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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
Why does the bloodflow to the kidney need to be kept at a constant high pressure?
-Needed to ensure efficient filtration
25
Why can the bloodflow vary to the gut?
-Increased flow needed after a meal
26
Why can the bloodflow alter so much in skeletal muscle?
-Needed during exercise to match supply to demand of O2
27
Why can the bloodflow to the skin vary so much?
-Thermoregulation
28
Describe the distribution of blood in the circulation at rest
- Arteries/arterioles->11% - Capillaries -> 5% - Heart and lungs -> 17% - Veins -> 67%
29
What are the two types of arteries?
-Elastic and Muscular
30
Name some large elastic arteries
- Aorta and its trunks - Pulmoary trunk which bifurcates into L and R pulmonary arteries - L and R common iliac arteries
31
Describe the bloodflow in large elastic arteries near the heart Hint: one word
-Pulsatile
32
Which arteries are the largest?
-Elastic
33
Which arteries have the widest lumen?
-Elastic
34
What determines bloodflow to organs?
-Resistance vessels (arterioles) and pre-capillary sphincters
35
Why does flow distribution need to be controlled?
-To restrict flow to the parts which are easily perfused and drive flow to those parts which are harder to perfuse
36
What is capacitance?
-Store of blood in the veins
37
Why is capacitance important?
-Provides the ability to cope with necessary changes in CO
38
Describe the lumen of veins
-Wide and irregular
39
What are the three layers of an artery wall?
- Tunica intima - Tunica media - Tunica adventitia
40
Describe the tunica intima of an elastic artery
- Thin - Endothelium running parallel to long axis - Subendothelial connective tissue - Discontinous internal elastic lamina
41
Describe the tunica media of an elastic artery
- Thick - Many smooth muscle fibres - Collagen - Many fenestrated elastic fibres - Thin external elastic lamina
42
Describe the tunica adventitia of elastic arteries
-Connective tissue containing vaso vasorum and nerve fibres
43
What are vaso vasorum?
-Vessels of vessels
44
How does the tunica intima of muscular arteries differ from elastic arteries?
-Thicker internal elastic lamina
45
How does the tunica media of muscular arteries differ from that of elastic arteries?
- Prominent external elastic lamina with fewer elastic fibres within the media itself - Smooth muscle connected by gap junctions to allow coordinated contraction
46
Why is the elastic lamina of tunica media fenestrated?
-To allow noradrenaline released from the nerve fibres in the adventitia to reach the smooth muscle
47
How does the tunica adventitia of muscular arteries differ from that of elastic?
-Less vasovasorum
48
What happens to the number of smooth muscle layers as diameter of arterioles decreases?
-Decreases
49
-What is the maximum diameter of an arteriole?
-0.1mm
50
How many layers of smooth muscle do arterioles have?
-1->3
51
Is there an internal elastic lamina present in all arterioles?
-No, only large ones
52
What happens to the tunica media in small arterioles?
-Consists of only 1 smooth muscle layer which encircles the endothelium
53
Is there an external elastic lamina in arterioles?
-No
54
What do arterioles branch into?
-Metarterioles
55
What do metarterioles branch into?
-Capillaries
56
What are the three types of capillary?
- Continuous - Fenestrated - Sinusoids
57
What are the supporting cells of capillaries?
-Pericytes
58
What is an end artery?
-An artery which supplies most or all of the blood to a body part with little collateral circulation
59
Why do end arteries propose a significant problem if occluded?
-They are the only blood supply to that body part and infarction will occur at that site
60
Provide an example of an end artery
- Coronary arteries - Splenic artery - Renal artery
61
Name 2 absolute end arteries
- Central artery to retina of eye | - Labyrynthine artery of the internal ear
62
How do metarterioles differ from arterioles?
-The smooth muscle layer is not continuous but confined to areas where there is branching
63
What is the name of smooth muscle cells of branching sites of metarterioles?
-Precapillary sphincters
64
What is the function of precapillary sphincters?
-Control blood flow into capillary beds
65
What is the function of lymphatic capillaries?
-Drain away excess extracellular fluid
66
Where does the excess extracellular fluid drained by lymphatic vessels go?
-Returned to the blood at the junctions of the internal jugular and subclavian veins
67
What ensures a short diffusion path in capillaries?
- One cell thick walls | - Narrow lumen-> RBCs fill almost entire lumen, minimising diffusion path to adjacent tissues
68
Where in the circulation is blood velocity at its lowest?
-Capillaries
69
Why is it beneficial for blood velocity to be low in capillaries?
-Allow adequate time for gas and nutrient exchange
70
What cell types are pericytes able to produce, and under what conditions would they be produced?
- Muscle cells for re-growth | - Fibroblasts during angiogenesis, tumour growth and wound healing
71
How are the endothelial cells of capillaries joined together?
-Through tight junctions
72
What are pericytes?
-Contractile cells that wrap around endothelial cells of capillaries and venules
73
Where are pericytes located within vessels?
-Within the basement membrane
74
How do pericytes communicate with endothelial cells?
-Direct contact and paracrine signalling
75
What is a fenestrated capillary?
-Capillary with pores present in the endothelium, which is bridged by a diaphragm
76
Where are fenestrated capillaries located?
- Gut - Endocrine glands - Renal glomerulus
77
How do sinusoids differ from fenestrated capillaries?
- Larger openings - Slower bloodflow - Discontinous basal lamina
78
What do the adaptions of sinusoid vessel walls allow which cannot happen in other capillaries?
-Passage of red and white blood cells
79
Where are sinusoids located?
-Bone marrow, lymph nodes and adrenal glands
80
What are discontinuous sinusoidal capillaries?
-They are sinusoids which do not have tight junctions between endothelia
81
Where are discontinuous sinusoids found?
-Liver and spleen (greater movement necessary)
82
Why does fluid drain into the post-capillary venules?
-Pressure is lower than that of capillaries and surrounding tissue
83
What is the maximum diameter of a venule?
-1mm
84
How do vein walls differ from artery?
- Thinner - More connective tissue - Fewer elastic of smooth muscle fibres
85
Describe the three layers of small veins
- Thin tunica intima - Thin tunica media - Well developed adeventitia
86
Which veins are the exception and have a well-defined tunica media?
-Superficial veins of the leg
87
What are venae comitantes?
-Deep paired veins, that in certain anatomical locations, accompany an artery, wrapped together in a sheath
88
What is the advantage of venae comitantes?
-Pulsatile artery promotes venous return within adjacent paired veins
89
Give an example of a venae comitantes
- Brachial - Ulnar - Tibial

Cardiovascular System (19 decks)

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