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Ten Trillion Cells Walked Into a Bar

A humourous and unusual perspective on how, exactly, a person is even able to stand up, let alone walk into a bar

Paul Ingraham • 20m read

You are a colony of (at least) ten trillion cells, both your own cells and a stupefying numbers of guests.1 We are full of critters. That is what a human being is — a very large social gathering of cells. Ten trillion is a conservative estimate, but it is one heck of a lot of cells. That is about 200,000 times more cells in a single person than there are people on planet Earth. That’s the sort of number that you really can’t get your head around. Even if you have a very big head.

We are, each of us, a multitude. Within us is a little universe.

Carl Sagan

So how do ten trillion cells walk into a bar?

How do they walk, I mean? Or even stand up? They are amazing,2 but it’s quite a trick for ten trillion cells to do that. Individually, they certainly couldn’t pull it off. A single cell would have trouble walking a centimetre for a hot date with another single cell.3

It’s a co-operative effort, obviously. There are probably many committees, subcommittees and review panels involved. But, in spite of the biological bureaucracy, the end product — walking — is quite efficient. Walking is so efficient, in fact, that it constitutes one of the great mysteries of how people work. We still can’t make a bipedal robot that can walk — not like us anyway.4 We simply don’t understand the details of our own locomotion.

Rocket science isn’t all that difficult. It’s not brain surgery.

a rocket scientist

But we do have some idea how we at least stay upright. Even I understand it. This superficially simple thing of rising up to a height of six feet or more is an impressive feat for a bunch of cells who are, individually, shorter than a coffee stain. But together they pull it off, and that basic accomplishment is what I’ll focus on here. This is stuff that cells probably learn in cell kindergarten.

You aren’t stacked

Contrary to popular opinion, bones are not really stacked on each other like bricks. We do not really rest on our joints as much as you might think, nor in the way you might think. There is compression and friction in joints due to gravity, but this is not the supportive principle by which we manage to get upright each morning and stay that way.

Vertebrae in particular are not really made for “support.” We are one of the few creatures on Earth with an upright spine, the odd animal out; all other vertebrates on Earth have a horizontal spine, which is much more obviously not built for bearing weight by stacking. In fact, the spine we have is really not particularly well-constructed for verticality. It’s as though we borrowed a tool used by other species for hammering nails, and decided, “Let’s use this for screwing in lightbulbs.” It’s a bit queer, really.5

In fact, rather than being stacked, we are held together and upright by muscles. Bare skeletons, as a general rule, fall over very easily. In the living body, even when we think that we are completely relaxed, our muscles are actually sustaining a constant level of tension — called “resting tone” — that holds joints together.6 When we are anaesthetized, surgeons must be cautious not to dislocate joints,7 because they become quite loose. This constant tension is what we really “stand on” — not bone resting on bone.

This idea, in which the rigid elements of a system “float” in a continuous tension network, was called “tensegrity” (tension/integrity) by Buckminster Fuller. For a long time the ideas were more widely known among architects than biologists.8 Biotensegrity could seem like quite a flaky concept at first glance, and the idea has certainly been co-opted for dubious purposes over the years,9 but “tensegrity biomechanics” and “biotensegrity” are slowly coming into their own as an important way of modelling and explaining biomechanical function. They are important structural principles at all scales — even the cellular and molecular scale.10

Bones float in muscle, functioning more like “spacers” than bricks. They provide rigidity for leverage and as foundations for complex arrangements of high-tension wires (muscles and tendons). We are pulled upright, and held upright, in much the same way a circus tent pole is erected and held upright — not because it is resting on itself, but because it is being pulled equally in all directions by ropes. Unlike a circus tent pole, we actually need to move around, so this arrangement is extremely dynamic and active, constantly at work even when we are sitting.

There is one other major principle that keeps us upright: hydrostatic pressure (“hydrostatic” meaning “latin for something”).

We are “bags of mostly water”

Once again, bones are of secondary importance to another more important substance: soft connective tissue. Some aliens on Star Trek: The Next Generation referred to humans as “ugly bags of mostly water.”11 Rude! But right they were, at least about the bags and water. Ugly is more of an eye-of-the-beholder issue. I married a very pretty bag of mostly water, for instance.

