Question

A national project on "Physiology Across the Curriculum" has identified gradient driven flow as one of the critical principles that physiology students need to know, understand, and master. Gradient driven flow means that the transport of something through space occurs as a result of a change in some variable over location in space concentration, pressure, temperature, voltage. In this class we've studied two gradient driven flow equations: Fick's law and the Hagen-Poiseuille equation. Pick one, describe what it tells us, and discuss what value understanding it has for making sense of something in biology. Note: Your answer will be judged not solely on its correctness, but for its depth, coherence, and clarity.

Answer 1

Hagen-Posiseuille equation:- This equation is used in Biology to find out head drop (pressure drop) in fluid flow through arteries and veins.

Due to drop in pressure as it flow through arteries and vein a pressure gradient established across the lengh of arteries and veins.

Pressure drop is given by ............(1)

where L is length of arter or vein

Q is flow rate of fluid.

R is radius of pipe.

is dynamic viscosity.

Lert us take a example.

Flow through artey is Q = 1m/s , Radius of arery R = 2.5 mm = 0.0025 m,

length of artery L= 20cm = 0.20 m

For blood   = 0.0027 N. s/m2

Put all value in equation 1 we get

= (8*0.0027*0.20*1)/(3.14*0.00254)

= 352 Pa.