The Living Fascia

Rethinking Our Assumptions

By Jean-Claude Guimberteau, MD

Fascia, the fibrillar network, is one of total tissue continuity. Understanding this crucial insight enables us to visualize our body as a “global” structure with a specific, three-dimensional architecture made up of elements that, while fragile, have a stubborn capacity for adaptation. This suggests there is an architectural system for all living organisms, the role of which is far more important than simply connecting things. It is actually constitutive.
After 20 years of intratissular endoscopic research carried out during more than 1,000 surgical procedures, I wanted to share my astonishment at the revelation that cells do not occupy the entire volume of the body, and are not responsible for form. In fact, the extracellular world, ignored during more than half a century of research, is as important as the cellular world.

Rethinking What We Know
Progress in digital endoscopic videophotography now allows us to see the living components of the human form. Observations made in vivo (Image 1) show structural elements that are difficult to identify from cadaveric dissection or from the study of preserved tissue samples (Image 2). Even the most sophisticated histological techniques fail to reveal these structures, but using digital videoendoscopy to observe living tissue, we see that a profusion of fibers, fibrils, and microfibrils are revealed at both the mesoscopic and microscopic levels This continuous network of fibers appears to extend throughout the body, suggesting we need to rethink our understanding of the way in which living matter is organized. We can no longer view the body as a collection of cell-based organs held together by connective tissue. Instead, we must now see it as a constitutive fibrillar framework in which the organs are but local, functional adaptations. Groups of cells with specific, specialized physiological functions are assembled within a multifibrillar network to form the organs. The cells are embedded in and supported by the fibrillar framework. This basic architectural pattern is the same for all the organs, as well as for the skin, fat, muscles, bones, tendons, nerves, and vessels.
Through my work studying the living body, I suggest a new model that describes the human body’s structural framework and the basic architecture of living matter—in other words, a new structural ontology.

A Journey Toward Discovery
Surgeons observe the same gross anatomy in all human beings. Our bodies are constructed from the same blueprint, so we all have two arms and two legs, and our internal organs are disposed in the same manner. However, when you begin to observe anatomical structures close up and in detail, you find that we are all different. The individual makeup of each human being is unique.
These observations of a questioning surgeon did not prepare me for what I found. I was simply trying to understand how tendons slide through neighboring tissues so that I could develop a technical procedure to surgically reconstruct the flexor tendons of the fingers. At the time, my intellectual curiosity stopped there.
I was aware of the existence of connective tissue that somehow enabled sliding of the tendon within the tendon sheath. I had learned about paratenons, peritenons, and virtual spaces with visceral and membranous sheaths. The description of these structures in classic anatomy books provided a reassuring and logical theory of the movement of tendons within their sheaths, but I found this to be completely inaccurate and hopelessly inadequate when I started observing living tissue through an endoscope.
I, therefore, began to pay close attention to the study of this connective tissue, which has long been neglected by surgeons and anatomists. I was surprised to discover that it is composed of a network of collagen fibers, which are arranged in a completely disorderly fashion with no apparent logic. I could have abandoned the task of trying to understand the complex organization of this tissue, but I was intrigued by the fact that it seemed to ensure the efficient, independent movement of adjacent structures with great precision and finesse. Could apparent chaos and efficiency coexist?
I soon realized that this sliding system, which I named the Micro-Vacuolar Collagenic Absorbing System (MVCAS), is found everywhere in the body and could be considered to constitute the primary framework of the body. I had noticed this during my early dissections. At the time, however, I did not understand what I was seeing. My logical, pragmatic, Cartesian mind was unprepared for this discovery.

What The Pictures Show Us
It’s All Connected
The first observation of intratissular endoscopy is that everything seems to be linked and interconnected. It is important to emphasize that it is not the cell that provides the link but a profusion of fibers, fibrils, and microfibrils. One gradually realizes that the body is shaped by a fibrillar network at every level, from macroscopic to microscopic, and from superficial to deep (Images 3A–3D). This fibrillary network plays a major role in shaping the substance of the body. It is not the cells alone that determine the form of the body; rather, they themselves are shaped and molded by the extracellular system in which they are embedded.

