Microcirculation Flashcards
The primary function of the circulatory system is __
- to transport and distribute essential substances
- to remove metabolic byproducts
What is microcirculation?
The circulation of blood through the smallest vessels of the body (arterioles, capillaries and venules)
What. is the pressure of small arteries? Why?
Small arteries: have higher pressures than 120 and that’s because the wall rigidity is changing and increasing in the small arteries.
What is the diameter of arterioles?
Below 300µm
Do arterioles contain smooth muscle cells?
Yes, they contain a large amount of smooth muscles
How can myogenic tone be expressed in arterioles?
They are single unit smooth muscle with a pacemaker activity.
-> There is always a contraction from these muscles providing a myogenic tone.
-> There is also a sympathetic innervation providing a sympathetic tone.
-> Both tones together are called the resting tone.
-> The sympathetic tone and myogenic tones can be different in different organs.
Make a Table with mean pressure, flow and resistance of vessel
The pressure decreases throughout the vessels reaching about __ in the venous system
zero
How to calculate the resistance?
by getting pressure difference over the flow.
What are the resistance vessels
Arterioles that have the highest resistance (this was for systemic circulation)
Compare the resistance in pulmonary and systemic circulations
The resistance in the pulmonary circulation is 1/10 of the resistance in the systemic circulation due to the large compliance.
Why do we consider arterioles as resistance vessels?
This is because if we take the reciprocal of the resistance the arterioles will have a higher resistance
In systemic circulation, calculate the mean arterial pressure?
= CO X TPR
In systemic circulation, is the Cardiac Output constant?
The cardiac output systematically will be constant as the heart is independently regulated.
What happen to the TPR If constriction of arterioles occurs ?
the TPR will increase
-> that will cause an increase in the mean arterial pressure
-> So constriction of arterioles can regulate the arterial pressure.
In a local level, will the resistance affect arterial pressure?
Np, because it’s a small part of the entire circulation
The constriction of arterioles will ____ (increase/decrease) the resistance and since the P is constant the flow (Q) will decrease.
increase
What are the 6 components of the microcirculation?
- terminal arterioles
- Metarterioles
- Precapillary sphincter
- True capillaries
- Postcapillary venule
- AV-shunt
Characteristics of terminal arterioles (diameter, feature, inneravation)
1) 10 - 30 µm
2) continuous smooth muscle layer
3) innervated sympathetically
Characteristics of metarterioles (diameter, feature, inneravation)
- Smaller than terminal arterioles
- discontinuous smooth muscle layer
- Not innervated => but locally regulated
Characteristics of precapillary sphincters
- Contain 1 - 2 smooth muscle cells
- Not innervated => but locally regulated
Characteristics of true capillaries
- Diamater -> 5 - 7 µm
- Inner surface -> 5000 - 7000 m2
- surrounded by endothelial cells
- contain pores which are filled with H2O
- Basal membrane -> filtration
What is so special about AV shunt (a component of microcirculation)
in the skin there is an exception which is the existence of an AV shunt and its important for thermoregulation.
What are the 4 different types of capillaries?
- Continuous
- Fenestrated
- Discontinuous
- Tight