6 Short Stories about Connective Tissue

The Ubiquitous Material

By Andrew Biel

Like oil, wood, and steel, connective tissue is a transformable material. Just as petroleum can be converted into plastic or fuel, and wood into planks or sawdust, connective tissue is a remarkable anatomical substance that is extremely versatile. It can form everything from liquid coverings to pliable sheets to stiff rods. And that’s just in your pinkie finger. As a diversified, ubiquitous, and three-dimensional tissue, connective tissue permeates every corner of our anatomy. It is so pervasive, in fact, that if we could magically extract everything out of us that is not connective tissue—muscle, nerve, and epithelial tissue—our shape would remain virtually the same (as displayed to the right by “Otto” and his connective tissue self).
And it’s not without variety in shape and composition. Your bones, fasciae, tendons, ligaments, bursae, joint capsules, cartilage, periosteum, blood and lymph fluids, adipose tissue, and mucus are all forms of connective tissue. They are separate in name only, for each of these structures is intertwined with all the others. None float alone. One tissue’s floor is another’s ceiling; one’s landing site is another’s launch pad.
At times, this tissue—in its various forms—will seem to be at cross-purposes: it separates some structures while connecting others. As active animals, our bodies must be able to move while simultaneously retaining structural integrity. Connective tissue does both jobs—it is essential for mobility, but also intrinsic to stability.

Story 1

A Detour Down the Meat Aisle
Connective tissue may be omnipresent, but it can still be difficult to visualize. To clear up matters, there’s nothing better than a detour down the meat aisle. Several domesticated vertebrates model some of the very same fascial tissues you are made of. With a choice of chicken, pork, or beef, we’ll go with the fowl.
Let’s say that you bought a small fryer from your local butcher. You bring it home, unwrap it, and set it on the counter (Image 1). You may not realize it, but the effects of the tensile fascial network are immediately evident. The fact that the chicken didn’t collapse like a blob of warm pudding is testament to the enmeshing and supportive nature of the connective tissues. Even in death, it holds its shape.
Grasp the skin and attempt to pull it away from the bird. It may shift a little, but it doesn’t lift off like a loose shirt because the fascia holds it in place. Using a sharp knife, carefully make a small incision in the leg. Working your finger under the skin, try to pull it away (Image 2) and note how the white webbing of the superficial fascia resists your tug.
Continue to trim back the skin to explore the muscles below. A thin, shiny layer of the fascia profunda will coat the muscle bellies. Gently grasp them and feel how they afford little movement. Even the individual muscle bellies, although visually distinct, are virtually inseparable.
Using your knife, delicately separate the muscle bellies and then cut crosswise into one of them for a closer look at the fascicles (bundles of fibers) (Image 3). If you were expecting loose fibers to tumble out, you’d be disappointed. The fascial network permeates into every single microscopic fiber of the muscles. Nothing escapes its encasement. Now, explore the ends of the muscle bellies and see where all of those intermuscular fascial layers bundle together to form a tendon.
We could continue to dissect other regions and discover how the fascia links to the ligaments, periosteum, bones, and organs (if your chicken still had them). You name it: the fascia would be there.
Finally, set your chicken in a pan and bake at 350? for two hours. When the timer dings, let it cool. If you cut into it, you’d be able to extract a bone with little additional tissue, an impossibility before the oven (Image 4). The tendons and ligaments are still in place, but the skin slides right off and the meat (muscle) falls off the bone.
What happened to those thin fascial tissues? They melted away, only to collect at the bottom of the pan as juice and fat. Collect this “stock,” set it in the fridge and observe how the collagen fiber-infused broth thickens as a gel beneath the fat. Even when dead and cooked, that wondrous protein­—collagen—still holds a pose.