Tissue Hydration
Another striking feature is the moistening of the tissues as soon as a surgical incision is made. Without a tourniquet, bleeding occurs immediately and hinders observation of the tissues. But even when a pneumatic tourniquet is applied so as to obtain a clear, bloodless field, fluid exudes from the wound and trickles along the sides of the incision. This is evidence that the underlying tissues are permanently hydrated. This phenomenon can be seen when you cut through any structure containing liquid, for example when you cut through the skin of an orange with a knife. Such structures quickly dry up when exposed to atmospheric pressure or to the heat emitted by the lights in the operating theater. The tissue structures, no longer hydrated, adhere slightly to surgical instruments and need to be moistened regularly during any surgical procedure.

No Empty Spaces
Unlike what we’ve seen in anatomy texts, all available space within the body is occupied by structures. There are no empty spaces. You can distinguish muscles, arteries, and veins, but moist, transparent veils of connective tissue surround them. This connective tissue fills the areas between the anatomical structures. You cannot distinguish areas of “virtual space” between anatomical structures, nor can you see surgical planes as described in traditional anatomy textbooks. Even though living matter contains distinct anatomical structures, which can be separated by dissection, a living organism is not simply a conglomeration or assemblage of separate parts.

Maintaining Form: Early Theories of Tissue Elasticity
When we massage, stretch, or pinch and lift the skin, we feel a little resistance to traction but the skin does not tear. When we let go, it returns to its initial position, as if from memory. The tissues respond instantly to the forces imposed on them by the manual therapist and then return to their initial state; the overall shape of the body is maintained. This ability of the body to restore form and maintain its integrity is important, but its significance often goes unnoticed.
In the past, physicians described this phenomenon using the terms elasticity, flexibility, and plasticity, but without providing a satisfactory physiological explanation. In the 20th century, authors of anatomical texts tried to explain it from a strongly mechanistic point of view by alluding to notions of virtual space and stratification of tissue. At the time, it was thought that the role of connective tissue was simply as packing or padding material filling the spaces between the organs, facilitating sliding between anatomical structures, and providing a link between structures such as bones, muscles, and nerves. Descriptive anatomy all but stopped there. Then came the era of the microscope, using optical, electronic, slot, scanning, and transmission techniques to explore human tissue, but at a very different level—that of the cell.
It might seem strange to have to discuss this concept of tissular continuity, but in the past, anatomists have tended to compartmentalize the body. However, connective tissue plays far more complex and important roles in the body than previously believed.

General Anatomical Conclusions
Tissue Continuity: No Layers, No Empty Spaces
To the naked eye, connective tissue seems at first to be fairly uniform, unimportant, and of little interest to the anatomist. But as the camera slowly approaches the area between distinct muscle groups, a real entwining and interweaving of opalescent fibers strikes us, and we see that these fibers create links of total continuity. During surgical dissection, these images transform into displays of sparkling, scintillating mobile mirrors and ephemeral lights, disappearing almost immediately only to be replaced by others (Image 4). What are these reflections? How and why are they produced? Why do they exist between muscular structures and under the skin?
During surgery, often without realizing it, the surgeon needs to separate, lacerate, and destroy this amalgam of structures that do not seem to be part of the organs and often hinder access to them. To expose the area that is to be worked on, the surgeon has to create a route of access and, in the process, must break through this mass of dense, heterogeneous fibers that appear to surround and wrap around all the internal organs, binding them together. This continuum of fibers, present in all spaces throughout the body, is what we commonly call connective tissue. It is important to emphasize that this so-called connective tissue is present everywhere within the body, linking separate structures from the muscular depths to the surface of the skin.
This continuity of a fibrillar network throughout the body is in accordance with the holistic view of many manual therapists. Contrary to conventional teaching, we now discover that there are no empty spaces, no separate layers of tissue sliding over each other. The global nature of connective tissue within the body is evident. But is this tissue solely connective? Is this really its only role?

