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organ systems > Vascular pt 1 > Flashcards

Vascular pt 1 Flashcards

0
Q

Tunica media consists of?

A
  • Smooth muscle

- External elastic lamina

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1
Q

Tunica intima consists of ?

A
  • Endothelium
  • Subendothelial layer of loose CT
  • Internal elastic membrane
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2
Q

Tunica externa (adventitia) contains?

A
  • Loose CT with collagen and elastin

- Contains vasa vasorum & nervi vascularis (autonomics) in larger arteries and veins

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3
Q

Large (elastic) artery contains?

– Eg. aorta, subclavian, common carotid

A
  • Tunica intima
  • Internal elastic membrane
  • Tunica media
  • Tunica adventitia
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4
Q

Medium (Muscular) contains ?

– Eg. ulnar, coronary a.

A
  • Tunica intima
  • internal elastic membrane
  • Tunica media – more SM, less elastic
  • Tunica adventitia (thick layer of collagen, with less elastin)
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5
Q

List Small arteries and arterioles functions and characteristics?

A

Both maintain an endothelium surrounded by basement membrane

arterioles are the primary site of smooth muscle control over blood pressure and flow regulation

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6
Q

capillaries contain?

A
  • Endothelium
  • Basement membrane
  • Pericytes (primitive smooth muscle cells)
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7
Q

Venules and veins contain?

A

-Small elastic fibers
-smooth muscle and CT
Pressures are low so walls are thin

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8
Q

Medium Veins contain?

A

• T. media
• T. adventitia (externa)
veins up to 10 mm diameter, many with valves, especially lower limb

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9
Q

Large Veins contain?

-eg. SVC, IVC portal vein, over 10 mm diameter

A
  • T. media: few smooth muscle layers

* T. adventitia: thick with CT (collagen & elastin) plus longitudinal smooth muscle

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10
Q

Blood distribution in the circulatory system

A 
•  Veins 64%
•  Arterial side 20%
	–  Arteries 13%
	– Arterioles and capillaries 7%
•  Heart/pulmonary 16%
Where the blood is depends on Blood Flow and Vascular Resistance
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11
Q

Q (flow) is the Cardiac Output, how is this determined?

A

– Determined by stroke volume and heart rate: Q = SV ∙ HR

– Regulated by neural and hormonal systems

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12
Q

R (resistance) is the Total Peripheral (Vascular) Resistance is regulated by?

A

Regulated by metabolic and neurohumoral mechanisms

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13
Q

ΔP (pressure gradient) is the Blood Pressure, how is this determined.

A

– derived from the interactions of the cardiac output (flow) and resistance.
– ΔP is estimated by various measures of blood pressure: systolic/diastolic, mean arterial pressure (MAP), pulse pressure, etc.

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14
Q

TOTAL PERIPHERAL (VASCULAR) RESISTANCE

A

R = ΔP/Q
• Pressure gradient is ΔP = (P aorta – P vena cava)
– Since P vena cava is negligibly small, it can be eliminated so that ΔP = P aorta

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15
Q

VELOCITY is similar to FLOW, but is a very different measure.

A
  • Flow is the amount of blood that passes a given point in a period of time (volume/sec)
  • Velocity is the rate of linear displacement of fluid (cm/sec).
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16
Q

For a given cardiac output (Q), velocity varies inversely with diameter of blood vessel

A
  • The more dilated the blood vessel, the slower the blood flow.
  • Fluid slows at it enters wider vessels and accelerates as it enters smaller vessels.
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17
Q

Highest velocity of blood flow is in __

Lowest Velocity is in __

A
  • Highest velocity of blood flow is in the aorta

* Lowest velocity in capillaries.

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18
Q

explain Laminar streaming

A
  • Fluid particles travel in concentric layers (lamina): from slowest near walls to fastest in the center, creating a velocity gradient
  • Velocity gradient is generated by viscosity
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19
Q

what is viscosity?

A
  • Viscosity is the inner friction in the fluid: it is generated by the interaction between molecules and particles in the blood and resists any relative motion among them
  • Increase in viscosity (η) reduces flow Q ~1/η
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20
Q

Velocity gradient is created by blood viscosity and friction from walls, what does a higher viscosity do to the velocity gradient?

