Micocirculation

Lesson 23. Microcirculation and Special Circulations 1. a. b. c. d.

Which of the following are pushing ultrafiltration out of the capillary (F= K[(Pc-Pi)-(np-ni)]) Intracapillary lateral pressure; interstitial oncotic pressure Plasma oncotic pressure; tissue turgor pressure Intracapillary lateral pressure; tissue turgor pressure Plasma oncotic pressure; interstitial oncotic pressure

1.

A: Intracapillary lateral pressure (Pc) and interstitial oncotic pressure (np) push filtration OUT OF THE CAPILLARY

2. Which of the following are opposing ultrafiltration out of the capillary i.e. reabsorbing (F= K[(Pc-Pi)-(np-ni)]) a. Intracapillary lateral pressure; interstitial oncotic pressure b. Plasma oncotic pressure; tissue turgor pressure c. Intracapillary lateral pressure; tissue turgor pressure d. Plasma oncotic pressure; interstitial oncotic pressure 2. B: Plasma oncotic pressure (Pi) and tissue turgor pressure (ni) want things to go back INTO the capillary and be reabsorbed into the blood stream. Q 1 and Q 2 are the starling hypothesis of fluid exchange. These 4 factors are starling forces. Using calculations, the pressure to filter out of the capillary at the arterial end is +16 and and the venous end is -14 (ie reabsorb opp. direction). Net filtration of 4-8 liters a day is returned to blood via lymph.

3. Use the graph below to select the incorrect statement:

a. Decreased capillary pressure promotes more reabsorption into the capillary/blood stream b. Decreased plasma protein level promotes less reabsorption back into the capillary/blood stream c. Increased capillary pressure promotes more filtration out of the capillary than decreased plasma protein level d. Decreased capillary pressure promotes more filtration out of the capillary than decreased plasma protein level 3. D is incorrect. The graph shows the filtration(out)-absorption(in) balance that occurs normally and when there are relative changes in capillary blood pressure and plasma protein concentration.

4. What is not true about the lymphatic system? a. Closed blind ends drain interstium -> lymph node -> subclavian/internal jugular vein b. Similar to plasma except with lower protein concentration c. Cannot take in larger protein or chylomicrons d. Have valves and smooth muscle contraction that can promote flow via breathing or flexing 4. C: Lymph can take larger proteins and vary in levels!

5. What is not a clinical condition that causes edema? a. Increased capillary lateral pressure: heart failure: b. Hypoproteinemia: low plasma protein albumin: low oncotic pressure to more fluid reabsorbed: i.e. during starvation or burns or into urine c. Hyperproteinemia: high plasma protein albumin: high oncotic pressure to more fluid filtered : i.e. during starvation or burns or into urine d. Lymphatic obstruction: due to parasites/cancer low water:protein flux ratio leaders to high lympathic protein caused by obstruction e. Increased capillary permeability: due to damage/infection localized edema; local vasodilation; local inflammation (mast/hist/bradykinin); local high capillary hydrostatic pressure 5. C: hypo not hyper :) 6. Interstitial fluid pressure increased in the legs due to standing but not enough to prevent capillary perfursion. Why doesn’t everyone develop edema when standing whereas CHF patients do? a. Drop capillary pressure via myogenic contraction of arteries b. Shutdown of arterioles of many capillaries c. Skeletal pump of veins d.Lymphatic contraction removes remaining free fluid e. All of the above 6. E: All of the above are true 7. A coronary blood flow of 80mL/min/100gtissue supports O2 use of 8mL/min/min/100gtissue.

What is not true about coronary circulation physiology? a. Dense heart muscle capillary: increase surface area and reduce diffusion distance b. Poor arterial interconnections: Collaterals only supply 10% c. Low O2 extraction: Low blood flow rate due to low O2 usage d. All of the above are true 7. C is wrong. The heart has a high O2 extraction.

