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Lecture 16

PHGY 210 Lecture Notes - Lecture 16: Viscosity, The Fluid, Cardiovascular Physiology

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PHGY 210
Melissa Vollrath

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phgy 210
lecture #:
February 8, 2017
Michael Guevara
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PHGY 210 Lecture 16 (Feb 8, 2017) Michael Guevara
Do not redistribute. Page 1 of 4 Written by: Yingshuo Song
P= F/A
Unit: pascal (Pa) = N/m2
Practical unit: cm H20; mmHg
Blood pressure = 120/80 mmHg
Central venous pressure = 5-10 cm H20
Bag filled with saline attached to a tube.
o If I want to create a pressure, but no flow.
o We close the end to the tube to have no flow and we squeeze on
the bag to create pressure
o The pressure exerted on the bag will be transmitted to the water
all along the tube.
o The pressure everywhere in the system is equal no net flow
static system (no movement)
o Pressure is exerting forces in all directions
Apply force over a distance, we are working W = Fd
o Work done on system to pressurize it so “pressure energy
stored in system
Conservation of E: the work applied to squeeze the system goes into
pressure energy in the fluid.
Creating a leak with a pin in the tube, the pressure decreases, the E
decreases and the E goes into the kinetic E of the flow through the
leak. So if there is a leak, the fluid won’t be completely removed. Only
a certain amount will. If the hole is left unchecked for a long time, the
pressure in the system will gradually drop to atmospheric pressure. In
addition, since there is no pressure E exerted on the system, the flow through the hole will stop.
Ventricle is creating pressurized system in the arteries!
If we have a flow, we have a pressure gradient in the direction of the vessel
Fright >Fleft, volume will go to the left
In fluid, we have internal friction (due to fluid viscosity), which creates heat. As we move down the tube, the
pressure E is going into heat.
Internal friction is created when some parts of the fluid is sliding over each other.
Pressure E is needed to overcome the frictional E in order for blood to flow.
Pressure down the Vascular Tree
The pressure decreases, as there is a flow moving down a pipe. The flow starts in the aorta. The decrease in
pressure is keeping the flow
Pressure of Aorta: about 100mm Hg. By the time we end up in the arterial, the pressure may be only 40 mmHg.
Eventually, we will end up in the capillaries where the pressure is only 20mmHg, etc.
Pressure in the Veins: about 5mm Hg
Essentially the function of the ventricle is to pump blood and exert a pressure on the aorta, which will create flow.
The pressure in bold are the
values you need to
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