- The Digestion Process (Organs and Functions) Center
- Take the Pancreatitis Quiz
- Boost Digestive Health
- Digestive Distress Slideshow: Problem Foods to Avoid
- Patient Comments: The Digestive Process (Organs and Functions) - Interest
The energy required for all the processes and activities that take place in our bodies is derived from the foods we ingest. The digestive system allows us to utilize food from such diverse sources as meat from an animal and the roots of a plant, and utilize them as an energy source. Whether it is the ability to coordinate the chewing of the food without injuring our tongue and lips or the propulsion of the food from the stomach into the duodenum while releasing the appropriate enzymes, our digestive system allows us to manage the process without much thought and often while performing other tasks.
What is digestion?
The process of digestion is a fascinating and complex one that takes the food we place in our mouth and turns it into energy and waste products. This process takes place in the gastrointestinal tract, a long, connected, tubular structure that starts with the mouth and ends with the anus. The food is propelled forward within the system, altered by enzymes and hormones into usable particles and absorbed along the way. Other organs that support the digestive process are the liver, gallbladder, and pancreas. The time it takes for food to travel from entering the mouth to be excreted as waste is around 30 to 40 hours.
The mouth is the entry point for food, but the digestive system often gets ready before the first piece of food even enters our mouth. Saliva is released by the salivary glands into our oral cavity when we smell food. Once the food enters the mouth, chewing (mastication) breaks food into smaller particles that can be more easily attacked by the enzymes in saliva. Our teeth can perform a cutting as well as grinding function to accomplish this task. The tongue assists in mixing the food with the saliva and then the tongue and roof of the mouth (soft palate) help move the food along to the pharynx and esophagus.
Quick GuideDigestive Disorders: Common Misconceptions
The pharynx and esophagus
The pharynx (throat) is the transition area from the mouth to the esophagus. From the pharynx there are two paths that the food bolus can take; 1) the wrong path, which is down the windpipe into the lungs, or 2) the correct path into the esophagus and then the stomach. The act of swallowing is a complex process that closes the windpipe (to protect our lungs) and moves food into the esophagus. This process is mostly automatic (reflex) but it is also partially under our direct control.
Once it enters the esophagus, food is moved down the esophagus and into our stomach. The esophagus is a muscular tube that contracts in a synchronized fashion (peristalsis) to move food down towards the stomach. While the muscles behind the food product contract, the muscles ahead of the food relax, causing the forward propulsion of the food. Peristalsis is the main mechanism by which food moves through our digestive system.
Once the food approaches the stomach, a muscular valve (the lower esophageal sphincter) relaxes and lets the food pass into the stomach. This sphincter has the important function of closing the stomach so no food or stomach acid reenters the esophagus (and therefore avoiding heartburn or regurgitation).
The stomach and small intestine
From glands that line the stomach, acid and enzymes are secreted that continue the breakdown process of the food. The stomach muscles further mix the food. At the end of this process, the food you placed in your mouth has been transformed to a thick creamy fluid called chyme.
This thick fluid is then pushed into the duodenum (the first part of the small intestine). With the help of enzymes from the pancreas and bile from the liver, further breakdown of the food occurs in the small intestine.
The small intestine has three segments. The first segment is the duodenum where further breakdown of the food takes place. The next two parts of the small intestine (jejunum and ileum) are mostly responsible for the absorption of nutrients from the processed food into the bloodstream through the walls of the intestine.
After the small intestine, the leftover waste leaves the upper gastrointestinal tract (upper GI tract) which is made up of everything above the large intestine, and moves into the large intestine or colon (the beginning of the lower GI tract).
The colon, rectum, and anus
The role of the lower GI tract is to solidify the waste product (by absorbing water), store the waste product until it can be evacuated (going to the bathroom) and help with the evacuation process.
The large intestine (colon) has four parts:
- ascending colon,
- transverse colon,
- descending colon and
- sigmoid colon.
All together the colon is approximately 7 feet long and connects to the rectum. Here as in most other parts of the GI system, the waste product is moved along by peristalsis. As the waste product passes through the colon, water is absorbed and stool is formed.
The stool from the colon is stored in the rectum. The anal sphincter provides the control over releasing stool or holding it. Once stool arrives in the rectum, a feedback to the brain makes the person aware of the need for a bowel movement. Voluntary control over the anal sphincter lets us hold the stool until we go to the toilet.
Three accessory digestive organs (pancreas, liver, gallbladder)
Three other organs are instrumental in the digestive process.
- Pancreas: Although the pancreas is mostly known for its blood sugar regulatory function with the production of insulin (as part of the endocrine system -- he insulin goesdirectly from the gland into the bloodstream), it is the main producer of digestive enzymes as part of the exocrine system (the enzymes produced by the gland pass through a duct into the intestines). These enzymes are released into the duodenum and help with the digestion of fats, proteins, and carbohydrates..
- Liver: The liver produces bile for fat digestion and elimination. In addition, nutrients are stored in the liver, and toxins and chemicals are filtered by liver.