The main point the aliens were trying to make was that humans are mostly water — and everyone knows that, right? More specifically, and less well known, is that our water really is contained in flexible membranes, like a bag. Or bags, rather — we are like balloon animals: just a bunch of shaped balloons all smushed together and nested inside each other. Water balloons.

The water (hydro) inside our bag of bags is under constant (static) pressure — hydrostatic pressure. The bags are tight. This is just like putting a tight elastic band around a water balloon: it squishes it into a more elongated shape. If you were to put several rubber bands in a row around a water balloon, it would start to look more like a tube than a balloon. In fact, it might start to resemble, say, a leg. If only it could balance, this “balloon leg” could stand upright — thanks to the pressure of the water inside.

The “bag” is made of our connective tissue, and we have more connective tissue than anything else.12 Specifically, the tissue is tough layers of Saran-wrap like tissue called “fascia” — exactly the same stuff as steak gristle. As a side note, "fascia" has faddishly become the darling tissue of massage therapy, with a pseudoscientific industry devoted to singing its praises, and it’s ridiculous: it is interesting as a tissue, but has literally zero clinical relevance to massage. More on this below.

Here is one way fascia can be medically significant: fascial compartments can swell like an overinflated balloon, which can get quite disastrous13 (trigger warning for the footnote, it’s got a seriously gory photo). “Compartment syndrome.”

Hydrostatic pressure is entirely how plants stand up. Spinach has no spine, no bones at all, but it still manages to stand up. Unless you don’t water it, and then it wilts — no water, no pressure, no standing up.

Another analogy: these compartments are like sausage wrappings, giving the relatively loose contents shape and firmness. Speaking of sausages, of course there is one part of the human body, the male human body specifically, that illustrates the principle perfectly.

Tongues are different though…

Muscular hydrostats

You can change the shape of a water balloon by squeezing it, and a tube full of muscles is like a water ballon that can squeeze itself into different shapes from the inside. Kooky!

So, fill one our watery anatomical balloons with the right kind of muscle, strategically attached to the walls of the compartment, and you’ve got yourself a “Muscular hydrostats”: yet another way for cells to stand up. Or stick out. Or curl or twist or do the hokey pokey. My wife, the aforementioned “pretty bag of water,” has the rare gift of a tongue that can touch her nose. Now that is one hell of a muscular hydrostat (trust me, you want to click that link, it’ll be the highlight of your day).

The tongue is the only common muscular hydrostats in the terrestrial animal kingdom, but elephant and Mr. Snuffleupagus trunks are the most dramatic. The ocean has a lot of muscular hydrostats: all those octopus/squid/cephalopod tentacles, plus a multitude of smaller critters with near infinite variations on the theme.

Ta da! How cells we stand up and walk around, summarized

Our ten trillion cells manage to walk into a bar by applying two major physical principles: biotensegrity and hydrostatic pressure. Our cells build tough membranes to tightly surround compartments of pressurized water, they make rigid bones to act as spacers and points of leverage, and they arrange themselves in complex systems of muscle tissue in order to literally “pull” us into the vertical position and keep us there like a tent pole.

And then ten trillion cells order a tall cold one and generate bad pick-up with a muscular hydrostat — the tongue — which is a watery compartment filled with muscle. And now I'll get my tongue out of my cheek and wrap up with three slightly more serious notes:

Are tensegrity and fascia clinically significant?

Not in sports and musculoskeletal medicine. Not for massage therapists and chiropractors and phsyios. Fascia and tensegirty are fascinating biology, but impractical, at least for therapy. Many healthcare professionals like to believe it is, though, and the idea of tensegrity is particularly beloved by massage therapists who are excited about fascia.14 The “logic” goes something like this:

Logic! That’s about all there is to it (so, not much, in case my sarcasm wasn’t clear).

Here’s an amusing example of this sloppyness: a bit of junky science published in the Journal of Manipulative & Physiological Therapeutics in 2013, a study that compares two kinds of massage for shoulder pain, regular Swedish versus “tensegrity-based” massage (which I have literally never heard of since I started studying massage in 1997, even though it’s obvious what they think they mean). I smell a pet theory! “Tensegrity-based” massage is not actually a thing. There is no TBM® or standard definition. It means about as much as “anatomy-based.” Massage “based on the tensegrity principle” is wide open to interpretation to the point of absurdity.15

This is about as legit as “tensegrity-based” therapy science gets. So not really at all.

