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Cardiovascular System > Session 1 - Histology of the CVS > Flashcards

Session 1 - Histology of the CVS Flashcards

0
Q

What factor has the largest effect on diffusion rate?

A

-Concentration gradient

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1
Q

What three main things effect the rate of diffusion?

A
  • Area available for exchange
  • Diffusion resistance
  • Concentration gradient
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2
Q

What determines the area available for exchange in diffusion?

A

-Capillary density (capillaries/unit volume)

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3
Q

What is the relationship between area for exchange and diffusion rate?

A

-Proportional -> increase area increase diffusion

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4
Q

What is advantageous about the branching of arterioles into capillaries?

A

-One arteriole branches into several capillaries -> increasing area for exchange

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5
Q

What is meant by diffusion resistance?

A

-The difficulty of movement through a diffusion barrier

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6
Q

What determines diffusion resistance?

A
  • Barrier nature
  • Nature of diffusing molecule
  • Diffusion pathlength
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7
Q

What is meant by the nature of the barrier when determining diffusion resistance?

A

-Whether the barrier is continuous or fenestrated

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8
Q

What is meant by the nature of the molecules when determining diffusion resistance?

A
  • Size of molecule

- Chemical properties eg lipophilic/hydrophilic

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9
Q

Will lipophilic or hyrdophilic molecules have a smaller diffusion resistance?

A

-Lipophilic as they do not need pores to diffuse (eg O2/CO2)

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10
Q

What is meant by pathlength when determining diffusion resistance?

A

-The distance/thickness of the barrier

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11
Q

What is the relationship between pathlength and the rate of diffusion

A

-Rate is proportional to (pathlength)2

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12
Q

What is the main factor in determining the concentration gradient between the capillaries and the tissues?

A

-The rate of blood flow

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13
Q

Why will a decreased blood flow decrease the concentration gradient between the capillaries and the tissues?

A

-Lower concentration of substances in the blood as it is being used by the tissues and not being replaced

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14
Q

How does an adequate flow rate help maintain concentration gradients between capillaries and tissues?

A

-Limits the amount the substrate drops by in the capillaries as the flow keeps replacing the substrate

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15
Q

What is the cardiac output, in an average male, at rest?

A

-5.0L/min

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16
Q

What is the maximum cardiac output in an average person?

A

-25L/min

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17
Q

Describe the amount of blood flow to the brain?

A

-Remains constant at 0.75L/min

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18
Q

Can bloodflow to the brain alter?

A

-No it cannot tolerate any changes

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19
Q

What is the minimum and maximum blood flow to the heart?

A

-0.3->1.2L/min

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20
Q

Describe the amount of bloodflow to the kidneys?

A

-Needs to be constant at 1.2L/min

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21
Q

What is the minimum and maximum bloodflow to the gut?

A

-1.4->2.4L/min

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22
Q

What is the minimum and maximum blood flow to skeletal muscle?

A

-1->16L/min

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23
Q

What is the minimum and maximum bloodflow to the skin?

A

-0.2->2.5L/min

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24
Q

Why does the bloodflow to the kidney need to be kept at a constant high pressure?

A

-Needed to ensure efficient filtration

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25
Q

Why can the bloodflow vary to the gut?

A

-Increased flow needed after a meal

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26
Q

Why can the bloodflow alter so much in skeletal muscle?

A

-Needed during exercise to match supply to demand of O2

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27
Q

Why can the bloodflow to the skin vary so much?

A

-Thermoregulation

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28
Q

Describe the distribution of blood in the circulation at rest

A
  • Arteries/arterioles->11%
  • Capillaries -> 5%
  • Heart and lungs -> 17%
  • Veins -> 67%
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29
Q

What are the two types of arteries?

A

-Elastic and Muscular

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30
Q

Name some large elastic arteries

A
  • Aorta and its trunks
  • Pulmoary trunk which bifurcates into L and R pulmonary arteries
  • L and R common iliac arteries
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31
Q

Describe the bloodflow in large elastic arteries near the heart

Hint: one word

A

-Pulsatile

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32
Q

Which arteries are the largest?

A

-Elastic

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33
Q

Which arteries have the widest lumen?

A

-Elastic

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34
Q

What determines bloodflow to organs?

A

-Resistance vessels (arterioles) and pre-capillary sphincters

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35
Q

Why does flow distribution need to be controlled?

A

-To restrict flow to the parts which are easily perfused and drive flow to those parts which are harder to perfuse

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36
Q

What is capacitance?

A

-Store of blood in the veins

37
Q

Why is capacitance important?

A

-Provides the ability to cope with necessary changes in CO

38
Q

Describe the lumen of veins

A

-Wide and irregular

39
Q

What are the three layers of an artery wall?

A
  • Tunica intima
  • Tunica media
  • Tunica adventitia
40
Q

Describe the tunica intima of an elastic artery

A
  • Thin
  • Endothelium running parallel to long axis
  • Subendothelial connective tissue
  • Discontinous internal elastic lamina
41
Q

Describe the tunica media of an elastic artery

A
  • Thick
  • Many smooth muscle fibres
  • Collagen
  • Many fenestrated elastic fibres
  • Thin external elastic lamina
42
Q

Describe the tunica adventitia of elastic arteries

A

-Connective tissue containing vaso vasorum and nerve fibres

43
Q

What are vaso vasorum?

