Three questiones

[Guest Billy]

Can someone please be so kind to answer these three questions? I’d be truly grateful!!

 

1) Why is the value of the hydrostatic pressure 0 kPa at the heart level instead of being 0 kPa at the top of the head? What are the physiological reasons for that?

2) Why is the venous system so important when talking about the impact of the hydrostatic pressure on the circulation?

3) How does the blood go through the foot capillary system (of a standing person!) if the pressure at the venous end is 12 kPa, and at the arterial end only 4 kPa?

 

Thank you all very very much

And, btw, I sincerely apologize for any grammar mistakes made – I’m still studying English.

 

Thanks again!

[husmusen]

I'm not sure about the values in your post(Q 3),

I am pretty sure that the venous system is far lower pressure than the arterial system(even in the foot).

 

As for how the venous system gets up, it's assisted by the contraction

of the leg muscles(e.g. calf) and the prescence of one way valves in

the veins. When these valves aer damaged you get varicose veins.

 

Cheers.

[Mokele]

1) it's the pumping mechanism, so the heart is given a base value of 0 as a reference point. For instance, the blood pressure in your legs changes if you elevate them above the heart. But the pressure in the heart doesn't change with body position, only with physiological causes like stress and McDonald's.

 

2) Because if there's no pressure in it, blood doesn't get back to the heart, which is very, very bad. It also gives us a measurement of pressure-loss in the capilaries.

 

3) Muscles in your legs assist in return of venous blood.

 

Mokele