Connective Tissue
Connective tissue is widely distributed throughout the body and in various forms creates the body’s supportive network. Types of connective tissue include fascia, bone, cartilage, ligaments, tendons, joint capsules, the periosteum of bones, blood, and adipose tissue. This section focuses on fascia, the type of connective tissue that plays many important functions in the body and directly impacts the body’s ability to move freely through space.
Components of Connective Tissue
Connective tissue varies in density, thickness, strength, elasticity, and rigidity depending on where it occurs in the body and its form. It has a consistency ranging from a watery sol state, to a semifluid sol state, to a viscous gel state, to the solid crystalline structure of bone. These differences mainly depend on the varying ratios of cells, ground substance, and fibers that are the primary components of connective tissue. The ground substance and fibers, which are outside the cells, are often referred to as the matrix.
Connective Tissue Cells
Fibroblasts (fibro = fiber + blast = maker) are the most abundant cells in connective tissue and produce the connective tissue matrix of ground substance and fibers. Fibroblasts are especially abundant in dense connective tissue such as ligaments, tendons, fascia, and joint capsules. Fibroblasts are key in tissue repair and are highly active during growth or healing processes. Their activity increases when soft tissues are placed under mechanical stress, and they are directly responsible for creating scar tissue and adhesions.
Mast cells are another component of connective tissue and often found along blood vessels where they produce heparin and histamine. Heparin is an anticoagulant that prevents blood from clotting, while histamine acts as a vasodilator and increases capillary permeability during an inflammatory response when tissue is injured or placed under stress. When you massage myofascia, mast cells initially respond to the pressure of strokes as if the tissue is being damaged, increasing circulation in the local region.
Macrophages, plasma cells, and leucocytes occur in connective tissue and provide immune defense, while adipocytes (fat cells) store fat and provide padding around kidneys, joints, and the body as part of the superficial layer of fascia.
Ground Substance
Ground substance is a fluid produced by fibroblasts that looks like egg white and surrounds all the cells in the body to support cellular metabolism. It provides nutritional support to cells while binding them together and providing a medium though which substances can be exchanged between blood and cells. It also serves as a lubricant and spacer between collagen fibers to keep them from sticking together. The composition of ground substance can fluctuate from location to location, from a fluid state to a thick, gel-like consistency. This phenomenon is called thixotropy. Massage can influence the consistency of ground substance.
Connective Tissue Fibers
The three different types of fibers found in the connective tissue matrix are collagen, elastin, and reticular fibers. Collagen is a protein that forms the tough rope-like strands that make up the fibrous content of skin, fascia, tendons, ligaments, cartilage, bone, blood vessels, and organs. Collagen strands are arranged in a variety of ways depending on where they occur in the body. Sometimes, they are crisscrossed to form a sheet-like structure, or piled on top of each other in layers. They might occur as parallel formations or knit into a sweater-like web. The proportion of collagen fibers and the state (between sol and gel) of ground substance differ depending on how the connective tissue is used. In healthy connective tissue, ground substance lubricates the collagen strands so that they can slide over each other without sticking and catching.
Elastic fibers are yellow and made of the protein elastin. These long, thin, crosslinked fibers can be stretched to one-and-one-half times their resting length and provide the elasticity of skin, blood vessels, and lung tissue, where elastic fibers are found in high concentrations. Reticular fibers are formed from smaller, more delicate collagen strands that cross over each other to create intricate and extensive networks that support skeletal and smooth muscle cells and nerves and that provide the framework for soft organs like the spleen and the lymph nodes. They are often found in basement membranes, lymphoid tissue, and adipose tissue.
Properties of Connective Tissue
As mentioned, connective tissue occurs in many forms based on the ratios of ground substance, cells, and fibers in its makeup. The thixotropic, viscoelastic, piezoelectric, and adhesive properties of connective tissue allow it to be altered, either positively or negatively, by lifestyle choices, chronic stress, injury, and massage techniques that manipulate soft tissue.
Thixotropy
Thixotropy is a phenomenon in which gels become more fluid when they are stirred up and more solid when they are undisturbed. The ground substance in connective tissue, especially fascia, has the unique ability to move between a more fluid sol state and a viscous gel state. Regular exercise, physical labor, stretching, proper hydration, and good nutrition promote a fluid sol state in fascia. The heat created in the tissue by movement warms and “stirs” the ground substance. On the other hand, a sedentary lifestyle, poor hydration, poor nutrition, little physical movement, and tissue trauma related to injury cause the ground substance to cool, thicken, and enter a stiffened gel state. A stiffened gel state might lead to a decrease in range of motion, patterns of tension in tissue that lead to postural imbalances, a greater risk for injury, pain, and overall lethargy. The application of massage techniques that lift, twist, compress, vibrate, and stretch the tissue mechanically stir the ground substance and raise energy levels in the tissue. This leads to greater range of motion, an environment where cellular metabolism is enhanced, a decreased fascial tension that may lead to better posture, the possibility of greater release and length in muscles, and less risk for injury, pain, and lethargy (Box 20-1).
