Microcirculation Flashcards
Describe the range of size for arterioles vs meta-arterioles vs capillaries.
Arterioles: 5 - 100 micrometers
Meta-arterioles: 10 - 20 Micrometers
Capillaries: 5 - 10 micrometers
What is responsible for the rhythmic oscillatory behavior seen in capillaries?
Contraction and relaxation of precapillary vessels
How does transmural pressure affect vasomotion in capillaries?
- Increase in Transmural pressure causes contraction of terminal arterioles
Compare contraction and vasomotion in Large arterioles and metarterioles vs terminal arterioles.
Lg Art + MetA —> Do not completely occlude blood flow when constricted
Terminal arterioles —> May arrest blood flow
What is he role of PG12?
Prostacyclin: Relaxes vascular smooth muscles via increase in cAMP
How is PG12 made?
- From Arachidonic acid
- PG12 Synthase
How is PG12 released, and how does it work?
- Released by increase in shear stress caused by faster blood flow
- Inhibits platelet adherence to endothelium, platelet aggregation, and prevents intravascular clot formation
- relaxation in a secondary function
Describe the function of NO and what causes it’s release.
- Released from endothelial cells stimulated by ACh, ATP, bradykinin, serotonin, substance P, histamine, or shear stress of blood flow
- Causes endothelium derived vasodilation
- No dilation in blood vessels lacking endothelium
What is the functioning of Nitroprusside?
- Increases cGMP in vascular smooth muscle
* Not endothelium related
What is the function of endothelin?
- Potential vasoconstrictor
- Affects Vascular the and BP
What is Fick’s Law?
Describes diffusion of substances across a membrane
For Capillaries:
J = -PS(Co - Ci)
P = capillary permeability by the substance S = capillary surface area Co = concentration of the substance outside the capillary Ci = concentration of the substance inside the capillary
What is the actions of Bee stings?
Alters capillary permeability
What 4 factors most influence capillary diffusion of O2?
- Diffusion coefficient for O2
- Capillary density and diffusion distances
- Blood flow
- Tissue O2 consumption: O
2 supply of normal tissue at rest + during activity is not limited by diffusion or by the number of open capillaries
How do capillaries in kidneys, intestines, and lover differ from others such a s skeletal?
Kidney/intestine: More porous and very permeable
Liver: Very porous and discontinuous endothelium (fenestrated)