- Parts and Functions
- Stomach/Small Intestine
What is the digestive system?
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 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 are the parts and and functions of the digestive system?
The process of digestion is a fascinating and complex one that takes the food we place in our mouths 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.
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, including:
- The wrong path, which is down the windpipe into the lungs
- 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 avoids 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 into 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 the 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 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).
- Surgery Doesn't Get Safer When Patient, Surgeon Are Same Gender
- Got GERD? Eat This Way to Help Avoid Symptoms
- Want to Avoid Knee Replacement? Build Up Your Thighs
- Breathing in Coal-Based Pollution Could Be Especially Deadly: Study
- Scans Show Brain Changes in People With Long COVID
- More Health News »
The colon, rectum, and anus
The role of the lower GI (gastrointestinal) 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
- 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 control over releasing stool or holding it. Once stool arrives in the rectum, 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 -- insulin goes directly 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 the liver.
- Gallbladder: Bile is stored and released from the gallbladder. When fatty food enters the duodenum, the gallbladder contracts, and releases bile.
Health Solutions From Our Sponsors
Top The Digestion Process (Organs and Functions) Related Articles
Cirrhosis (Liver)Cirrhosis 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.
Colonoscopy Procedure and PreparationA 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.
Constipation Myths and FactsConstipation results in fewer bowel movements. Laxatives, home remedies, and diet changes may bring constipation relief. Change habits that constipate you and adopt lifestyle changes to benefit your intestines and bowel. Bloating and chronic constipation are relieved with the right medical treatments.
Digestive Disorders: Worst Foods for DigestionDiscover which foods to avoid in order to prevent diarrhea and digestive problems. Find out which foods can trigger diarrhea and other digestive problems such as gas, bloating, indigestion, heartburn and more.
Diverticulitis SlideshowDiverticulitis (diverticulosis) is a condition in which the diverticulum or diverticula rupture in the colon, causing infection. Medical treatments such as antibiotics and surgery can treat diverticulitis (diverticulosis).
Endoscopy (EGD) Procedure
Endoscopy 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, nausea, vomiting, difficulty swallowing, or intestinal bleeding.
Gastric Emptying StudyA gastric emptying study is a procedure that is done by nuclear medicine physicians using radioactive chemicals that measures the speed with which food empties from the stomach and enters the small intestine. A gastric emptying study often is used when there is a possibility of an abnormal delay in food emptying from the stomach. Medically, this is called delayed gastric emptying. The two most common causes of delayed gastric emptying are gastric outlet obstruction and gastroparesis.
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 (Internal and External)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.
Low FODMAP Diet for IBS
FODMAPs are foods that contain sugar alcohols and short chain carbohydrates. The gut can't digest them very well. There are "low" FODMAP foods and "high" FODMAP foods. Foods high in FODMAPs lay in the gut and ferment, which causes symptoms of:
- Excessive gas
- Abdominal pain
Some people with digestive diseases and disorders, for example, IBS, microscopic colitis, IBD (Crohn's disease and ulcerative colitis), and other functional bowel disorders often are placed on a low FODMAP diet to decrease the amount of high FODMAPs foods in the diet, which create uncomfortable symptoms.
MRI (Magnetic Resonance Imaging Scan)MRI (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, Changes, Texture and FormStool 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.
Top 12 Foods for Constipation ReliefConstipation is a common problem, and almost everyone has been constipated at one time or another. There are foods that can help prevent constipation and also provide relief, for example, kiwi, prunes, beans (your choice of type), berries, certain seeds, potatoes, and popcorn.