Silly question about blood

[golgiapparatus88]

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I was talking with my younger brother about blood today and in a nutshell, he asked: why do you bleed even when a vein or artery is not punctured.

I thought about it for a little and told him that capillaries lose about 10% of the fluid that is lost from hydrostatic pressure. Even though most of the fluid is picked up by the lymph system, some is still left over. That answer is not satisfying me though because I know when you bleed, you aren't leaking ECF.

Anyone have a good/correct answer?

 

[lorenzomicron]

actually, you only bleed when blood vessels are damaged. but this is very easy because capillaries are basically everywhere and are some small (1-cell layer) that they are really easily damaged. so, you bleed because of ubiquitous tiny blood vessels...
what do u mean bleed when a blood vessel isnt punctured? that makes no sense....

 

[golgiapparatus88]

that makes sense. As far as "punctured," I probably shouldn't have used that word. What I meant was that you obviously bleed even though a vein or artery has not been damaged. Thanks for the answer. (feels pretty obvious now 😛 )

 

[lorenzomicron]

sweet. u had me confused there too. lol. =)