[PHYSIO]LEC_207_VASCULAR_DISTENSIBILITY.pdf

(007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS...

(007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 OUTLINE ↑ Volume = ↑ Distensibility; Inversely related to the ↑ pressure and original volume I. VASCULAR DISTENSIBILITY NOTE: If 1 mmHg causes a vessel that originally II. UNITS OF VASCULAR DISTENSIBILITY contained 10 millimeters of blood to increase its volume III. VEINS MORE DISTENSIBLE THAN THE ARTERIES by 1 milliliter, the distensibility would be o.1 per mmHg, IV. VASCULAR COMPLIANCE OR VASCULAR or 10 percent per mmHg. CAPACITANCE V. VOLUME-PRESSURE CURVES OF THE ARTERIAL III. VEINS MORE DISTENSIBLE THAN ARTERIES AND VENOUS CIRCULATIONS Example: Femoral artery and femoral vein VI. EFFECT OF SYMPATHETIC STIMULATION OR Veins is 8x more distensible than the arteries. o Given increase in pressure causes about eight times SYMPATHETIC INHIBITION ON THE VOLUME- as much increase in blood in a vein as in an artery of PRESSURE RELATIONS OF THE ARTERIAL AND comparable size. VENOUS SYSTEMS Pulmonary arteries are about one sixth of those in the VII. DELAYED COMPLIANCE (STRESS- systemic arterial system. RELAXATION) OF VESSELS o PA distensibility are about six times greater than VIII. ARTERIAL PRESSURE PULSATIONS distensibility of systemic arteries. IX. ABNORMAL PRESSURE PULSE CONTOURS X. TRANSMISSION OF PRESSURE PULSES TO THE IV. VASCULAR COMPLIANCE OR VASCULAR PERIPHERAL ARTERIES CAPACITANCE XI. PRESSURE PULSES ARE DAMPED IN THE Example: Blood vessels in arteries and arterioles Defined as the total quantity of blood that can be stored SMALLER ARTERIES, ARTERIOLES, AND in a given portion of the circulation for each mm Hg CAPILLARIES pressure rise. XII. BLOOD PRESSURE Vascular compliance = XIII. NORMAL ATRIAL PRESSURES AS MEASURED BY Increase in volume / Increase in pressure THE AUSCULTATORY METHOD XIV. VEINS AND THEIR FUNCTIONS Vascular Directly Increase Volume XV. SPECIFIC BLOOD RESERVOIR Compliance Proportional Vascular Inversely Increase Pressure Compliance Proportional I. VASCULAR DISTENSIBILITY When there is ↑ of pressure there is also an ↑ of total All vascular vessels are distensible. amount of blood Valuable characteristic of the vascular system A highly distensible vessel that has a small volume may Allows vessels to accommodate the pulsatile output of have far less compliance than a much less distensible the heart and to average out the pressure pulsations. Provides smooth, continuous flow of the blood through vessel that has a large volume. the very small blood vessels of the tissues. Compliance of a systemic vein is 24 x than corresponding VENOUS SYSTEM artery. o The most distensible by far of all the vessels o about 8 times as distensible and has a volume about o slight increases in venous pressure cause the veins 3 times as great (8 x 3 = 24) to store 0.5 to 1.0 liter of extra blood. o provide a reservoir for storing large quantities of V. VOLUME-PRESSURE CURVES OF THE ARTERIAL extra blood. AND VENOUS CIRCULATIONS Volume pressure curve II. UNITS OF VASCULAR DISTENSIBILITY o convenient method for expressing the relation of Expressed as the fractional increase in volume for each pressure to volume in a vessel or in any portion of millimeter of mercury rise in pressure. the circulation. Vascular distensibility = An increase in vascular tone throughout the systemic Increase in volume circulation can cause large volumes of blood to shift into Increase in pressure x Original volume the heart, which is one of the principal methods that the body uses to rapidly increase heart pumping. Vascular Directly Increase Volume Distensibility Proportional Vascular Inversely Increase Pressure and Distensibility Proportional Original Volume Page 1 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 SYMPATHETIC INHIBITION o decreases the pressure at each volume. IMPORTANCE IN THE ARTERIES o Valuable means for diminishing the dimensions of one segment of the circulation. o Transferring blood to other segments, IMPORTANCE IN VENOUS SEGMENT: o Stab wound with severe hemorrhage → reduces the vessel sizes enough to maintain adequate circulation when there is 25% blood loss. Enhancement of sympathetic