8. What factors influence coronary circulation?

I. Mechanical: Reduction of coronary blood flow in left side during systole/diastole II. Autoregulation: Keeps flow constant by increasing resistance of coronary vessels III. Autoregulation: Dilate for flow via low pO2, high K/ adenosine(myokinaseATPto5’nucleotidaseAdenosine) + B2epinephrine IV. ANS: B2R on arterioles dilate w sympathetic (large arteries constrict with sympathetic), PS only tiny vasodilation a. I, I, IV b. I, III, IV c. I, II, IV d. I, II, III, IV 8. All of them are factors!

9. Cerebral circulation receives 15% of cardiac output but only represents 2% of body mass.

What is not true? a. Higher in grey matter b. Stoke can be caused by artery obstruction or cerebral hemorrhage c. BBB cells have tight jnx and lack fenestrations/cleft and are played with astrocytes/glial cells so most water-soluble stuff restricted d. There is lymphatic vessels in brain 9. D: No lymph in brain 10. What are factors influencing cerebral circulation?

I. ANS: Sympathetic response negligible; some constriction to large arteries; PS only dilates meningeal vessels maybe causes headaches II. Autoregulation: Flow is constant due to arteriole pressure and chemical environment III. Autoregulation: Increase in brain flow, perfusion, PCO2 can all vasodilator IV. pCO2 primary cerebral regulator (more pCO2= less regulation ability due to impact on increasing acid levels H+ leading to vasodilation) a. I, II, IV b. I, II, III, IV c. I, IV, II d. I only 10. B: again, all of them are correct; don’t want to confuse 11. Pulmonary artery venous blood -pulmonary vein> Left heart (all cardiac output). More thin than systemic veins and less smooth muscle in arteries. Their capillary surface is huge with a tiny diffusion distance. What is false? a. Pulmonary resistance is 1/8 of systemic to blood flow b. Pulmonary pressure is super low c. Pulmonary vessels are just larger and thus have less resistance d. High distensibility of pulmonary vessels does not change pulmonary blood flow 11. D: High distensibility does change due to flood flow very quickly. Resistance decreases exponentially as perfusion pressure increases due to distensibility. It also recruits previously closed vessels. The fall in resistance during exercise and increase in pressure can allow for increased blood flow. Increased inflation pulls on capillaries due to expanded alveoli recoil.

There is reported smaller differences between plasma oncotic pressure and capillary pressures in the lung so that net filtration (out of capillary) is favored.

11. Factors influencing pulmonary circulation are: I. Metabolic autoregulation: Unlike in arteries, acidosis or low oxygen constricts pulmonary arteries to divert blood.

II. ANS: little control over pulmonary a. I b. II c. I & II d. none 11. C. Both are true 12. Acral skin arteriovenous anastomoses (AVAs) can bypass capillaries to shunt blood for warmth. It is variable and influenced by sympathetic nerve activity from the hypothlamus. What does not happen to regulate a rising core temperature? a. Flow to AVA decreases and flow to acral skin increases b. Flow to AVA increases and flow to acral skin decreases c. Nonacral skin sweat glands + vasodilation d. Kinogen-Kallikrein>Kallidin*->Bradykin* to vasodilator 12. B: Flow to AVA decreases and flow to acral skin increases. B2R help dilate, a1R help constrict in cold (impact of NE is higher in cold due to more affinity to A1R) Prolonged cold exposure actually causes vasodilation due to protacylcin release and hunting reaction. Local low pO2 and high pCO2 cause vasodilator (ie redness after compression).

13. Muscles receive 20% of blood flow but represent 40% of body mass. Blood flow during exercise can increase 10x due to vasodilation + capillary recruitment that lowers vascular resistance. This can sometimes be stopped because: a. Muscle contractions raise tissue pressure b. Muscle contractions decrease tissue pressure c. Restriction of venous outflow d. Facilitation of arterial inflow 13. A: Muscle contractions raise tissue pressure which allows venous outflow but inhibits arterial inflow from time to time