Story 2

The Properties of Soft Tissues
The term “soft tissue” includes fasciae, tendons, ligaments, cartilage, retinacula, adipose, joint capsules, and synovial membrane, as well as muscle tissue/muscles, nerves, and blood vessels. It excludes bones.
Soft connective tissues (such as those mentioned above) connect, support, or enclose other structures of the body. Since much of your bodywork will most likely be focused on the soft tissues of the body, let’s take a closer look—tableside—at their characteristics.
You’re in session, working on Tony. He’s supine and you take his hands up overhead for a big pull of his shoulder girdles. His soft connective tissues stretch—they demonstrate the ability to lengthen without being damaged or injured. This elongating capacity is fundamental for motion. (For instance, just try to scratch your ear without lengthening any tissues.) Since chronically shortened structures can be easily injured, your lengthening exercise with Tony is performed slowly and gently (Image 5).
Tony exhales and you bring his arms back to his sides (Image 6). Due to the property of elasticity, his tissues don’t remain in their previously stretched state (that would be awkward). This elastic capacity to recoil or rebound to an original length or shape after being stretched (or deformed) is also seen in rubber bands and trampoline springs. Do Tony’s dense connective tissues (like ligaments and fasciae) possess elasticity? Although composed of nonelastic collagen fibers, they still possess a small degree of pliability—mostly due to collagen’s crimped design.
As a former gymnast, Tony’s flexible ligaments, joint capsules, and fasciae still allow him to possess an impressive range of motion (Image 7). After years of continually lengthening his tissues, they illustrate plasticity—the capacity to be altered and retain that new configuration. This is different from elasticity. When a tissue is deformed—either compressed or elongated—its elastic quality will restore it to its original length. When a tissue exceeds its elastic threshold, however, then it will behave plastically and remain at that new length.
From working a desk job, Tony’s posture leaves a bit to be desired. His forward-head position has shortened some tissues and lengthened others within his neck and shoulders (Image 8). This gradual change in shape, or creep, occurs when tissues are subjected to a slow, continuous force—from either compression, tension, or twisting. Such forces could be caused by gravity or posture­­—or even bodywork.
If the change occurs within the tissue’s elastic range, the creep is temporary. However, when the change exceeds the elastic threshold and enters the plastic range, the change becomes potentially permanent. Creep can be beneficial, such as when you perform slow, deep-tissue work on Tony’s shoulders to shorten overstretched tissues and elongate compressed ones.
Before you work deeply on Tony’s shoulders, you’ll want to warm up his tissue (Image 9). Luckily, his ground substance will be happy to cooperate. It is thixotropic, meaning it responds to changes in temperature (or other disturbances such as pressure) by transforming from a gel to a liquid and vice versa. Lava, honey, and silly putty also display thixotropic qualities.  
When cold and stationary, ground substance becomes thick and viscous. Warm it up with movement or other frictional effect and it becomes thin and watery. You can see and feel this when you exercise and your muscle contractions heat up your joints and connective tissues. By manually manipulating Tony’s tissues (or using a heat pack), you’ll use thixotropy to liquify regions of thick, cold ground substance. This might just soften the connective tissue, making it more elastic.
Tensile Strength
For this property, we’ll turn our attention from Tony to you. As you mobilize Tony’s shoulder, your own arms display the tensile strength of your connective tissues. This ability to be pulled in two different directions without damage (in other words, to withstand tension) is courtesy of your collagen fibers. As you support his leg, the tissues of your brachialis are subjected to tension.
For example, lifting his leg pulls the muscles and fascia of your arm in opposite directions. Your muscle fibers shorten in length while your connective tissues are pulled apart. To endure this tension, your fascia needs to possess the necessary tensile strength.
To be clear, stretching is different from tensile strength. Stretching deals with how long a tissue can become, while tensile strength involves how much pulling force it can resist (whether in a shortened or lengthened position).

Story 3

The Functional Types of Connective Tissue
Each type of connective tissue performs a range of functions. Bones serve as levers, ligaments support joints, while other tissues transport nutrients, defend against disease, repair tissue, store energy, and protect and insulate internal organs. But for our purposes here, connective tissues can be functionally divided into two groups—compression tissues and tension tissues.
Before we discuss these two groups, we need to first pose a simple, yet crucial, question. If your body is to swing bones, hoist limbs, and bend over, how shall it be supported?
An initial, wild guess might involve poles from below or puppet strings from above (Images 10 and 11). As ridiculous as these two ideas sound, they aren’t far off.  We’ll just need to incorporate both concepts and build them inside the body (no small order).
The reason this “stick and string” idea isn’t so far fetched is that there are only two ways to hold up a structure (at least in this universe)—with compressive or tensile forces. In other words, propped or suspended. For example, skyscrapers are propped and mobiles are suspended (Images 12 and 13).
Everything around you—a chair, plant, teacup, house, trampoline, or your body—is based on one of these designs, with all structures using both forces as the need arises.
For instance, sit on a stool—a classic propped device—and sense how it primarily uses compression as a force to support your weight. The top and bottom of each leg squeeze together while lesser tensile forces expand each leg’s girth (Image 14).
In contrast, lie in a hammock—a quintessential suspended structure—and feel how it principally uses tension as a force to support your body. Its ropes stretch apart, while other compressive energy pushes together the cords’ fibers, making them thinner (Image 15).
This dynamic dance between both compression and tension can be easily felt on a third resting option, a fitball. The top and bottom compress together, while the sides bulge apart with tension (Image 16).
Now, let’s look at what all of this has do with your connective tissues.