tone, especially to the veins, reduces the vessel sizes enough that the circulation continues to operate almost normally even Figure 1. Volume-pressure curves of the systemic arterial and when as much as 25 percent of the total blood volume venous systems, showing the effects of stimulation or inhibition of has been lost. the sympathetic nerves to the circulatory system. In ARTERIAL SYSTEM, (Green line) when there is a volume of about 700ml, VII. DELAYED COMPLIANCE (STRESS- the pressure in this area is about 100 mmHg. However, (Red RELAXATION) OF VESSELS line) when the volume decreases to about 400ml, the pressure in that area will become 0 mmHg. In the VENOUS SYSTEM (the normal volume present here is about 2500-3500ml) ARTERIAL SYSTEM Small amount of blood loss in this segment will abruptly causes physiologic change. The slight decrease of volume (at about 700ml to 400ml) causes a SIGNIFICANT physiologic effect to the body making the pressure abruptly to 0 mmHg VENOUS SYSTEM Small amount of blood loss in this segment will NOT CAUSE SIGNIFICANT physiologic change. There is a need of a greater blood loss (about 3500ml to 2200ml) to achieve a significant physiologic effect in the Figure 2. Effect on the intravascular pressure of injecting a body. volume of blood into a venous segment and later removing the Ex: blood transfusion excess blood, demonstrating the principle of delayed compliance. In a reverse type (blood transfusion), in a venous system with a 2000 ml volume of blood and a pressure of EXAMPLE RESULT MECHANISM 0, the additional volume that was transfused will give an Blood The pressure abruptly The vessel will try to additional volume of 500 ml (2000 ml to 2500 ml) along Transfusion increases from 5 mm compensate, through a with an increase pressure of 10 mm Hg from 0. This (2 bags, Hg to 12 mm Hg progressive delayed increase of pressure does not give an abrupt change in 1000ml) stretching of smooth the venous system with an increase amount of blood. In muscle, allowing the contrast with the arterial system, an additional volume of 200 ml (500 ml to 700 ml), the pressure will then change pressure to return abruptly to 100 mm Hg from 60 mmHg. (decrease) to the normal Venous system is more compliant in the circulatory pressure over a period system as compared to the arterial system with their (20 to 45 min). BUT it will differences in the physiologic changes. NOT go down to its original pressure due to VI. EFFECT OF SYMPATHETIC STIMULATION OR the amount of blood that was transfused in the SYMPHATETIC INHIBITION ON THE VOLUME area. PRESSURE RELATIONS OF THE ARTERIAL AND Abrupt Mitral valve prolapses Due to continuous VENOUS SYSTEMS rupture of to LA (abrupt increase amount of blood over SYMPATHETIC STIMULATION papillary amount of volume) time, the LA will become o Increase vascular smooth muscle tone. muscle from pulmonary vein BIGGER, thus will be o Increases the pressure at each volume of the (Flail mitral and LV. Since it is able to comply with the arteries or veins. valve small, there will be amount of blood leaked Page 2 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 leaflet due increase of pressure ininto the space/cavity Compliance of blood vessels will be dampened as it goes to LA, this pressure will be PLUS the volume of to the most peripheral segment of the vascular system. detachment transmitted to the blood from pulmonary With each beat of the heart a new surge of blood fills the from the pulmonary circulation –circulation. Henceforth, arteries LV) onset of dyspnea. the pressure in LA will not If vascular distensibility is absent: increase abruptly, o All this new blood would have to flow through the overtime the patient will peripheral blood vessels almost instantaneously. be ASYMPTOMATIC as o Only during cardiac systole and no flow would occur compared when the heart during diastole. is not compliant or big to ARTERIAL COMPLIANCE o Normally reduces the pressure pulsations to almost receive large amount of no pulsations by the time the blood reaches the blood. capillaries. Table 1. Example of Delayed Compliance and mechanism o Tissue blood flow is mainly continuous with very little pulsation. DELAYED COMPLIANCE o means that a