Do all humans have the same number of veins and arteries? If so, how does the body know how many and where to make these veins and arteries?
In: Biology
There is not a perfect match. In the extremities, there is usually a paired set of veins next to each artery, that when viewed in cross-section creates a triangular arrangement of three circles. This is evident when doing ultrasound exams. In the cerebral (brain) circulation, the paired vertebral and internal carotid arteries, which terminate in numerous small arteries (for the vertebrals/basilar artery) and finally at the circle of Willis (see the Wikipedia page on the circle of Willis – good diagram). However, the venous (veins) drainage of the brain does not parallel this at all ([https://en.wikipedia.org/wiki/Dural_venous_sinuses](https://en.wikipedia.org/wiki/Dural_venous_sinuses)).
In the trunk of the body, the aorta (artery) runs parallel to the inferior vena cava (vein), so there is a 1:1 match there, but there is also the azygous and hemiazygous venous system that is returning blood towards the heart, with no matching arteries. Then there are venous plexuses, which are tangled networks of veins. We have one in our spine (Batson’s plexus), and how do you count how many veins that consists of?
Overall, in terms of count, veins probably win.
Source: I’m an MD that teaches anatomy to med students.
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