Is this genetic? Do they change over time or stay the same from birth? Why are they not the same compared to the opposite side of the body (ex. rt hand vein pattern vs lt hand vein pattern)? Are there health benefits or negatives to the shape of the pathway (not including the obvious ease or difficulty with blood draws/IVs)?
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Some kinds of it *can* be genetic, in the sense that traits are passed on, but often they’re genetic in the sense that the coding instructions got a little messed up at some point during development. There *is* a general template for how the major veins and arteries are arranged throughout the body, including up to and through the hand/fingers. This is predictable and very reliable. You may be comparing some of the vessels on the surface of your hand, but the body is [fairly symmetric](https://www.lemaitre.com/sites/default/files/styles/2_column_img_text/public/images/2017-11/Patients_%20Vascular%20Anatomy_1.jpg?itok=yP24dWAN) most of the time, or at least predictable.
Once you get away from the major ones, the smaller and smaller blood vessels/capillaries are less based on template and more based on local cells shouting “over here! I need more blood over here!” through hormones. Hormones in those low-flow areas are released which recruit the building/expansion of blood vessel networks, and this happens throughout your life from embryo to death. In fact, you probably have areas of your body right now where you can see that this went a little out of control – [red moles](https://www.womansworld.com/wp-content/uploads/2019/09/red-moles.jpg?w=715). Those are actually tiny areas where there was too much “expand to here” hormone and now you have a bundle of blood vessels that give you a red dot on your skin. Totally benign, virtually everyone has them.
There are definitely negatives to the shapes of pathways. The more tortuous, or bendy/twisty, a vessel is the more likely the walls of that vessel are to be under stress and dilate, thicken, or slow flow down. If this is in an artery, it could potentially cause an aneurysm or contribute to high blood pressure (takes more pressure to go through a twisty pipe than a straight one). If it’s in a vein, it can cause swelling/distension/pain of the affected area and may be more prone to blood clots. These are in relatively major examples though, most of the time it doesn’t make that big of a difference.
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