The Digestive System

What Does The Digestive System Do?

The human digestive system is a series of organs that converts food into essential nutrients that are absorbed into the body and moves the unused waste material out of the body.

Digestive System

What Makes Up The Digestive System?

The Digestive system consists of your mouth, esophagus, stomach, small intestine, large intestine – also called the colon – rectum and anus. The pancreas, gallbladder and liver are also involved in digestion.

How Does The Digestive System Work?

Mouth And Salivary GlandsDigestion begins in the mouth. When we see, smell, taste, or even imagine a tasty meal, our salivary glands, which are located under the tongue and near the lower jaw, begin producing saliva.

As the teeth tear and chop the food, saliva moistens it for easy swallowing. A digestive enzyme called amylase, which is found in saliva, starts to break down some of the carbohydrates (starches and sugars) in the food even before it leaves your mouth.

Swallowing, which is accomplished by muscle movements in the tongue and mouth, moves the food into the throat, or pharynx. The pharynx, a passageway for food and air, is about 5 inches long. A flexible flap of tissue called the epiglottis reflexively closes over the windpipe when we swallow to prevent choking.

EsophagusFrom the throat, food travels down a muscular tube in your chest called the esophagus. Waves of muscle contractions – called peristalsis — force food down through the esophagus to the stomach. A person normally isn’t aware of the movements of the esophagus, stomach, and intestine that take place as food passes through the digestive tract.

At the end of the esophagus, a muscular ring or valve called a sphincter allows food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the esophagus.

StomachThe stomach muscles churn and mix the food with acids and enzymes, breaking it into much smaller, digestible pieces. Glands in the stomach lining produce about 3 quarts of these digestive juices each day. Food normally stays in the stomach for one or two hours being digested.

When it’s empty, an adult’s stomach has a volume of one fifth of a cup (1.6 fluid ounces), but it can expand to hold more than 8 cups (64 fluid ounces) of food after a large meal.

By the time food is ready to leave the stomach, it has been processed into a thick liquid called chyme. A walnut-sized muscular valve at the outlet of the stomach called the pylorus keeps chyme in the stomach until it reaches the right consistency to pass into the small intestine. Chyme is then squirted down into the small intestine, where digestion of food continues so the body can absorb the nutrients into the bloodstream.

Small IntestineThe small intestine is made up of three parts: the duodenum, the C-shaped first part, which is normally about one foot long; the jejunum, the coiled midsection, normally about eight feet long; and the ileum, which is usually about 12 feet long, the final section that leads into the large intestine

The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi. The villi are the vehicles through which nutrients can be absorbed into the body.

The liver (located under the ribcage in the right upper part of the abdomen), the gallbladder (hidden just below the liver), and the pancreas (beneath the stomach) are not part of the alimentary canal, but these organs are essential to digestion.

The liver produces bile, which helps the body absorb fat. Bile is stored in the gallbladder until it is needed. The pancreas produces enzymes that help digest proteins, fats, and carbs. It also makes a substance that neutralizes stomach acid. These enzymes and bile travel through special channels (called ducts) directly into the small intestine, where they help to break down food. The liver also plays a major role in the handling and processing of nutrients, which are carried to the liver in the blood from the small intestine.

Large IntestineFrom the small intestine, undigested food (and some water) travels to the large intestine through a valve that prevents food from returning to the small intestine. By the time food reaches the large intestine, the work of absorbing nutrients is nearly finished. The large intestine’s main function is to remove water from the undigested matter and form solid waste that can be excreted.

The large intestine, or colon, extends from the cecum up the right side of the abdomen – this part is called the ascending colon – across the upper abdomen – through what is called the transverse colon – and then down the left side of the abdomen through the descending colon, finally connecting to the rectum. The rectum is where feces are stored until they leave the digestive system through the anus as a bowel movement.

What Can Go Wrong With Your Digestive System?

Problems With The Esophagus

5 Interesting Facts About The Digestive System

  1. Every day the salivary glands produce about 1.9 quarts of saliva.

  2. Your small intestine is about 20 to 25 feet long!

  3. Your large intestine is only about five feet long. Obviously “small” and “large” refer to diameter, not length, where your intestines are concerned.

  4. The noise created by passing gas in influenced by the volume of gas, the force with which it is expelled and the tightness of the anal sphincter.

  5. Your stomach changes shape depending on how much food is in it and whether you are standing or lying down. It can hold up to eight cups (64 fluid ounces), or more.
  • Esophagitis (inflammation of the esophagus)

    Esophagitis can be caused by infection, certain medications, or GERD.

  • Gastroesophageal Reflux Disease(GERD)

    With GERD, the esophageal sphincter (the valve that connects the esophagus with the stomach) doesn’t work well and allows the acidic contents of the stomach to move backward up into the esophagus. GERD often can be corrected through lifestyle changes, such as dietary adjustments. Sometimes, though, it requires treatment with medication.