vessel exposed to increased volume at first exhibits a large increase in pressure. o Progressive delayed stretching of smooth muscle in the vessel wall allows the pressure to return toward normal over a period of minutes to hours. o It is a valuable mechanism by which the circulation can accommodate extra blood when necessary. Decrease intravascular volume: Hemorrhage Causes contraction of vein. RESULT: maintain a high-pressure overtime STRESS RELAXATION o the volume of blood injected causes immediate Figure 4. Pressure pulse contour in the ascending aorta. elastic distention of the vein, but then the smooth muscle fibers of the vein begin to “creep” to longer PRESSURE PULSATION lengths, and their tensions correspondingly o Systolic pressure decrease. - Pressure at the top of each pulse - 120 mmHg VIII. ARTERIAL PRESSURE PULSATIONS o Diastolic pressure - Lowest point of each pulse - 80 mmHg o Pulse pressure - difference between the systolic and the diastolic pressure of the body. - 40 mmHg o This is the pulsation of the aorta, the aorta will give us a pressure of about 120 mm Hg during ventricular contraction and during diastole the pressure in aorta will be decreased up to a point that the valves will be closing, and then as the pressure will decrease up to certain point of around 80 mm Hg. TWO MAJOR FACTORS AFFECT THE PULSE PRESSURE: o The stroke volume output of the heart o The compliance (total distensibility) of the arterial tree Figure 3. Changes in the pulse pressure contour as the pulse o 3rd less important factor: character of ejection from wave travels toward the smaller vessels. the heart during systole Page 3 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 Pulse pressure = Stroke volume/arterial compliance AORTIC STENOSIS SV = EDV-ESV o Valves do not open widely, so there is impediment to 𝐸𝐷𝑉−𝐸𝑆𝑉 flow during ejection/contraction, there will be little EF= × 100 𝐸𝐷𝑉 amount of blood going to the aortic vessel. DEC EF= PP o Dampen systolic pressure. End systolic volume (ESV) – volume of blood that is PATENT DUCTUS ARTERIOSUS retained in the LV during contraction/ejection. o Blood from aorta goes to pulmonary circulation. o Abrupt decline in DBP. During diastole most of the End diastolic volume (EDV) – volume of blood that is blood in the aorta will go to the ductus arteriosus present in the LV during relaxation. going to the pulmonary circulation. So, there will be Pulse Pressure is directly proportional to Stroke lower volume in the aorta as well as the pressure. Volume, so the higher the stroke volume the higher the o One half or more of the blood pumped into the aorta Pulse pressure. Likewise, if there is more ejection of by the left ventricle flows immediately backward blood, the higher the pressure over the diastolic pressure, through the wide-open ductus into the pulmonary so the pulse difference is increased. artery and lung blood vessels, thus allowing the Pulse Pressure is inversely proportional to Arterial diastolic pressure to fall very low before the next Compliance. heartbeat. GREATER STROKE VOLUME OUTPUT (AORTIC AORTIC REGURGITATION REGURGITION) o Valves do not coaptate o Greater the amount of blood that must be o After systole, blood goes back to LV. accommodated in the arterial tree with each o Abrupt decline in DBP heartbeat. o Abnormal valve closure= no INCISURIA o Greater the pressure rises and fall during systole and diastole. The more volume the higher the pressure, X. TRANSMISSION OF PRESSURE PULSES TO THE so systolic pressure will increase. During diastole, PERIPHERAL ARTERIES since there is a leaked from the aorta to the LV, there will be decreased volume in the aorta therefore pressure will increase abruptly. o Greater pulse pressure = 160mmHg - 0mmHg NON-COMPLIANT ARTERIES (ATHEROSCLEROSIS) o Arteries have become hardened. o Rise in pressure for a given stroke volume of blood pumped into the arteries. o Pulse pressure rises to twice normal. o NORMAL (120-80 = 40mmHg) o OLDER ADULTS (160-80 = 80mmHg) o Since the arteries of the elderly people is not compliant anymore due to the calcification (no dilation), hence there would be abrupt increased of volume in that area, the pressure will abruptly increase. IX. ABNORMAL