The Push and Pull of your Tissues
What do compression and tension have to do with your connective tissues? Pretty much everything. You see, between gravity, hard flooring, chairs, contracting muscles, and more, there are many internal and external forces that will affect your soon-to-be-built body. We’ll have to construct your connective tissues accordingly so they can best support you. Other functional aspects such as location, usage, and design need to be considered, but it really comes down to this question: Will a type of connective tissue mainly need to withstand compression or tension? In other words, is it going to be primarily squished or stretched?
Bones and cartilage are built to bear your weight during most types of activities (for instance, when you are charging up a trail). They will serve as your compression tissues (Image 17). Although they possess tensile attributes, their material—cellular on up—will primarily be pushed together.  
All of the other connective tissue types, known as fascial tissues—proper fasciae, tendons, ligaments, and many others—will serve as your tension tissues. When you perform activities such as bounding up that trail, they will be predominately stretched (Image 18).
In this way, bones (your body’s “sticks”) will serve as spacers and prop up your mass, while your fascial tissues (your “strings”) will suspend your limbs, organs, and other structures. This dynamic duo of pushed and pulled tissues will together create an ideal, internal framework for your moving body.

Story 4

Fascia and Muscle Fibers
A common storyline involves a muscle belly attaching to a bone, crossing a joint, and connecting to another bone. There’s only one problem with this tale: skeletal muscle tissue can’t attach to bone; it needs a connective tissue middleman. Enter fascia.
Muscle cells, also known as muscle fibers, are elongated tubes possessing incredible movement potential. Yet, without the supportive, organized wrapping offered by fascial tissues, they couldn’t generate a lick of useful motion. This inseparable pairing leads some to call a “muscle” a myofascial unit. Let’s take a moment to quickly build one—specifically, the rectus femoris.
First, we’ll roll up a muscle fiber onto a sheet of fascia (endomysium) (a). Then we’ll repeat this process a dozen times, bundling the fibers into fascicles with perimysium (b). At either end, we’ll bundle up the extra fascial material to form two tendons and sheathe the entire belly in epimysium (c). Finally, we’ll wrap the entire lower appendage in fascia profunda (deep fascia) (d). Although dramatically oversimplified, this—in a nutshell—is the myofascial unit that is your rectus femoris.
What’s so fascinating about these multiple layers of fascia is that—although we’ve separated them here for construction purposes—they’re all one entity. You might be able to tease them apart with your mind, but don’t try it with a scalpel.

Story 5

Stacked and Compressed?
Let’s clear up two common misconceptions about your bones. The first misconception is that your skeleton is a tower of stacked and balanced building blocks. The problem with this concept is that bones can’t actually maintain vertical assemblage, let alone hold themselves together. Their articular ends are not squared off, but include rounded and uneven surfaces. This explains why a classroom skeleton hangs from a hook or sits on a stand, and is fastened together with bolts and wires. Bones don’t stack because they can’t (Image 19).
    If this is true, how then does your skeleton bear weight and form a structural framework? A hint—it receives help from surrounding fascial tissues. This leads to the second fallacy, which is that the body is basically a compression structure comprised of stacked units that bear weight down on the parts below. The theory goes like this: the head sits on the neck; they press down on the trunk; the head, neck, and trunk all rest on the pelvis and so forth to the feet. Yes, your feet take the brunt of the body’s pressures and strains, yet it does not pass from head to toe only through your bones.
It turns out that the body is less like a brick wall and more like a tensegrity toy (Image 20). This ingenious device demonstrates how dowel rods (bones) and rubber bands (fasciae) can combine their qualities of tension and compression to produce a dynamic framework. This teamwork occurs in the body as well (Image 21), with the placement of the bones balanced by the tensile forces of the fasciae (and the enveloped muscle bellies).

