Microcirculation, Lymphatics, & Local Control of Blood Flow - Quiz 8 Flashcards
What is Capillary Filtration?
Net movement of water from Capillary to Interstitial Space
What is Osmosis?
Osmosis is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential to a region of low water potential, in the direction that tends to equalize the solute concentrations on the two sides.
What is Capillary Reabsorption?
Net movement of water from Interstitial space to Capillary
What are the Starling forces regarding Capillary Filtration/Reabsorption? (3)
- Fluid filtered out from Capillary Pressure
- Fluid reabsorbed from Plasma Osmotic Pressure
- Fluid in = fluid out
Positive Net Driving Force = ?
Capillary Filtration
What is the Capillary Hydrostatic Pressure at the Arteriolar end vs Venous end?
Arterial Capillary Pressure: 30 mmHg
Venous Capillary Pressure: 10 mmHg
What NDF favors fluid movement into the capillary?
The capillary plasma colloid osmotic pressure (πc), which tends to cause osmosis of fluid inward through the capillary membrane.
Negative Net Driving Force = ?
Capillary Reabsorption
What are the Net Driving Forces in a Pt. w/ CHF?
Back-up of blood increases Capillary Hydrostatic Pressure = Capillary Filtration
What does the Lymphatic System do?
Another route that pumps fluid, proteins, and large matter away from tissue space to capillaries
How does the Lymphatic System return Plasma Filtrate back to circulation? (4)
1 Tissue Pressure
2 Intermittent Skeletal Muscle Activity
3 Lymphatic Vessel Contraction
4 One-Way Valves
Thoracic Duct (3)
Largest Lymphatic Vessel
Found b/t Left IJ & Left Subclavian Vein
Collects most of Body’s Lymph
In terms of Microcirculation, what would cause Edema? (4)
↑Capillary Hydrostatic Pressure
↑Capillary Permeability
↓Plasma Oncotic Pressure
Lymphatic Obstruction
What are Metarterioles?
(Terminal Arterioles)
Precapillary Sphincters that regulate flow into capillaries
What are the Methods of Exchange across the Capillary? (4)
- Diffusion - O2, CO2, Lipid-Solubles
- Bulk Flow - H20, electrolytes
- Vesicular Transport - Proteins
- Active Transport - Ions, glucose, amino acids
What are the two major opposing Hydrostatic Forces?
Capillary Hydrostatic Pressure & Tissue Interstitial Pressure
What are the two major opposing Oncotic Pressures?
Capillary Plasma Oncotic Pressure & Tissue Oncotic Pressure
What is the Gibbs-Donnan Effect?
Extra osmotic pressure caused by Na+, K+, and other cations
Capillary ________ is favored at the arteriolar end
Capillary _______ is favored at the venous end
Filtration at arteriolar end
Reabsoprtion at venous end
How would Dehydration look in Microcirculation?
↓Capillary Hydrostatic Pressure: Less Filtration
Net Capillary Reabsorption
How much fluid enters the Lymphatic Capillaries?
1/10th of Fluid
~2-3 L/day
What are the endogenous vasoconstrictors? (5)
- Catecholamines - epi, norepi, dopamine
- Endothelin
- Serotonin
- Angiotensin II
- Vasopressin
What are the endogenous Vasodilators? (8)
Histamine
Adenosine
Nitric Oxide
CO2
H+
Prostaglandins
Acetylcholine
Bradykinin
What is Metabolic Mechanism?
An event that results in inadequate O2 supply for metabolic needs causing formation of vasodilator substance to increase blood flow
What are substances that cause Metabolic Mechanism? (6)
Adenosine
Potassium Ions
CO2
H+
Lactic Acid
Inorganic Phosphates
What is Myogenic Mechanism?
Sudden stretch of blood vessel cause smooth muscles to reactively contract to restore vessel diameter & resistance
What is Reactive Hyperemia?
The rush of blood flow by 4-7x normal when the blood flow of a blocked tissue becomes unblocked
Increased blood flow lasts as long as period of occlusion.
What is Blood Flow Autoregulation?
- Ability of organs to maintain constant blood flow despite changes in perfusion pressure
- This is done using both Metabolic & Myogenic Mechanisms
What are the Endothelial Factors that help regulate Blood Flow? (4)
- Nitric Oxide - Endothelium-Derived Relaxing Factor
- Prostacyclin - vasodilator
- Endothelin - vasoconstrictor
- Endothelial-Derived Hyperpolarizing Factor
How would Nitric Oxide help with one lung ventilation?
It selectively dilates pulmonary vasculature in ventilated areas of the lung. It has a rapid onset of action and short half life that results in essentially no effect on systemic vessels making it a highly selective, short acting pulmonary dilator.
What is Nitric Oxide? (4)
- Most important Endothelial-Derived Relaxing Factor
- Lipophilic Gas, made from L-Arginine
- Decreases Free Calcium –> Increases cGMP
- Half Life: 6 seconds
What happens when there is damage to the Endothelial Cells?
Decreased Nitric Oxide & Prostacylcin
+
Increased Endothelin
=
Vasoconstriction, Vasospasm, Thrombosis
What is Long Term Blood Flow Control? (3)
Controlled changes over days, weeks, months.
Provide better Control of Flow
Increase/Decrease Size & Number of blood vessels
What is Vasomotion?
Cyclical Opening & Closing of Precapillary sphincters and Metarterioles
What is Active Hyperemia?
Increased organ blood flow with Increased Metabolic Activity
What stimulates Nitric Oxide Production? (7)
Shear Stress
Angiotensin II
Insulin
Substance P
Acetylcholine
Bradykinin
Histamine
What is the most potent endogenous inhibitor of platelet aggregation?
Prostacyclin
Inhibits platelet aggregation by increasing cAMP
What is Angiogenesis?
Generation of New Blood Vessels for long term bloodflow regulation.
Prolonged increase in tissue metabolism = Increase in vascularity
What is Collateral Circulation?
- Formation of a new vascular channels as a result of a blocked vein or artery to resupply affected tissue.
- When formations of new channels can’t keep up with blockages, coronary insufficiency & heart attacks happen