PRESSURE PULSE CONTOURS Figure 6. Progressive stages in transmission of the pressure pulse along the aorta. When heart ejects blood into the aorta during systole o Proximal portion of the aorta becomes initially distended. o The inertia of the blood prevents sudden blood movement all the way to the periphery. Rising pressure in the proximal aorta o Rapidly overcomes this inertia. o The wave front of distention spreads farther and farther along the aorta (this phenomenon is called transmission of the pressure pulse in the arteries) Figure 5. Aortic pressure pulse contours in arteriosclerosis, aortic stenosis, patent ductus arteriosus, and aortic regurgitation. Page 4 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 XI. PRESSURE PULSES ARE DAMPED IN THE Pressure at which the Korotkoff sounds completely disappear should be used as the diastolic pressure. SMALLER ARTERIES, ARTERIOLES AND o AR and AVF CAPILLARIES If the BP is 90/60 and then your BP becomes 130/80 DAMPING although the blood pressure that is measured is 130 over Progressive diminution of the pulsations in the periphery. 80, but your previous BP is 90 over 60. Any blood The aorta will receive pressure from the LV and normal pressure that is increase more than 20 mmHg from pulsation will be present in the aortic level. the baseline is already considered abnormal. NOTE: Only when the aortic pulsations are extremely large or the arterioles are greatly dilated can pulsations be observed in the capillaries CAUSES 1. Resistance to blood movement in the vessels o Small amount of blood must flow forward at the pulse wave front to distend the next segment of the vessel. o Greater the resistance, the more difficult it is for this to occur. 2. Compliance of the vessels o Greater the quantity of blood required at the pulse wave front to cause an increase in pressure. Degree of Damping= Resistance x Compliance Degree of Damping is directly proportional to the resistance and compliance of the blood vessels. ↑ resistance, ↑ degree of dampening and ↑ compliance, ↑ Figure 7. The auscultatory method for measuring systolic and degree of dampening. diastolic arterial pressures. XII. BLOOD PRESSURE XIII. NORMAL ATRIAL PRESSURE AS MEASURED ABNORMAL BP: 140/90 above Auscultatory Method BY THE AUSCULTATORY METHOD Stethoscope is placed over the antecubital artery and a Effects of aging on the blood pressure control mechanism blood pressure cuff is inflated around the upper arm. results progressive increase in pressure with age. When the cuff pressure is great enough to close the o Slight extra increase in systolic pressure usually artery during part of the arterial pressure cycle occurs beyond the age of 60 years. Palpatory Method o Due to the decreasing distensibility, or “hardening”, of the arteries. Feeling the pulses as you inflate the cuff until the o Result of atherosclerosis: ↓compliance of the arterial Korotkoff sound, or the pulsation is absent. When you do wall = ↑ systolic blood pressure. But the diastolic not feel the arterial pulse anymore, that is the highest pressure will still be on that same level. The result pressure that you should remember first. Deflate the will be widening of mean arterial pressure. valve about 2-3 mmHg per second until you feel the radial pulse again. The measurement of the first pulse Kidneys are primarily responsible this long-term coinciding the pressure in BP apparatus that is palpatory regulation of arterial pressure. systolic blood pressure. KOROTKOFF SOUNDS - appreciated o A sound is then heard with each pulsation. o Caused by blood jetting through the partly occluded vessel and by the vibrations of the vessel wall. o Jet causes turbulence in the vessel beyond the cuff and sets up the vibrations heard through the stethoscope. o NO Korotkoff sounds are heard in the lower artery Blood begins to flow through the artery beneath the cuff during the peak of systolic pressure. One begins to hear tapping sounds from the antecubital artery in synchrony with the heartbeat. As soon as these sounds begin to be heard, the pressure level indicated by the manometer connected to the cuff is Figure 8. Changes in systolic, diastolic, and mean arterial about equal to the