Calculation of the
Blood Volume that Moves through the Dorsal Blood Vessel
in Lumbriculus
variegatus (Oligochaeta, California blackworm)
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MEASUREMENT STEPS:
1) Use a
microruler to estimate the diameter of the dorsal blood vessel. Use a whole
worm (or a worm fragment) that is confined to a narrow space to restrict its
movements. NOTE: Worm confinement options include:
http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/toolbox-V.htm
http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/looking2.JPG
http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/worms-in-caps.htm
2) Use a microruler to estimate velocity of the pulse wave. Do this my determining the number of seconds it takes for the pulse to travel 1 mm.
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CALCULATION STEPS:
Measurement or
Calculation
Sample Values
Estimated diameter (D) of dorsal blood vessel in mm |
D = 0.2 mm |
Calculate radius (r) of dorsal blood vessel [r = 1/2 D] |
r = 0.1 mm |
Estimated velocity (c) of pulse wave |
c = 1 mm in 5 sec = 0.2 mm/sec |
Calculate cross-sectional area of dorsal blood vessel A = π x r^{2 }or A = 3.14 x (0.1)^{ 2} |
A = 0.0314 mm^{2} |
Calculate volume (V) of blood moved per second V = c x A (same formula as volume of a cylinder = area x length) V = 0.2 mm/sec x 0.0314 mm^{2} |
V = 0.00628 mm^{3}/sec |
Convert V/sec to V/day (multiple by 60 sec/min, 60 min/hr, 24 hr/day) |
V = 542 mm^{3}/day |
Convert mm^{3}/day to ml/day (1000 mm^{3 }= 1 cm^{3} = 1 ml) |
V = 0.542 ml/day |
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By comparison, 1 ml water = 1 gram
(about 20 drops). So, the worm pumps about 0.5 ml, or 0.5 gram of blood,
through its dorsal blood vessel per day. If a normal-size worm weighs
0.010-0.015 grams (= 10-15 mg), then the worm pumps about 50 times its body weight in blood
per day.
[Q: How does this compare to the human circulatory system? A: An average human heart pumps about 5 liters blood/min, or 7,200 kg/day. If a human weighs 72 kg (= 160 pounds), then the amount of blood pumped per day is about 100 times the body weight of a human.]