Problems With The Stomach And Intestines

  • Diarrhea And Constipation

    Almost everyone has experienced Diarrhea or Constipation. With diarrhea, muscle contractions move the contents of the intestines along too quickly and there isn’t enough time for water to be absorbed before the feces are pushed out of the body. Constipation is the opposite: The contents of the large intestines do not move along fast enough and waste materials stay in the large intestine so long that too much water is removed and the feces become hard.

  • Gastrointestinal Infections

    These can be caused by viruses, by bacteria (such as Salmonella or E. coli), or by intestinal parasites (such as amebiasis and giardiasis). Abdominal pain or cramps, diarrhea, and sometimes vomiting are the common symptoms of gastrointestinal infections. These usually go away on their own without medicines or other treatment.

  • Appendicitis

    This is an inflammation of the appendix which is located in the cecum, part of the small intestines. The classic symptoms of appendicitis are abdominal pain, fever, loss of appetite, and vomiting.

  • Gastritis And Peptic Ulcers

    These arise when a bacterium, Helicobacter pylori, or the chronic use of drugs or certain medications weakens the protective mucous coating of the stomach and duodenum, allowing acid to get through to the sensitive lining beneath. This can irritate and inflame the lining of the stomach (gastritis) or cause peptic ulcers, which are sores or holes in the lining of the stomach or the duodenum that cause pain or bleeding. Medications usually successfully treat these conditions.

  • Inflammatory bowel disease (IBD)

    This is chronic inflammation of the intestines. There are two major types: ulcerative colitis, which usually affects just the rectum and the large intestine; and Crohn’s Disease, which can affect the whole gastrointestinal tract from the mouth to the anus as well as other parts of the body. Both are treated with medications and, if necessary, intravenous (IV) feedings to provide nutrition. In some cases, surgery may be necessary to remove inflamed or damaged areas of the intestine.

  • Celiac Disease

    This is a disorder in which the digestive system is damaged by the response of the immune system to a protein called gluten, which is found in wheat, rye, and barley and a wide range of foods, from breakfast cereal to pizza crust. People with celiac disease have difficulty digesting the nutrients from their food and may experience diarrhea, abdominal pain, bloating, exhaustion, and even depression when they eat foods with gluten. Symptoms can be managed by following a gluten-free diet. Celiac disease runs in families and can become active after some sort of stress, such as surgery or a viral infection. A doctor can diagnose celiac disease with a blood test and by taking a biopsy of the small intestine.

  • Irritable Bowel Syndrome (IBS)

    A common intestinal disorder, IBS affects the colon and may cause recurrent abdominal cramps, bloating, constipation, and diarrhea. There is no cure, but IBS symptoms may be treated by changing eating habits, reducing stress, and making other lifestyle changes. A doctor may also prescribe medications to relieve diarrhea or constipation. No one test is used to diagnose IBS, but a doctor may identify it based on symptoms, medical history, and a physical exam.

Problems With the Pancreas, Liver, and Gallbladder

Conditions affecting the pancreas, liver, and gallbladder often affect the ability of these organs to produce enzymes and other substances that aid in digestion. Examples include:

  • Cystic Fibrosis

    This is a chronic, inherited illness that not only affects the lungs but also causes the production of abnormally thick mucus to block the ducts or passageways in the pancreas. This mucus also prevents digestive juices from entering the intestines, making it difficult to properly digest proteins and fats. This causes important nutrients to pass out of the body unused. To help manage their digestive problems, people with cystic fibrosis can take digestive enzymes and nutritional supplements.

  • Hepatitis

    A condition with many different causes, Hepatitis is when the liver becomes inflamed and may lose its ability to function. Viral hepatitis,, such as Hepatitis A, B, or C, is highly contagious. Mild cases of hepatitis A can be treated at home; however, serious cases involving liver damage may require hospitalization.

  • Gallstones

    The gallbladder can develop gallstones and become inflamed — a condition called Cholecystitis.

How Do Your Keep Your Digestive System Healthy?

To keep your Digestive system healthy, follow these 3 rules:

  1. Eat a healthy diet with the right mix of carbohydrates, fats, proteins, water, salts, vitamins, and soluble and insoluble fiber.

  2. Drink adequate water.

  3. If you hare having digestive problems, stick to easy-to-digest foods. Avoid hard-to-digest foods such as dairy products, spicy foods, acidic foods such as tomato sauce and citrus fruits, fatty foods, fried foods, processed foods, alcohol, caffeine, sweet and salty foods.

This article is part of a series called “Your Body: An Owner’s Manual” which explains how your body systems work and how to maintain them. The first article in the series included a picture of my wife, fitness coach Kathie Lamir, who exemplifies a healthy body. Pictures of Kathie were so well received that I have included one with each article in the series

Fitness Coach Kathie Lamir

2 thoughts on “The Digestive System

  1. Great articles so far. I look forward to each day so I can read about how my body really works and not how I think it works. Keep up the good work and the good workout.

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