Im right handed. why is the vein in the top of my hand more prominent there than anywhere else.

Swollen hand veins.: Hand veins can swell for many reasons but the most common is certainly hereditary . Other factors would be level of hydration, aging, sun exposure and loss of elasticity and volume. In your case, since this is your dominant hand, most likely there is increased blood flow in it since you use it more. This could lead to more engorged veins on that side.