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scoliendo OP t1_itpu5x5 wrote

Reply to comment by penicilling in How does vasoconstriction reduce blood pressure in haemostasis? by scoliendo

So as I theorised, the vasoconstriction is occurring proximal to the injury, rather than at the site of the injury? This makes the most sense to me, which is why I theorised it, I just wish my course materials had explained this!

From what I understand based on this... blood is flowing at standard pressure until it reaches an area of vasoconstriction. Beyond this area is a damaged blood vessel. The constricted vessels allow less blood through per second, thus reducing the blood pressure in areas distal to this vasoconstriction, along the same artery/arteriole network, reducing the pressure on the damaged area. Is this accurate?

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Emily_Ge t1_itqneku wrote

It‘s like pinching a hose. Despite the pressure at the pinch point being higher, distal to the pinchinung the pressure is massively reduced, and only a tricky come out the end of the hose.

Just like you said at the end.

The part you missed is that the injury site itself, keeps the same diameter. To any reduction in diameter proximal to the injury reduces the blood flow. Which reduces the pressure at the site of injury.

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