Some of Marsh's favorite scenes are of small things we take for granted but never visualize — our salivary glands. "It's almost like an alien monster, squirting out," he said.
To get the shot, Barlow squirted lemon juice into the back of a hungry subject's mouth and used a high-speed camera to capture the reaction of the salivary glands.
As the documentary notes, the glands are also a part of our immune systems, since saliva contains an enzyme that destroys bacteria. And tiny as they are, the glands produce a half gallon of saliva every day.
This documentary also surveys, in often stunning images, many of the reasons we change so much as we age. For instance, our cells clone themselves every day to reduce the wear and tear on our organs. Old cells die; new copies take their place.
But as that process goes on, we also copy the imperfections in our DNA, and those defects accumulate as we age. If you've ever used a photocopier, you know what happens: Copies made from copies lose a little quality with each duplication.
Over a lifetime, according to the documentary, we completely replace the bone in our face every 10 years; so your 70-year-old face is a seventh-generation copy of your baby face.
And the imperfections are exaggerated with each copy.
"It's all one complex system that is ticking along, according to this clock that we know eventually will end our lives," Barlow said. "But in the meantime, that's what makes us such a marvelous machine."
The technology used for the National Geographic Channel is also clearly on its way to helping revolutionize medical care. Palter contributed to the development of what's called an auto-fluorescent laparoscope, which exposes diseased tissue inside the body that a surgeon couldn't otherwise see.
"Instead of using visible light, it makes the disease fluoresce," Palter said. "If you look with your naked eye, you see nothing. When you switch on the light and the filters, all of a sudden the disease is glowing green, and you can see disease that's beyond the resolution of your naked eye."
Hippocrates, the fifth century B.C. physician who is considered the father of modern medicine, was known for taking the fear of mystical superstition out of medicine. Marsh believes that some fear still exists in the discomfort many people feel about their bodies, and that having the ability to see what's inside those frontiers, and how they work, will help add balance to the most important of all fields of medicine: how we treat ourselves.
"We're given one chance to have our life," Marsh said. "Modern society has taken us away from our physical beings, and I think that's had a damaging effect, in many ways, on how we live our lives, what we eat, how we behave. Hopefully, this [technology] can redress the balance in saying, 'Hey, this is who we are, this is what we've got. Listen to it, and don't be afraid of it.'"