Spinal curvature chaos: our cells don’t stand up in quite the same way twice in a row

Anatomical illustration of a side view of the spine with the lumbar curvature highlight and labelled “lordosis.”

When humans cells stand up, they like variety. In fact, our spinal curvature is rarely the same for two stand-ups in a row … so good luck identifying a poor posture. In a 2018 experiment, Schmidt et al. measured and re-measured lumbar spinal curvature (lordosis) in hundreds of people using a handy curve-o-meter, and found that it changed from one test to the next to a surprising degree … and continued to do so with repeat tests. Measure a spine five times in a row, get five results!16

Every postural assessment you’ve ever been given by a massage therapist or a chiropractor was invalid for this reason (and others, but this one at least). Poor posture is a very over-rated sin.17

In that study, there was also no difference between spinal position in 350 people versus 80 with with back pain. And there was also no difference between athletes and non-athletes. Age, gender, height, and weight made no difference either. In everyone, standing posture was “highly individual and poorly reproducible.” Which is one major reason why quick one-stop posture assessments are nonsense. It’s unreliable even using an objective measuring gadget — never mind the biased eyeballing of a trainer or massage therapist looking for postural trouble to shoot.

Why do our ten trillion cells “stand up” in the first place … and is that a problem for backs?

Bipedality is one of the great puzzles of human evolution, with several competing explanations and no real answer, or even much hope of a real answer. The question of bipedality as a driver of low back pain is only slightly more tractable. We have some clues, but we don’t really know.

Being bipedal probably is a little more stressful for spines than being quadrupedal. Old data from studying “primitive” people in societies where people squat a great deal — which eliminates the lumbar curve for much of their lives — showed fewer signs of strain on their lumbar vertebrae than the habitual non-squatters of the “civilized” world.18 But the authors also note that degeneration is more prevalent in all animal spines in just the places you’d expect: right where the curves are sharpest, and where the gravitational strains are the greatest, regardless of whether the spines are upright or horizontal. Plus sitting in chairs also flattens the lumbar curve… and we may sit in chairs even more than squatters squat.

So it’s complicated, and it’s definitely not clear that verticality corrodes spines.

And even if standing really does lead to more spinal degeneration, by no means does that mean that vertical backs actually suffer more. Back pain is infamously estranged from obvious causes that can be seen on an X-ray or MRI. The general explanation for this is that back pain is a function of a multitude of other factors that collectively drown out the obvious. This is a theme throughout the world of pain, which is often very weird.

About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter., or subscribe:

Related Reading

This article is part of the Biological Literacy series — fun explorations of how the human body works, what I think of as “owner’s manual stuff.” Here are ten of the most popular articles on this theme:

What’s new in this article?

Sep 18, 2023 — Added a fresh citation (first note) about the number of cells we have: roughly thirty trillion, according to a new paper.

2023 — Added two short new sections about muscular hydrostats, bipedality, and variations in spinal posture — some riffs on the theme of “standing up” that seemed like a long overdue way of making this weird article more relevant to the rest of the website (which is always was, but it’s quite a bit clearer now). I also did some general editing … and was a little freaked out by how much useful work there was to do on this ancient page.

2022 — A little bit of editing, some new colour about microbiology, and a new citation about the role of biotensegrity in cells and molecules.

2005 — Publication.


  1. The ten trillion number is in the middle of a wide range of possibilities suggested by experts over the last century. The highest estimate I’ve ever seen, published in 2003 in the popular book A Short History of Nearly Everything, by Bill Bryson, was in the quadrillions — that’s right, quadrillions, as in thousands of trillions! (And that is probably wrong.) In 2006 in National Geographic, citing various experts, Joel Achenbach reported the popular myth that the microbes living in our bodies outnumber our own cells by the crazy ratio of 10 to 1, and there are a hundred trillion microorganisms in the intestines alone — so those figures would also put the total for the whole organism well into the quadrillions. In fact, our bacterial passengers probably do not outnumber our own cells by anywhere near that much, and almost all of them are in the poop chute, as opposed to a widespread population of symbiotes: see Scientists bust myth that our bodies have more bacteria than human cells.

