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 <br> </td> <td width="2" bgcolor="#ffcc33"><img src="http://www.vhlab.umn.edu/atlas/graphics/yellowstroke.gif" alt=" " width="2" border="0"></td> <td width="789" valign="top" class="headbkgimage"> <table width="789" border="0" cellpadding="0" cellspacing="0"> <tr> <td colspan="8" align="left"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/index.shtml"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutHeader.gif" alt="Physiology Tutorial" width="789" height="29" border="0"></a></td> </tr> <tr> <td width="64"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/blood.shtml" onmouseout="MM_swapImgRestore()" onmouseover="MM_swapImage('PhysTsub_0161','','/atlas/graphics/PhysTutsub_01-over.gif',1)"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutsub_01.gif" alt="Blood" name="PhysTsub_0161" width="64" height="45" border="0" id="PhysTsub_0161"></a></td> <td width="77"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/blood-vessels.shtml" onmouseout="MM_swapImgRestore()" onmouseover="MM_swapImage('PhysTsub_0261','','/atlas/graphics/PhysTutsub_02-over.gif',1)"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutsub_02.gif" alt="Blood Vessels" name="PhysTsub_0261" width="77" height="45" border="0" id="PhysTsub_0261"></a></td> <td width="67"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/blood-flow.shtml" onmouseout="MM_swapImgRestore()" onmouseover="MM_swapImage('PhysTsub_0361','','/atlas/graphics/PhysTutsub_03-over.gif',1)"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutsub_03-over.gif" alt="Blood Flow" name="PhysTsub_0361" width="67" height="45" border="0" id="PhysTsub_0361"></a></td> <td width="100"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/the-human-heart.shtml" onmouseout="MM_swapImgRestore()" onmouseover="MM_swapImage('PhysTsub_0461','','/atlas/graphics/PhysTutsub_04-over.gif',1)"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutsub_04.gif" alt="The Human Heart" name="PhysTsub_0461" width="100" height="45" border="0" id="PhysTsub_0461"></a></td> <td width="120"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/cardiovascular-function.shtml" onmouseout="MM_swapImgRestore()" onmouseover="MM_swapImage('PhysTsub_0561','','/atlas/graphics/PhysTutsub_05-over.gif',1)"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutsub_05.gif" alt="Cardiovascular Function" name="PhysTsub_0561" width="120" height="45" border="0" id="PhysTsub_0561"></a></td> <td width="100"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/coronary-circulation.shtml" onmouseout="MM_swapImgRestore()" onmouseover="MM_swapImage('PhysTsub_0661','','/atlas/graphics/PhysTutsub_06-over.gif',1)"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutsub_06.gif" alt="Coronary Circulation" name="PhysTsub_0661" width="100" height="45" border="0" id="PhysTsub_0661"></a></td> <td width="100"><a target="_blank" href="http://www.vhlab.umn.edu/atlas/physiology-tutorial/references-and-sources.shtml" onmouseout="MM_swapImgRestore()" onmouseover="MM_swapImage('PhysTsub_0861','','/atlas/graphics/PhysTutsub_08-over.gif',1)"><img src="http://www.vhlab.umn.edu/atlas/graphics/PhysTutsub_08.gif" alt="References and Sources" name="PhysTsub_0861" width="100" height="45" border="0" id="PhysTsub_0861"></a></td> <td width="161" align="left"></td> </tr> </table> <table width="789" border="0" cellpadding="0" cellspacing="0"> <tr valign="top"> <td valign="top" width="779" class="descbkgimage"> <table width="779" border="0"> <tr valign="top"> <td width="15" height="15"></td> <td width="764" height="15"></td> </tr> <tr valign="top"> <td></td> <td> <table border="0" cellspacing="0" cellpadding="0"> <tr valign="top"> <td class="tutorialtext"> <p>The task of maintaining an adequate interstitial homeostasis (the proper nutritional environment surrounding all cells in your body) requires that blood flows almost continuously through each of the millions of capillaries in the body. The following is a brief description of the parameters that govern flow through a given vessel. All bloods vessels have certain lengths (L) and internal radii (r) through which blood flows when the pressure in the inlet and outlet are unequal (Pi and Po respectively); in other words there is a pressure difference (ΔP) between the vessel ends, which supplies the driving force for flow. Because friction develops between moving blood and the stationary vessels walls, this fluid movement has a given resistance (vascular), which is the measure of how difficult it is to move blood through a vessel. One can then describe a relative relationship between vascular flow, the pressure difference, and resistance (i.e., the basic flow equation):</p> <table border="0" cellspacing="5" cellpadding="0" align="center"> <tr> <td nowrap="nowrap">Flow =&nbsp;</td> <td nowrap="nowrap" align="center">pressure difference<hr noshade="noshade" size="1">resistances</td> <td nowrap="nowrap">or Q =&nbsp;</td> <td nowrap="nowrap" align="center">ΔP<hr noshade="noshade" size="1">R</td> </tr> </table> <blockquote>where Q = flow rate (volume/time); ΔP = pressure difference (mm Hg); and R = resistance to flow (mm Hg x time/volume).