Gastrointestinal System

Gastrointestinal System The gastrointestinal system is the body system that eats and digests food. It also gets rid of waste after digestion. The gastrointestinal system starts at the lips and ends at the anus. The gastrointestinal tract is the gut and other organs that help us digest food. The gut is the round tubes that food goes through and is digested Mouth It is the hole in the face where we put food when we eat. It is the first part of the gastrointestinal system. It has teeth to help chew the food. Pharynx It comes after the mouth and before the esophagus. Food and air go through the pharynx. The pharynx keeps food and liquids out of the lungs.

Esophagus Also called the gullet, is the part of the gastrointestinal system between the mouth and the stomach. It is lined with muscle. This muscle pushes the food bolus (ball) down into the stomach. The esophagus can contract or expand to allow for the passage of food. Stomach It is part of the digestive system. It is a big sack between the esophagus and the small intestines. The stomach keeps food after we eat it. Food we eat is mixed in the stomach. Then the stomach gives the food to the small intestine where most of the nutrition from the food is taken up. One reason the stomach is a big sack is to hold all the food we eat at a meal. Then it can slowly give the food to the small intestine. The stomach has a lot of acid in it. The cells of the stomach make acid. This protects us from bacteria in the food we eat. It kills the bacteria. But the acid in the stomach can cause problems. It can make peptic ulcer disease worse. It can also cause gastroesophageal reflux (or heartburn.) This is pain in the chest when acid from the stomach refluxes (goes back into) the esophagus. When food goes back up your esophagus and then out of your mouth, this is called vomiting. Small intestine The small intestine is composed of the duodenum, jejunum, and ileum. It averages approximately 6m in length, extending from the pyloric sphincter of the stomach to the ileo-caecal valve separating the ileum from the caecum. The small intestine is compressed into numerous folds and occupies a large proportion of the abdominal cavity. The duodenum is the proximal C-shaped

section that curves around the head of the pancreas. The duodenum serves a mixing function as it combines digestive secretions from the pancreas and liver with the contents expelled from the stomach. The start of the jejunum is marked by a sharp bend, the duodenojejunal flexure. It is in the jejunum where the majority of digestion and absorption occurs. The final portion, the ileum, is the longest segment and empties into the caecum at the ileocaecal junction. The small intestine performs the majority of digestion and absorption of nutrients. Partly digested food from the stomach is further broken down by enzymes from the pancreas and bile salts from the liver and gallbladder. These secretions enter the duodenum at the Ampulla of Vater. After further digestion, food constituents such as proteins, fats, and carbohydrates are broken down to small building blocks and absorbed into the body's blood stream. The lining of the small intestine is made up of numerous permanent folds called plicae circulares. Each plica has numerous villi (folds of mucosa) and each villus is covered by epithelium with projecting microvilli (brush border). This increases the surface area for absorption by a factor of several hundred. The mucosa of the small intestine contains several specialised cells. Some are responsible for absorption, whilst others secrete digestive enzymes and mucous to protect the intestinal lining from digestive actions. Large Intestine The large intestine is the last part of the digestive system. It lies between the small intestine and the anus in the Gastrointestinal system. It connects the small intestine to the rectum and anus. It is about 1.5 meters long or 5 feet. It is shorter than the small intestine. But its diameter is bigger, so its name is large intestine.It is composed of the appendix, cecum, ascending, transverse and descending colon, sigmoid, rectum, and anal sphincter. The long intestine functions to absorb water, form feces, move/store feces and absorb electrolytes. The cecum is a part of the large intestine. It is comes before the colon and after the ileum in the gastrointestinal system. The appendix is connected to the cecum. The colon is a part of the large intestine. It is between cecum and the rectum. The colon takes water from the feces that goes through it. The rectum is a part of the gastrointestinal system. It is where feces is stored before coming out of the anus. Feces in the rectum causes a desire to make that feces come out. A toilet is a place where feces can be put.

The anus is the hole in the human body that is between the buttocks. It is at the end of the gastrointestinal system (including the organs that digest food), where waste comes out of the body. Other organs that are part of the gastrointestinal system but are not part of the gut are: Liver •

The liver makes bile. This is a yellow-green liquid that goes into the small intestines to help digest the food we eat.

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The liver stores glucose when we eat and then puts the glucose into the blood when our blood glucose level goes down (when we did not eat for a while.)

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The liver takes protein and fat and turns it into glucose. This is important if we have no food to eat. We can use the fat we have saved, and make it into glucose to use.

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The liver also makes some fats and cholesterol

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The liver metabolizes (breaks down) many things in the blood: o

hemoglobin

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proteins like enzymes and insulin

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Ammonia

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toxins (substances that are poisons) and waste from the body

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The liver stores (keeps) vitamins and minerals

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The liver makes many proteins:

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proteins that make your blood clot – called coagulation proteins.

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proteins like albumin

In fetuses when they are very small, the liver makes red blood cells

The gallbladder is a pear-shaped organ in your abdomen that stores about 50 ml of acidic liquid (bile) until the body needs it for digestion. The gallbladder is about 7-10cm long in humans and is dark green in color because of the bile in it, not its tissue. It is connected to the liver and the duodenum by the biliary tract. The pancreas is an organ that releases hormones and enzymes to help digestion. It releases substances through special cells called the Islets of Langerhans.