Defining Fascia, Not-So-Simple
There is no end-all, be-all definition of Fascia as it is very complex and can be used rather broadly. Considering this it comes as little surprise that fascia is not so simple to define. The International Federation of Associations of Anatomists (IFAA) requested that there be a consensus on the anatomical definition of Fascia. The IFAA is responsible for maintaining the Terminologia Anatomica, which sets the international standard for terminology in human anatomy. This is important because there was once a time when 5,000 structures in the body were referred to by approximately 50,000 different terms. This request was met on September 17, 2015, by the Nomenclature Committee of the Fascia Research Congress. And a day later, September 18, 2015, Carla Stecco MD presented the new, medical definition of fascia. She declared:1
“Fascia, is a sheath, a sheet, or any number of other dissectible aggregations of connective tissue that forms beneath the skin to attach, enclose, and separate muscles and other internal organs.”
Defining The Fascial System
While some favored this simplistic definition, not everyone liked or agreed with this definition. I say simplistic because, Robert Schleip and Thomas Findly had a much more longer, comprehensive, and detailed definition back in 2007.2 Many where asking, how could such as integral tissue – some call fascia the “the organ of form” – be limited by such a narrow definition? If one is curious about the way fascia behaves, then I agree that a much broader definition is necessary. For fascia is both a tissue and a system, and as such it has certain attributes and functions that were not hinted at in this 2015 definition. This fascia “system” had not been addressed then, but it has more recently. On the Fascia Research Committee website, the fascia system has a separate definition, which is defined as:3
“The fascial system consists of the three-dimensional continuum of soft, collagen containing, loose and dense fibrous connective tissues that permeate the body. It incorporates elements such as adipose tissue, adventitiae (outermost connective tissue) and neurovascular sheaths, aponeuroses, deep and superficial fasciae, epineurium, joint capsules, ligaments, membranes, meninges, myofascial expansions, periostea, retinacula, septa, tendons, visceral fasciae, and all the intramuscular and intermuscular connective tissues including endo-/peri-/epimysium. The fascial system surrounds, interweaves between, and interpenetrates all organs, muscles, bones and nerve fibers, endowing the body with a functional structure, and providing an environment that enables all body systems to operate in an integrated manner.”
Now that we have a simple definition of “a fascia” and a comprehensive definition of the fascia “system,” let us begin our understanding of fascia. Fascia is the most universal and perhaps misunderstood tissue in the body. As I give a brief overview of fascia it is most important that you keep foremost in your mind, at all times, that the fascia net is one continuous structure throughout the body. As far, as the body is concerned, the fascia is all one – one complex, holistic, self-regulating organ. Again, fascia is literally everywhere in throughout the body. Often fascia is referred to and used interchangeably with the term “connective tissue.” What does fascia look like? This is much better seen via pictures, but for the sake of this writing I’d like to use our imagination. Imagine a silvery-white material, flexible and sturdy in equal measure – a substance that surrounds and penetrates every muscle, coats every bone, covers every organ, and envelops every nerve. If you have ever butchered an animal or have seen organ meats such as liver and heart then you may be familiar with what people call the silver skin, this is fascia.
Four Groups (Classifications) of Fascia
To separate fascia, so that we may look at how different fascia layers function, we divided the fascia into four groups based on location.
The first we shall discuss is referred to as the Superficial fascia, which is often described as a fibrous layer of loose connective tissue. It is located on the fascial layer, which lays directly underneath a slightly more superficial layer of adipose tissue under the skin. It separates the skin from the muscles to allow for normal sliding action on each other. This layer is connected to the deep fascia.
Deep fascia is a dense, well-organized fibrous layer that covers the muscles. This is the layer that butchers and hunters, as mentioned earlier, refer to as the “silver skin.” The deep fascia is the body stocking or catsuit layer, with the innermost aspect of peeling away to form a discrete pocket around each muscle. This serves to keep everything separated, yet interconnected and in healthy fascia, sliding on each other. This is also the layer that myofascial force transmission takes place.4 It is well known that a muscle transmits force longitudinally across a joint, via the myotendinous junction, to create an action.
Next up is Meningeal fascia, which surrounds the nervous system and the brain. Like muscles, nerves are encased in fascia, and in the same configuration.5 The basic anatomy of all peripheral nerves is a three-layer fascial arrangement of tubes and bundles of tubes just like muscles. There are three times as many sensory neurons as there are motor neurons. This ratio seems to indicate that the body’s need for sensory awareness and refinement is greater than its need for motor control. These sensory nerves, or sensory receptors, are also called fascial mechanoreceptors. The nerves responsible for proprioception (unconscious perception of movement and spatial orientation arising from stimuli within the body itself) are sensory nerves and they are embedded in the fascia. Collectively, the sheer amount of sensory information being relayed throughout this network is greater than even that of vision. Thus, fascia can be thought of as the body’s largest sensory organ.6
The fourth group of fasciae is Visceral fascia this includes the fascia surrounding the lungs, heart, and abdominal organs.7 This fascia suspends the organs within their cavities and includes visceral ligaments that serve both to attach the organs to the body wall and allow for physiological motion. Organs are wrapped in a double layer of fascia with a sliding layer in between the two. In the simplest terms, visceral fascia is a protective double bag around each organ with a sliding layer in the middle to keep everything lubricated and moving.