    At the other extreme, some estimates of the number of cells we have go as low as tens of billions. That's probably too low.

    A 2023 paper has a fairly trustworthy seeming estimate of (very roughly) thirty trillion cells per adult.

    In any case, we have a lot of cells! Even a few tens of billions is a stupefying number.

  2. From a long New Yorker article about the quest to build a basic cell, by James Somers:

    Today, we take for granted that we are made of cells—liquidy sacs containing the Golgi apparatus, the endoplasmic reticulum, the nucleus. We accept that each of us was once a single cell, and that packed inside it was the means to build a whole body and maintain it throughout its life. “People ought to be walking around all day, all through their waking hours, calling to each other in endless wonderment, talking of nothing except that cell,” the physician Lewis Thomas wrote, in his book “The Medusa and the Snail.” But telescopes make more welcome gifts than microscopes. Somehow, most of us are not itching to explore the cellular cosmos.

    Well, I am itching. Astronomy probably is more popular than cellular biology, but that’s partly because it’s just so much more difficult to “explore the cellular cosmos.” You cannot buy a microscope powerful enough to reveal cells the way a surprisingly cheap telescope can reveal Jupiter or the Andromeda Galaxy. If only!

  3. If you do the math, “walking” a centimetre for a cell is like us walking about a kilometre — not too far for a hot date.
  4. “We” meaning the “geniuses at Boston Dynamics.” And “the Japanese.” Eventually this footnote is going to be obsolete, because there will finally be robots that walk like us, or at least as well as us (if not better). Here’s a bipedal robot doing parkour in 2021. Okay, so maybe we’re already there…
  5. Just because humans have spent a couple million years erect doesn’t mean that we are perfectly adapted to it in every way. What it means is that, in the merciless math of natural selection, the benefits of bipedality outweigh whatever problems it causes us. Evolution is chock-a-block with such trade-offs.
  6. There is just one joint in the body that can maintain its integrity after complete muscular dissection: the hip joint. The socket of that joint is so deep and perfectly fitted to the ball of the femur, and the capsule of ligaments around it so sturdy and air tight, that it is held nicely in place by “suction.” However, cut a tiny hole in the capsule with a scalpel, and the joint immediately dislocates!
  7. Casey AT, O’Brien M, Kumar V, et al. Don't twist my child's head off: iatrogenic cervical dislocation. BMJ. 1995 Nov 4;311(7014). PubMed 7488905 ❐ PainSci Bibliography 57060 ❐

    It’s probably less of a problem than popularly believed, because muscles aren’t truly or completely “paralyzed” under anaesthesia (see Muscles at Rest). Nevertheless, “extreme care must be taken in the positioning of the anaesthetised and paralysed child where the normal protection from cervical musculature is lost: extremes of neck rotation in children are dangerous.”

  8. Tensegrity.
  9. Carlos Castaneda abused “tensegrity” thoroughly, and Dr. Levin writes that he has “moved to the term ‘biotensegrity’ to try and clearly distinguish what is science and what is ‘new wave mysticism’ in regards to biologic structures.” Also, many therapists claim that tensegrity has significant clinical implications, which is quite a pretentious reach, and one of the best examples of making too much out of basic biology. For instance, tensegrity comes up routinely as a vague justification for manipulating fascia. Biotensegrity is nifty biology, but it has about as much to do with hands-on therapy as quantum physics does.
  10. Charles B. Reilly, Donald E. Ingber. Multi-scale modeling reveals use of hierarchical tensegrity principles at the molecular, multi-molecular, and cellular levels. Extreme Mechanics Letters. 2018;20:21 – 28. “These computer simulations also confirmed that tensegrity principles are indeed utilized at the level of individual molecules, multi-molecular assemblages, and whole living cells.”
  11. Sabaroff, Robert et al. and ibid and lorem ipsum. “Home Soil,” Star Trek: The Next Generation, Episode #18, Season 1, Original air date: February 22, 1988. Paramount Television. I also have an entire article about this quote. Seriously. See: Ugly Bags of Mostly Water: The chemical composition of human biology
  12. We really do have a lot of connective tissue, but connective tissue also includes some surprising and counterintuitive tissues like blood and fat.
  13. A gory example of compartment syndrome is available in the free introduction to my shin splints tutorial. This is what a surgically released compartment (fasciotomy) looks like:

    Gory clinical photo of surgical repair of acute compartment syndrome. The photo shows a horrible bulging wound in a calf about 20cm long.

