Microcirculation Flashcards

1
Q

How do capillaries modify the blood coming into them

A

Pre-capillary sphincter - it is not actually a physical structure but the arterioles leading up to capillaries have a lot of SM

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2
Q

Processes allowing transfer materials from blood to tissue

A

Diffusion
Filtration
Pinocytosis

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3
Q

Factors affecting quantity of substance diffused across capillaries per unit time

A

Capillary permeability to substance
Capillary SA
Concentration in and outside (not as relevant)

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4
Q

Filtration/Reabsorption

A

Movement of a volume of protein-free fluid out of the capillary (filtration) and back (reabsorption)

Net fluid transfer creates bulk flow

Important in determining distribution of ECF

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5
Q

Driving forces affecting movements of fluid (filtration/reabsorption)

A
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6
Q

Role of hydrostatic pressure in filtration/reabsoprtion

A

Capillary hydrostatic pressure pushes fluid out via filtration (Pc)

Interstitial fluid hydrostatic pressure works to push fluid back into capillary via reabsorption (Pi)

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7
Q

Role of osmotic pressure in filtration/reabsoprtion

A

Presence of proteins like albumin in capillary draws water into it via filtration as it cannot leave (πc)

Presence of proteins in interstitium that draw water out of capillary

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8
Q

What happens to pressure upstream and downstream of an arteriolar constriction

A

Increase pressure upstream
Decrease pressure downstream
- Hydrostatic pressure decreases in capillary and driving force of fiiltration is reduced

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9
Q

What happens to pressure upstream and downstream of a venular constriction

A

Hydrostatic pressure increases upstream
- Capillary filtration is favoured

Pressure decreases downstream

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10
Q

Which pressures are more significant in terms of regulating filtration/reabsorption

A

Capillary Hydrostatic Pressure
- Increase favours filtration

Plasma colloid osmotic pressure
- Increase favours reabsorption

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11
Q

Effect of liver damage on filtration/reabsorption

A

There will be less albumin produced, affecting osmotic pressure and reducing reabsorption

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12
Q

Effect of lymphatics on hydrostatic pressure during microcirculation

A

Effective drainage affects inerstitial fluid hydrostatic pressure so if there is poor lymphatic drainage, filtration will be favoured

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13
Q

Describe the changes in capillary hydrostatic pressure (Pc) & capillary colloid osmotic pressure (πc) from arteriole to venule

A

Pc drops across a capillry

πc remains about constant

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14
Q

Describe relationships between capillary hydrostatic pressure (Pc) and capillary colloid osmotic pressure (πc) for filtration/reabsorption

A

If Pc > πc, net filtration

If Pc < πc, net reabsorption

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15
Q

Describe the bulk flow at arterioles, capillaries and venules

A
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16
Q
A

Kf is filtration coefficient

17
Q

Describe the changes that would occur to this graph with an increase in pre-capillary vasoconstriction

A
18
Q

Describe the changes that would occur to this graph with an increase in venous pressure

A
19
Q

Microcirculatory causes of oedema

A

Lymphatic Obstruction
Increased venous pressure (greater filtration)
Changes in protein levels
Hypervolaemia (increased fluid in vascular system)
Inflammation (vasodilatation & increased permeability)