Fibrillar Continuity: Cells Are Not Found Everywhere
Undeniably, the recognition of the cell as the basic morphological unit and the understanding of its role in protein production were crucial scientific discoveries. Shape is determined by the grouping together of cells, be they adipocytes, myoblasts, or osteocytes. The liver, thyroid gland, and bone are all examples of dense cellular structures, each with its own specific function. However, the cellular elements that compose them, while certainly essential, are not entirely responsible for their form. Sometimes, cells are too scattered to influence the shape of anatomical structures (Image 5).
The cell is sensitive to external conditions and needs some kind of architectural support to live and function. It does not exist in isolation. The study of the cell has monopolized scientific attention and mobilized vast resources, but the extracellular world is still largely unexplored. It is, for all intents and purposes, a scientific desert. If we study only cells through the lens of a microscope, we are at risk of forgetting what surrounds them. Whereas areas of the body may be completely absent of cells, the same cannot be said of the fibrillar extracellular matter. For tissue of such abundance, it is surprising that diagrams in most anatomy and histology textbooks represent it as simply a few lines of collagen or elastin fibers between the mast cells and fibroblasts. Why was it illustrated in such a simplistic way? If it is so simple, why are there several terms to describe it, such as connective tissue, extracellular matrix, ground substance, and interstitial spaces?
Our observations show that the extracellular fibrillar world—complex and all-encompassing—is of huge importance. It surrounds the cell and helps to provide and maintain shape and form, but it can only really be appreciated and fully understood in the living state.

Architectural Continuity: Fibrillar Intertwining and Microvolumes
After cutting through the skin, if you apply light traction upward with small hooks on either side of the incision, structural elements that are initially stacked and piled up on each other will gradually unfold (Image 6)
These elements are flattened, but create volume and participate in the creation of shape and form by their superposition on one another. The common assumption that the cells under the skin are arranged in a regular fashion is false.
The observation of living structures at magnifications between 10x and 60x reveals a mesh, a woven network, based on the repetition of a polyhedral unit that I have named the microvacuole. The microvacuole is the volume created in the space between the intersections of fibrils.
The shape of the microvacuole is polyhedral—completely irregular, yet simple (Image 7). Each microvacuole has its own shape and form; no two are exactly the same. The fibrils run in all directions and, surprisingly, show no pre-established pattern; their arrangement has no apparent logic. They interconnect and interact with each other. The fibrils are a few microns in diameter, with extremely variable lengths and irregular thicknesses, giving a disordered and chaotic appearance—a latticework of stems, branches, stalks, and tendrils.
It is important to emphasize that everything in this extracellular world tends to be irregular and polyhedral. These polyhedrons are simple shapes but with sides that are mainly triangular, quadrilateral, pentagonal, or hexagonal. They are rarely more complicated. This is a constant, unvarying observation.
Diversity is everywhere. We observe long and short fibrils, which are vertical, oblique, or transverse; close together or far apart; and of varying density. This formation, which some biophysicists call chaotic, displays another characteristic—the fractalization of this irregular network. This is, admittedly, somewhat surprising and can be confusing, because it contradicts what conventional teaching would lead us to expect. However, it is an undeniable fact and cannot be ignored. Smaller structures of similar design are found within large microvacuoles, and they fit together like Russian dolls.
It begs the question: If the same multifibrillar architecture is found throughout the body, from the skin to the muscle and from the tendon to the periosteum, permitting constant intra- and interfibrillar movements and housing cells of different specifications, could the role of this fibrillar architecture be more important than has previously been supposed? Could it be that the connective tissue is not just inert packing tissue but the constitutive tissue from which the organs are developed? If we were to find this to be the case, it would be a significant paradigm shift.

