Fascial Layers, Part 1 + Anatomy of a Muscle

While it’s true that the fascia is one big continuous and completely connected piece of tissue, it looks and acts differently depending on where it’s located in the body. In order to gain a better understanding of the fascial system as a whole and also have it be less overwhelming, we’ll break it down into more digestible bites. 

Just beneath your skin there is a layer of fatty tissue that provides the body with necessary insulation, blood and lymphatic flow and energy storage. Just beneath that is the superficial fascia. It anchors the skin to the tissues and organs below and is rich in blood and lymphatic vessels, nerves and some general sensory receptors which I’ll describe in detail in a later post. This thin and fibrous but highly elastic layer is classified as loose connective tissue. In this case loose just means it lacks any regular pattern or strong organization. 

Unlike the superficial fascia, the deep fascia is dense and well-organized. As far as I’m concerned, it’s the coolest layer of fascia because of the incredible and stunningly beautiful way it surrounds, supports and separates yet also connects every single structure in your body. The deep fascia is rich in sensory receptors that are sensitive to things like pressure and movement, which I will also cover in detail in another post. First let’s look at the anatomy of a muscle. Understanding the fascial anatomy of a muscle is essential for truly understanding how yoga and massage create change for people and actually really “work”.

Let’s consider a muscle from the outside in, or anatomically speaking, superficial to deep. Every muscle as a whole is wrapped in a sleeve of fascia called the epimysium. Epi- meaning on and my- meaning muscle. Epimysium means on the muscle.

Within each muscle are groups of muscle cells that have been bundled together into what’s called fascicles. Each fascicle is wrapped in its own layer of fascia called the perimysium. Peri- meaning around and my- meaning muscle. Perimysium means around the muscle. 

Each individual muscle cell also has its own layer of fascia called the endomysium. Endo- meaning within, my- meaning muscle. Endomysium meaning within the muscle. 

Each of these three layers comes together to form the tendons that connect muscle to bone. The layer of fascia that surrounds each bone is called the periosteum.

In part two we’ll look at the fascial layers that surround the brain, nerves and organs as well as the anatomy of a nerve.

Collagen + Mechanical Properties of Fascia

Fascia has several mechanical properties that dictate how it functions. The main three are thixotropy, piezoelectricity and viscoelasticity.

Thixotropy refers to the ability of fascia to fluctuate between a gel (viscous) state and a sol (fluid) state, and it’s because of the ground substance that this can happen. Fascia is everywhere, and fascia has more ground substance than other types of connective tissue so while you’ve heard that we are made up of mostly water (about 70%), here is exactly what that means. The extracellular matrix (all the space outside of your cells in your connective tissue) is made up of about 90% water, and suspended in that water are a bunch of water-loving peptides called glycosoaminoglycans (GAGs). The GAGs attract water to keep the ground substance fluid so it can serve its purpose as a lubricant for the connective tissue. When connective tissue becomes dehydrated or injured, the ground substance loses fluid, causing fibers to stick together rather than slide and glide. We experience these areas called adhesions in our bodies as tension or knots. Hydrogen bonds the collagen fibers together, so when we release an adhesion through myofascial release or massage therapy, it’s the breaking down of the hydrogen bonds that can create that burning sensation we sometimes feel.

Let’s talk more now about how any of this applies to yin yoga and massage therapy. Piezoelectricity is another of fascia’s mechanical properties. It is derived from the Greek word ‘piezein’, meaning pressure or to squeeze. When subjected to gradual, sustained pressure, connective tissue produces a small electrical current across its surface. The current stimulates fibroblasts, the cells that produce fiber and ground substance. Pressure and movement increase the piezoelectric properties of fascia which in turn stimulate the healing process and contribute to the soft and loose feeling we often experience after a yoga class or a massage. This is why I often include elements of self massage and myofascial release in my classes. The third main property of fascia is the reason why that soft, loose feeling eventually goes away and ultimately why slow and steady wins the race when it comes to to reducing adhesions/pain and increasing flexibility, and why frequency matters more than duration.

In my classes I encourage the use of lots of props and for students to back away from their edge in their stretch. The reason is viscoelasticity: connective tissue’s ability to extend and then rebound rather than stretch and recoil. I mentioned in my introduction to fascia and connective tissue that collagen fibers have the ability to lengthen but they aren’t elastic so they can’t stretch without also sustaining structural damage. How is that?

