How to Build a Body

songyan

(From the Anatomy Trains book)
How to build a body

To stand and walk, a human requires diverse and complex building materials. As a thought experiment, imagine that we were going to build a body out of things that could be bought in a local hardware store or builder’s supply. We will imagine that we have already engaged Apple® (of course) to build the computer to run it, and that we have already obtained little servo-motors an actual working model of the body’s structure? Put less archly, what kind of structural materials can connective tissue cells fashion?

You might suggest wood, PVC pipe, or ceramic for the bones, silicon or plastic of some sort for the cartilage, string, rope, and wire of all kinds, hinges, rubber tubing, cotton wool to pack the empty places, cling-wrap and plastic bags to seal things off, oil and grease to lubricate moving surfaces, glass for the lens of the eye, cloth and plastic sacks, filters and sponges of various kinds. And where would we be without Velcro®, and duct tape?

The list could go on, but the point is made: Connective tissue cells make biological correlates of all these materials and more by playing creatively with the two elements of the ECM: the fiber matrix and the viscous ground substance. The fibers and ground substance, as we shall see, actually form a continuous spectrum of building materials, but the distinction between the two – non-water-soluble fiber and hydrophilic proteoglycans - is commonly used and useful. The ECM, as we will learn in the section on tensegrity, is actually continuous with the intra-cellular matrix as well, but for now, once again the distinction is useful.

The following chart summarises the way in which the cells alter the fibers and the interfibrillar elements of connective tissue to form all the building materials necessary to our structure and movement:

Tissue type Cell / Fiber types / Interfibrillar elements
Bone Osteocyte / Collagen / Replaced by mineral salts, Ca Ostoblast, osteoclast Carb, Ca Phos

Cartilage Chondrocyte / Collagen & elastin / Chondroitin
sulfate

Ligament Fibroblast / Collagen (& elastin) / Minimal proteoglycans between fibers

Tendon Fibroblast / Collagen / Minimal proteoglycans

Aponeurosis Fibroblast / Collagen mat / Some proteoglycans
Fat Adipose / Collagen / More proteoglycans
Areolar Fibroblasts / Collagen & elastin / Significant
WBC, Adipose, Mast proteoglycans
Blood RBC, WBC / Fibrinogen / Plasma

Let us take a common example to help us understand this chart: The bones you have seen in your biology classroom (presuming you are old enough to have handled real, as opposed to plastic, skeletons) are really only half a bone. The hard, brittle object we commonly call a bone is really only half the material of the original bone – the calcium salts part, the interfibrillar part on the chart. The fibrillar part, the collagen, had been baked out of the bone at the time of its preparation; otherwise it would decay and stink.

Perhaps your science teacher helped you understand this by taking a fresh chicken bone and, instead of baking it, soaking it in vinegar. By doing this for a couple of days (and changing the vinegar once or twice), you can feel a different kind of bone. The acid vinegar dissolves the calcium salts and you are left with the fibrillar element of the bone, a collagen network the exact shape of the original bone, but much like leather. You can tie a knot in this bone. Living bone, of course, includes both elements, and thus combines the collagen’s resistance to tensile forces with the mineral salt’s reluctance to succumb to compressive forces.

To make the situation more complex (as it always is), the ratio between the fibrous element and the calcium salts changes over the course of your life. In a child, the proportion of collagen is higher, so that long bones will break less frequently, having more tensile resilience. When they do break, they will often break like a green twig in spring, fracturing on the side that is put into tension, and rucking up like a carpet on the side that goes into compression. Difficult to break, but also hard to put back together properly, though it will often mend quickly enough.

In an older person, by contrast, where the collagen is frayed and deteriorated, and thus the proportion of mineral salts is higher, the bone is likely to break like an old twig at the bottom of a pine tree, straight through the bone in a clean fracture. Easily put back in place but hard to heal, precisely because it is the collagen that must cross the break and reknit to itself first, to provide a fibrous scaffolding for the calcium salts to bridge the gap and recreate solid compressional support. For this reason, bone breaks in older people are often pinned, to provide solid contact between the surfaces for the extra time required for the remaining collagenous net to link up across the fracture.

Likewise, the various types of cartilage merely reflect different proportions of the elements within it. Hyaline cartilage – as in your nose – represents the standard distribution between collagen and the silicon-like chondroitin sulfate. Elastic cartilage – as in your ear – contains more of the yellowish elastin fibers within the chondroitin. Fibrocartilage – as in the pubic symphysis or intervertebral discs – has a higher proportion of tough fibrous collagen compared to the amount chondroitin.

