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PHSL 232 > L9 > Flashcards

L9 Flashcards

1
Q

what is the structure of a capillary wall

A

a basement membrane and a endothelial cell layer

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2
Q

what is the primary function of the capillaries

A

Primary function: exchange of nutrients and metabolic end products

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3
Q

do capillaries have smooth muscle associated with them

A

no but endothelial cells still contain actin/myosin

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4
Q

what % of total blood volume is in the capillaries

A

6%

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5
Q

how is capillary circulation adaptable

A

there are several routes between arterioles and venules.

the pathway that the RBC take is controlled by local metabolic factors
precapillary sphincters and metarterioles

main factor is metabolic demands

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6
Q

what are precapillary sphincters

A

bands of smooth muscle in the capillaries

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7
Q

what are metarterioles

A

i think they are the bits of capillary that blood can be shunted down

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8
Q

how big is the capillary network

A

it is very dense and is so big that in a adult they extend 40 000km

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9
Q

what is angiogenesis

A

increased capillary networks

it is a way that the body adapts to meet metabolic demands

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10
Q

what is the purpose of angiogenesis

A

increased capillaries = reduced diffusion distance

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11
Q

what is the relationship between angiogenesis and cancer cells

A

it enables the growth of cancer

this is because cancer cells have high metabolic demands. if the cancer cells are close to the capillaries then they send signals for more capillaries to be formed.

the increases capillary number means that the cancer cells have more nutrients for their metabolic demands allowing then to grow

A new therapy is working to try and stop the capillary growing to starve the cancer cells

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12
Q

what forces regulate fluid exchange across the capillary

A

starling’s forces

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13
Q

what are starling’s forces

A

capillary hydrostatic pressure (perfusion pressure)

interstitial hydrostatic pressure

capillary osmotic force due to plasma protein concentration (albumina)

intestinal osmotic force due to interstitial fluid protein concentration

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14
Q

which of starlings forces drive fluid out of the capillaries

A

capillary hydrostatic pressure (perfusion pressure)

and

osmotic force due to interstitial fluid protein concentration (interstitial osmotic force)

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15
Q

which of starlings forces drive fluid into of the capillaries

A

interstitial hydrostatic pressure

osmotic force due to plasma protein concentration (albumina) (osmotic capillary)

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16
Q

how d you find out what direction (the balance) fluid is moving in

A

ballance = out - in

capillary hydrostatic pressure and osmotic force due to interstitial fluid protein concentration

interstitial hydrostatic pressure and osmotic force due to plasma protein concentration

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17
Q

what are the most important determinants of fluid movement

A

capillary hydrostatic pressure and osmotic force due to plasma protein concentration

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18
Q

what is the resting value for capillary hydrostatic pressure in the arterioles

A

35 mmHg out

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19
Q

what is the resting value for interstitial hydrostatic pressure in the arterioles

A

0 mmHg

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20
Q

what is the resting value for osmotic force due to plasma protein concentration in the arterioles

cappilary osmotic pressure

A

28 mmHg into

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21
Q

what is the resting value for osmotic force due to interstitial fluid protein concentration in the arterioles

interstitial osmotic force

A

3 mmHg out

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22
Q

what is the balance of H2O in the arterioles

A

there is 10 mmHg pf pressure driving H2O out of the start of the capillaries

this is filtration

23
Q

what are starlings forces in the venules

A

capillary hydrostatic pressure = 15 out

osmotic force due to plasma protein concentration = 28 in

interstitial hydrostatic pressure = 0

osmotic force due to interstitial fluid protein concentration = 3 out

24
Q

what is the balance of H2O in the venioles

A
  • 10 mmHg in

this is re(absorption)

25
Q

why are there different pressures at the different ends of the capillaries

A

because pressure drops as you move through the ventricular system

26
Q

what is the major determinant of capillary hydrostatic pressure

A

resistance in the small arterioles upstream

when they dilate there is a decrease in resistance therefore an increased in hydrostatic pressure causing a higher pressure for fluid to move out of the capillary

