Connective Tissue: keeping us together

Connective tissue is incredibly important to all of us. Not only does it form our solid inner structure, it pads us to protect us, it cushions our joints and forms our blood. The classification of blood as a connective tissue seems a bit counter-intuitive, however, all types of blood cells originate in the connective tissue of our bone marrow, some white blood cells move freely between blood and other connective tissues and the chemical composition of blood plasma (plasma is what you get when you remove all the cells from blood) is very similar to that of the fluid that occupies the space between our tissues and skin (known as the interstitial space). 

Connective tissue is one of the four main body tissues. The others are nervous, muscular and epithelial (epithelial tissue lines surfaces, including the epidermal layer of our skin). Connective tissue is then broken down into different types:

Ordinary/Specialised

Loose/Dense

Regular/Irregular

I won’t go right into the details of each of these here, except to explain Ordinary and Specialised as they are the ones I am most focussed on. Ordinary connective tissue is your everyday garden variety connective tissue. It is comprised of extracellular fibres, extracellular fluid known as ground substance (I will explain more about this later), and cells, all in relative proportions.

Within the ordinary connective tissue classification there occurs some very different forms of specialised connective tissue. Examples include bone, cartilage and lymphoid tissue (lymph nodes, spleen, tonsils, bone marrow, etc.). I will probably write an article on the Lymphatic system and its tissues down the track, as it is also a pet subject of mine.

The term ‘connective tissue’ is often used to refer to just the ordinary type, and this is the connective tissue I have most experience with. Ordinary connective tissue includes: the superficial and deep fascial sheaths, nerve and muscle sheaths, the supporting framework of internal organs, aponeuroses (layers of broad flat tendons, we have aponeuroses over our skull, in our abdomen and also our lower back), ligaments, joint capsules, periosteum (a layer of tissue around our bones) and tendons. Unfortunately our knowledge of these has been gathered somewhat slower than our other more exciting body parts, as Anatomists had a habit of cutting connective tissue away to get to muscles, organs and blood vessels. During the time I worked as a Remedial Massage Therapist and Teacher there seemed to be a push forward with knowledge and research of connective tissue. One particular pioneer in soft tissue treatment was Biochemist Ida Rolf, who developed a treatment method now commonly referred to as ‘Rolfing’ but which was actually named ‘Structural Integration’. Many students of this treatment method have gone on to develop their own theories and treatment methods, notably Tom Meyers who has authored several books and developed the theory of Anatomy Trains. For more info on Tom click through to his website here. As an aside, one of the stranger moments of my career was when a patient rang the practice I was working at and asked if someone could ‘Rolf’ his groin. No one at the practice knew about Rolfing so it created a great deal of confusion and, I must admit, giggling.

The white sections in this image from Grey's Anatomy are all connective tissue - fascia. The fascia that envelops our 'six pack',  properly known as Rectus abdominus is called the Linea alba (white line)

What is fascia?

Fascia is a specialised type of connective tissue. It surrounds supports and protects all the visceral and bodily structures. Fascia provides insulation, padding and the pathway for nerves, blood and lymphatic vessels; it stores water and fat, and allows the skin and underlying structures to move independently of one another.

Fascia can be viewed as a large, complex, body-wide net, or web. (T. Myers), Grey’s anatomy refers this as the ‘extracellular matrix’ (ECM). The fascial web or ECM is composed of three types of fibre: collagen, elastin and reticulin, and ground substance.

• Collagen: is the most common and tensile/least elastic of the three fibres and is found in fascia, bones, tendons and ligaments.
• Elastin: as the name suggests is more elastic and is found mostly in the lining of arteries.
• Reticulin: is the most elastic of the three fibres and is found in the supporting structures surrounding the glands and lymph nodes.
• Ground substance: a viscous gel-like substance which acts like a mechanical barrier to foreign matter and is a medium for the diffusion of nutrients and waste products. It can change its state to meet local needs e.g. in a still area of the body it will become more gel-like to receive and store metabolites and toxins. Small amounts of ground substance are found throughout every tissue, but the synovial fluid in joints and the aqueous humour of the eye are examples of areas where it can be observed in large quantities.

Collagen fibrils from inside a knee sourced from here

Due to the fact that the fibres in fascia run in all directions it is able to move in all directions to allow for changes in muscle bulk and for stretching. Fascia shrinks when it is inflamed. It is also slow to heal because of poor blood supply and is a focus of pain because of its rich nerve supply.

A useful metaphor is viewing the body like a tent, our bones as tent poles which cannot support the structure of the body without guy ropes (the fascia), to keep just the right amount of tension to allow the tent (or body) to remain upright with proper equilibrium!

