If you’ve been reading this blog, by now you’ll know that the oxygen and nutrients your cells depend upon first enter the cell’s neighborhood by means of your crowded capillaries. Molecules then diffuse outward across the interstitial fluid to reach most cells in your body. The cardiovascular system is the most obvious “support system” in the body because it circulates the blood that keeps your cells alive. It also works with the kidneys to remove wastes. I’d also add the lymphatic system (see lymph nodes) which drains excess interstitial fluid and filter pathogens from it. And, I’d include the nervous system which carries a crucial pipeline of information that many cells depend on to do their job.
But who supports the “support system”? Do your blood vessels, lymph vessels and nerves simply meander through the body, or is there a structure – a scaffolding — that holds them in place? Yes, there is – our unsung hero, the connective tissues of the body.
In a typical organ like your stomach, lungs, or skin, you’ll have one or more layers of epithelium at the surface (shown in yellow) to interact with your food, air, or the external environment. Always behind that epithelium you’ll have connective tissue (shown in brown) which carries the blood vessels, lymph vessels, and nerves that serve that region of the body. Even a muscle layer (for example in the stomach), as seen at far right, actually contains, between the muscle cells, a great deal of intervening connective tissue, which is where the vessels and nerves travel. (This is the endomysium, the “first class seat” that supplies all the muscle cell’s needs.)
As you go about your business indoors, at work or home, think of the wall surfaces as an epithelium. They provide electrical outlets, faucets, heating vents and other necessities for life. But all of these things come to you through an infrastructure of electrical wires, water and sewage pipes, ventilation ducts, and internet cables that travel, unseen, through the walls. Inside your body, that role of the “internal wall space”, which supports and conceals the “support system” of the body, is served by connective tissue.