A
  • Higher viscosity increases the velocity gradient .
  • A greater velocity gradient increases shear stress which alter vascular properties
  • Excess rbc synthesis in response to hypoxia (polycythemia) increase viscosity, impairing blood flow
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21
Q

in capillaries rbc’s travel in single file and adhere less to the vessel wall. what does this do for viscosity?

A

there is less viscosity; in fact there is a water space between cells and the capillary wall (Fåhræus‐Lindquist effect).

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22
Q

according to Bernoulli’s principle:
Constricting a blood vessel?
Expanding a blood vessel?

A
  • increases blood velocity and shear stress

* decreases blood velocity by increasing lateral (transmural) pressure

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23
Q

explain Shear Stress

A

• Excess velocity of laminar flow produces shear stress (viscous drag) on endothelial cells
• Temporary shear stress can be compensated by autoregulation that vasodilates the vessel and slows the flow
• Shear stress (τ)
– increases with viscosity, flow and velocity
– decreases with radius

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24
Q

what are the problems with prolonged shear stress

A
  • Excess shear stress associated with occlusion can alter gene expression via cytoskeletal signaling
  • can lead to inflammation, remodeling, atherosclerosis involving the extracellular matrix (ECM), smooth muscle and endothelium.
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25
Q

Turbulence develops under the conditions of:

A 
high velocity (V), large vessel diameter (D), high fluid density (ρ) and low viscosity (η).
–  Combined into the Reynold’s number which determines the threshold of turbulence.
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26
Q

Turbulence can occur in __

Turbulence produces sounds called __

A

narrow, atherosclerotic vessels (high velocity), aortic arch (large diameter), bifurcations, eg aorta

called bruits (blood vessels) and murmurs (heart)

27
Q

Turbulence produces greater levels of transmural pressures that increase the chance of endothelial injury & subsequent plaque formation. this manifests as?

A

an Aortic aneurism: involves rupture of endothelium and infusion of blood into the tunica media creating a false lumen
• Because it separates the aortic wall layers, it is called a “dissecting aortic aneurism”

28
Q

Differences in resistances affect blood flow in the vascular system how?

A
  • Blood flow through individual organs depends on the resistance of organ’s vessels
  • Blood flow through the entire system depends on the TPR
29
Q

generalize how TPR and MAP are caclulated

A

Organ vascular systems are arranged in parallel and the sum of the individual resistances determine not just local pressures, but also the resistance and pressure of the entire system.

30
Q

Blood flow through individual organs is determined mostly by regulation of

A

arteriolar resistance

31
Q

Generalize central control of vascular system

A

-mostly vasoconstrictive

Autonomic neurons and endocrines regulate total vascular system maintain overall blood pressure and flow

32
Q

Generalize local control ( autoregulation )

A

mostly vasodilatory

  • maintaining constant blood flow to an organ with a steady metabolic rate in the face of changing blood pressure
  • adjusting blood flow to an organ according to local changes in its metabolic activity
33
Q

explain ANS regulation of organ blood blow (i.e. arteriolar resistance)

A

Mainly sympathetic nervous system (NE & EPI)
- Alternating increased or decreased sympathetic activity produces constriction and dilation respectively via alpha‐1 receptors

34
Q

explain alpha 1 receptors

A

most common vascular adrenergic receptors; found in all arterioles .
– binding with norepinephrine or epinephrine leads to vasoconstriction via IP3

35
Q

Explain β2 receptors

A

found in arterioles of skeletal and cardiac muscle (non‐innervated; hormonal only)
– binding of mostly epinephrine leads to vasodilation via cAMP

36
Q

During sympathetic response (eg. exercise) blood is directed to?

