The Ocean Within Us

OK, backtrack a second.

Of course, the medical world has known for centuries that there is structural material throughout the body, networks of collagen and elastin that give shape to our tissues and organs.

We call this stuff connective tissue, or fascia, or extracellular matrix.

What Neil and his colleagues saw for the first time was that this connective tissue isn't just an inert scaffold.

It's a dynamic, flexible system.

So they hypothesised, what if these structures were less like walls, holding everything in the body apart, and more like channels, connecting everything up? They called it the interstitium.

Interstitium literally means the in-between.

And so these alternating layers at the microscopic level of stiff collagen and more viscous fluid flowing through it create a body-wide communication network.

And there are no gaps.

Everywhere you look, they're all interconnected with each other.

in the skin the organs the coverings of the brain the coverings around all nerves around every vessel it's all one continuous network and the interstitium is actually four or five times larger than the cardiovascular system recently becky was talking about this and said you know we really should consider maybe it's a third circulatory system we have the lymphatic system we have the cardiovascular system and we have the interstitial

I think of the lymphatic and the blood systems as tubes, but I think that the interstitium is something different.

That's Becky to

Neil, Dr Rebecca Wells to us.

She's a colleague of Neil's and professor of medicine and bioengineering at the University of Pennsylvania.

Neil wondered if he could bring some of his tissue specimens and look at them with the microscopy that we have at the University of Pennsylvania to see if the structure would be consistent with what Neil was proposing.

We were in a dark room looking at samples, and when the first images came up, We realized that, yes, in fact, the hypothesis that collagen surrounded spaces through which fluid flowed, that was in fact true.

And so we were just in the dark kind of yelling, you know, this is great.

We could see it right in front of us that this was what was happening.

So the idea that fluid moves through the body via the interstitium, why was that an important

discovery? It suggests there's a way of fluid moving around the body other than through the lymphatics and the vasculature.

I think one way of thinking about it is as the groundwater into which the body's organs are lying.

It's fairly easy to imagine our cardiovascular system, the blood flowing in our veins and arteries, as kind of like a network of rivers and streams.

Fast-flowing, dynamic, bringing valuable nutrients downstream.

Then there's the lymphatic system, which directs our immune response.