- Gallbladder: Bile is stored and released from the gallbladder. When fatty food enters the duodenum, the gallbladder contracts and releases bile.
Digestive Disorders Resources
"Digestive System." Stanford Health Library.
Top The Digestion Process (Organs and Functions) Related Articles
AppendectomyAppendectomy is the removal by surgery of the appendix, the small worm-like appendage of the colon (the large bowel). An appendectomy is performed because of probable appendicitis, inflammation of the wall of the appendix generally associated with infection.
Blood in the Stool (Rectal Bleeding)
Blood in the stool or rectal bleeding (hematochezia) refers to the passage of bright red blood from the anus. Common causes include
- anal fissures,
- Crohn's disease,
- colon and rectum polyps, and
The color of the blood in the stool may provide information about the origin of the bleeding. The color of stool with blood in it may range from black, red, maroon, green yellow, gray, or white, and may be tarry, or sticky. Treatment of blood in the stool depends on the cause.
CirrhosisCirrhosis of the liver refers to a disease in which normal liver cells are replaced by scar tissue caused by alcohol and viral hepatitis B and C. This disease leads to abnormalities in the liver's ability to handle toxins and blood flow, causing internal bleeding, kidney failure, mental confusion, coma, body fluid accumulation, and frequent infections.
Symptoms include yellowing of the skin (jaundice), itching, and fatigue.
The prognosis is good for some people with cirrhosis of the liver, and the survival can be up to 12 years; however the life expectancy is about 6 months to 2 years for people with severe cirrhosis with major complications.
ColonoscopyA colonoscopy is a procedure whereby a docotor inserts a viewing tube (colonoscope) into the rectum for the purpose of inspecting the colon. Colonoscopy is the best method currently available to diagnose, detect, and treat abnormalities within the colon.
DiarrheaDiarrhea is a change is the frequency and looseness of bowel movements. Symptoms associated with diarrhea are cramping, abdominal pain, and the sensation of rectal urgency. Causes of diarrhea include viral, bacterial, or parasite infection, gastroenteritis, food poisoning, and drugs. Absorbents and anti-motility medications are used to treat diarrhea.
Elimination DietEver wonder if a certain food causes your headaches or makes you tired or uncomfortable? You might try to find out with an elimination diet.
10 Probiotic FoodsProbiotics are beneficial bacteria and yeasts found in probiotic foods and fermented products like kimchi, kombucha, and kefir. Good bacteria may provide health benefits like weight loss and improved immunity. Lactobacillus is a type of probiotic bacteria. Learn the health benefits of yogurt.
Diverticulitis SlideshowDiverticulitis (diverticulosis) is a condition in which the diverticulum or diverticula rupture in the colon causing infection. Change in diet and medical treatments such as antibiotics and surgery can ease the symptoms of diverticulitis (diverticulosis).
EndoscopyEndoscopy is a broad term used to described examining the inside of the body using an lighted, flexible instrument called an endoscope. Endoscopy procedure is performed on a patient to examine the esophagus, stomach, and duodenum; and look for causes of symptoms such as:
- abdominal pain,
- difficulty swallowing, or
- intestinal bleeding.
Heartburn Foods SlidesLearn the symptoms of heartburn and which foods cause heartburn or GERD. Discover home remedies and which foods may provide treatment for heartburn relief.
Hemorrhoids (Piles)Hemorrhoids (piles) are swollen veins in the rectum and anus. Causes include pregnancy, obesity, diarrhea, low-fiber diet, and prolonged sitting on the toilet. Treatment varies depending upon the severity of the hemorrhoids. Some treatment options include over-the-counter creams and suppositories, stool softeners, warm sitz baths, and hemorrhoidectomies.
Intestines PictureThe intestines are a long, continuous tube running from the stomach to the anus. See a picture of the Intestines and learn more about the health topic.
Liver Blood TestsAn initial step in detecting liver damage is a simple blood test to determine the presence of certain liver enzymes in the blood. Under normal circumstances, these enzymes reside within the cells of the liver. But when the liver is injured, these enzymes are spilled into the blood stream, and can lead to diseases like fatty liver, type 2 diabetes, obesity, and hepatitis. Several medications also can increase liver enzyme test results.
MRI ScanMRI (or magnetic resonance imaging) scan is a radiology technique which uses magnetism, radio waves, and a computer to produce images of body structures. MRI scanning is painless and does not involve X-ray radiation. Patients with heart pacemakers, metal implants, or metal chips or clips in or around the eyes cannot be scanned with MRI because of the effect of the magnet.
Stool Color ChangesStool color changes can very from green, red, maroon, yellow, white, or black. Causes of changes of stool color can range from foods a person eats, medication, diseases or conditions, pregnancy, cancer, or tumors. Stool can also have texture changes such as greasy or floating stools. Stool that has a uncharacteristically foul odor may be caused by infections such as giardiasis or medical conditions.