Microcirculation Flashcards
What is blood flow rate?
Volume of blood passing through a vessel per unit time. The overall aim for the CVS is the adequate blood flow through he capillaries to deliver respiratory substrate and remove excretory products
What is the equation for blood flow rate?
πΈ=βπ/πΉ
Equation relates blood flow with pressure gradient /vascular resistance
What is vascular resistance?
Hindrance to blood flow due to friction between moving fluid and stationary vascular walls
What is a pressure gradient?
Pressure between two defined regions (A-B), increasing pressure gradient increases the flow rate
What are the three main factors that influences vascular resistance?
Blood viscosity
Vessel radius
Vessel length
What is the relationship between resistance and vascular radius?
Resistance is directly proportional to π/π^π
Which factor most influences vascular resistance?
Vessel radius
Blood viscosity and vessel length is fairly CONSTANT ο resistance changes are thus attributed to vessel radius alterations.
What two main factors is blood flow determined by?
Pressure difference in the vascular bed
Vascular resistance
An increase in blood pressure ___ pressure difference?
Increases
How does arteriolar vasoconstriction influence vascular resistance?
Increases resistance
How does increased blood pressure influence blood flow?
Increases blood flow
How does arteriolar vasoconstriction influence blood flow?
Decreases blood flow
What is the approximate blood pressure referred to as?
Mean arterial blood pressure
Why can systolic and diastolic pressure be used to calculate mean arterial pressure?
There is minimal deviations through the arteriole supply
How does the vascular system facilitate effective nutrient exchange?
As blood traverses through the capillary bed, low velocity is required system enables blood to decelerate through vasoconstriction
What is the average value for venous blood pressure?
Negligible 0mmHg
What is the only factor that contributes to blood flow?
Resistance since the blood pressure gradient is equal to arteriole pressure
Why do arteriolar Smooth muscles display a state of partial constriction?
Describes as vascular tone. Partial contraction enables alterations to blood flow through constriction and dilation (room to accommodate movements)
What are the two main functions of independent radius adjustment of arterioles?
Match blood flow to the metabolic needs of specific tissues
Increase in metabolic activity within the muscle
How is blood flow matched to local tissues?
Match blood flow to the metabolic demands of specific tissues (regulated by intrinsic control - local endothelial-derived mediators), tissue determines blood requirement
What is the active hyperaemia?
Increase in organ blood flow, associated with increased metabolic activity of tissue
How does radius influence hyperaemia?
Increase in radius causes a decrease in vascular resistance, this increases blood flow resulting in active hyperaemia.
How is systemic arterial blood pressure regulated?
Regulated by extrinsic controls (nervous influence and hormonal control)
What is myogenic autoregulation ?
Reduction in blood temperature: Vasoconstriction arises (Relevant for peripheral vessels β the integumentary system). Decrease in radius, increases vascular resistance to subsequently decrease blood flow to superficial surface (Less heat radiation).
Baroreceptors detect stretch and blood pressure.