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PHA112 > The Circulatory System 4 > Flashcards

The Circulatory System 4 Flashcards

1
Q

what do blood vessels do?

A

direct flow of blood from heart to organs + tissues and back to the heart

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2
Q

what do blood vessels consist of?

A
  • arteries
  • arterioles
  • capillaries
  • venules
  • veins
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3
Q

arteries

A

carry blood away from heart to tissues

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4
Q

arterioles

A

smaller branches of arteries with organs

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5
Q

capillaries

A

smaller branches of arterioles within organs; facilitate exchanges between blood and surrounding cells

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6
Q

venules

A

formed when capillaries re-join; return blood to heart

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7
Q

veins

A

formed when venues re-join; return blood to heart

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8
Q

the walls of blood vessels are composed of up to 3 tunics. what are these?

A
  • tunic externa (adventitia)
  • tunic media
  • tunic interna (intima)
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9
Q

tunic externa (adventitia)

A

outer layer comprised of connective tissue elastin fibres

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10
Q

tunic media

A

middle layer composed of smooth muscle

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11
Q

tunic interna (intima)

A
  • innermost lining of squamous endothelium
  • basement membrane
  • layer of elastin
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12
Q

what are the main functions of the arteries?

A
  • serve as rapid-transit conduits for blood from heart to organs
  • act as pressure reservoirs
  • prov driving force for blood during diastole
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13
Q

what are the 2 main types of arteries?

A
  • elastic arteries (aorta + p.artery)
  • muscular arteries (femoral + coronary arteries)
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14
Q

elastic arteries

A
  • numerous layers of elastin fibres in vessel wall
  • expand when pressure of blood rises + recoils
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15
Q

muscular arteries

A
  • less elastic but thicker layer of smooth muscle
  • diameter changes slightly as BP rises + falls
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16
Q

what are arterioles?

A

smaller branches of arteries within organs

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17
Q

what do arterioles contain the highest % of?

A

smooth muscle

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18
Q

arterioles are the major ….. vessels

A

major

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19
Q

vessel radius supplying individual organs can be adjusted independently. give examples of this?

A
  • distribute cardiac output among systemic organs
  • depending on body momentary needs
  • helps regulate arterial blood pressure
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20
Q

control of tone of arterioles is mediated through what…

A

nervous + chemical mechanisms

21
Q

what does a large pressure drop facilitate blood flow to?

A

organs

22
Q

what is vasoconstriction caused by?

A
  • inc in myogenic activity
  • inc in oxygen (O2)
  • dec in CO2
  • inc in endothelin
  • inc in sympathetic stimulation vasopressin, angiotensin II
23
Q

what is vasodilation caused by?

A
  • dec in myogenic activity
  • dec in O2
  • inc in CO2
  • inc in nitric oxide
  • dec in sympathetic stimulation histamine release
24
Q

what are capillaries?

A

smaller + dense branches off arterioles + metarterioles within organs

25
Q

what do precapillary sphincters regulate?

A

blood flow

26
Q

there are .. main types of capillaries depending on … of pores

A

3

size

27
Q

exchange of materials largely occurs via what…

A

diffusion

28
Q

what do the very thin walls of capillaries consist of?

A

single layer of flat endothelial cell + thin basement membrane

29
Q

walls of capillaries are perforated by water filled pores. what does this permit?

A

passage of small water-soluble substances

30
Q

what are the 3 main types of capillaries?

A
  • continuous
  • fenestrated
  • discontinuous (sinusoidal)
31
Q

continuous

A
  • endothelial cells = continuous/closely joined
  • narrow intercellular pores (~4nm) permit passage of molecules
  • skeletal + cardiac muscle, lungs + adipose tissue
32
Q

fenestrated

A
  • have larger holes (20-100nm) in addition to narrow pores
  • have greater permeability + rapid exchange
  • kidneys, intestine + endocrine glands
33
Q

discontinuous (sinusoidal)

A
  • endothelial cells = discontinuous —> v large pores + leaky capillaries
  • liver, spleen + bone marrow
34
Q

what does transcytosis bring?

A

proteins and macromolecules across endothelium

35
Q

what are the 2 mechanisms of capillary exchange between blood + surrounding tissues?

A
  • passive diffusion
  • bulk flow
36
Q

what is passive diffusion?

A

movement of solutes down conc gradient

37
Q

what is bulk flow?

A

ultrafiltration + reabsorption of protein-free plasma

38
Q

what are the determinants of bulk flow?

A
  • capillary blood pressure (Pc)
  • plasma-colloid osmotic pressure (πp)
  • interstitial fluid hydrostatic pressure (Pif)
  • interstitial fluid colloid osmotic pressure (πif)
39
Q

formula for net exchange pressure?

A
40
Q

what is the venous system?

A

low resistance system that returns blood from tissue to the heart

41
Q

what does the venous system comprise of?

A
  • venules
  • small veins
  • large, systemic veins
42
Q

systemic veins

A
  • large radius –> low resistance to flow
  • thing walls with little smooth muscle/elastin –> high distensibility + little elastic recoil
  • serve as blood reservoir/capacitance vessels
  • one-way valves ensure blood flow to heart
43
Q

what does an increase in venous return lead to?

A
  • inc in end-diastolic volume
  • inc in stroke vol
  • inc in cardiac output
44
Q

what are the short term factors that facilitate an increase in venous return?

A
  • inc in blood volume
  • inc in sympathetic vasoconstrictor activity
  • respiratory pump - dec pressure in chest veins –> inc in pressure gradient
  • skeletal muscle pump - inc in venous pressure –> inc in pressure gradient
  • cardiac suction effect - dec pressure in heart –> inc in pressure gradient
  • pressure imparted to blood by cardiac contraction - inc in venous pressure –> inc in pressure gradient
45
Q

what are the relative thickness layers in endothelium walls?

A

all blood vessels same thickness

46
Q

what are the relative thickness layers in elastic fibre walls?

A

arteries have greatest thickness then veins

47
Q

what are the relative thickness layers in smooth muscle walls?

A

arteries have greatest thickness followed by arterioles AND veins

48
Q

what are the relative thickness layers of collagen fibre walls?

A

arteries have greatest thickness followed by veins and then arterioles

PHA112 (37 decks)

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