Is blood in the arteries under lower pressure than it is in the veins? (Yes/No)

A

No - it is under higher pressure

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9
Q

How do elastin fibres help in arteries?

A

Enable them to withstand the force of the blood pumped out of the heart and can stretch to take the larger blood volume

(stretching is restricted within limits maintained by collagen)

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10
Q

What do elastin fibres do in arteries inbetween the contractions of the heart?

A

They recoil and return to their original length to help even out the surges of blood pumped from the heart to give a continuous flow.

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11
Q

Can the arteries completely eliminate the feeling of a pulse when the heart contracts? (Yes/No)

A

No - a pulse can still be felt

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12
Q

What about the endothelium in an artery allows blood to flow easily over it?

A

The endothelium is smooth

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13
Q

What do arterioles link?

A

The arteries and the capillaries

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14
Q

How are arterioles different to arteries?

A

Arterioles have more smooth muscle and less elastin in their walls due to having little pulse surge, but can constrict or dilate to control the flow of blood into different organs

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15
Q

When the smooth muscle in the arteriole contracts, what does it constrict?

A

The vessel - this prevents blood flowing into a capillary bed

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16
Q

When smooth muscle in the wall of an arteriole relaxes where does blood flow?

A

Through into the capillary bed

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17
Q

What is the process of the arterioles contracting and relaxing called?

A

Vasodilation

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18
Q

How wide is the aorta compared to a medium-sized artery and an arteriole?

A

Aorta = 2.5cm
Medium-sized artery = 0.4cm
Arteriole = 30 um (micrometers)

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19
Q

What is an aneurysm?

A

A bulge or weakness in a blood vessel

20
Q

Where are the most common places for aneurysms to occur?

A

In the aorta or in the arteries of the brain.

21
Q

Statement: Most people are not aware that they have an aneurysm until it bursts, which can prove to be very serious or indeed fatal. True of false?

A

True

22
Q

Name one factor that increases a person’s risk of having an aneurysm.

A

High blood pressure

23
Q

Scientists have discovered changes in the proportion of collagen and what other arterial component in the aorta wall that might allow for doctors to predict who is at risk of an aortic aneurysm so they can have regular aortic screening?

A

Elastin

24
Q

What are capillaries?

A

Microscopic blood vessels that link the arterioles with the venules - they form an wide network through all tissues of the body

25
Q

How small are the lumen in capillaries?

A

7.5 - 8um (micrometers); this is so small, red blood cells have to travel through in single file.

26
Q

In capillaries, where are substances exchanged?

A

Through the capillary walls between the tissue cells and the blood

27
Q

Are the gaps between the endothelial cells that make up the capillary walls in most areas of the body relatively small or relatively large? What happens in those gaps?

A

Relatively large; many substances pass out of the capillaries into the fluid surrounding the cells.

28
Q

Are there any exceptions where capillaries have very tight junctions between cells in their walls?

A

Yes - within the central nervous system

29
Q

Statement: In most organs of the body, the blood entering the capillaries from the arterioles is deoxygenated. True or false?

A

False - it is oxygenated

30
Q

By the time blood leaves the capillaries for the venules, which of the 2 gases within the gas exchange system is there less/more of? Are there any exceptions?

A

Less oxygen
More carbon dioxide

Exceptions: a) lungs, b) placenta; deoxygenated blood enters capillaries, oxygenated blood leaves in the venules.

31
Q

In which 3 ways are capillaries adapted for their role?

A
  • Large surface area for substance diffusion in/out of blood
  • Relatively slow movement of blood through capillaries credited to the total cross-sectional area of the capillaries always being greater than the arteriole supplying them
  • Walls are a single endothelial cell thick; gives very thin layer for diffusion
32
Q

In what direction do veins carry blood?

A

Away from the cells of the body and into the heart?

33
Q

Do veins carry oxygenated or deoxygenated blood?

A

Deoxygenated blood

34
Q

Are there any exceptions where veins carry oxygenated blood?

A

Yes;

  • pulmonary vein carries oxygenated blood from the lungs to the heart
  • umbilical vein during pregnancy carries oxygenated blood from the placenta to the fetus
35
Q

Fill in the blank: Deoxygenated blood flows from the capillaries into very small veins called _______ and then into larger veins.

A

Venules

36
Q

What are the two main vessels carrying deoxygenated blood back to the heart?

A
  • Inferior vena cava from the lower parts of the body

- Superior vena cava from the head and upper body

37
Q

Do veins have a pulse? (Yes/No)

A

No - the surges from the heart pumping are lost as the blood passes through the narrow capillaries.

38
Q

Statement: Veins hold a small resevoir of blood - only up to 30% of our blood volume is in veins at any one time. True or false?

A

False - veins hold a large resevoir of blood, up to 60% at any given time.

39
Q

What do medium-size veins have to prevent the backflow of blood?

A

Valves

40
Q

What are the components of veinous walls, starting from the outermost layer?

A

1) tough collagenous outer layer - large quantity
2) muscle layer
3) elastic layer - relatively little
4) endothelium - smooth, thin
5) lumen - wide

41
Q

What do venules do?

A

Link capillaries with veins; they have very thin walls with just a little smooth muscle.

42
Q

Complete the sentence: Several venules join to form a ____.

A

Vein

43
Q

What are the relative proportions of large veins, medium sized veins and venules?

A

Large veins = >1cm
Medium sized veins = <1cm
Venules = 0.1mm

44
Q

Why must deoxygenated blood in the veins be returned to the heart?

A

So that it can be pumped to the lungs and re-oxygenated.

45
Q

Which 3 adaptations of veins have allowed the blood to move against gravity whilst still at a low pressure?

A
  • one-way valves that prevent backflow
  • muscle contractions squeezing blood to the heart
  • chest breathing movements act as a pump

Biology AS (148 decks)

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