Across the whole planet, humans eat on average between 1 and 2.7 kg of food a day. That’s over 365 kg a year per person and more than 28,800 kg over the course of a lifetime. And every last scrap makes its way through the digestive system, comprised of 10 organs covering 9 meters and containing over 20 specialized cell types. This is one of the most diverse & complicated systems in the human body. Its parts continuously work in unison to fulfill a singular task: transforming the raw materials of your food into the nutrients and energy that keep you alive.
Spending the entire length of your torso, the digestive system has 4 Main Components:
First, there’s a Gastrointestinal Tract A twisting channel that transports your food and has an internal surface area of between 30 and 40 square meters, enough to cover half a badminton court. Second, there’s the pancreas, gallbladder, and liver, a trio of organs that break down food, using an array of special juices.
Third, the body’s enzymes, hormones, nerves and blood all work together to break down food, modulate the digestive process, and deliver its final products.
Finally, there is the mesentery, a large stretch of tissue that supports and positions all your digestive organs in the abdomen, enabling them to do their jobs.
The digestive process begins before food even hits your tongue, anticipating a tasty morsel glands in your mouth start to pump out saliva. We produce about 1.5 liters of this liquid each day. Once inside your mouth, chewing combines with the sloshing saliva to turn food into a moist lump called a Bolus. Enzymes present in the saliva, break down any starch. Then your food finds itself at the rim of a 25-centimeter-long tube called Esophagus. down which it must plunge to reach the stomach.
Nerves in the surrounding esophageal tissue sense the bolus’s presence and trigger
Peristalsis, a series of defined muscular contractions. That propels food into stomach, where it’s left in the mercy of muscular stomach walls, which pound the bolus, breaking it into chunks. Hormones secreted by cells in the lining, trigger to release acids and enzymes-rich juices from stomach wall that starts to dissolve the food and break down its proteins. These hormones also alert the pancreas, liver, and gallbladder to produce digestive juices and transfer bile, a yellowish-green liquid that digests fat, in preparation for the next stage. After three hours inside stomach, the once shapely bolus is now a frothy多泡的 liquid called Chymeand is ready to move into small intestine.
The liver sense bile to the gallbladder which secretes分泌 it into the first portion of the small intestine called the Duodenum. Here, it dissolves the fats floating in the slurry of chyme, so they can be easily digested by the pancreatic and intestinal juices that have leeched into the scene. These enzyme-riche juices break the fat molecules down into fatty acids and glycerol for easier absorption into the body. The enzymes also carry out the final deconstruction of proteins into amino acids and carbohydrates into glucose. This happens in the small intestine’s lower regions, the Jejunum and ileum, which are coded in millions of tiny projections called Villi. These create a huge surface area to maximize molecule absorption and transference into the bloodstream. The blood takes them on the final leg of their journey to feed the body’s organs and tissues.
But it’s not over quite yet. Leftover fiber, water and dead cells sloughed off during digestion make it into the large intestine also known as the Colon. The body drains out most of the remaining fluid through the intestinal wall. What’s left is a soft mask called stool. The colon squeezes this byproduct into a pouch called the rectum, where nerves sense it expanding and tell the body when it’s time to expel the waste. The byproducts of digestion exit through the anus肛门 and the foods long journey typically lasting between 30 and 40 hours is finally complete.