The superficial and deep fascial sheaths:

Superficial fascia 

Superficial fascia is subcutaneous and blends with the bottom layer of the dermis. It is comprised of loose connective tissue and adipose tissue and is the layer that primarily determines the shape of our body. Superficial fascia is also found surrounding organs, glands, neurovascular bundles and stores fat and water. It also acts as a passageway for lymph, nerve and blood vessels and as a protective padding to cushion and insulate.

Deep fascia

Deep fascia is a dense fibrous connective tissue which interpenetrates and surrounds muscles, bones, nerves and blood vessels. It also functions as a connection and 

communication system in the form of aponeuroses, ligaments, tendons, retinacula, joint capsules and septa. The deep fascia envelops the bones (periosteum and endosteum); cartilage (perichondrium), and blood vessels (tunica externa) and becomes specialised in muscles (epimysium, perimysium and endomysium) and nerves (epineurium, perineurium and endoneurium). Its high concentration of collagen fibres gives the deep fascia great strength and integrity.

Scar tissue

Scar tissue is the most common form of connective tissue used by the body to help repair or replace damaged areas. Scar tissue is generally less flexible than the tissue it replaces. When scar tissue forms, often more tissue than necessary is created, and adhesions (fibrous bands) form. After the acute phase of an injury connective tissue massage can be beneficial. Indeed, this was something I did a lot in my practice. From around twelve weeks on a scar can be treated with Myofascial release - a gentle stretching technique designed to align the fibres and mobilise the fascia. It worked incredibly well with patients who had had a mastectomy and found the scar was pulling into their armpit or across where the breast had been.

Adhesions

When an area of the body is immobile (through injury, underuse or decreased use) lubrication between the collagen fibres is not maintained, the ground substance changes and adjacent collagen fibres move closer together, this is the beginning of microadhesions. Microadhesions are responsible for restricted joint movement, not only a loss in range of motion, but also a reduction in the quality of the movement of the joint. Immobility leads to stiffness, and stiffness leads to more stiffness! (So keep moving!)

Thixotropy

Connective tissue fascia is Thixotropic! It can be transformed from a more solid state (gel) to a more liquid state (sol) with the application of a gentle shearing force.

“Thixotropy Definition: The property of a material which enables it to stiffen or thicken on a relatively short time upon standing but upon agitation or manipulation to change to a very soft consistency or a high viscosity fluid; a reversible process. The materials are gel-like at rest but fluid when agitated and have high static shear strength and low dynamic shear strength, at the same time.”  (Dictionary of Composite Materials Technology,
Stuart M. Lee)

Examples of thixotropic materials are silly putty and a solution of cornstarch and water. (Seriously, try it! Just don’t whack it too hard or you might hurt your hand!)

This becomes important when you are having your fascia massaged. A lot of therapists work on the theory that getting in ‘hard and deep’ is the only way to correct areas of tension. However, if you apply a large amount of direct force at a thixotropic substance it will resist and behave like a solid. So in actual fact, if you are trying to improve mobility in an area that has tightened, applying gentle shearing force, or vibration, will allow you to manipulate and stretch the fascia, potentially reducing adhesions, and restoring a greater range of movement for that area. It also allows you to move past the fascia and contact the muscle underneath for further treatment.

Conditions which affect connective tissue

Ehlers Danlos Syndrome is a genetic condition that affects connective tissue. Usually it is an issue with Collagen producing genes, which can manifest as hypermobility of joints, thinly walled veins and arteries, super stretchy skin, and a whole other range of symptoms. There are many conditions that affect connective tissue, Lupus and Rheumatoid Arthritis are both immune system diseases where the body starts viewing connective tissue as ‘non-self’ and starts attacking it. There are other genetic conditions such as Marfan’s Syndrome, which famously the Pharaoh Tutankhamen had. Because connective tissue is so very important in how the body operates these conditions can be devastating and sometimes fatal. I consider myself lucky in that regard, I just have extra stretchy Ordinary connective tissue, and no obvious vascular/heart problems (although I bruise ridiculously easily).

I hope this brief overview has given you a greater appreciation for our amazing connective tissue, and perhaps you will give more thought to your connective tissue, the guy ropes and bones and sheaths. We simply couldn’t exist without it.

NB. This blog post stems from part of the course notes I composed while teaching the Diploma of Remedial Massage in 2009. I decided to share them firstly as part of a promise to my friends and fellow connective tissue ‘zebras’ at EDSAUS - a site for Ehlers Danlos Support in Australia, secondly my original plan for this Blog was to include posts on anatomy, and this seemed like a useful topic. If you have any questions about this post, please leave a comment :)