In regard to fat, the experienced hands-on practitioner will recognize that some fat allows the intervening hand in easily, enabling the therapist to reach layers below the fat layer, while other fat is less malleable, seeming to repel the practitioner’s hand and to resist attempts to feel through it. (No prejudice implies here, but rugby players come to mind.) The difference here is not so much in the chemistry of the fat itself, but in the proportion and density of the collagenous fascia that surrounds and holds the fat cells.

In summary, the connective tissue cells meet the combined need of flexibility and stability in animal structures by mixing a small variety of fibers within a matrix that varies from very fluid to gluey to solid.

Connective tissue plasticity

While the building metaphor and the chart go some distance toward showing the variety of materials connective tissue has at its disposal, it falls short of the mark in portraying the versatility and responsiveness of the matrix even after it has been made and extruded into the intercellular space. Not only are the connective tissue cells able to make all these materials, these elements also rearrange themselves and their properties – within limits, of course – in response to the various demands placed on them by individual activity and injury. How could supposedly ‘inert’ intercellular elements change in response to changes in demand? The mechanism though which this works is important to understand in myofascial intervention with human structure and movement.

Stress going through a material deforms the material, thereby ‘stretching’ the bonds between the molecules. This creates a slight electric flow known as a piezo- (pressure) electric charge. This charge can be ‘read’ by the cells in the vicinity of the charge, and the connective tissue cells are capable of responding by augmenting, reducing, or changing the intercellular elements in the area.

As an example, the head of most everyone’s femur is made of cancelous, spongy bone. An analysis of the trabeculae within the bone shows that they are brilliantly constructed, to an engineer’s eye, to resist the forces being transmitted from the pelvis to the shaft of the femur. Such an arrangement provides the lightest bones within the parameters of safety, and could be easily explained by the action of natural selection. But the situation is more complex than that; the internal bone is shaped to reflect not only species needs but individual form and activity. If we were to section the femur of someone with one posture and someone else with a quite different posture, we would see that each femoral head had slightly different the trabeculae, precisely designed to best resist the forces which that particular posture characteristically creates.

With the concept of piezo-electric currents, this seeming-miracle becomes easier to understand. Inside and around the bone are a sparse but active community of two types of osteocytes: the osteoblasts and osteoclasts. Osteoblasts lay down new bone; osteoclasts clean up old bone. While osteoblasts are allowed to lay down new bone willy-nilly anywhere within the periosteum, the osteoclasts are proscribed: they are not permitted to ‘eat’ bone that is piezo-electrically charged. Allow the cells to operate this way over time, and a femoral head is produced that is both specifically designed to resist individual forces coming through the femoral head, but also capable of changing (given some reaction time) to meet new forces when they are consistently applied.

This mechanism explains how dancers feet get tougher bones after a summer dance camp: the increased dancing creates increased forces which create increased piezo-electric charges which reduce the ability of the osteoclasts to remove bone while the osteoblasts carry on laying it down. This is also part of the explanation for why exercise is helpful to those with incipient osteoporosis: the forces created by the increased stress on the tissues serve to discourage the osteoclastic uptake. The reverse process operates in the astronauts and cosmonauts: deprived of force of gravity to create the pressure charge through the bones: the osteoclasts have a field day and the returning heroes must be helped off their ship in wheelchairs until their bones become less porous.

Another level of responsiveness of the connective tissue system shows up in certain cases of non-union fracture in the ulna. Held horizontal in a sling, the ulna has little or no piezo-electric charge, either from gravity or effort, going through the bone. In some people, the ulna does not rejoin, but instead demonstrates the remarkable plasticity of the system: the two ends of the fractured bone start to develop cartilaginous surfaces, and the periosteum begins to develop into a joint capsule. In other words, the person begins to develop a ‘mid-ulnar’ joint – where no joint has ever been, and certainly there are no genes to cover such a joint.

This extraordinary ability to respond to demand accounts for the wide variety in joint shapes and types across the human spectrum, despite the consistent pictures averaged into most anatomy textbooks. The non-union fractures can often be reversed by creating a current flow across the break, by which the collagen ‘knows’ which way to orient itself and begins the process of bridging the gap, to be followed by the calcium salts and full healing.