Story 6

Collagen, Demand, and Flushing
Let’s finish these stories by stringing together three physiological details that might shed a little more light on the relationship between connective tissue and movement. First, you’re a collagen-producing machine. Second, your body responds to demand. Third, movement flushes out the old and pumps in the new.
To the first point: like a limitless spring that gushes from the earth, your body continuously generates collagen. As the main component of connective tissue—found abundantly in tendons, ligaments, cartilage, bone, intervertebral discs, and more—this miracle protein not only separates structures, but also binds them together.  
As you can imagine, this requires quite a balancing act. On the one hand, too much collagen could result in a sticky situation that limits range of motion; too little might culminate in instability.  
Complicating matters further is the fact that not all regions require the same level of collagenous material. Your low back (heavily stabilized by the thoracolumbar aponeurosis) will demand a lot of collagen, while the muscle fibers in your deltoid (highly mobile) will require comparatively less material.
The situation is yet more complex because not all areas mobilize equally. Your elbows, for instance, might move quite a bit throughout the day, while your neck or hips might not stretch nearly as much as they were designed to.  
So how does your body know where to lay down collagen fibers? Well, it doesn’t “know.” Instead, it relies on cues—especially your movement cues.  
Which brings us to the second point: your body responds to demand. “Use it or lose it” isn’t just a cute rhyme, but a blunt gospel about healthy tissue and range of motion. Move your body and your tissues will adapt to maintain that mobility; don’t move and your body will modify your tissues accordingly.  
Probably the best illustration of this fact occurs when you join the crew of the International Space Station for two months in zero gravity. Under such weightless conditions, your joints, bones, muscles, and other tissues—devoid of earthly stresses—begin to atrophy and shrink soon after blastoff. Conversely, train for the Hawaiian Ironman and feel how your bones and myofascial tissues are augmented and strengthened by the stresses of your balanced and healthy workout regimen.
For a more mundane (yet regrettable) example, find yourself in a neck brace for three weeks and, upon removal of the apparatus, note the diminished mobility of your cervical spine. Aside from proprioceptive recalibration that will have occurred in your neck muscles (where a muscle redraws its “blueprint” to determine its appropriate resting length), the stiffness you feel is largely due to unchecked development of collagen fibers in and around these bellies.  
The body thinks, “Oh, we’re not moving the neck anymore? Fine. We’ll just lay that collagen down thick for extra stability.” The body is always listening and adapting.
This brings us to one of movement’s less touted features, its ability to flush out and engender the new—collagen fibers, that is.
If you’d like to cha-cha when you’re 80, it is not only critical for you to move your body, but also to move the stuff that is inside of your body. For instance, a significant portion of your bodily fluids resides outside the vessels of your cardiovascular system. Because there is no built-in pumping system, they can become stagnant in the swampy hinterlands of your tissues. Instead, interstitial fluids, enzymes, and microscopic particulates must rely primarily on the propulsive suck-and-draw of your joints and undulating tissues to be recycled. Thus, movement not only mobilizes your joints, but also filters and revitalizes the fluids that surround those very joints and tissues.  
Together, these three notions—collagen, demand, and flushing—represent the continual dance between your fascial tissues, mobility, and stability.
And there you have it—a half-dozen tales of connective tissue. Hopefully, they’ll shed a little light on this miraculous substance the next time you hike up a trail, move your client’s limbs, or cut up a chicken.

Scar Tissue
Tony’s body has been around the block once or twice and received its fair share of bumps and bruises. As a result of such incidents, the body has wisely laid down collagen fiber-based scar tissue in and around the tissues for repair and stability. Sometimes, however, the body does too good of a job and secretes excessive amounts of this gluey material, bonding two separate tissues together. Because these adhesions limit healthy motion, one of the benefits of your bodywork—along with exercise and general mobility—will be the breakdown of some of this scar tissue.

The Connective Tissue Tent
Sure, fascia and muscle depend on each other, but so do fascia and bone. Fascia’s naturally tensile (pulling) disposition relies on the space and lift provided by rigid bones. Without your osseous “tent poles,” your fascial “tent fabric” would collapse to the ground. On the other hand, without your fascial rigging, your skeleton—which is really just an unstackable ensemble of compression-ready sticks—would collapse in a heap. Each needs the other, with your body ultimately stacked, as well as suspended.

Andrew Biel, LMP, is the author of Trail Guide to the Body: How to Locate Muscles, Bones and More (Books of Discovery, 2010) and the president of Books of Discovery. This is an excerpt from his forthcoming book Trail Guide to Movement: Building the Body in Motion (Books of Discovery, 2014). He lives outside of Lyons, Colorado, with his wife, Lyn Gregory, and two children, Grace and Elias.

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