a) Determine the volume flow rate of blood under normal conditions.You will need
ID: 1322589 • Letter: A
Question
a) Determine the volume flow rate of blood under normal conditions.You will need to look up the stroke volume of the heart and the number of beats of the heart per minute, and calculate the volume flow rate of blood from these quantities.
b) From your volume flow rate of blood, calculate the speed of the blood in the aorta. Look up dimensions of the aorta as needed.
c) The diameter of a typical capillary is 3 microns and the blood speed in the capillary is measured to be 0.80 mm/s. From these quantities determine the number of capillaries.
Explanation / Answer
An average person has a resting heart rate of 70 beats/minute and a resting stroke volume of 70 mL/beat. The cardiac output for this person at rest is:
Cardiac Output = 70 (beats/min) X 70 (mL/beat) = 4900 mL/minute.
= 81.67 ml/s
= 81.67 cc/s
average dia of the aorta = 3 cm
Av = volume flow rate
thus A = pi x d^2
A = 3.14 x .03^2 = 28.26 cm^2
v = 81.67 / 28.26 = 2.88 cm/s
capillary dia = 1 x 10^-6 m = 1 x 10^-4 cm
area = 3.14 x 10^-8 cm^2
velocity = 0.08cm/s
volume flow rate per capillary = 2.512 x 10^-9 cc/s or ml/s
no of capillaries = 81.67 /2.512 x 10^-9 = 3.25 x 10^10
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