systolic pressure. pressures with age. The shaded areas show the approximate normal ranges. Page 5 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 ↑ age = ↑ blood pressure (Compared to the systolic and Right Atrial Pressure diastolic, Systolic will have higher blood pressure Regulations of Cardiac Output same as CVP; when the increase) ejection fraction is good the cardiac fraction is also good. Mean Arterial Pressure Cardiac Output = Stroke Volume x Heart Rate Average of the arterial pressures measured by millisecond by millisecond over a period of time. Amount of blood pumped by the heart depends: Cardiac cycle has longer diastolic phase ≠ average of o Ability of the heart to pump SBP and DBP o Tendency for blood to flow into the heart from the Remains nearer to diastolic pressure than to systolic peripheral vessels. pressure during the greater part of the cardiac cycle Normal right atrial pressure is about 0 mm Hg: Once the Exception in tachycardia: Diastolic phase of cardiac cycle inferior vena cave and superior vena cava inserts in right will be shortened almost like systolic cycle. The mean atrium the pressure is almost 0. arterial pressure moves towards the systolic phase or in Increase to 20-30 mm Hg under very abnormal the middle and not near the diastolic phase. conditions. More volume = More pressure o CHF and massive BT MAP = 2(DBP) + SBP/3 Lower limit to the RAP is -3 to -5 mm Hg below atmospheric pressure. XIV. VEINS AND THEIR FUNCTIONS o Similar pressure in the chest cavity that surrounds Provide passageways for flow of blood to the heart. the heart. Capable of constricting and enlarging. o Severe hemorrhage o Storing either small or large quantity of blood and In heart failure the heart is unable to pump out the blood making this blood available when it is required. in left ventricle which results in increase in end diastolic Venous Pump volume because not all have been ejected. o Peripheral veins can also propel blood forward. If the right heart is pumping strongly, the right atrial o Help to regulate cardiac output. pressure decreases and vice versa. Vein has the characteristic to act as the heart of the lower Any effect that causes rapid inflow of blood into the right extremity or the peripheral vascular system. atrium, elevates the RAP. VENOUS PRESSURE – RIGHT ATRIAL PRESSURE (CENTRAL Venous Resistance VENOUS PRESSURE) Large veins have so little resistance to blood flow when Venous pressure should be assessed to know if patient they are distended. Also have an increase in pressure in has a good forward flow of blood going to the heart. It is some areas but lower pressure than the rest of vascular measured by: system. o Inserting a catheter in femoral vein. The catheter o 0 mm Hg – no importance will be forwarded to inferior vena cava to right atrium. o Radial vein- forward catheter to subclavian to brachiocephalic then to superior vena cava o Jugular vein- catheter forwarded to jugular venous vein segment then to brachiocephalic – vena cava- right atrium. CENTRAL VENOUS PRESSURE = RAP Blood from systemic veins flows into the right atrium of the heart. Regulated by the following: Ability of the heart to pump blood out of the right atrium and ventricle into the lungs. Tendency for blood to flow from the peripheral veins into the right atrium. Factors Increasing Venous Return: Increased blood volume Increased vessel tone → resultant increased peripheral venous pressures Dilation of the arterioles → decreases the peripheral resistance → allows rapid flow of blood from the arteries into the veins. MAP Page 6 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 Figure 9. Effect of gravitational pressure on the venous pressure Deep Vein thrombosis (DVT) - clots found in legs will throughout the body in the standing person. dislodge and will go to the inferior vena cava, right atrium Venous Resistance and Peripheral Venous Pressure and lodge in pulmonary trunk. Results in decrease or LOW RESISTANCE AREA absence of blood flow from right ventricle going to Large veins that enter the thorax are compressed by the pulmonary trunk because of the obstruction. Right surrounding tissues. ventricle will increase in pressure and it will be