The Structuring Role of the Multimicrovacuolar
When the surgeon makes an incision in the skin and parts the tissues to gain deeper access, small bubbles appear at the surface of the exposed structures, be they muscle, tendon, or indeed any organ within the body (Image 8). This occurs a few minutes after the incision has been made. These microbubbles, which can measure as much as 1 millimeter in diameter, are the manifestation of naturally existing volumes within the tissues—the microvacuoles. They are revealed because air at normal atmospheric pressure has entered them, either breaking through or diffusing across their walls. This is because the internal pressure of the microvacuoles is different from that of atmospheric pressure. This observation is fundamental, because it introduces the idea of a pressurized microvolume with clearly defined boundaries. We see this regularly during in vivo endoscopic exploration. It is central to all our observations.
If we grasp with surgical forceps the tissue in which the microbubbles have formed, the traction creates strange movements brought about by the bursting of these bubbles at atmospheric pressure (Image 9). This phenomenon indicates the existence of some kind of hydraulic system with pressure differences. We can see this hydraulic pressure phenomenon whenever traction is applied to the connective tissue surrounding the tendons. A froth of small bubbles appears immediately, which seems to constitute the sliding tissue in its entirety. However, this happens only if traction is applied to these tissues in vivo. This phenomenon is not so readily observed in a cadaver, and not at all in preserved tissue.
The term microvacuole was chosen to emphasize the notion of a volume that is unoccupied by cells. Here again, we must stress that everything in the extracellular world tends to be polyhedral and irregular. Diversity is the norm. The fibrils are long, short, vertical, horizontal, or oblique. They can be close together or far apart, woven tightly or loosely. The fibrils interconnect and interact with each other. They branch off randomly in all directions. We must, therefore, abandon our search for any discernible regularity.
The microvacuolar filling, being aqueous, is primarily composed of:
• Highly hydrated proteoglycan     gel: 72%
• Collagen type I: 23%
• Lipids: 3%
• Collagen types III, IV, and VI: 2%
Lipids are hydrophilic and probably play a role in the exchange of fluids between neighboring microvacuoles and between the microvacuoles and the circulatory system. This would explain the relatively high lipid content of the microvacuoles. Each microvacuole can change shape during movement while its volume remains constant. Even though the intravacuolar volume appears to be globally incompressible, the internal pressure varies locally, depending on the movement required by the tissue in which the microvacuoles are found. This ensures the transmission of pressure throughout the microvacuolar network. The greater the movement required, the smaller and more densely packed are the microvacuoles within the tissue.

Mechanical Behavior of Fibrils and Fibers During Mobility
At no time does the fibrillary network of the connective tissue and fascia system move spontaneously. An applied force is needed, whether it be external, such as during massage, or internal, as a result of muscle contraction or the movement of tendons.
When a tendon slides through the surrounding connective tissue, the fibrils divide and intertwine and there is movement of fibers and fibrils in the vicinity of the tendon as it slides through the surrounding connective tissue. First, the fibers react immediately to the slightest mechanical constraint by quivering intensely, then the larger fibers move and lengthen. Both fibrils and fibers are capable of movement. Insofar as the microvacuoles are formed by fibers and fibrils, they also adapt to movement by stretching, widening, and shortening, while being able to return to their original shape. To achieve this, all the components must possess certain inherent qualities, such as elasticity and intrinsic cohesion.
It’s important to note that all the fibrils participate in the local tissue response to the traction: the microvacuoles change shape in response to the constraint, and their volumes are compressed (which also alters the internal pressure). The fibrils stiffen as strain is put on their collagen structure, and the number of fibers involved increases as the traction increases, which likely explains the tissular resistance that is felt as more traction is applied. This suggests a correlation between the increased number of fibers under tension and the resistance felt by surgeons during traction, and by manual therapists during soft-tissue manipulation.
When the collagen fibrils reach their maximum stretching potential, they are unable to perform further movement. There are two solutions:
• Either the fibers fracture or rupture, which is an unacceptable physiological solution, or
• It could be that there is another mechanical solution that involves a more general fibrillar response.
Each fiber, before it reaches its maximal stretching point, recruits the adjacent fiber, which is then put under tension, but this tension is now slightly decreased. The second fiber will behave in the same way, and before it reaches its own maximum stretching point it will recruit another adjacent fiber, and so on. This would explain the dispersion of the force—a dilution that avoids the risk of fibrillar rupture. The closest fibers are fully distended, and the fibers furthest away are only slightly involved. This system is reminiscent of a suspension system.
We can now explain how it is possible to accommodate two apparently contradictory roles simultaneously—efficient optimal movement in full contact with the vector and energy absorption at the periphery—without disturbing the surrounding tissues in a continuous, mobile crisscross of fibrils.
If this mechanical hypothesis, which is based on careful observation, is proved to be generally correct, then it constitutes a surprising and elegant solution to the requirements of living matter for optimal movement.

Interfibrillar Movements Between Individual Fibrils
A variety of complex interfibrillar movements ensure that the contradictory roles of movement and energy absorption are carried out simultaneously.

