A question from a curious 7 year old which I was stumped by. (edited for an adult audience)
Our skeletons are symetrical, as are the muscle arrangements so why are the veins in my arms and on the back of my hands not the same on each side?

Like I say, I was stumped…any ideas?

If you look closely enough, nothing in the body is symmetrical. It just appears that way at first glance.

confuses vampires

I know there are slight variations but the bone structure in my 2 hands is pretty similar, as are the muscles and where they are joined to the bones.
You can then find arteries serving those muscles in similar areas.
However the veins are all over the shop, there is no correlation at all between my two hands…

Do vampires not go for arteries?

because I’m right handed

I’d guess at a heart that pumps differently around each side of the body (ie, the left ventricle pumps more into the body, the right to the head).

Or something like that.

Can’t believe I’ve just googled this…

Veins do tend to follow a pattern, although they are more likely to be asymmetrical the further out you go from the body: http://www.ncbi.nlm.nih.gov/pubmed/8363046

Arteries are actually very variable too – it’s just not as obvious as they’re deeper. But if you inject some dye up the arm into an artery and take x-ray pictures, there’s a huge variation in the pattern of arteries both in one person and between people.

Well there we go. Thanks!

because I’m right handed

i’d be inclined to go with that. I’d be surprised if the same veins aren’t there in both hands (if she disects you to see) but that muscle shape / tone etc makes the more/less prominent. Handedness makes the muscle definition different in each hand.

Obviously if you look at a “map” of the veins in the body it is not symmetrical either as the heart is off centre.

The whole circulatory system is asymmetrical. Biology, isn’t it?

<sheepish admition> I’d sort of forgotten that the heart was off centre when trying to answer this!

I’m going to guess at this:

The structure of the organs and limbs etc are programmed by the DNA, but I’d imagine that the blood vessels (and nerves) grow on an on-demand basis like the roots of a plant. They spread automatically to provide oxygen where it’s needed. The more oxygen you need in a particular spot the more blood vessels get stimulated to grow there.

That’s why when you exercise you can increase blood flow and nerve activation to your muscles, I think.

Even the heart gets it wrong, http://en.m.wikipedia.org/wiki/Dextrocardia

Chaos theory and intrauterine development? I assume it’s like neural development – as long as stuff gets to where it needs to go, the developing body doesn’t give a stuff how it gets there.
Handedness – you can get increases and modifications of established circulatory systems, but I suspect the organisation of the circulatory system doesn’t depend on which hand you write with..

Nothing in the body is symmetrical from anything other than a gross viewpoint, really. Many organs aren’t. The brain might look symmetrical, but functionally it’s not (a lot of the time – certain deep structures have some symmetry). And if you look at photos of people’s faces which have been “symmetricalised” they look really odd.. http://www.toxel.com/inspiration/2011/03/20/symmetrical-faces/

Molgrips – you don’t increase nerve activation to your muscles with exercise – you can increase the efficiency with which muscle groups can fire for a given signal, though 🙂

lister – Member
<sheepish admition> I’d sort of forgotten that the heart was off centre when trying to answer this!
POSTED 23 HOURS AGO # REPORT-POST

It’s not off centre, it’s just the bit pumping around the majority of your body is like Cavendish’s thighs, the other side is just less developed.