Gut: The Inside Story of Our Body’s Most Underrated Organ

by Giulia Enders

Saliva is basically filtered blood. The salivary glands sieve the blood, keeping back the red blood cells, which are needed in our arteries, not in our mouth. But calcium, hormones, and some products of our immune system enter the saliva from the blood. That explains why each person’s saliva is slightly different.

Our stomach sits much higher in our abdomen than we think. It begins just below the left nipple and ends below the bottom of the ribcage on the right. Any pain felt farther down than this lopsided little pouch cannot be stomachache. Often, when people say they have stomach problems, the trouble is actually in the gut.

So our stomach is not simply lopsided; rather, it has two sides with different specializations. One side copes better with fluids, the other with solids. Two stomachs for the price of one, so to speak.

But those who do get the rare opportunity of seeing their small intestine by swallowing a pill-sized camera are likely to be surprised. Most expect to encounter a gloomy tunnel, but what they see is a very different creature: moist, pink, with a velvety sheen and somehow delicate looking.

In total, the surface area of our digestive system is about one hundred times greater than the area of our skin.

Emotions like fear or stress can reduce the ability of the smooth muscle to stretch, making us feel full—or even nauseous—after eating just a small portion of food.

Looking closer at human beings, it becomes clear that each of us is a world of our own. Our forehead is a breezy meadow, our elbows are arid wastelands, our eyes are salty lakes, and our gut is the most amazing giant forest ever, populated by the weirdest of creatures.

While we lounge about feeling bored, any number of exciting things are happening inside us.

Our gut’s microbiome can weigh up to 4½ pounds (2 kilos) and contains about 100 trillion bacteria.

More than 95 percent of the world’s bacteria are harmless to humans. Many are extremely beneficial.