Microcirculation, Lymphatics, & Local Control of Blood Flow

What is Capillary Filtration?

Net movement of water from Capillary to Interstitial Space

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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.

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What is Capillary Reabsorption?

Net movement of water from Interstitial space to Capillary

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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

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Positive Net Driving Force = ?

Capillary Filtration

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What is the Capillary Hydrostatic Pressure at the Arteriolar end vs Venous end?

Arterial Capillary Pressure: 30 mmHg

Venous Capillary Pressure: 10 mmHg

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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.

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Negative Net Driving Force = ?

Capillary Reabsorption

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What are the Net Driving Forces in a Pt. w/ CHF?

Back-up of blood increases Capillary Hydrostatic Pressure = Capillary Filtration

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What does the Lymphatic System do?

Another route that pumps fluid, proteins, and large matter away from tissue space to capillaries

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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

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Thoracic Duct (3)

Largest Lymphatic Vessel

Found b/t Left IJ & Left Subclavian Vein

Collects most of Body’s Lymph

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In terms of Microcirculation, what would cause Edema? (4)

↑Capillary Hydrostatic Pressure

↑Capillary Permeability

↓Plasma Oncotic Pressure

Lymphatic Obstruction

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What are Metarterioles?

(Terminal Arterioles)

Precapillary Sphincters that regulate flow into capillaries

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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

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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

Microcirculation, Lymphatics, & Local Control of Blood Flow - Quiz 8 Flashcards