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
Wasn’t there a recent post that said babies are being born with an extra artery in their arms nowadays?
How does the body know how and where to make arms and legs?
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DNA contains sequence of genes which in fact is functional design specification of a body. According to this specificaton body know how to develop. Basically almost all humans have the same number of veins and arteries, but sometimes deviations may occur due to “typos” in specification.
As others have said: generally large veins are consistent among people and small veins differ and the former is part of your DNA.
What I haven’t seen mentioned is two interesting things:
1. Sometimes there are surprisingly major changes that follow in family lines – normally we’d class these as genetic defects but sometimes they lead to totally functional people with weird quirks. There’s a lot of redundancy in the system so it can handle even major modifications.
2. Related to the above, things like major injuries, varicose veins or surgery can lead to your body restructuring your veins. My father, for example, had several major blood clots and had his entire Greater Vein of Saph removed, so several of his other leg veins have changed significantly to compensate for its loss.
When humans are conceived the DNA we get from our mom and the DNA we get from our dad combine to make one big blueprint of the entire human body. It’s ~99% similar for all humans. It’s why we all have a brain, liver, kidneys, etc. All the major stuff is the same in each human because of the blueprints we share in our DNA.
I think you might be thinking of *capillaries*, though? Arteries and Veins are like the highway system for blood in the human body while capillaries (small blood vessels) are like the side streets. Capillaries help deliver blood to tissues away from the “highway”. The bigger a person is (both in terms of height and body fat) the more capillaries they need.
TL;DR: We’re born with the major veins and arteries we need, but the body builds capillaries and blood vessels on demand.
This is an amazing video from Michael Levin from Tufts about how the body might know how to build these complex structures:
It’s long but fascinating. TLDR version is that all cells have connections with their neighbours similar to the ones neurons in our brains do. These connections create bio-electrical “maps” for where things go. For example, with a small change to those connections he made a zebra fish’s gut turn into an eye with all the parts of an eye. Not gene editing, not manipulating cell by cell, just changing the bio electrical map.
Quite incredible watch!
Largely yes, all the major veins and arteries follow a similar pattern in everyone. If its important enough to have a name, everyone probably has it! Your body knows how and where to make these just like it knows how and where to make your bones and organs – it’s all described in your dna.
But on a smaller level, your capillary networks will be different because they change depending on what you need. The body is amazing creating new vascular pathways when necessary. For example, if one vessel is damaged, alternative vessels will be created to carry to blood flow instead. We also see changes when people build muscle: that muscle tissue needs a blood supply so you’ll be gaining blood vessels as well as biceps. This is also true of tumors which are very good at keeping themselves alive by ensuring that the body provides a blood supply for them, which is one of the reasons that enlarged blood vessels in a localised area can be an indication of cancer
There are some veins in the inner side of the elbow that sometimes differ. The medial cubital and medial antebrachial veins. I don’t remember the exact ways (there are 5 or 6 ways of which 2 are common), but I know in some cases there’s a vein missing or just very underdeveloped. I remember this because my one arm doesn’t have one of the veins but the other does. It always frustrates doctors when they try to put an IV in.
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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