The digestive system is made up of the digestive tract and other organs that help the body break down and absorb food. It is a long, twisting tube that starts at the mouth and goes through the oesophagus, stomach, small intestine, large intestine and anus. Show The digestive system breaks down food into nutrients such as carbohydrates, fats and proteins. They can then be absorbed into the bloodstream so the body can use them for energy, growth and repair. Unused materials are discarded as faeces (poo). Other organs that form part of the digestive system are the pancreas, liver and gallbladder. How does the digestive system work?Each organ of the digestive system has an important role in digestion. MouthWhen someone eats, the teeth chew food into very small pieces. Glands in the cheeks and under the tongue produce saliva that coats the food, making it easier to be chewed and swallowed. Saliva also contains enzymes that start to digest the carbohydrates in food. OesophagusThe oesophagus is the muscular tube that carries food from the mouth to the stomach after it is swallowed. A ring of muscle at the end of the oesophagus relaxes to let food into the stomach and contracts to prevent stomach contents from escaping back up the oesophagus. StomachThe stomach wall produces gastric juice (hydrochloric acid and enzymes) that digests proteins. The stomach acts like a concrete mixer, churning and mixing food with gastric juice to form chyme — a thick, soupy liquid. Small intestineBile from the gallbladder and enzymes in digestive juices from the pancreas empty into the upper section of the small intestine and help to break down protein into amino acids and fat into fatty acids. These smaller particles, along with sugars, vitamins and minerals, are absorbed into the bloodstream through the wall of the small intestine. It is called small because it is about 3.5cm in diameter, but it is about 5m long to provide lots of area for absorption. Most of the chemical digestion of proteins, fats and carbohydrates is completed in the small intestine. Large intestine and anusThe lining of the large intestine absorbs water, mineral salts and vitamins. Undigested fibre is mixed with mucus and bacteria — which partly break down the fibre — to nourish the cells of the large intestine wall and so help keep the large intestine healthy. Faeces are formed and stored in the last part of the large intestine (the rectum) before being passed out of the body through the anus.  What are common conditions related to the digestive system?Gastro-oesophageal refluxGastro-oesophageal reflux (GORD) occurs when acidic stomach contents move from the stomach back up the oesophagus. It causes a burning sensation in the chest or throat. DiverticulitisDiverticulitis is caused by inflammation or infection of abnormal pouches in the lower part of the large intestine. It can cause mild or severe pain on the lower left-hand side of the abdomen. Stomach ulcersStomach ulcers are commonly caused by the bacterium Helicobacter pylori that can live in the stomach of about 4 in 10 Australians. They can cause long-term, low-level inflammation of the stomach lining in some people. It is not well understood why they cause stomach ulcers in some people and not in others. HaemorrhoidsHaemorrhoids are itchy or painful lumps that occur in and around the anus. The lumps contain swollen blood vessels. Haemorrhoids can cause bleeding when you go to the toilet (do a poo) — you might notice bright red blood on the toilet paper or in the toilet. If you find blood on the toilet paper or in the toilet, always seek medical advice.
The digestive system consists of several organs that function together to break down the foods you eat into molecules your body can use for energy and nutrients. The digestive tract includes the mouth, esophagus, stomach, intestines, and anus. So-called "accessory" organs include the liver, pancreas, and gallbladder; food doesn't move through these organs, but they secrete hormones and chemicals that are essential to digestion. Here's what to know about your digestive system organs and functions.
WIN-Initiative / Getty Images Digestion begins in your mouth. Your teeth grind the food you eat and mix it with saliva to form a kind of ball, known as a bolus. During the mixing, an enzyme called salivary amylase starts breaking down carbohydrates. Once the food is soft and relatively flexible, the tongue pushes it to the back of your mouth and into the esophagus.
SEBASTIAN KAULITZKI/SCIENCE PHOTO LIBRARY / Getty Images Your esophagus is a flattened muscular tube that connects your mouth to your stomach. As food is swallowed, your esophagus expands. It takes food about three seconds to pass through your esophagus, depending on the texture and consistency.
Common problems of the esophagus include heartburn, acid reflux, and gastroesophageal reflux disease (GERD), which are caused by acid flowing up from the stomach and irritating the lower part of the esophagus.
Toshiro Shimada / Getty Images Your stomach is a J-shaped muscular pouch, which receives food from your esophagus and sends it to your small intestine. Inside your stomach, food is mixed with enzymes and acid until it becomes a liquid, called chyme. The stomach is the main site for protein digestion and uses powerful enzymes, known as pepsins, as well as hydrochloric acid, to digest foods like meats, milk, and cheese.
OpenStax College / Wikimedia Commons / CC-BY-3.0 The small intestine is an approximately 20-foot-long muscular tube, which is divided into three distinct parts: the duodenum, the jejunum, and the ileum. Each of the three parts plays a major role in digestion and absorption. Absorption is a crucial part of the digestive process that brings the molecules from the digested food into the blood and, ultimately, the cells.
Problems with your small or large intestine can affect the way your body absorbs and digests food, leading to malnutrition. People who are missing parts of their intestines or have limited intestinal mobility may require total parenteral nutrition (TPN), a type of nutrition that bypasses the digestive system.
PIXOLOGICSTUDIO/SCIENCE PHOTO LIBRARY / Getty Images The last part of the digestive tract, the large intestine, is a muscular tube that is about 6 feet long. It's divided into the cecum, the colon, and the rectum. Together, these segments complete any nutrient absorption and process the waste into feces. Problems with your large intestine can be caused by diseases such as inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative colitis as well as celiac disease. If parts of these organs become seriously diseased, they may require surgical removal. When this happens, an ostomy may be necessary to aid digestion and elimination.
The anus is the last organ of the digestive system. It is a 2-inch long canal consisting of pelvic floor muscles and two anal sphincters (internal and external) which allow you to hold in feces until you are able to get to a bathroom to release the contents into the toilet.
PIXOLOGICSTUDIO / Getty Images The pancreas is one of the three "accessory" digestion-related organs. Your pancreas assists your small intestine by secreting pancreatic juice, a liquid filled with enzymes and sodium bicarbonate that is able to stop the digestion process of pepsin. It also secretes insulin, which helps your body regulate your blood sugar.
PIXOLOGICSTUDIO/SCIENCE PHOTO LIBRARY / Getty Images Your liver has many functions. First, it produces bile, which the small intestine uses to help digest the fats in food. It also metabolizes proteins, carbohydrates, and fats; helps regulate blood sugar levels; stores glycogen for quick energy; makes fibrinogen, which clots blood; makes vitamin A; and recycles worn-out red blood cells.
Diseases of the liver, such as hepatitis, can have major complications that affect other parts of the body as the liver is involved in so many essential functions, like digestion.
MedicalRF.com / Getty Images Tucked under the liver, your gallbladder is a storage container for bile, a yellow-green fluid made up of salts, cholesterol, and lecithin. Your small intestine uses bile to digest fats. Most people never think about their gallbladder until a problem with gallstones or gallbladder disease, such as cholecystitis, develops. If you have a gallbladder-related disease, you may experience jaundice. This happens when the bile cannot leave the gallbladder. Instead, the bile enters the bloodstream, which can cause your skin, eyes, and nails to appear yellow.
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The esophagus stomach and small intestines all function together to digest food and absorb nutrients
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