Lecture 09 Overview of Circulation Flashcards
Blood flow resistance is indirectly proportional to which of the following? Viscosity Vessel diameter Density Viscosity and density
Vessel diameter
84% of the blood volume is in the systemic circulation. Of this, 64% is in what type of vessel?
Veins
If rate of blood flow through the entire circulatory system (cardiac output) = 100ml/sec AND the pressure difference from the systemic arteries to the systemic veins = 100 mmHG, what is the total peripheral resistance equal to?
1 PRU
Reynolds number is a measure of what parameter?
Tendency for turbulence
What represents the viscosity of blood with a hematocrit of 38-42?
3.0
What are the functional parts of the circulation?
Aorta, arteries, arterioles, capillaries, venules and veins
What is the arterial pressure during systolic?
120 mm Hg
What is the arterial pressure during diastolic period
80 mm Hg
When does the arterial pressure drop to 0 mm Hg?
By the time it reaches the termination of the vena cava
What is the pressure range of the systemic capillary?
35 mm Hg to 10 mm Hg
What is the systolic pulmonary artery pressure?
25 mmHg
What is the Pulmonary diastolic pressure?
8 mm Hg
What parts of the circulatory system make up the systemic system?
Aorta, large arteries, small arteries, arterioles, capillaries, venules, small veins, large veins, vena cava
What makes up the pulmonary system?
Pulmonary arteries, arterioles, capillaries, venules, pulmonary veins
What is the major function of arteries?
Transport under high presssure
What do arterioles control?
Conduits
What are the functions of capillaries?
Exchange between blood and extracellular fluid
84% of blood volume is in the systemic circulation. How much of this blood volume is in the veins, arteries and systemic arterioles/capillaries?
64% in veins
13% in arteries
7% in systemic arterioles and capilaries
How much % of blood is in the heart and lungs?
16%
What is the equation of velocity of blood flow?
V = F/A F = volume of blood flow A = vascular cross-sectional area
What is the first principle of the circulatory system?
Rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the tissue need
What is the second principle of the circulatory system?
The cardiac output is controlled mainly by the sum of all the local tissue flows
What is the third functional principle of the circulatory system?
Arterial pressure regulation is generally independent of either local blood flow control or cardiac output control
What type of vessels monitor tissue needs?
Microvessels
What do O2, other nutrients, CO2 accumulation, tissue wast product accumulation all do to local blood vessels?
Act directly on local blood vessels and dilate or constrict accordingly
What does the heart respond to in the second functional principle?
Demands of tissues. And nerve signals may be needed to help the heart pump required amount of blood
If arterial pressure falls below 100 mm Hg, nervous reflexes:
Increase force of heart pumping
Constrict large venous reservoirs
Generally constrict most of the arterioles throughout the body (increases arterial pressure)
Kidneys may later play important role in pressure control
What are factors that determine blood flow?
Pressure difference (pressure gradient) Resistance
How can the flow through a vessel be calculated?
by Ohm’s law
F = Change of P/R
Change of P = P1-P2
ml/min or liters/min
What is the overall blood flow of an adult at rest?
5000 ml/min
which is the cardiac output
What is laminar blood flow?
Streamline flow in layers
What are the characteristics of streamlines?
Each layer maintains same distance from vessel wall
Central - most portion of the blood stays in the center
Each layer slips easily past surrounding layers
Velocity of fluid flowing in center is greater than that of fluid flowing towards the outer edge
When does turbulent flow occur?
When flow is too great
Blood passes an obstruction within the vessel
Blood has to make a sharp turn
Blood passes over a rough surface
When does blood flow with greater resistance?
When eddy currents occur
What is directly proportional and inversely proportional to the tendency for turbulent flow to increase?
Direct proportion to velocity of blood flow
Direct proportion to the diameter of the vessel
Direct proportion to the density of the blood
Inversely to the viscosity of the blood
What is the Reynolds number equation (Measure of the tendency for turbulence to occur)?
Re=(vdp)/n
Re= reynolds number
v= mean velocity of blood flow in cm/sec
d = vessel diameter in cm
p = density (normally only slightly greater than 1)
n = viscosity (in poise) (blood viscosity normally = 1/30 poise)
When will the turbulent flow occur in some regions of a vessel?
At Re above 200-400
When will turbulence occur even in a straight vessel?
When Re rises above 2000
What is blood pressure
The force exerted by the blood against any unit area of the vessel wall
How can pressure be measured?
With a mercury manometer or with electronic transducers
