Microcirculation Flashcards
(35 cards)
Label the microcirculation
What is the overall aim of the Cardiovascualr system?
Adequate blood flow through capillaries
What is the blood flow rate and give the equation of Darcy’s Law
Blood flow rate is the volume of blood passing through a vessel per unit time
Darcy’s Law:
Pressure gradient= Flow Rate x Resistance
What is the pressure gradient across the microcirculation
Difference in pressure between 1st order arteriole and end of arteriole (middle of capillary bed)
Pressure A- pressure B
How can you get more blood to a tissue
Increase the pressure gradient across the microcirculation by mainly increasing pressure at the start of arteriole
What causes resistance in blood flow (physics concept)
Hindrance to blood flow due to friction between moving fluid and stationary vessel walls
What is the equation for Resistance
Pseullmoiles law
L- Vessel length
r- vessel radius
N- blood viscosity
Why is arteriole the major determinant of resistance?
Has lots of smooth muscles that can dilate; hence affect pressure
What determines the pressure at te start if the arteriole in microcirculation
Mean arteriole pressure
Why is there greatest resistance at the middle of capillary bed (end of arteriole)
Lowest radius
What is the flow rate of blood across an organ? What factor is the real determinant of flow rate
F= P/R : F is flow rate, P= pressure gradient, R =resistance
greatest determinant of flow rate IS RESISTANCE
pressure gradient is MAP (Mean arteriole pressure) ;since pressure in venule is zero.
What is vascular tone and it’s importance
When arteriole smooth muscle display a state of partial construction at rest.
It is important because it allows the smooth muscle to easily constrict and dilate when needed
The radii of arteriole are adjusted independently to accomplish 2 functions which are:?
- Match blood flow to the metabolic needs of specific tissues depending on the body’s momentary needs
- Help regulate systemic arterial blood pressure
What regulates the ability of arterioles to reduce radii to match blood flow to metabolic needs f tissues?
Regulated by local intrinsic controls and independent of nervous or endocrine stimulation
What regulates the ability of arteriole to help regulate systemic arterial blood pressure (by adjusting it’s rain independently)
Regulated by extrinsic controls which travel via nerves or blood and are usually centrally coordinated
What is active hyperaemia and what causes it?
VASODILATION OF ARTERIOLES
this may be driven chemically by:
- increased metabolites
- increased oxygen usage
this chemical change is detected by chemoreceptors on arterioles anhence causing vasodilation
What is myogenic auto regulation and what causes it?
VASOCONSTRICTION of arterioles
this may be PHYSICALLY DRIVEN by:
- Reduced blood temperature
- increased stretch of arterioles due to high blood pressure
Describe how the graph of perfusion pressure, flow rate and resistance will change with and without autoregulation
draw it
What is the equation for MAP in terms of Cardiac output
MAP= cardiac output x total peripheral resistance
Describe how the neural network help to regulate arterial blood pressure
Cardiovascular control centre in medulla
send impulses down to arterioles smooth muscle and this causes vasoconstriction
this could divert blood from specific organs
What are the different Hormones that can regulate arteria;l blood pressure and what do they do?
- Vasopressin/ADH via V1 receptors
- Angiotensin II- MOST powerful vasoconstrictor
- Adrenaline/noradrenaline
they all cause vasoconstriction
Describe the parameters of a capillary endothelial cell and also the features of the network
- 7 micrometers lumen diameter
- 1 micrometer cell width
- very narrow
- highly branched network; so that no tissue cell is far away from capillary
this all helps capillary to carry out it’s function
What is the purpose of capillary exchange
Delivery of metabolic substrates to the cells of the organism which is the ultimate function of the CVS
Do all tissues have te same capillary density?
No, the more metabolic active a tissue is, the more capillary density it has/needs.
