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Why does arteriole dilation increase capillary pressure and flow but venous dilation does not?
Wiki User
∙ 15y ago
Blood flow in the circulatory system is as follows:
arteries->arterioles->capillaries->venules->veins.
if you dilate the arteriole you are in fact lowering the resistance of the vessel (Poiseuille's Law), and it follows that net flux will increase.
If capillary resistance remains the same, but the net flux has increased, then there will be an upwards change in pressure (Ohm's law).
As far as veins go, it has a high compliance, which means that it can store large amounts of blood without raising venal pressure. If your question asked whether or not capillary pressure increases when venous dilates then the answer is no. Capillary blood flow will be less restricted as they flow into venules->vein and therefore will not have an increased pressure.
If the question asked whether or not the venal pressure increases, then the answer is yes, but it is negligible (it has high compliance).
Wiki User
∙ 15y ago
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Will an increase in capillary pressure shift fluid into the capillaries?
An increase in capillary pressure will shift fluid into or out of the capillaries
Does arteriole blood pressure increase in response to increased heart rate?
Blood pressure.
How is blood pressure affected when you increase dilation?
Blood pressure drops as dilation increases. This occurs because of decrease resistance.
Why water and dissolved substances leave the arterioles end of the capillary and enter the venule end?
Water and dissolved substances leave the arteriole end of the capillary due to hydrostatic pressure being higher than osmotic pressure and enter the venule of the capillary due to osmotic pressure being higher than hydrostatic pressure.
Water and solutes flow form the arteriole end of the capillaries into the tissues due to what?
Hydrostatic pressure(inside capillary) is higher than osmotic pressure it re-enters the capillary on venule end because inside the hydrostatic pressure is now lessthan osmotic pressure drawing water back in
Why is glomerulus a high pressure capillary bed?
The diameter of the afferent renal arteriole narrows progressively more and more into the glomerular capillaries, with the same blood flow, leading to an increase in pressure within the glomerulus. This is so that the high pressure can force solutes and water across into the Bowman's capsule for the renal tubules.
How high blood pressure built up in the glomerulus?
It builds up because the calibre of the efferent arteriole is less than that of the afferent arteriole. The cappilary pressure is opposed by the lower osmotic pressure or the blood and the lower filtrate hydrostatic pressure in the glomerular capsule.
Function of arterioles?
An arteriole is a very small blood vessel that leads an artery to a capillary. The main function of the arteriole is to change the blood pressure and velocity of blood flow.
Is the glomerular filtration rate the same when the efferent arteriole is constricted and dilated?
OLD, INCORRECT ANSWER: Changes in the diameter of the efferent arteriole will either increase (dilation) or decrease (constriction) the blood flow to the glomeruli. An increased flow means a more blood getting filtered over time. NEW, CORRECT ANSWER The 'efferent' arteriole leaves the renal corpuscle. It is easy to remember which direction efferent and afferent things are going by thinking e=exit and a=arrive. If you constrict the efferent arteriole, you actually inhibit blood from leaving the glomerulus, thus increasing the outward hydrostatic pressure pushing fluid into Bowman's capsule and increasing filtration. If you dilate the efferent arteriole, then you reduce pressure in the glomerular capillaries and reduce filtration.
What is the effect of constricted arterioles in the glomerular filtration rate?
Decreasing the diameter of the efferent arteriole would increase the hydrostatic pressure inside the glomerulus and effectively increase the glomerular filtration rate. If you increase the diameter of the afferent arteriole you would achieve the same effect.
What causes the transfer of materials between capillaries and tissue fluid?
As blood enters the capillary bed on the arteriole end, the blood pressure in the capillary vessel is greater than the osmotic pressure of the blood in the vessel. The net result is that fluid moves from the vessel to the body tissue.At the middle of the capillary bed, blood pressure in the vessel equals the osmotic pressure of the blood in the vessel. The net result is that fluid passes equally between the capillary vessel and the body tissue. Gasses, nutrients, and wastes are also exchanged at this point.On the venue end of the capillary bed, blood pressure in the vessel is less than the osmotic pressure of the blood in the vessel. The net result is that fluid, carbon dioxide and wastes are drawn from the body tissue into the capillary vessel.
Why At the arteriole end of the capillary more fluid leaves the capillary than enters as a result of differences in what?
The reason fluid leaves at the arterial end of the capillary bed and returns to the venous end of the capillary bed is the difference in hydrostatic pressure. This means the pressure against the inside of the vessel is greater that the pressure on the outside of the vessel on the arterial end and vice-versa on the venous end. Also, loss of water at the arterial end very slightly raises the oncotic pressure on the venous end, although to what degree this adds to the return of fluid to the vasculature is unknown.
