Ten Trillion Cells Walked Into a Bar

You are a colony of (at least) ten trillion cells, both your own cells and stupefying numbers of guests.1 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 humans 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 And right they were, at least about the bags and the water. Ugly depends on which bag of water we’re talking about (but let’s not go there).

The point the aliens were trying to make was that humans are mostly water — and everyone knows that, right? More specifically, and less widely known, is that our water is contained in flexible membranes. A bag. The “sack” is made of our connective tissue, intricate layers of a substance somewhat like Saran Wrap that literally holds us together. We have more connective tissue than anything else.12

The water (hydro) inside of us is under constant (static) pressure — hydrostatic pressure. The bag is 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 balloon analogy is surprisingly apt, because our anatomy actually is subdivided into balloon-like subdivisions defined by thin, tough layers of Saran-wrap like tissue called “fascia” — same stuff as the gristle in steak. The compartments can swell even like a balloon (which can be quite disastrous).13 An even better analogy is that these are like sausage wrappings, giving the loose contents shape and firmness.

This 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. Speaking of sausages, of course there is one part of the human body, the male human body specifically, that illustrates this principle perfectly.

Ta da!

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.

How ten trillion cells order a tall cold one and generate bad pick-up lines is a completely different mystery altogether.

Is tensegrity clinically useful?

Not in sports and musculoskeletal medicine. Not for massage therapists and chiropractors and phsyios. It’s basic biology, fascinating 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:

• Tensegrity is an important and nifty principle in biomechanics.
• Fascia is an important part of the biology of tensegrity.
• Therapists can pull on fascia.
• Therefore, pulling on fascia is biomechanically important!

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.

About Paul Ingraham

I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org 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:

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Related Reading

• Biotensegrity: A new way of modeling biologic forms (biotensegrity.com). Biology and anatomy coolness! Dr. Stephen Levin is an orthopedic surgeon with a special interest in tensegrity biomechanics and biotensegrity — the physics of anatomy and how living things are able to move and maintain their shapes. His website is a starting place for technical reading about tensegrity, as it has a well-annotated page of links. There is much of interest here for the true therapy geek. For example, Levin discusses the role of muscle tension in posture in some detail: Muscles at Rest. The history page is a good introduction to the site.

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:

• The Unstretchables — Eleven muscles you can’t actually stretch hard (but wish you could)
• When To Worry About Shortness of Breath … and When Not To — Three minor causes of a scary symptom that might be treatable
• Micro Muscles and the Dance of the Sarcomeres — A mental picture of muscle knot physiology helps to explain four familiar features of muscle pain
• Why Do We Get Sick? — The curious and tangled connections between pain, poor health, and the lives we lead
• Does Fascia Matter? — A detailed critical analysis of the clinical relevance of fascia science and fascia properties
• Organ Health Does Not Depend on Spinal Nerves! — One of the key selling points for chiropractic care is the anatomically impossible premise that your spinal nerve roots are important to your general health
• Why Does Pain Hurt? — How an evolutionary wrong turn led to a biological glitch that condemned the animal kingdom — you included — to much louder, longer pain
• Tissue Provocation Therapies — Can healing be forced? The laws of tissue adaptation & therapies like Prolotherapy & Graston Technique
• 35 Surprising Causes of Pain — Trying to understand pain when there is no obvious explanation
• Toxins, Schmoxins! — The idea of “toxins” is used to scare people into buying snake oil
• Healing Time — Can healing be hurried? Would we even notice if it was?

Notes

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 estimating extreme, some estimates of the number of cells we have go as low as tens of billions. But, regardless, we have a lot of cells!

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. Wikipedia.com.
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 is available in the free introduction to my shin splints tutorial. Just scroll down until you find a freaky picture of a dude’s messed up leg.
14. Ingraham. Does Fascia Matter? A detailed critical analysis of the clinical relevance of fascia science and fascia properties.  ❐ PainScience.com. 31352 words. 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.
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.