Special Report: Building Bodies

Plumbing 101: Building the body’s tubes and branches.

By Bob Holmes 01.28.2020

Lungs, blood vessels, kidneys and more: Our bodies are full of branching pipes. Their development follows a handful of basic principles.

At first glance, our bodies seem impossibly complex, with dozens of organs built to precise specifications in exactly the right places. It seems almost miraculous that all this could develop automatically from a single fertilized egg. 

But look a little closer and you’ll see that evolution, the master architect, has been economical with that complexity, relying on the same components again and again in different contexts. Take tubes, for example. “We’re basically a bag of tubes,” says Celeste Nelson, a developmental bioengineer at Princeton University. “We have a tube that goes from our mouth to our rear end. Our heart is a tube. Our kidneys are tubes.” So, too, are lungs, pancreas, blood vessels and more — most of them intricate systems of tubes with many branches.

Branching tubes appear so often because they are the best solution to a key problem that organisms face as they get bigger: As an animal grows, its volume goes up faster than its surface area. That simple physical relationship means that the logistical challenges of supplying oxygen and nutrients, and removing waste products — all of which ultimately depend on diffusion through the surfaces of cells — get more daunting with size.

But a dense forest of branching tubes increases the available surface area enormously. “They allow us to be big,” says Jamie Davies, a developmental biologist at the University of Edinburgh.

If something goes wrong in our physical development or if we have had injuries at birth or in childhood, the logistical challenges of supplying oxygen and nutrients and removing CO2 in the correct amount, which depends on diffusion through the surfaces of cells, will be even more difficult when we are grown and these problems might develop just as we finish growing.

And problems involving oxygen, nutrients and carbon dioxide ratio’s will surely affect our brains and our minds. ….and will likely result in abnormal vital signs, especially respiratory rate.

Just like in the case of Paula.

And in Dr Kraepelin’s patients long ago.

Diagnosis requires more than interviewing the patient. The patient has no insight into their autonomic nervous system mechanisms.

Diagnosis requires checking that normal physiological function is occurring during their depression.

And this requires checking respiratory rate, heart rate, blood pressure and body temperature.

The results will probably alarm you.

So we need to figure out how to treat these patients and we need to learn not to panic.