The many faces of areolar connective tissue

The many faces of areolar connective tissue

Areolar connective tissue, like connective tissues in general, holds us together.  Like all connective tissues, it contains a lot of nonliving material — the extracellular matrix.  In this case the matrix is loose and unspecialized, with a large amount of interstitial fluid, making it an ideal “filler” between many structures in the body.  In particular, it is found on the back side of almost every epithelium in the body, including the lining of blood vessels.  As a result, every molecule that crosses between the blood and surrounding tissues, has to diffuse across areolar connective tissue — the “middleman” of exchange.

Epithelia line not just the blood vessels, but every other surface and cavity of the body.  This means they can function not only as an exchange surface, but also a barrier to microorganisms.  Here again, areolar connective tissue plays a vital role — as the “second line of defense”, harboring immune cells that attack any invaders that breach our defenses.

I’ve already paid homage to some of our other connective tissues.  The dense connective tissues are distinguished by large amounts of collagen, making them strong, though flexible.  Bone tissue contains a rigid mineral component making it an ideal structural support.  Areolar connective tissue, by comparison, is weak and shapeless.  But this unpretentious mass of matrix and cells is arguably even more important for our survival.

Which tissue do we need the most?

Which tissue do we need the most?

The entire body is composed of only four basic tissue types.  Muscle tissue, of course, allows you to move around.  But it’s also what moves your internal organs – the beating of the heart, the rumbling of the stomach.  Even your blood vessels have muscle tissue, which controls the distribution of blood in the body.  It’s hard to argue we could live without muscle.

But most of our muscles wouldn’t be much good without nervous tissue, which responds to stimuli and coordinates the activity of your organs.  It’s true that many of the slower, internal processes do not depend on nervous input – they may instead involve hormones, for example.  But what good is a body without a brain to give it meaning?

Epithelium, though, really is essential at the most basic level.  This is the tissue that lines all your external surfaces and your internal spaces.  Every substance that enters the body (food, water, oxygen) must cross an epithelium to do so.  These tissues are therefore the “gatekeepers” to the body, in charge of exchange with the environment – although, under the command of nervous tissue.

So the tissues must work together, and there’s no better example of this than the fourth basic type, connective tissue.  As the name suggests, it is the “putty” that holds the body together, filling in all the spaces between epithelium, muscle and nervous tissue.  But it also provides pathways for the movement of materials within the body.  This is the most diverse tissue type, including blood, the essential medium of transport, but many other types such as bone and cartilage.  The key feature of connective tissue is the presence of a large amount of nonliving “stuff” in between the living cells – the extracellular matrix.  Water is often abundant here, and this interstitial fluid forms another major transport medium for substances to move among all the tissues.

So of course, it’s hard to say any one basic tissue is more important than another.  I don’t know about you, but this “exchange” about the “connections” has been a “moving” subject for me that touches a “nerve”.  Pass the box of tissues!