Blood...

[lifesagift]

So we have this amazing muscle which just carries on banging away for 50 to 100 years without even stopping !! that is incredible.

And it manages to oxygenate our blood and push it round our body, and then when the blood returns, re-oxygenate it and send it on it's way.

And we have miles of arteries/veins/vessels/capillaries .... but we don't have return valves, or mid point pumps...

So how the hell does the blood get back from your earlobe to you heart when all the heart does is pump?

And blood is thick and needs pushing.... I'm wondering how on earth we don't get blockages (apart from clots) and trouble all over !

[DramaQueen]

I didn't read my textbook (I'm the biggest procrastinator) , I'm just subscribing (is there another way)

Heparin?
And don't blood vessels have a smooth muscular tissue?

[Napoléon]

[Endo]

Part of "pumping" is "sucking". Also, it's a liquid, meaning non-compressible up to a certain (stupidly high) pressure, so it pushes itself to some degree.

[Cyberman]

Apart from the whole blood system being circulatory, meaning it all goes around and around, the blood vessels are fitted with one-way valves which prevents the blood from being pulled the wrong way when the heart readies itself for the next beat.

Honestly, this is all very reminiscent of the classic exchange from The Blood Donor:

Tony Hancock: It's a funny thing, this blood business.

Hugh Lloyd: Yes, I suppose it is.

Hancock: It all looks the same and yet... it's all different. Yes, it's a very funny stuff, blood.

Hugh: Yes. I don't know where we'd be without it.

Hancock: That's true. That's very true. Where would we be without it? Yes, it's very important, blood. Circulates right round the body you know.

Hugh: Yes, so I believe.

Hancock: Yes. It starts at the heart, it gets pumped right round, goes through the lungs, back into the heart, and round it goes again.

Hugh: What for?

Hancock: What for? Well, it speaks for itself, doesn't it? I mean, the heart's got to have something to pump round... there's no point in it banging away all day long for no reason at all.

Hugh: Well, why have a heart then?

Hancock: Well if you didn't the blood wouldn't go round, would it? It'd all stay in one place. When you stood up, it'd all sink to the bottom of your legs. It'd be very uncomfortable, wouldn't it? It'd feel like you were walking around with a bootful of water. Your heart saves you keep having to stand on your head, and jumping about to keep it moving. It does it for you.

Hugh: But I still don't see what good blood is, though.

Hancock: Well... your body's full of veins, isn't it?

Hugh: Yes.

Hancock: Well you've got to fill them up with something, haven't you?

Hugh: Ah yes, I see. Are you a doctor, then?

Hancock: Well, no not really. I never really bothered.

[HopOnPop]

The heart is actually only the main pump. In fact there are countless muscles all over the body that assist in circulation. Every artery wall, for instance, has involuntary smooth muscles that constantly squeeze and relax to help the heart to circulate blood outward to the organs and body extremities. The veinous system (return to heart) is the more superficially located web of tubes and largely depends upon your moment to moment voluntary body movements and muscle flexures to aid the passage of blood back. This is why we get the urge to stretch and yawn and fidget in our chairs when we become sedentary for too long.

[vorlon13]

And we haven't even discussed the bosperous gland yet . . .

[pocaracas]

The heart pushes blood to the arteries.... there's already some blood there from the last time the heart pushed blood in, so this blood gets pushed further away, which pushes the blood in front of it also further away, and so on and so on...
Since it runs in a closed circuit, eventually, the blood returns to the point of origin and restarts the cycle.

I think I once read that it takes about 50 heart beats for one full "lap"... but I may be mistaken!

[lifesagift]

Thank-you for some eye opening information. But can I move away from arteries and veins and look at the smaller end... for example in your ear lobes or finger tips.. I imagine the body's blood vessels to be like branches on a tree.. a huge trunk, many large boughs leading to smaller branches, and twigs and offshoots. So not like a central heating system in terms of returning water.

I imagine a complete dive suit full of honey, and a honey pump in the centre. How does the honey in the finger tips get back to the pump?

[Cyberman]

Heart -> arteries -> arterioles -> capillaries -> venules -> veins -> heart.

There isn't a part of the body that isn't connected to the system.