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Cardiovascular System > Special Circulations > Flashcards

Special Circulations Flashcards

1
Q

What are the 2 lung circulations?

A

Bronchial circulation

  • part of systemic circulation
  • for metabolic requirements of the lungs

Pulmonary circulation

  • blood supply to alveoli
  • required for gas exchange
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2
Q

What are features of the pulmonary circulation?

A

Low pressure
- lower than systemic

Low resistance

  • short wide vessels
  • lots of capillaries
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3
Q

What are the adaptations of the vessels for gas exchange?

A

High density of capillaries - large SA
Short diffusion distance
Large surface area

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4
Q

What is the optimal V/Q ratio?

A

0.8

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5
Q

How is the V/Q ratio maintained?

A

Blood is diverted away from poorly ventilated alveoli

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6
Q

What is hypoxic pulmonary vasoconstriction?

A

Mechanism - regulating pulmonary vascular tone

Alveolar hypoxia results in vasoconstriction of pulmonary vessels

Poorly ventilated alveoli are less well perfused

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7
Q

What is the effect of chronic hypoxic vasoconstriction?

A

Right ventricular failure

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8
Q

Why does chronic hypoxic vasoconstriction cause right ventricular failure?

A

Chronic increase in vascular resistance
Chronic pulmonary hypertension
High afterload on RV

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9
Q

What can cause chronic hypoxic vasoconstriction?

A

Altitude

Lung disease

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10
Q

What is the effect of exercise on pulmonary blood flow?

A

Increased CO
Small increase in pulmonary arterial pressure
Opens apical capillaries
Increased O2 uptake

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11
Q

How is tissue fluid formed?

A

Hydrostatic pressure of blood in capillary
- pushes fluid out of capillary

Oncotic pressure - exerted by large molecules
- draws fluid into capillary

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12
Q

What is the effect of low capillary pressure in the lungs?

A

Low tissue fluid / lymph at lungs

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13
Q

What can cause pulmonary oedema?

A

Lung capillary pressure increases

Mitral stenosis

  • increase LA pressure
  • increase pulmonary vein pressure

LV failure

  • more blood in LV
  • increase pulmonary vein pressure
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14
Q

What is the effect of pulmonary oedema?

A

Impairs gas exchange

- affected by posture

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15
Q

What are features of cerebral circulation?

A

High capillary density
- large SA

High basal flow rate

High O2 extraction

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16
Q

Why is good blood supply to brain vital?

A

Neurones are very sensitive to hypoxia

Few seconds = loss of consciousness

4 minutes = irrerversible damage

17
Q

How is blood supply secured?

A

Structurally
- anastomoses between basilar and internal carotid arteries

Functionally

  • myogenic autoregulation maintains perfucion during hypotension
  • metabolic factors control blood flow
  • brainstem regulates other circulation
18
Q

What is myogenic autoregulation?

A

Repsonse to changes in BP

Increase BP = vasoconstriction
Decrease BP = vasodilation

19
Q

What is metabolic regulation?

A

Cerebral vessels are sensitive to changes in Pco2

Hypercapnia = vasodilation 
Hypocapnia = vasoconstriction
20
Q

What is the effect of changes in regional activity?

A

Increases neuronal activity = increased blood flow

21
Q

What is Cushing’s reflex?

A

Response to raised ICP

Raised ICP impairs cerebral blood flow
Impaired blood flwo to vasomotor control regions
Increases sympathetic vasomotor activity
- increases arterial BP
- helps maintain cerebral blood flow

22
Q

What are features of coronary circulation?

A

Deliver O2 at a high basal rate
High capillary density
Short diffusion distance
Continuous production of NO

23
Q

When does left coronary artery flow mainly occur?

A

Diastole

During systole - increased LV pressure

24
Q

What happens to blood flow with increased O2 demand?

A

Blood flow increases

25
Q

What are features of skeletal muscle circulation?

A

Must increase O2 and nutrient delivert during exercise

Regulate BP

Resistance vessels

26
Q

What is the structure of skeletal muscle circulation?

A

High vascular tone - allows lots of dilatation

At rest only 1/2 of capillaries perfused

Precapillary sphincters - allow more capillaries to be perfused

27
Q

What are the roles of cutaneous circulation?

A

Temperature regulation

BP regulation

28
Q

What are artereovenous anastomoses?

A

Connections between arteries and veins in apical skin under neural control

Decrease temperature

  • increases sympathetic tone in AVAs
  • decreases flow to skin

Increase temperature

  • opens AVAs
  • blood to veins on surface

Cardiovascular System (16 decks)

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