    Acute compartment syndrome is no joke

    To treat acute compartment syndrome, the muscle compartment is sliced open to relieve the pressure. Tissue bulges like a hot sausage spilling out of its casing. The result is a massive surgical wound that takes months to heal & leaves substantial scarring.

  14. Many massage therapists are selling “fascial therapy” to patients. The main idea is that fascia — sheets of tough connective tissue found throughout the body — can get tight and restricting, and needs to be “released” by pulling on it. Fascia science is considered an exciting frontier in manual therapy. Unfortunately, although some fascia biology is interesting, the stuff does not seem to have any properties that are actually relevant to healing and therapy. Key examples of fascia research either fail to support fascial therapy or actually undermine it. Enthusiasm about fascia seems to be an unjustified fad. See Does Fascia Matter? A detailed critical analysis of the clinical relevance of fascia science and fascia properties.
  15. Kassolik K, Andrzejewski W, Brzozowski M, et al. Comparison of Massage Based on the Tensegrity Principle and Classic Massage in Treating Chronic Shoulder Pain. J Manipulative Physiol Ther. 2013 Jul. PubMed 23891481 ❐ The defining characteristic of tensegrity-based treatment offered in the abstract of this paper is merely where massage was applied (not how): “directing treatment to the painful area and the tissues … that structurally support the painful area.” As opposed to foot massage, perhaps? Meanwhile, the control group massaged “tissues surrounding the glenohumeral joint.” So, shoulder massage compared to … shoulder massage. This comparison may be about as meaningful as a taste-test of tomatoes and tomahtoes. Giving these researchers a little benefit of the doubt, perhaps they were trying to describe the size of the treated area, also known as “less thorough” and “more thorough.” That would be a somewhat interesting comparison, though not really useful for validating a treatment idea as vague as “tensegrity-based massage.” I can think of a few (about 17) non-tensegrity-based reasons why more thorough massage might work well. “Be thorough” is pretty much the first lesson in massage school. The shocking conclusion? They found that “more thorough” worked much better.
  16. Schmidt H, Bashkuev M, Weerts J, et al. How do we stand? Variations during repeated standing phases of asymptomatic subjects and low back pain patients. J Biomech. 2018 Mar;70:67–76. PubMed 28683929 ❐ PainSci Bibliography 53085 ❐
  17. Posture is only a minor factor in most kinds of pain, but it’s clinical importance is exaggerated to justify misguided physical therapy. There is no ideal posture, and the idea of poor posture as careless habitual body positioning is mostly simplistic nonsense. Many habitual postures are adaptations to anatomical quirks, and it’s difficult and unwise to try to change them. Most other “poor posture” is adaptation to bad ergonomics, which causes postural stresses — which also exaggerated (e.g. “text neck” is not a thing). When people seem to be vulnerable to postural stresses, the vulnerability is usually the problem, not the posture itself. Working on posture is usually a misguided approach to chronic pain, and advanced “posturology” is mostly speculative nonsense. Stretching is a particularly futile approach to fixing alleged “muscle imbalances.” So is strengthening (but at least that has clear fitness side benefits). If it matters at all, posture is best improved by addressing major factors like insomnia and fitness, which would be worth working on regardless of posture. See Does Posture Matter? A detailed guide to posture and postural correction strategies (especially why none of it matters very much).
  18. Fahrni WH, Trueman GE. Comparative Radiological Study of the Spines of a Primitive Population With North Americans and Northern Europeans. J Bone Joint Surg Br. 1965 Aug;47:552–5. PubMed 14341078 ❐ PainSci Bibliography 53604 ❐


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