digestive tract
Meaning of digestive tract: A single tube open at both ends, so its contents count as outside the body until they cross the lining.
Definition of digestive tract
The digestive tract is the continuous muscular tube running from the mouth to the anus through which swallowed food and drink pass. It takes in the mouth, throat, esophagus, stomach, small intestine, large intestine, rectum and anus. Along its length food is broken apart, useful material is absorbed into the blood, and the residue is stored and then expelled.
How is it different from the digestive system?
The tract is only the tube. The digestive system also takes in organs that food never enters: the salivary glands, liver, gallbladder and pancreas, which manufacture juices and deliver them through ducts into the tube. That distinction matters, because a problem in the pancreas or the bile ducts disrupts digestion without any blockage of the passage itself. The older name for the tube alone is the alimentary canal, and gastrointestinal tract is used for the same thing, although strictly those words name the stomach and intestines rather than the whole run.
What does each section do?
| Section | Main job |
|---|---|
| Mouth and throat | Chewing, moistening, and the swallow itself |
| Esophagus | Muscular waves carry the swallowed mass down |
| Stomach | Acid and churning reduce food to a semi-liquid paste |
| Small intestine | Most digestion and nearly all nutrient absorption |
| Large intestine | Water and salt recovered, resident bacteria ferment the rest |
| Rectum and anus | Storage and controlled release |
Why is its lining replaced so often?
The surface facing the food is a single layer of cells one deep, worn away constantly by acid, enzymes and friction, and rebuilt from below every few days. No other large tissue in the body turns over that fast. The advantage is repair; the cost is vulnerability, because any treatment aimed at rapidly dividing cells strikes this lining alongside its target, which is why mouth soreness and diarrhea follow so predictably. The same surface is also a border. Whatever sits in the tube has not entered the body until it crosses that layer, and the tract accordingly carries more immune tissue and more nerve cells than any organ outside the brain, running its own muscular rhythm even when its connection to the brain is cut.
Also known as
Used in a sentence
Contrast studies showed no obstruction anywhere in the digestive tract.
Good to know
Material inside the tube has not entered the body until it crosses the lining, and that lining renews faster than almost any other tissue, which is why treatments directed at rapidly dividing cells so reliably cause mouth soreness and diarrhea.
Word origin
Where “digestive tract” comes from
Digestive comes from the Latin digerere, to separate or distribute; tract comes from the Latin tractus, a drawing out or stretch.