opposite for constriction

27
Q

what is net filtration

A

the collection of fluid in the interstitial space

28
Q

is fluid exchange equal

why

A

no

you need to have a balance otherwise we would become swollen

absorption and filtration are tissue specific

eg kidneys have net filtration and lungs are net absorption

29
Q

what is it called when you have damaged or ineffective lymphatics

A

lymphedema

30
Q

how do we not have pooling of the fluid

A

because of the lymphatic system

31
Q

what is the lymphatic system

A

Drain excess interstitial fluid back into systemic circulation

It puts fluid back into the circulatory system just before the heart

32
Q

what is the role of veins and venules

A

Collect blood from capillaries and take back to the heart

33
Q

what is the structure of the veins

A

The veins have a little bit of fibrotic tissue around the outside

As you get to the larger ones then you start to get that elastic tissues back

The thickness if the walls in the veins are very thin

34
Q

what % of TBV resides in the veins

A

40%

35
Q

what are the characteristics of the veins

A

they are low pressure and low resistance system

they are the compliant vessels therefore they are the volume reservoir

36
Q

explain why the veins are so compliant

A

The thin walls of the veins are really stretchy therefore highly compliant

Small increases in pressure lead to big changes in volume therefore they are able to accommodate for lots of blood

37
Q

what is the plateau phase in vascular compliance

A

Large increase in pressure = small increase volume

near max volume therefore they cant stretch anymore

38
Q

the arteries are also complaint vessels. why are they not know as the compliance vessels

A

because the veins are more compliant

the arteries need very high pressures to stretch i the same way that veins do

veins are 10x more compliant

39
Q

what % of blood is in the venous system

A

60% in the venous system

40% in the veins and 20% in the venioles

40
Q

what is the determinant of pressure i the venous system

A

we know that the pressure from the heart decreases over distance

the pressure in the venous system is from the amount of volume that is in that system (60%)

the sympathetic nervous system also has an effect

41
Q

what is the effect of the sympathetic nervous system on venous pressure

A

SNS release noradrenaline which acts on a1 adrenergic receptors which causes venoconstriction

In the veins with vENoconstriction you get an increase in flow above the vASoconstriction whereas in the arteries you get a decrease in flow below the constriction

42
Q

what effect does venous pressure have on the heart

A

venous pressure determines venous return

the more blood going into the heart = more blood coming out of the heart

therefore increase in venous pressure increases CO

this is starlings law

43
Q

what is an external factor that has a major effect on determining venous pressure

A

posture

when you are lying down the effect of gravity is balanced across the body therefore venous pressure is balanced

when you are standing up the different parts of the body are at different heights therefore the effect of gravity is different therefore venous pressure increases below the heart

44
Q

how do we overcome venous pooling

A

Unidirectional valves in veins and the skeletal muscle pump and the respiratory pump

45
Q

how to the valves help us to overcome gravity

A

the ensure that the blood flows towards the heart as they split the veins into mini columns which reduce the effect of gravity

46
Q

how does the skeletal muscle pump work

A

The veins are compressible and they run through the muscles

When the muscles contract they squeeze the veins which push the blood back up the the heart

valves prevent backflow

47
Q

what overrules the skeletal muscle pump

A

thermoregulation

this changes the blood distribution as the cutaneous veins in the extremities dilate and blood is redirected to the skin

48
Q

explain the respiratory pump

A

You can increase venous return by taking deep breaths

when you inhale the diaphragm contracts which decreases intrathoracic pressure and increases intra abdominal pressure.

this pulls blood in the thoracic vena cava and compresses abdominal vena cava therefore increasing venous return

this is the opposite for exhalation

this is important during exercise

49
Q

Venoconstriction causes:

A: no change in venous return

B: an increase in venous return

C: a decrease in venous return

D: a increase in arterial pressure

A

B

50
Q

The movement of water across the capillary wall is determined by the balance between capillary hydrostatic pressure and capillary colloid osmotic pressure

BECAUSE

a major determinant of
capillary pressure is the amount of resistance in the small arterioles.

A

both statements are true but not causal

NOTE they are related but because the question does not say anything about the direction they are not causal (it would also depend on what they said about the direction)

51
Q

The walls of the capillaries are made of:

A: endothelium

B: endothelium and smooth muscle cells

C: endothelium, smooth muscle and elastic connective tissue

D: endothelium and fibrous connective tissue

A

A

future hayley- is it not D??

52
Q

The skeletal muscle pump increases venous return

BECAUSE

sympathetic nerve activity induces contraction of the smooth muscle cells to constrict the veins.

A

both statements are true but not causal

53
Q

Vasodilation of arterioles facilitates fluid reabsorption from the capillaries

BECAUSE

increased arteriole resistance decreases capillary hydrostatic pressure.

A

the first is false and the 2nd is true

PHSL 232 (30 decks)

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