</blockquote> <p>This equation may be applied not only to a single vessel, but can also be used to describe flow through a network of vessels (i.e., the vascular bed of an organ or the even your entire systemic circulatory system). It is known that the resistance to flow through a cylindrical tube or vessel depends on several factors (described by Poiseuille) including: 1) radius, 2) length, 3) viscosity of the fluid (blood), and 4) inherent resistance to flow, as follows:</p> <table border="0" cellspacing="5" cellpadding="0" align="center"> <tr> <td nowrap="nowrap">R =&nbsp;</td> <td nowrap="nowrap" align="center">8 L η<hr noshade="noshade" size="1">π r<sup>4</sup></td> </tr> </table> <blockquote>where r = inside radius of the vessel, L = vessel length, and η = blood viscosity.</blockquote> <p>It is important to note that a small change in vessel radius will have a very large influence (4th power) on its resistance to flow; e.g., decreasing vessel diameter by 50% will increase its resistance to flow by approximately 16 fold. </p> <p>If one combines the preceding two equations into one expression, which is commonly known as the Poiseuille equation, it can be used to better approximate the factors that influence flow though a cylindrical vessel:</p> <table border="0" cellspacing="5" cellpadding="0" align="center"> <tr> <td nowrap="nowrap">Q =&nbsp;</td> <td nowrap="nowrap" align="center">ΔP π r<sup>4</sup><hr noshade="noshade" size="1">8 L η</td> </tr> </table> <p>Importantly, flow will only occur when a pressure difference exists. Hence, it is not surprising that arterial blood pressure is perhaps the most regulated cardiovascular variable in the human body, and this is principally accomplished by regulating the radii of vessels (e.g., arterioles and metarterioles) within a given tissue or organ system. Whereas vessel length and blood viscosity are factors that influence vascular resistance, they are not considered variables that can be easily regulated for the purpose of the moment-to-moment control of blood flow. Regardless, the primary function of the heart is to keep pressure within arteries higher than those in veins, hence to create a pressure gradient to induce flow. Normally, the average pressure in systemic arteries is approximately 100 mm Hg, and which decreases to near 0 mm Hg in the great caval veins (superior and inferior vena cavae). </p> <p>The volume of blood that flows through any tissue in a given period of time (normally expressed as mL/min) is called the local blood flow. The velocity (speed) of blood flow (expressed as cm/sec) can generally be considered to be inversely related to the vascular cross-sectional area, such that velocity is slowest where the total cross-sectional area is largest.</p> </td> </tr> </table> </td> </tr> </table> </td> <td width="10"><img src="http://www.vhlab.umn.edu/atlas/graphics/circles_line_01.gif" alt=" "></td> </tr> </table> </td> </tr> </table> <img src="http://www.vhlab.umn.edu/atlas/graphics/yellowstroke.gif" alt=" " width="980" height="2" border="0"><br> <table width="980" border="0" cellpadding="0" cellspacing="0"> <tr><td> <div align="center"> <small>© 2021 Regents of the University of Minnesota. All rights reserved. The University of Minnesota is an equal opportunity educator and employer. <a target="_blank" href="http://privacy.umn.edu/">Privacy Statement</a></small> </div> <p></p> </td></tr></table> </body> </html></td></tr></table></body></html> What are the factors regulating coronary blood flow?Regulation of coronary blood flow is understood to be dictated through multiple mechanisms including extravascular compressive forces (tissue pressure), coronary perfusion pressure, myogenic, local metabolic, endothelial as well as neural and hormonal influences.
Which increases blood flow in coronary artery?Coronary blood flow and myocardial oxygen supply are improved by balloon inflation that leads to augmentation of diastolic pressure and blood flow to the failing heart.
Which of the following factors have the greatest effect on regulating coronary vascular resistance?Within each beat, the tissue oxygen level exerts the most powerful effect on coronary vascular resistance within the myocardium.
What is the flow of the coronary circulation?Coronary circulation is the circulation of blood in the blood vessels that supply the heart muscle (myocardium). Coronary arteries supply oxygenated blood to the heart muscle. Cardiac veins then drain away the blood after it has been deoxygenated.
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The primary factor regulating blood flow through the coronary arteries is which of the following?
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