I’ve read that we have approximately 60,000 miles of blood vessels in our bodies, that a 155 pound person has 11 pints of blood and that blood travels through the lungs at the rate of once per minute. I realize that individual blood pressure varies and will affect the rate, but that makes it look as though our blood goes 60,000 miles a minute! Wouldn’t we just explode? Obviously the math must be a lot more complicated than I’m making it.
That high speed would be true if your blood had to go around one continuous loop.
But an individual blood cell that ends up in your big toe before coming back doesn’t have to go everywhere else in your body before or after. If I used that technique commuting to work, I would have to zig-zag over every stretch of road in the city every day. Yes, I would have to go very fast for that.
And welcome to the SDMB!
Thanks. But, really, how fast does it travel? Does the velocity of blood through the circulatory system vary, depending on where it’s going?
agrecian - No, the velocity of a blood is different in different parts of your body. Not by much, but it is different. It depends on things like viscosity and pressure. For instance, blood entering your heart is doing so through large arteries. Therefore the volume is such that it is going quite fast. However, in the small capilaries located in your nose, there is but a fraction the volume that there would be in an vein or artery, and the blood is traveling slightly slower…it’s not very marked. Check this cite
This gives a rough order-of-magnitude estimate of 425 cm/s (around 9.5 mph).
This pdf puts the peak velocity at the aorta at 80-130 cm/s. (I guess their mileage did vary:p)
My guess: the velocity will go up and down during the beat but the stretchiness of your veins will make that even out the farther it is from the heart.
The speed varies at different points of the body due to lots of factors.
If the flow were unimpeded, the same volume of blood would travel per second, causing narrower veins to carry blood at higher rates of speed.
Like squeezing a garden hose makes a thinner stream squirt farther.
But, there’s the counter effect of arterial branching, so the cross secional area of all branches must be considered together.
However, friction becomes the dominate factor at some point, so by the time you reach the capilaries the original pulse is lost and flow is steady.
Clearly the speed varies based on where it’s flowing and how much branching is happening. But I’m just curious about rough estimates about how long it takes blood in my heart to reach, say, my wrist (basically, traveling down large trunks, avoiding the issue of getting into all the nooks and crannies).
I’m curious about that, too. Is there a way to measure that?
Sure it can be measured.
Some sort of die can be injected into a vein and then tracked with imaging equipment. (MRI, CAT scan, etc.)
Or you could ask a crack-head how long it takes the high to go from his lungs, through the heart, and then to the brain. Probably just seconds, then calculate the distance and divide by time. :dubious:
I can’t believe no one can answer this. I really thought this would be an easy one.
Whew! Found it, I think. Apparently, blood moves at the rate of about 1 mph, leaving the heart, but of course slows down as it heads into the home stretch back to the heart. So pretty slowly, although at the size of a blood cell that’s probably relatively fast. Here’s the link, if anyone else was curious about this:
Thanks, everyone, for your help.