If it is true then what kind of adaptation is happening due to this “abruptly changing pressure”??
I’ve searched the internet but it sounds so confusing to me. I’m 15 and learning IGSCE this year.
edit : Thank you for such detailed explanations!
In: Biology
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Med student here. First of all, if you plugged capillaries directly into your aorta or another big vessel–yes, it wouldn’t be good for them. But there are literally thousands and thousands of branches (called arterioles) that come off of one small-sized artery, let alone the very big ones. This means you have a dropoff in pressure as you go further down in size.
Another big factor: a lot of capillaries have an actual sphincter (circular muscle) right as they branch off of an arteriole. This contracts and relaxes (automatically, of course) to adjust blood pressure to make sure there isn’t too much or too little going through.
Finally, there are plenty of conditions where you can have too much pressure in the capillaries! It usually leads to edema, which is when excess water starts leaking out of the capillaries because of the pressure. An example is people with heart failure–if the heart can’t pump strongly enough, the blood gets “backed up” waiting to get pushed out to the rest of the body and the pressure rises in the lung capillaries to the point where they start leaking fluid and the person starts drowning from the inside. This is why it’s called “congestive” heart failure, and why people with this condition often need to restrict the amount of water they drink and take diuretics (which make you pee out excess fluid).
First off, high blood pressure is still relatively low pressure.
Now, on to the fluid dynamics. When a fluid goes from a larger tube to a smaller tube, the pressure drops and the flow velocity increases as per Bernoulli’s principle. Imagine blowing through a straw. The pressure in your mouth is higher, but the air speeding up and entering the straw causes the pressure to decrease to below ambient air pressure. When it comes out the other end it collides with the air, slows down, and its pressure rises to ambient. Thus, pressure goes high->low->medium and the loss in total energy as it travels is caused by the frictional forces in the fluid.
Mostly there shouldn’t be a sudden change in any vital parameters of your body, like blood pressure. Because it can damage organs, your body makes sure everything is set in a proper range via feedback mechanisms. This is done by putting receptors critical locations, listening changes continuously and responding them. If abnormal blood pressure is detected by these receptors, your body can change pumped blood volume, blood viscosity and vessel diameters and many more molecular mechanisms.
Arteries carrying HBP (i.e. branches of aorta) *smoothly* becomes smaller and smaller, eventually blood flow gets slower, while they branching in your body. Look how tiny the vessels located in your eyes are. They should get very tiny so that they can let oxygen and food transfer to cells, making sure every cell is oxygenated.
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