The molecular component of a collagen fiber is called tropocollagen. Several tropocollagen fibers wind together and arrange themselves in a parallel alignment to form one collagen fibril, then multiple collagen fibrils wind together, also in parallel alignment, to form one collagen fiber. The fibers are all arranged into a triple helix which gives the fascia a great deal of tensile strength, meaning for the most part you can stretch it without it breaking. Collagen fibers do not stretch, but they do lengthen. When gradual, sustained pressure is applied, the collagen fiber unravels from its triple helix shape and eventually reaches its full length. This process of unwinding and extending can only happen when the force is applied gradually and repeatedly. When the force is sudden or extreme (such as bouncing in a stretch or going so deep into a stretch that your muscles are shaking), the collagen fibers resist and become even more bound. When the pressure is gradual and mindful, fibroblasts are stimulated to produce more tropocollagen, which forms new collagen and adds to the resting length of the existing fiber. This is why I teach so slowly and with so many props, it’s for the greater good of the fascial
system as a whole.

Sometimes almost as quickly as the release comes, we lose it. If you’re looking for increased flexibility, a decrease in pain, improved immunity, better sleep, a clearer mind and lots of other great things... stretch slowly and often, breathe deeply and give yourself permission to generally slow down. Keep your tissues hydrated by drinking lots of water and moving your body often, make the time to go to yoga, spend the money on the massage. The fascia is our internal environment and caring for it properly is essential for our overall health, happiness and wellbeing.

An Intro to Fascia + Connective Tissue

The body is filled with all kinds of tissue (four different types, to be exact), the most abundant being connective. Ligaments, tendons, cartilage, joint capsules, fascia, adipose, even your blood and your bones are all classified as connective tissue. I’m mostly going to be talking about fascia in this series, but it’s worth mentioning that all types of connective tissue are made up of various amounts of the following three things: cells, fibers and a watery fluid called ground substance. 

What Kind of Cells?
Fibroblasts are the most abundant cells in connective tissue and their job is to produce the various types of fibers found in the various types of connective tissue. I’ll be talking lots more about collagen specifically in upcoming parts of this series and the role it plays in yin yoga and massage therapy.

Mast cells, which are associated with the processes of inflammation and healing, are found all throughout connective tissue but are the most highly concentrated around blood vessels. They secrete heparin (an anticoagulant that prevents blood clotting) and histamine (which causes the blood vessels to open wider, aiding in the inflammatory response).

The third type of cell present in all connective tissue is a type of phagocyte called a macrophage. Macrophages play a key role in general immune defense by eating and thereby destroying microbes and cellular debris that make it past other physical and chemical barriers like skin and mucus membranes. Macrophage translates to “big eater” so these cells can ingest up to 100 foreign objects before they die and we eliminate them.

What Kind of Fibers?
There are three types of fibers found in connective tissue, all are made up of protein chains secreted by the fibroblasts. Collagen is the thickest, strongest and most abundant protein in the body. It’s highly concentrated in load bearing structures like tendons, ligaments and bones. There’s also elastin, a smaller more flexible protein that can stretch up to 150% it’s normal length without tearing and then quickly recoil. This is very different from collagen in that collagen doesn’t have the ability to stretch without causing structural damage (though it can and does lengthen, more on that later). Reticulin is a thinner, much more delicate and also flexible type of collagen and can be found surrounding and supporting organs and nerves. It can also be found in the endomysium, which is the layer of fascia that surrounds each individual muscle cell.

What is Ground Substance?
In his book “Fascia: What it is and why it matters” David Lesondak says, “Ground substance is a viscous, fluid environment where chemical exchanges take place in the body, and molecular exchanges between blood, lymph and tissue cells happen.” To add to that, Deane Juhan wrote in his book “Job’s Body” that ground substance is “the immediate environment of every cell in your body.” It functions as the lubricant of all connective tissue, so when it’s dehydrated the fibers lose their ability to slide and glide over one another and adhesions (aka knots) form. Fascia is different from other types of connective tissue because it contains more ground substance than say a bone or ligament.

What is Fascia?
At the Fourth International Fascia Research Congress in 2015, Carla Stecco declared that, “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.” Before that though, at the First International Fascia Research Congress in 2007 it had been defined by Robert Schleip and Thomas Findley as “the soft tissue component of the connective tissue system that permeates the human body, forming a whole-body continuous three-dimensional matrix of structural support. It interpenetrates and surrounds all organs, muscles, bones and nerve fibers, creating a unique environment for body systems functioning.”

The fascia is similar to saran wrap. You know what a mess that is to unstick once you get it balled up? When fascia is healthy its fibers are meant to slide and glide past one another and other structures. When it’s unhealthy and dehydrated, adhesions form and a decrease in immune function and healing processes can occur. More info about adhesions (what they are and how they form) coming in a later post. You can read all about the facial layers here and here.