reflected Arms veins are compressed by their sharp angulations in right atrium. Blood flow will not occur from Right over the 1st rib. ventricle to the pulmonary trunk and it will go back Right Neck veins pressure often falls leads veins to collapse atrium. Causing higher volume and higher pressure. due to a very low atmospheric pressure. As it goes HOW TO ASSESS RAP INDIRECTLY? upward, they are prone to collapse. Jugular veins Jugular venous pressure measurement - put a ruler in collapse because the neck vein pressure is very low. sternal angle of Louis where you measure the distance Abdomen veins are often compressed by different organs from the highest column of blood to the sternal angle of and by the intra-abdominal pressure. Creates a little Louis then add 5 mmHg (distance from the sternal angle higher than normal venous pressure which is about 5-6 of louis to the right atrium) mmHg higher than the rest of venous segment. Other: catheter forwarded in radial vein in femoral vein- NOTE: these are invasive. Large veins have some resistance to blood flow. Initially the right atrial pressure may accommodate up to Supine position: PVP in small veins is +4 to +6 mm Hg > 4-6 mmHg that is why even though there is a peripheral RAP. All pressure in venous segment is 0 however venous pressure that is elevated it will not still be seen because of some venous segment, it will try to recoil and clinically. In early stages of heart failure, there will be create a pressure of 4-6 mmHg than the right atrial no symptoms, just like shortage of breath because the pressure for it to forward some of the blood towards the right atrial pressure can still accommodate up to +4 to +6, inferior vena. It needs a little higher pressure in the periphery so that the blood will flow back to the heart. Effect of Intraabdominal Pressure on Venous Pressure of Leg Pressure in abdominal cavity of a recumbent person normally averages about +6 mmHg. Factors will increase IAP (> +15 to +30 mmHg) o Pregnancy o Large tumor o Abdominal obesity o Ascites (excessive fluid in the abdominal cavity) IAP causes increase venous pressure in the leg. o Abdominal veins will open and allow the blood to flow from the legs to the heart. o If the intra-abdominal pressure is +20 mmHg the lowest possible pressure in the femoral veins is also about +20 mmHg. Varicose vein if present, there will be increase in abdominal pressure this pressure will be reflected in lower extremity. Figure 10. Compression points that tend to collapse the veins STANDING POSITION entering the thorax. o Right atrium remains about 0 mmHg. o Because the heart pumps into the arteries any Effect of High Atrial Pressure on Peripheral Venous Pressure excess of blood that attempts to accumulate at this Blood begins to back up in the large veins. point Collapse points in the veins open up. STANDING ABSOLUTELY STILL Rise in peripheral venous pressure in the limbs o Pressure in the veins of the feet is about +90 mmHg. o Because of the gravitational weight of the blood in RAP +4 to +6 mm Hg the veins between the heart and the feet o Peripheral venous pressure is not a noticeably elevated. The venous pressures at other levels of the body are o Even in the early stages of heart failure at rest proportionately between 0 and 90mmHg. WHAT CAUSES RAP INCREASE? Subclavian vein pressure: +6 mmHg Atrial septal defect - left to right shunting in the heart in Total arm venous pressure: +35 mmHg congenital heart disease. More blood from left atrium will go to right atrium causing more volume of blood, thereby, Effects of Gravitational Factor on Arterial and other Pressure creating a higher pressure in right atrium. A standing person who has a MAP of 100 mmHg at the Tricuspid regurgitation - addition of blood going to right level of the heart has an arterial pressure in the feet of atrium instead of going to pulmonary circulation. about 190 mmHg. Therefore, when the arterial pressure is 100 mmHg. Page 7 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 o It means that 100 mmHg is the pressure at the gravitational level of the heart but not necessarily elsewhere in the arterial vessels. Venous Valves and the "Venous Pump”: Their Effects on Venous Pressure The gravitational pressure effect would cause the venous pressure in the feet always to be about +90 mmHg in a standing adult if with absent venous valve. o Leg movement: tightens the muscle and compresses the veins in or adjacent to the muscles → which squeezes the blood out of the veins. “Venous Pump” or “Muscle Pump” o Efficient enough maintain pressure less than (60% of all blood in the circulatory system is usually in the veins - because of its compliance - it serves as circulatory 5. TRUE OR FALSE: A decrease in the stroke volume cause a blood reservoir. decrease in pulse pressure. 