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Viscoelasticity
The term viscoelasticity comes from words parts meaning viscous (thick, sticky, gummy) and elastic (stretchy, expandable, flexible). If a substance is viscous, it will become deformed when an outside force manipulates it and will remain deformed. Imagine pressing your fist into a piece of clay. The clay will flatten and remain flattened. If a substance is elastic, it will deform when manipulated by an outside force but then snap back into its original shape when the outside force is removed (think of stretching and releasing a rubber band). The viscoelasticity of connective tissue makes it plastic, whereas muscle is elastic. When connective tissue is deformed by an outside force like massage techniques or by stretching, the tissue will remain in the deformed state after the outside force has been removed for a certain period of time and then slowly return to its original shape. For example, if the techniques you use elongate chronically contracted tissue, the tissue will remain elongated for some period of time after the massage. Regular massage and adaptations in movement patterns can lead to positive long-term changes in the shape and length of fascia. Some types of connective tissue have more elastin fibers in their makeup (the connective tissue that forms the lungs, for example, or the more elastic ligaments that occur between the vertebrae) and so are less plastic and more elastic.
Piezoelectricity
Piezoelectricity means “pressure electricity.” It refers to the ability of living tissue to generate electrical potentials in response to mechanical deformation. Mechanical deformation that might cause piezoelectricity includes activities like walking, running, dancing, or any weight-bearing movement, or the manipulation of soft tissue or bone as might occur during a massage or a chiropractic session. Research has demonstrated that keratin, elastin, collagen, hyaluronic acid (found in connective tissue), and the actine and myosin in skeletal muscles exhibit piezoelectric properties.1 It is believed that these electrical potentials stir ground substance and improve the health of connective tissue. One common example is the use of electrical machines that simulate piezoelectricity and increase osteogenesis to speed the healing of fractures.2 During massage, soft tissue is electrically stimulated in a positive way by techniques, and this leads to improved tissue health.3
Adhesiveness
Collagen is formed by fibroblasts as a long chain of amino acids. Because of the tension created by atomic attraction and repulsion in proteins, these amino acid chains twist to the left creating a long corkscrew shape. These single chains float about as fragile incomplete collagen spirals until they come into contact with other spirals and then start to coil around each other (this time to the right) in groups of three, creating a three-stranded helix. Hydrogen molecules are attracted to the oxygen radicals that stick out from the sides of the individual protein strands and attach to the oxygen radicals, forming hydrogen bonds that hold the helix together and give collagen its great strength. Now fully formed within the fibroblast, the new collagen molecule is secreted into the ground substance as a separate unit to take on whatever form is needed in the local area. As people age, or because of injury, postural habits, habitual movement patterns, lack of movement, or soft-tissue stress, collage fibers start to pack more tightly together, increasing hydrogen bonding. This thickens and binds the tissue causing a decrease of range of motion, postural imbalances, structural tension, and increased possibility for injury. In fact, two structures that are designed to be functionally separate but which reside side by side may become “glued” to one another so that they don’t slide over each other freely (e.g., two muscles). Bodywork, physical therapy, and movement re-education all help to break or prevent unnecessary hydrogen bonding to promote greater freedom in the myofascia network.
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<TITLE>Concept Brief: Connective Tissue
Types:
Fascia, bone, cartilage, ligaments, tendons, joint capsules, periosteum, blood, adipose tissue
Components:
Cells: Fibroblasts, macrophages, plasma cells, mast cells, adipocytes, leucocytes
Ground Substance: Produced by fibroblasts with egg white consistency.
Fibers: Produced by fibroblasts—three types
- Collagen = protein that forms rope-like strands = very tough
- Elastic = stretchy protein
- Reticular = delicate form of collagen
Properties:
Thixotropy: Phenomenon where gels become more fluid or more solid
Viscoelasticity: Viscous + elastic = plastic quality of connective tissue
Piezoelectricity: Ability of tissue to generate electrical potentials in response to mechanical deformation including massage.
Adhesiveness: Packing of collagen fibers and increased hydrogen bonding that occurs in response to tissue stress
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