Digestion Is an Extremely Complex Process

Armen Hareyan's picture

Your digestive system starts working even before you sit down for lunch or raid the cookie jar. Your brain tells your mouth to start planning, and saliva begins to form. And the digestive process is underway. "Every time we eat, this extremely complex process happens again and again, seamlessly and without our conscious awareness. The body truly is a remarkable machine," says Robert Summers, M.D., UI Hospitals and Clinics gastroenterologist.

Digestion begins in your mouth when food is broken down through mechanical digestion: chewing and churning (in the stomach) and chemical digestion, enzymes to turn food into a form cells can absorb. This process occurs in the mouth, stomach, and small intestines.

The real action begins in your stomach where enzymes or gastric juices begin working to digest proteins, and food is reduced to liquid form called chyme. This watery liquid is then emptied into the small intestine.

The busiest place in the entire digestive system is the small intestine. The small intestine is where the final stages of enzyme digestion occur and where almost all nutrients are absorbed. Food spends approximately four hours in the small intestine.

When food is in the small intestine, the juices of the pancreas and liver continue the process of digestion. The pancreas provides a mixture of digestive enzymes critical for digestion of fats, carbohydrates, and protein. Your liver produces bile, necessary in the absorption of fats. Bile is stored in the gall bladder.


The leftover waste, the remnants of food that your body can't use, goes to the large intestine where excess water from chyme is absorbed and used by the body. The colon, part of the large intestine, is the body's last chance to absorb water and minerals into the blood. From the colon the waste moves to the rectum and then the anus. Digestion complete.

Things to know about Digestion

  • Burping or belching is caused by swallowing air from eating or drinking too fast, carbonated beverages, sucking hard candies, not chewing food completely.

  • Most ulcers are caused by:

The use of pain medications (aspirin, ibuprofen, naproxen) and can be cured with time and stomach-protective medications.

Bacterial infections can be cured with antibiotics. Spicy food often aggravates ulcer symptoms. Stress and the use of alcohol or cigarettes can interfere with healing.

  • Your stomach growls when it receives signals from your brain to begin digestion but the stomach is empty.

  • Flatulence or gas is created through bacterial action in the bowel. Ten to 18 passages per day are normal. Primary gases are harmless and odorless. Noticeable smells can be traced to food intake. Foods that cause gas include dairy products, baked beans, cauliflower, broccoli, cabbage, potatoes, fruit, corn, and wheat.

  • Heartburn is a common problem caused by reflux of gastric acid and can be eliminated by avoiding smoking, fatty foods, caffeine, chocolate, peppermint, overeating, and tight-fitting clothes.

  • You can swallow upside down because the muscles around the esophagus are strong enough to push the food up to your stomach.