6. Determine the disorder. One half or more of the blood pumped THE SPLEEN AS A RESERVOIR FOR STORING RED BLOOD into the aorta by the left ventricle flows immediately backward CELLS through the wide-open ductus into the pulmonary artery and lung In stab wound that is affecting the spleen or liver and the blood vessels, thus allowing the diastolic pressure to fall very low patient will not have a surgical repair immediately, the before the next heartbeat. patient will die because of increase blood loss. A. Patent ductus arteriosus Sinuses can swell the same as any other part of the B. Aortic stenosis venous system and store whole blood. C. Aortic regurgitation D. All of the above Page 9 of 10 CMED 1C  (007) VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE ARTERIAL AND VENOUS SYSTEMS DR. L. ASUNCION-VIADO | 01/25/21 reveal that the patient has a right atrial pressure of 10 mm Hg. An 7. Auscultatory method is 100% accurate. increase in which of the following would be expected in this A. True patient? B. False A. Plasma colloid osmotic pressure C. It depends on the situation. B. Interstitial colloid osmotic pressure C. Arterial pressure 8. Mean arterial pressure is therefore determined about ___ D. Cardiac output percent by the diastolic pressure and percent by the systolic E. Vena cava hydrostatic pressure pressure. A. 60,40 17. Which of the following parts of the circulation has the highest B. 40,60 compliance? C. 50,50 A. Capillaries D. 30,70 B. Large arteries C. Veins 9. Korotkoff sounds is named after: D. Aorta A. Nikolai Korotkoff E. Small arteries B. Nicholas Korotkoff C. Nicki Korotkoff 18. Which of the following sets of physiological changes would be D. Korotkoff Nikolai expected to occur in a person who stands up from a supine position? 10. The degree of damping is almost directly proportional to the product of resistance times compliance. A. Somehow B. False C. True 11. Effect of stretching of veins to its cross-sectional areas. A. Increase B. Decrease C. No Change 12. Effects of edema to the skin. A. Painful 19. Which of the following would decrease venous hydrostatic B. Weak pressure in the legs? C. Gangrenous A. Increase in right atrial pressure. D. Ulcerate B. Pregnancy E. All of the above C. Movement of leg muscles D. Presence of ascitic fluid in the abdomen 13. Treatment to varicose vein are the following except: A. Tight binder 20. All are true about Right Atrial Pressure except: B. Long compression stockings A. Also known as the central venous pressure C. Elevation of legs at least heart level B. Weakness of the cardiac muscle can cause increase D. Elevation of legs below heart level in the RAP. C. Elevated with increased Venous return. 14. At least how many percent of all blood in the circulatory system D. Elevated with strong pumping of the right heart. is usually in the veins? A. 50% D TRUE B FALSE TRUE A B A A C A E D B C E C B C D B. 60% Answers: C. 70% D. 80% 15. Specific blood reservoir that is not part of the systemic venous REFERENCES reservoir system. 1. Berne, R. M., Koeppen, B. M., & Stanton, B. A. A. Liver (2010). Berne & Levy Physiology. Philadelphia, PA: B. Spleen Mosby/Elsevier. C. Heart 2. Costanzo, L. S. (2014). Physiology (Fifth edition.). D. Venous plexus Philadelphia, PA: Saunders/Elsevier. 3. Guyton, A.C., Hall, J. E. Guyton and Hall Textbook 16. A 65-year-old man is suffering from congestive heart failure. of Medical Physiology. 13th ed., W B Saunders, 2015. He has a cardiac output of 4 L/min, arterial pressure of 115/85 mm Hg, and a heart rate of 90 beats/min. Further tests by a cardiologist Page 10 of 10 CMED 1C