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What is the digestive system?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. Your digestive system is made up of a series of organs that allows your body to get the nutrients and energy it needs from the food we eat. As food travels through the digestive system it is broken down, sorted, and reprocessed before being circulated around the body to nourish and replace cells and supply energy to our muscles. Digestion starts in the mouth where chewing and saliva breaks down food so it is more easily processed by your body. Esophagus: The esophagus is a muscular tube that connects the pharynx (throat) to the stomach. The esophagus contracts as it moves food into the stomach. A “valve” called the lower esophageal sphincter (LES) is located just before the opening to the stomach. This valve opens to let food pass into the stomach from the esophagus and it prevents food from moving back up into the esophagus from the stomach. Medical conditions related to the esophagus:
Stomach: An organ with strong muscular walls, the stomach holds the food and mixes it with acid and enzymes that continue to break the food down into a liquid or paste. Small Intestine (Small Bowel): Almost 20 feet long, the small intestine is the workhorse of the digestive system. It will continue to break down food with enzymes released by the pancreas and bile released from the liver. It is made up of three segments, the duodenum, which continues the breakdown of food; and the jejunum and ileum, which are mainly responsible for the absorption of nutrients. Medical conditions related to the small bowel:
Pancreas: Your pancreas is located behind your stomach and is attached to both your gall bladder and your small intestines. Among other functions, the pancreas aids in digestion by producing digestive enzymes and secreting them into the duodenum (the first segment of the small intestine). These enzymes break down protein, fats, and carbohydrates. Medical conditions related to the pancreas:
Liver: An organ with many functions, your liver’s two main responsibilities in the process of digestion are to make and secrete bile and to process and purify the blood containing newly absorbed nutrients that are coming from the small intestine. Bile has two main purposes: to help absorb fats and to carry waste from the liver that cannot go through the kidneys. Medical conditions related to the liver:
Bile Ducts: Bile made in the liver travels to the small intestine through the bile ducts. If the bile isn’t needed immediately, it is stored in the gallbladder. Medical conditions related to the bile ducts:
Gallbladder: A pear-shaped reservoir located just under the liver that receives and stores bile made in the liver. The gallbladder sends this stored bile into the small intestine to aid in the digestion of food. Colon (Large Intestine): A 5- to 7-foot-long muscular tube that connects the small intestine to the rectum and is responsible for processing waste so that defecation is easy and convenient. It is made up of the ascending (right) colon, the transverse (across) colon, the descending (left) colon and the sigmoid colon, which connects to the rectum. Medical procedure related to the colon:
Rectum: An 8-inch chamber that connects the colon to the anus. The rectum receives stool from the colon, sends signals to the brain if there is stool to be evacuated, and holds stool until evacuation can happen. Anus: The last part of the digestive tract, the anus, consists of pelvic floor muscles and two anal sphincters (internal and external). Together their jobs are to detect rectal contents, whether they are liquid, gas or solid, and then control when stool should and shouldn’t be excreted from your body. University of Michigan program related to the anus:
Medical Conditions Involving Multiple Digestive OrgansThere are many medical conditions that involve more than one digestive organ. These include:
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How do the organs work together in the digestive system
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