Total length of blood vessels in human body- thousands of miles?

[ridcully70]

I remember decades ago when reading schoolbooks a "fact" often given- if all the blood vessels in a person were laid end to end they would be thousands of miles long- it was usually "to the moon and back" or circle the equator 4 times. In other words about 60,000 miles at the least. I read this again recently  and it got me wondering.

This has always seemed incredible to me. Not only incredible as in amazing, but literally "in-credible" as in not believable. There is literally 4 times around the equator lying within my 6 foot body?

Is it true, or just another myth that gets perpetuated through the years? I i know some supposed science facts are just not true- sinks don't drain in opposite directions in the northern and southern  Hemispheres, and celery does not have negative calories. Even in music there is a myth that gets perpetuated even by music teachers, that the "tritone" was banned in medieval times. It's just not true yet even highly regarded music scholars are guilty of spreading this myth.

Science can be amazing, and I'm prepared to be amazed and apologize for my scepticism, but....60,000 miles of blood vessels?

[dimreepr]

"A grain of sand is halfway in size between an atom and the planet earth"

[exchemist]

40 minutes ago, ridcully70 said:

I remember decades ago when reading schoolbooks a "fact" often given- if all the blood vessels in a person were laid end to end they would be thousands of miles long- it was usually "to the moon and back" or circle the equator 4 times. In other words about 60,000 miles at the least. I read this again recently  and it got me wondering.

This has always seemed incredible to me. Not only incredible as in amazing, but literally "in-credible" as in not believable. There is literally 4 times around the equator lying within my 6 foot body?

Is it true, or just another myth that gets perpetuated through the years? I i know some supposed science facts are just not true- sinks don't drain in opposite directions in the northern and southern  Hemispheres, and celery does not have negative calories. Even in music there is a myth that gets perpetuated even by music teachers, that the "tritone" was banned in medieval times. It's just not true yet even highly regarded music scholars are guilty of spreading this myth.

Science can be amazing, and I'm prepared to be amazed and apologize for my scepticism, but....60,000 miles of blood vessels?

An internet search for this returns a large number of sources quoting such numbers, many of which look fairly authoritative to me. It would not surprise me, given how tiny capillaries can be. But in the end such numbers are pretty meaningless: it's just a matter of scale. I mean, you can be amazed, if you are that sort of person, to be told there are 6 x 10²³ molecules in  18 gms of water.  But, frankly, so what? Ditto @dimreepr's contribution. Gosh wow, er, or not.  

Edited September 26, 2021 by exchemist

[StringJunky]

Who are we to say what should amaze us as individuals.... very narrow-minded views, I must say.

.

Edited September 26, 2021 by StringJunky

[Phi for All]

5 hours ago, ridcully70 said:

Science can be amazing, and I'm prepared to be amazed and apologize for my scepticism, but....60,000 miles of blood vessels?

Iirc, half of that is the capillaries, which are incredibly thin-walled (normally a single cell in width). Hair is roughly five times thicker, but you only have about 100,000 of them, so if they were a foot long you'd have about 19 miles of hair. Remember that blood goes to every cell in your body, so the circulatory system is incredibly elaborate and dense. 

[StringJunky]

60,000, it seems so with 80% of that capillaries. I just read a  heart can move 3+ supertankers worth of blood in a lifetime: a million barrels.... and we are trying to make it do more!

Edited September 26, 2021 by StringJunky

[Phi for All]

1 hour ago, StringJunky said:

60,000, it seems so with 80% of that capillaries.

Here's one relevant paper, Spatial and temporal dynamics of the endothelium, from the Journal of Thrombosis and Hemostasis. There's a breakdown of their findings that includes the measurements. The paper itself is more about how the phases of hemostasis are far more integrated than previously thought, but the research quotes the relevant studies they're based on. There's 154 references, and I'll bet one of them is the actual measurement parameters.

[Kaiwatson1]

Hey I confirm this fact is false. The original study was done in 1923, and used a bit of frog muscle. Which has way more blood vessels than human muscle. And the ‘human’ used has 50kg of muscle, weighing 120 or so kg which most people do not. 

It’s just been repeated as dogma for long enough that everyone forgot the original study.

Until Kurzegagt made a YouTube video about it. —- popular science channel.

it’s actually not even once around the globe.

[Phi for All]

3 hours ago, Kaiwatson1 said:

Hey I confirm this fact is false. The original study was done in 1923, and used a bit of frog muscle. Which has way more blood vessels than human muscle. And the ‘human’ used has 50kg of muscle, weighing 120 or so kg which most people do not. 

It’s just been repeated as dogma for long enough that everyone forgot the original study.

Until Kurzegagt made a YouTube video about it. —- popular science channel.

it’s actually not even once around the globe.

Thank the stars we have more trusted sources than YT!

https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC7867635&blobtype=pdf

Quote

The capillary bed constitutes the obligatory pathway for almost all oxygen (O2) and substrate molecules as they pass from blood to individual cells. As the largest organ, by mass, skeletal muscle contains a prodigious surface area of capillaries that have a critical role in metabolic homeostasis and must support energetic requirements that increase as much as 100-fold from rest to maximal exercise. In 1919 Krogh’s 3 papers, published in the Journal of Physiology, brilliantly conflated measurements of muscle capillary function at rest and during contractions with Agner K. Erlang’s mathematical model of O2 diffusion. These papers single-handedly changed the perception of capillaries from passive vessels serving at the mercy of their upstream arterioles into actively contracting vessels that were recruited during exercise to elevate blood-myocyte O2 flux. Although seminal features of Krogh’s model have not withstood the test of time and subsequent technological developments, Krogh is credited with helping found the field of muscle microcirculation and appreciating the role of the capillary bed and muscle O2 diffusing capacity in facilitating blood-myocyte O2 flux. Today, thanks in large part to Krogh, it is recognized that comprehending the role of the microcirculation, as it supports perfusive and diffusive O2 conductances, is fundamental to understanding skeletal muscle plasticity with exercise training and resolving the mechanistic bases by which major pathologies including heart failure and diabetes cripple exercise tolerance and cerebrovascular dysfunction predicates impaired executive function.

It seems the numbers have been adjusted by reclassifying certain capillaries as not part of the measurable, active system. Some of the vessels involved in microcirculation are now assessed differently. This isn't a "false fact" or "dogma" as much as it is part of the methodology, further clarifying what defines a blood vessel. Similar to how Pluto got redefined. That it used to be a planet isn't a false fact or dogma.

[CharonY]

It is also somewhat concerning that one might think that knowledge is lost until it is shown on youtube of all places.

[sethoflagos]

The main issue the YT clip addressed were the multitude of locations, not just web but science papers too, where the 60 kmile figure was produced with no authentic source quoted. The 'correct' figure was of secondary interest; the main issue was traceability.

They obviously put a lot of work into both research and presentation.

[CharonY]

43 minutes ago, sethoflagos said:

the 60 kmile figure was produced with no authentic source quoted.

That would be rather poor science. I got curious and quickly did a lit search. It seems that a lot are pop-sci articles (e.g. Scientific American), physics articles, books  and a handful of physician-type articles. Plus two biochemical articles. At least it does not seem to pop up regularly in anatomical papers.

 

[joigus]

This whole question reminds me of fractals, and the problem of measuring the coastline.

On 9/26/2021 at 3:15 PM, dimreepr said:

"A grain of sand is halfway in size between an atom and the planet earth"

Nice comment, Dim. The point being that you can make a lot of convolutions fit even inside the width of an atom.