Fibrils Lengthen
It seems that as soon as movement begins, the fibrils are able to stretch out, thereby increasing their length. This ability of the fibrils to lengthen is the first property we see. The fibers can increase their length by as much as 15−20 percent. This is the initial fibrillar response and the most commonly observed, whether light or heavy traction is used. During the lengthening of certain fibrils, we can sometimes see small annular bulges inside the fibrils that stretch out during traction. This is similar to the behavior of an earthworm or a spring. It implies that molecules, perhaps of elastin, are prearranged so as to allow for distension and retraction in that area of the fibril, permitting the fibril to return to its initial position. However, these bulging rings are not always found, and the fibrils often lengthen without revealing any hint of their internal architecture.

Fibrils Migrate
The migration of fibrils along other fibrils was another commonly seen phenomenon during my research. It is the existence of mobile junctions that enables one fibril to slide along another. In this way, energy is dispersed and absorbed throughout the fibrillar network. This ensures efficient distribution of the constraint as it is applied to the tissue.

Fibrils Divide
During stronger traction, the fibril is capable of dividing into two, three, or four smaller fibrils. This means the distribution of energy is spread across several fibrils simultaneously, and is thus absorbed more efficiently.

Fibrils Are Linked and Fixed
Sometimes interfibrillar crossings, or links, are stable and do not seem to be dynamically involved. This real and distinct stability explains the overall permanence of the form during movement, and suggests a structure with a predetermined architecture and behavior that are not entirely random. Other links are not visible but reveal that they must exist when new fibers appear mid-sequence.

Fibrils Within Fibrils
Observation at high levels of magnification reveals a network of interwoven fibrils that are themselves made up of smaller fibrils. These fibrils are wavelike in appearance when they are not under tension. This is further evidence of the fractal nature of the fibrillar architecture.

Global Mechanical Result
A veritable firework display of fibrillar movement explains the global dynamic behavior of the fibrillar network. The fibrils intertwine, intersect, and overlap each other, but behave in a harmonious manner when traction is applied to the tissue. The fibrils align themselves in the direction of the force imposed on the tissue. The lengthening seems to be the primary response in dealing with the mechanical constraint and appears to play a leading role in facilitating movement. The combined division, sliding, and fractal organization of the fibrillary network ensures that the force is diffused throughout the network.
The combination of lengthening, dividing, and sliding also permits mobility of the tissue in any direction and in three dimensions, and in particular during movement. These phenomena also explain how the applied force dissipates and loses its strength beyond a certain distance. The fact that these forces have no effect on the surrounding tissues demonstrates the energy-absorbing capacity of the fibrillar system.
The combined action of these three distinct, yet closely related, types of fibrillary behavior enables the fibrillar network to adapt to the constraint in three dimensions, while at the same time dispersing and reducing the force of the constraint and also preserving the capacity of the structures to return to their resting positions. This astonishing fibrillary behavior involves the simultaneous movement of billions of fibrils. The dynamic potential of the combination of these three movements is incalculable.

From chaos to efficiency
Through the course of my research, I experienced great difficulty in moving away from the tranquil certainty of rationality to enter a world of fractals and apparent chaos. I came to recognize that this seemingly chaotic fibrillar disorder, together with tissue continuity, ensures the efficiency of the living organism. The concept of order and proportionality suddenly seemed to lose ground to nonlinearity and apparent disorder, which in fact permit creative adaptability and the tendency for life to auto-organize in the most efficient way.
After 20 years studying fascia, I say with certainty that the importance of the role of the extracellular matrix must be reconsidered. This will provide new, more coherent theories, particularly in the fields of embryology, morphogenesis, and phylogenetics. I believe that surgical exploration must be a cornerstone of this modern research, and an essential point of reference, because it is the only way to provide a clear and precise description of the anatomy of human living matter as it really is.
Nature is certainly a symphony of fragility and complexity, but it is gradually becoming more comprehensible.

Jean-Claude Guimberteau, MD, is co-founder and former scientific director of the Institut Aquitain de la Main, and past president of the French Society for Plastic and Reconstructive Surgery. He has developed the profession’s knowledge of the structure and function of tendon physiology, and pioneered techniques for secondary flexor tendon repair. His innovative use of videoendoscopy to investigate fascia in vivo resulted in his text Architecture of Human Living Fascia (Handspring Publishing, 2015), from which this article is adapted. For more information about Guimberteau, visit his website at