Microcirculation Flashcards
Can arteriole constrict and dialate more than the venule
Arterioles constrict more
What is blood flow rate
Volume of blood passing through a vessel per unit time
What is darcy’s law
Flow rate = pressure gradient / resistance
When will the viscosity of blood change
During scuba diving
Helium used to make up composition of the air (rest of gas exchange material)
How does the flow change in the arterioles
Flow (organ) = Difference in pressure / Resistnace (organ)
Difference in pressure remains fairly constant
Without pressure difference blood would not reach tissue capillary beds
What are the two distinct functions of arterioels
Match blood flow to metabolic needs of specific tissue (local instrinsic controls and independent of nervous or endocrine)
Helpe regulate systemic arterial blood pressure (regulated by extrinsic controls which travel via nerves or blood and usually centrally coordinated)
What is active hyperaemia
Vasodilation of arterioles to increase metabolites and increase oxygen usage
What is called myogenic autoregulation
Increase in blood pressure causes increase in stretch (distension) to keep blood flow consistant
What could be vasoconstriction be driven by
Decreased blood temperature
Increase stretch
What is the formula for cardiac output blood pressure and peripheral resistance
Cardiac output= blood pressure / total peripheral resistance
Where is the cardivascular control centre
In the medulla
What causes the vascular tone
Smooth muscle sympathetic nerve activity
What hormones cause vasoconstriction
Angiotensin 2
ADH
Adrenaline/noradrenaline
Why is capillary density important
Minimise difusion
Maximise surface area
Ficks Law
Where is the most dense capillary netwroks
Lungs - pumonary circulation 3500cm^2/g
Myocardium/brain = 500cm^2/g - ischemic incident dangerous
What are the different types of capillaries
Continuous
Fenestrated - basement membrane is still continuous
Discontinuous
Why is the babies brain so much more vulnerable
Leakier blood brain barrier
What type of organ is discontinuous capillary
Liver
Capillary ike structures called sinosoids
How does blood filter out
Hydrostatic pushing force out
Pulling oncotic in
No proteins enter capillaries
What happens during ultrafiltration
Pressure inside the capillary > in the intistitial fluid
What happens during reabsorption in the capillaries
Inward driving pressure > outward pressures across the capillary
Diagram of the capillaries pressures
What is the significance of the fact that ultrafiltration is more effective than reabsorption
Net loss of fluid
Information about the lymphatic system
No pump to induce flow
Drains into the right lymphatic duct - thoracic ducts
Drain into the right and left subclavian veins
3L per day
Greater density in periphery
Might not measure blood pressure on arm because axillary lymph nodes taken out in breast cancer
What happens during elephantiasis
Rate of production (fluid accumulation (rate of production) is bigger than rate of drainage
Parasitic blockage of lymph nodes could be a cuse
What is the pressure of the arterioles entering and leaving
93mmHg vs 37 mmHg
What are starlings forces
Hydrostatic pressure (physical pressure) and oncotic pressure (colloid osmotic pressure)
How would you describe the lymphatic system
Blind-ended, signle layered and contains large permeable water-filled one-way channels
How is lymph flow directed
Skeletal and respiratory pumps
