Healthcare and Medicine Reference
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tissue to form all the building materials necessary to our
structure and movement.
Let us take a common example to help us understand
the table: the bones you have found in the woods or seen
in your biology classroom (presuming you are old
enough to have handled real, as opposed to plastic,
skeletons) are really only half a bone. The hard, brittle
object we commonly call a bone is in fact only part of
the material of the original bone - the calcium salts part,
the interfibrillar part in the table. The fibrillar part, the
collagen, had been dried or baked out of the bone at the
time of its preparation; otherwise it would decay and
stink.
Perhaps your science teacher helped you understand
this by taking a fresh chicken bone and soaking it in
vinegar instead of baking it. By doing this for a couple
of days (and changing the vinegar once or twice), you
can feel a different kind of bone. The acid vinegar dis-
solves the calcium salts and you are left with the fibrillar
element of the bone, a gray collagen network the exact
shape of the original bone, but much like leather. You
can tie a knot in this bone. Living bone, of course,
includes both elements, and thus combines the colla-
gen's resistance to tensile and shearing forces with the
mineral salt's reluctance to succumb to compressive
forces.
To make the situation more complex (as it always is),
the ratio between the fibrous element and the calcium
salts changes over the course of your life. In a child, the
proportion of collagen is higher, so that long bones will
break less frequently, having more tensile resilience. 1 7
When they do break, they will often break like a green
twig in spring (Fig. 1.9A), fracturing on the side that is
put into tension, and rucking up like a carpet on the side
that goes into compression. Young bones are difficult to
break, but also hard to set back together properly, though
they often mend quickly enough due to the responsive-
ness of the young system and the prevalence of collagen
to reknit.
In an older person, by contrast, where the collagen is
frayed and deteriorated, and thus the proportion of
mineral salts is higher, the bone is likely to break like an
old twig at the bottom of a pine tree (Fig. 1.9B), straight
through the bone in a clean fracture. Easily put back in
place but hard to heal, precisely because it is the network
of collagen that must cross the break and reknit to itself
first, to provide a fibrous scaffolding for the calcium
salts to bridge the gap and recreate solid compressional
support. For this reason, bone breaks in older people are
often pinned, to provide solid contact between the sur-
faces for the extra time required for the remaining col-
lagenous net to link up across the fracture.
Likewise, the various types of cartilage merely reflect
different proportions of the elements within it. Hyaline
cartilage - as in your nose - represents the standard
distribution between collagen and the silicon-like
chondroitin sulfate. Elastic cartilage - as in your ear -
contains more of the yellowish elastin fibers within the
chondroitin. Fibrocartilage - as in the pubic symphysis
or intervertebral discs - has a higher proportion of tough
fibrous collagen compared to the amount of silicon-like
chondroitin. 1 8 In this way, we can see that bone and
cartilage are really dense forms of fascial tissue - a dif-
ference in degree, rather than a true difference in type.
In regard to fat, the experienced hands-on practitio-
ner will recognize that some fat allows the intervening
hand in easily, enabling the therapist to reach layers
below the fat layer, while other fat is less malleable,
seeming to repel the practitioner's hand and to resist
attempts to feel through it. (No prejudice implied here,
but certain former rugby players of the author's acquain-
tance come to mind.) The difference here is not so much
in the chemistry of the fat itself, but in the proportion
and density of the collagenous honeycomb of fascia that
surrounds and holds the fat cells.
In summary, the connective tissue cells meet the com-
bined need of flexibility and stability in animal struc-
tures by mixing a small variety of fibers - dense or loose,
regularly or irregularly arranged - within a matrix that
varies from quite fluid, to gluey, to plastic, and finally
to crystalline solid.
Connective tissue plasticity
While the building metaphor goes some distance toward
showing the variety of materials connective tissue has
at its disposal, it falls short of the mark in portraying the
versatility and responsiveness of the matrix even after
it has been made and extruded into the intercellular
space. Not only do connective tissue cells make all these
materials, these elements also rearrange themselves and
their properties - within limits, of course - in response
to the various demands placed on them by individual
activity and injury. How could supposedly 'inert' inter-
cellular elements change in response to demand?
The mechanism of connective tissue response and
remodeling is important to understand if we intend to
A
B
Fig. 1.9 (A) Young bone, with a higher fiber content, breaks like
green wood. (B) Old bone, with a proportionally higher calcium
apatite content, breaks like dry wood. (Reproduced with kind
permission from Dandy 1998.)
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