﻿ Calculation of the Blood Volume that Moves through the Dorsal Blood Vessel in Lumbriculus variegatus

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 r2  or A = 3.14 x (0.1) 2 A = 0.0314 mm2 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 mm2 V = 0.00628 mm3/sec Convert V/sec to V/day (multiple by 60 sec/min, 60 min/hr, 24 hr/day) V = 542 mm3/day Convert mm3/day to ml/day (1000 mm3 = 1 cm3 = 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.]