Why doesn't your stomach digest itself?

Why doesn't your stomach digest itself?

If you unraveled your digestive system, it would stretch across an entire school bus. It's a continuous, nine-meter tube running right through your core. Food enters the mouth, slides down the esophagus, churns in the stomach, and winds through the intestines.

Think of this entire tract as a highly specialized conveyor belt. At every station, specific enzymes and acids break your meal down into raw energy.

But the most hostile station is right in the middle: the stomach. It's a holding tank filled with hydrochloric acid so strong it can dissolve metal. Which begs the question: why doesn't this meat-sack melt itself?

The inside of your small intestine isn't a smooth pipe. It is covered in millions of tiny, finger-like structures called villi, creating a microscopic velvet forest.

Let's zoom in on just one of these villi. The outer wall is only one cell thick, so nutrients easily slip through. Inside, a net of tiny blood vessels called capillaries grabs sugars, while a central green tube called a lacteal absorbs fats.

Because of this microscopic folding, your small intestine has the total surface area of a tennis court. It guarantees that almost no nutrients go to waste.

Just above your stomach sits the liver, a massive chemical plant. Its main job in digestion? Manufacturing a biological soap called bile, and storing it in a tiny green pouch called the gallbladder.

When you eat a greasy meal, the gallbladder squeezes. It shoots this highly concentrated bile down a duct directly into the duodenum—the very first stretch of your small intestine.

Fats don't mix with water, so they clump into huge, indigestible blobs. But the bile acts just like dish soap, blasting those giant fat globs into millions of tiny droplets so your enzymes can actually break them down.