A

skeletal muscle and heart (β2 vasodilation) and away from the internal organs (α1 vasoconstriction)
– However, most vasodilation in continuing muscle activity is due to build up of metabolites

37
Q

Mechanisms for autoregulation include:

A

Metabolic
Myogenic
Endothelial

38
Q

Explain Active Hyperemia

A

the increase in organ blood flow (hyperemia) associated with increased activity of an organ or tissue.
• consumes O2 , generating local hypoxia, this vasodilates arterioles by inducing formation of vasodilator metabolites.
• Increased blood flow washes out metabolites and vessels constrict back to normal

39
Q

Metabolic vasodilators are specific to organs and include:

A
  • Adenosine (Ado) inhibits contraction via cAMP in coronary and possibly muscle arterioles
  • K+ & PO4 dilate skeletal muscle vasculature
  • CO2, H+ dilate cerebral vasculature
40
Q

Major vasodilator in most blood vessels

A

Nitric oxide (NO)

41
Q

how is NO synthesized?

A

Synthesized from arginine via nitric oxide synthase, NOS.

42
Q

How is NO released?

A

• NO is released from endothelial cell & enters smooth muscles cells
• Released from endothelium by:
– Shear forces of blood flow (flow mediated vasodilation)
– Chemical means: ACh, ATP, hypoxia, histamine, bradykinin

43
Q

what does NO generate?

A
  • NO generates cGMP which inhibits Ca++ actions on myosin light chain kinase, leading to its relaxation
  • NO also regulates proliferation of SM cells
44
Q

Prostaglandins (prostacyclin), PG does what?

A

uses cAMP to inhibit Ca++ mediated smooth muscle contraction

45
Q

how is endothelin ET-1 released?

A

Released in response to vasoconstrictors

46
Q

NO and PG are counterbalanced by ?

A

• NO and PG counterbalanced by ET‐1 which contracts smooth muscle (vasoconstriction)

47
Q

What is ET function?

A

• ET both constricts and induces proliferation of smooth muscle cells

48
Q

ET-1 and NO roll in hypertesion?

A

• In hypertension, ET‐1 is up regulated, while NO is down regulated. Endothelial cells hypertrophy and smooth muscles proliferate

49
Q

Smooth muscle cells secrete ?

A

collagen, elastin and proteoglycan

50
Q

Even though blood pressure derives from direct interaction of CO and R, it can also be affected by?

A

renal regulation of fluid volume and salt concentration

51
Q

Parasympathetic vasodilation is localized to a few structures:

A

eg. cerebral and genital vessels

52
Q

Blood flow (Q) is related to

A 
blood pressure (ΔP) and vascular resistance (R)
Q = ΔP/R
53
Q

Define Total peripheral resistance

A

TPR = ΔP/Q = P aorta/CO
P (aorta) is estimated by the Mean Arterial Pressure
TPR = MAP/CO

54
Q

Explain how resistance is inversely proportional to 4th power of vessel radius

A

– small decreases in arteriolar radius (vasoconstriction) causes significant increases in resistance, reducing flow or increasing pressure differences.
– Tube with twice the radius yields 16 times the flow.

55
Q

Velocity is a function of

A

flow and cross‐sectional area

56
Q

what does local control (autoregulation) use to optimizes blood flow and O2 delivery ?

A

uses metabolites, myogenic and endothelial mechanisms

57
Q

Alpha & beta receptors both bind NE & EPI, but

A

produce opposite responses
α1 receptors: Vasoconstriction via IP3
β2 receptors: Vasodilation via cAMP

58
Q

During exercise blood is shunted away from the GI tract to the skeletal muscles and the heart by ?

A

epinephrine

59
Q

Autoregulation maintains constant blood flow to the organ/tissue by constricting or dilating arterioles via ?

A

metabolites, NO, or myogenic actions

60
Q

Without autoregulation, blood flow would

A

increase with rise in perfusion pressure

61
Q
  • If pressure drops __

* If pressure increases__

A

blood vessels dilate to maintain flow

blood vessels constrict to reduce blood flow

62
Q

Pressure enhances smooth muscle contraction by activating cell pathways that increase

A

both Ca++ influx and Ca++ binding to myosin light chains

63
Q

___ minimize arterial pressure build up in legs and feet during standing

A

Myogenic responses

64
Q

Smooth muscle contains?

A
  • elastic & reticular fibers

- proteoglycans between SM cells

65
Q

what does collagen do in arteries

A

limits expansion

66
Q

what does elastin do in arteries ?

A

creates recoil pressure during diastole

organ systems (20 decks)

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