This same process of response occurs across the entire extracellular fibrous network, not just inside the bones. We can imagine a person who develops, for whatever reason - e.g., shortsightedness, depression, imitation, or injury - a common ‘slump’: the head goes forward, the chest falls, the back rounds. The head, a minimum of one-seventh of the body weight in most adults, must be restrained from falling further forward by some muscles in the back. These muscles must remain in isometric / eccentric contraction for every one of this person’s waking hours.

Muscles are designed to contract and relax in succession, but these particular muscles are now under a constant strain, and the strain creates a piezo-electric charge that runs through the fascia within and around the muscle (and often beyond in both directions along the myofascial meridians). Essentially, these muscles or parts of muscles are being asked to act like straps.

Muscle is elastic, fascia is plastic. Stretched, a muscle will attempt to recoil back to its resting length. Stretch fascia quickly and it will tear (the most frequent form of connective tissue injury). If the stretch is applied slowly enough, it will deform plastically: it will change its length and retain that change. Slowly make a stretch in a plastic carrier bag to see this kind of plasticity modeled: the bag will stretch, and when you let go, the stretched area will remain. Fascia does not ‘snap back’ – although over time and given the opportunity, it will lay down new fibers which will rebind the area. Getting reality on this concept is fundamental to the successful application of sequential fascial manipulation. Practicing therapists in our experience make frequent statements that betray an underlying belief that the fascia is either elastic or contractile, even though they ‘know’ it is not. The plasticity of fascia is its essential nature – its gift to the body and the key to unraveling its long-term patterns.

Back to our slump: Eventually, fibroblasts in the area (and additional mesenchymal stem cells or fibroblasts may migrate there) secrete more collagen in and around the muscle to create a better strap. The collagen molecules, secreted into the intercellular space by the fibroblasts, are polarized and orient themselves like compass needles along the line of piezo-electric charge, in other words, along the lines of tension. They bind with each other via the interfibrillar glue (proteoglycans or ground substance), forming an inelastic strap-like matrix around the muscle.

Meanwhile, the muscle, overworked and undernourished, may show up with reduced function, trigger-point pain, weakness, and increased metabolite toxicity. Fortunately – and this is the tune sung by structural integration, yoga, and other myofascial therapies – this process works pretty well in reverse: strain can be reduced through manipulation or training, the fascia reabsorbed, and the muscle restored to full function. Two elements, however, are necessary to successful resolution of these situations, whether achieved through movement or manipulation: 1) a reopening of the tissue in question, to help restore fluid flow, muscle function, and connection with the sensory-motor system, and 2) an easing of the pull that caused the increased stress on that tissue in the first place. Either of these alone produces temporary or unsatisfactory results.

In the slump pictured in figure 1.7, the muscles in the back of the neck and top of the shoulders will have become tense, fibrotic, and strained, and will require some work. But the pull in the front, be it from the chest, belly, hips, or elsewhere, will have to be lengthened, and the structures beneath it rearranged to support the body in its ‘new’ (or more often ‘original’) position. In other words, we must look globally, act locally, and then act globally to integrate our local remedies into the whole person’s structure. In strategizing our therapy in this global-local-global way, we are acting exactly as the ECM itself does, as we will explore below in the section on tensegrity. Cells produce ECM in response to local conditions, which in turn affect global conditions which reimpinge on local conditions in an unending recursive process. Understanding of the myofascial meridians assists in organizing the search for the both the silent culprit and the necessary global decompensations – reversing the downward spiral of increasing immobility

More serious deformations of the fascial net may require more time, peri-articular manipulation (such as is found in osteopathy and chiropractic), outside support such as orthotics or braces, or even surgical intervention, but the process described above is continual and ubiquitous. Restoration of postural balance, whether via the ‘Anatomy Trains’ scheme or any of the other good models currently available, is attainable using non-invasive techniques, and a preventive program of structural awareness could even be fairly easily and productively incorporated into public education.

With these prefatory concepts, we are now ready to frame our particular introduction to fascia within three specific but interconnected ideas, three metaphors: physiologically by looking at it as one of the ‘Holistic Communicating Systems’, embryologically through seeing it as a ‘Double Bag’, and geometrically through comparing it to a ‘Tensegrity’ structure. Taken together, they expand the notion of the role of the fascial net as a whole, and form a supporting framework for the Anatomy Trains concept