The Systems of the Body
The Digestive System
Back to the Basics — Our Body
By Greg and Barbara Petty
January 2010
This month we kick off a new column, a review of the systems of the body. Each month we will briefly examine the 12 systems, an overview of their functionality as well as some common ailments. We start off this series with the digestive system.
The major systems of the human body are (listed alphabetically):
- Cardiovascular system: the blood circulation with heart, arteries and veins
- Digestive system: processing food with mouth, esophagus, stomach and intestines
- Endocrine system: communicating within the body using hormones
- Immune system: defending against disease-causing agents
- Integumentary system: skin, hair and nails
- Lymphatic system: the lymph conduits and the lymph tissues
- Muscular system: moving the body with muscles
- Nervous system: collecting, transferring and processing information with brain and nerves
- Reproductive system: the sex organs
- Respiratory system: the organs used for breathing, the lungs
- Skeletal system: structural support and protection through bones
- Urinary system: eliminating wastes from the body
Digestive System Overview
Don’t you just love all of those noises that emanate from our bodies? Burps, hiccups, gurgles, not to mention gas. Children especially delight in these sounds, while adults have been known to cringe in embarrassment when one of these unforeseen noises erupts unexpectedly. Cheer up, gentle readers—you can blame it on your digestive system.
The digestive system is made up of organs that break down food into protein, vitamins, minerals, carbohydrates, and fats, which the body needs for energy, growth, and repair. After food is chewed and swallowed, it goes down the esophagus and enters the stomach, where powerful stomach acids further break it down. From the stomach the food travels into the small intestine. This is where your food is broken down into nutrients that can enter the bloodstream through tiny hair-like projections. The excess food that the body doesn’t need or can’t digest is turned into waste and is eliminated from the body.With all those acids churning, it’s no wonder we can be a bit noisy.
The digestive system has two main groups: the alimentary canal (also called the gastrointestinal (GI) tract), and the accessory digestive organs. It breaks down (digests) the food into smaller bits and pieces so that it can be absorbed into the blood through the intestines.
The alimentary canal is comprised of the mouth, pharynx, esophagus, stomach, small and large intestine. The accessory digestive organs are the teeth, tongue, gallbladder, and all the digestive glands—the salivary gland, the liver and the pancreas.
Digestion Process
THE MOUTH AND ESOPHAGUS: The food is ground up by the teeth and moistened with the enzymes in saliva to make it easy to swallow and begin the digestion process on the way to the stomach.
THE STOMACH: The food passes through a sphincter into the stomach. The stomach is a muscular bag and it churns the food to help break it down mechanically and chemically with gastric juices. The food is then passed through a second sphincter into the first part of the small intestine.
THE SMALL INTESTINE: Once in the small intestine, the food is mixed with more digestive enzymes from the pancreas and bile from the liver.
PANCREAS: The pancreas secretes digestive juices and the hormone insulin which helps to regulate the amount of sugar in the blood. Diabetes is a condition caused by problems with insulin production.
LIVER: The liver plays several roles in the body, including:
- Breaking down fats
- Processing proteins and carbohydrates
- Filtering and removing impurities such as drugs and toxins
- Production of glucose for short-term energy needs
ABSORPTION HAPPENS IN THE SMALL INTESTINE: The jejunum and the ileum assist with nutrients being absorbed. The ileum, which is lined with millions of finger-like projections called villi, place nutrients into the bloodstream.
THE LARGE INTESTINE: Once all the nutrients have been absorbed, the waste is moved into the bowel (large intestine). Water is then removed and the waste (feces) is stored in the rectum to be passed out of the body through the anus.
BACTERIA PLAY AN IMPORTANT ROLE: A large reservoir of microbes, such as bacteria, live within the large intestine and the rest of the digestive system.
Common Digestive Issues
ESOPHAGITIS (inflammation of the esophagus) can be caused by a variety of infections, or certain medications.
GASTROESOPHAGEAL REFLUX DISEASE (GERD) — caused by the esophageal sphincter not working well and allowing the acidic contents of the stomach to move backward up into the esophagus. The condition can be corrected through lifestyle changes or treatment with medication.
THE STOMACH AND INTESTINES — During 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. When constipation occurs the opposite condition exists; rhe 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.
Other stomach and intestinal disorders include:
- Gastrointestinal Infections can be caused by viruses or bacteria (Salmonella, Shigella, Campylobacter, or E. coli). They can also be caused by intestinal parasites (such as amebiasis and giardiasis). Symptoms include abdominal pain or cramps, diarrhea, and sometimes vomiting. The infections usually go away on their own without medicines or other treatment.
- Appendicitis, an inflammation of the appendix that requires surgery to correct. The classic symptoms of appendicitis are abdominal pain, fever, loss of appetite, and vomiting.
- Gastritis and Peptic Ulcers arise when bacteria or the chronic use of certain medications weakens the protective mucous coating of the stomach and duodenum. This weakening allows acid to get through to the sensitive lining beneath and can irritate and inflame the lining or cause peptic ulcers. Medications usually successfully treat these conditions.
- Inflammatory Bowel Disease (IBD) is chronic inflammation of the intestines. There are two major types: ULCERATIVE COLITIS, which commonly affects the rectum and the large intestine; and CROHN’S DISEASE, which can affect the whole gastrointestinal tract. In some severe cases, surgery may be necessary to remove inflamed or damaged areas of the intestine, but medications relieve most symptoms.
- Celiac Disease 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. Individuals with celiac disease cannot digest the nutrients from their food. They can experience diarrhea, abdominal pain, bloating, exhaustion, and even depression when they eat foods with gluten. Patients manage the condition by eliminating gluten from their diet.
IRRITABLE BOWEL SYNDROME (IBS) is a common intestinal disorder of the colon. Symptoms include recurrent abdominal cramps, bloating, constipation, and diarrhea. Patients are treated by changing their eating habits and making lifestyle changes.
PANCREAS, LIVER, AND GALLBLADDER ISSUES — 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 is a chronic, inherited illness. The condition is caused by the production of abnormally thick mucus that blocks the ducts or passageways in the pancreas and prevents its digestive juices from entering the intestines. Thus proteins and fats are not properly digested and nutrients pass out of the body unused. Individuals with cystic fibrosis can take digestive enzymes and nutritional supplements to relieve the condition.
- Hepatitis is a condition with a variety of different causes. The liver becomes inflamed and may lose its ability to function. Hepatitis, such as hepatitis A, B, or C, is highly contagious as it is viral. Serious cases may require hospitalization.
GALLSTONES and INFLAMMATION OF THE GALLBLADDER is common in those who have sickle cell anemia or persons who are being treated with certain medications.
SOURCES
Human Anatomy & Physiology textbook (by Elaine N. Marieb and Katja Hoehm).
Wikipedia.com
Kidshealth.org
Betterhealth.vic.gov
Righthealth.com
Innerbody.com