A

-Vessels of vessels

44
Q

How does the tunica intima of muscular arteries differ from elastic arteries?

A

-Thicker internal elastic lamina

45
Q

How does the tunica media of muscular arteries differ from that of elastic arteries?

A
  • Prominent external elastic lamina with fewer elastic fibres within the media itself
  • Smooth muscle connected by gap junctions to allow coordinated contraction
46
Q

Why is the elastic lamina of tunica media fenestrated?

A

-To allow noradrenaline released from the nerve fibres in the adventitia to reach the smooth muscle

47
Q

How does the tunica adventitia of muscular arteries differ from that of elastic?

A

-Less vasovasorum

48
Q

What happens to the number of smooth muscle layers as diameter of arterioles decreases?

A

-Decreases

49
Q

-What is the maximum diameter of an arteriole?

A

-0.1mm

50
Q

How many layers of smooth muscle do arterioles have?

A

-1->3

51
Q

Is there an internal elastic lamina present in all arterioles?

A

-No, only large ones

52
Q

What happens to the tunica media in small arterioles?

A

-Consists of only 1 smooth muscle layer which encircles the endothelium

53
Q

Is there an external elastic lamina in arterioles?

A

-No

54
Q

What do arterioles branch into?

A

-Metarterioles

55
Q

What do metarterioles branch into?

A

-Capillaries

56
Q

What are the three types of capillary?

A
  • Continuous
  • Fenestrated
  • Sinusoids
57
Q

What are the supporting cells of capillaries?

A

-Pericytes

58
Q

What is an end artery?

A

-An artery which supplies most or all of the blood to a body part with little collateral circulation

59
Q

Why do end arteries propose a significant problem if occluded?

A

-They are the only blood supply to that body part and infarction will occur at that site

60
Q

Provide an example of an end artery

A
  • Coronary arteries
  • Splenic artery
  • Renal artery
61
Q

Name 2 absolute end arteries

A
  • Central artery to retina of eye

- Labyrynthine artery of the internal ear

62
Q

How do metarterioles differ from arterioles?

A

-The smooth muscle layer is not continuous but confined to areas where there is branching

63
Q

What is the name of smooth muscle cells of branching sites of metarterioles?

A

-Precapillary sphincters

64
Q

What is the function of precapillary sphincters?

A

-Control blood flow into capillary beds

65
Q

What is the function of lymphatic capillaries?

A

-Drain away excess extracellular fluid

66
Q

Where does the excess extracellular fluid drained by lymphatic vessels go?

A

-Returned to the blood at the junctions of the internal jugular and subclavian veins

67
Q

What ensures a short diffusion path in capillaries?

A
  • One cell thick walls

- Narrow lumen-> RBCs fill almost entire lumen, minimising diffusion path to adjacent tissues

68
Q

Where in the circulation is blood velocity at its lowest?

A

-Capillaries

69
Q

Why is it beneficial for blood velocity to be low in capillaries?

A

-Allow adequate time for gas and nutrient exchange

70
Q

What cell types are pericytes able to produce, and under what conditions would they be produced?

A
  • Muscle cells for re-growth

- Fibroblasts during angiogenesis, tumour growth and wound healing

71
Q

How are the endothelial cells of capillaries joined together?

A

-Through tight junctions

72
Q

What are pericytes?

A

-Contractile cells that wrap around endothelial cells of capillaries and venules

73
Q

Where are pericytes located within vessels?

A

-Within the basement membrane

74
Q

How do pericytes communicate with endothelial cells?

A

-Direct contact and paracrine signalling

75
Q

What is a fenestrated capillary?

A

-Capillary with pores present in the endothelium, which is bridged by a diaphragm

76
Q

Where are fenestrated capillaries located?

A
  • Gut
  • Endocrine glands
  • Renal glomerulus
77
Q

How do sinusoids differ from fenestrated capillaries?

A
  • Larger openings
  • Slower bloodflow
  • Discontinous basal lamina
78
Q

What do the adaptions of sinusoid vessel walls allow which cannot happen in other capillaries?

A

-Passage of red and white blood cells

79
Q

Where are sinusoids located?

A

-Bone marrow, lymph nodes and adrenal glands

80
Q

What are discontinuous sinusoidal capillaries?

A

-They are sinusoids which do not have tight junctions between endothelia

81
Q

Where are discontinuous sinusoids found?

A

-Liver and spleen (greater movement necessary)

82
Q

Why does fluid drain into the post-capillary venules?

A

-Pressure is lower than that of capillaries and surrounding tissue

83
Q

What is the maximum diameter of a venule?

A

-1mm

84
Q

How do vein walls differ from artery?

A
  • Thinner
  • More connective tissue
  • Fewer elastic of smooth muscle fibres
85
Q

Describe the three layers of small veins

A
  • Thin tunica intima
  • Thin tunica media
  • Well developed adeventitia
86
Q

Which veins are the exception and have a well-defined tunica media?

A

-Superficial veins of the leg

87
Q

What are venae comitantes?

A

-Deep paired veins, that in certain anatomical locations, accompany an artery, wrapped together in a sheath

88
Q

What is the advantage of venae comitantes?

A

-Pulsatile artery promotes venous return within adjacent paired veins

89
Q

Give an example of a venae comitantes

A
  • Brachial
  • Ulnar
  • Tibial

Cardiovascular System (19 decks)

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