Blood pressure in humans is normally expressed as a ratio x / y , where x is the

Question

Blood pressure in humans is normally expressed as a ratio x/y, where x is the maximum arterial pressure in mmHg, called the systolic pressure, and y is the minimum arterial pressure in mmHg, called the diastolic pressure. A typical blood pressure is 120/70. Blood pressure readings are normally taken as the same level as the heart, and blood at 37 C has a density of around 1060 kg/m3.

Part (A) Consider a (tall) person whose head is 0.50 m above her heart and whose toes are 1.50 m below her heart. Assuming static conditions, compare the blood pressure in her head to the blood pressure in her toes. (In form B.P (head) = x/y and B.P (toes) = x/y)

Part (B) If a tube were connected to the artery in which the blood pressure was being measured, what would be the maximum height that blood would rise in the tube?

Explanation / Answer

part A)

h1 = 0.50 m = 500 mm

density of blood , p = 1060 Kg/m^3

h2 = 1.50 m = 1500 mm

pressure change in head , p1 = 1060 * 500/13560

p1 = 39.1 mm

B.P(head) = (120 - 39.1)/(70 - 39.1)

B.P(head) = 80.9/30.1

for the pressure in toes ,

pressure change in toes

p2 = 1060 * 1500/13560

p2 = 117.3 mm of Hg

B.P(toes) = (120 + 117.3)/(70 + 117.3)

B.P(toes) = 237.3/187.3

part B)

for the maximum height is h

p * g * h = total pressure

1060 * 9.8 * h = 120 * 9.8 * 10^-3 * 13560

h = 1.53 m

the maximum height of blood in artery is 1.53 m

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