Digestive System Alicia C, Binali, Cole, and Tom

Main Function of the Digestive System The function of the digestive system is digestion and absorption. Digestion is the breakdown of food into small molecules, which are then absorbed into the body. The digestive system is divided into two major parts: The digestive track is a continuous tube with two openings: the mouth and the anus.

Main Organs and their Functions

Mouth The teeth chew up food and break the food into pieces. Saliva in the mouth assists in breaking down the food.Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.

Esophagus The esophagus is a muscular tube extending from the pharynx (throat) to the stomach. By peristalsis, a series of contractions, the esophagus delivers food to the stomach. The lower esophageal sphincter prevents food from passing backwards into the esophagus.

Stomach The stomach holds the food while it secretes acid and powerful enzymes that continue the process of breaking down the food. When it leaves the stomach, food is the consistency of a liquid or paste. From there the food moves to the small intestine.

Liver The liver has multiple functions, but its main function within the digestive system is to process the nutrients absorbed from the small intestine. Bile from the liver secreted into the small intestine also plays an important role in digesting fat. In addition, the liver is the body’s chemical "factory." It takes the raw materials absorbed by the intestine and makes all the various chemicals the body needs to function. The liver also detoxifies potentially harmful chemicals. It breaks down and secretes many drugs.

Small Intestine There are three segments of the small intestine, the duodenum, jejunum, and ileum. The small intestine uses enzymes released by the pancreas and bile from the liver. Bile is a compound that aids in the digestion of fat and eliminates waste products from the blood. Peristalsis moves food through and combines it with digestive secretions. The duodenum is largely responsible for continuing the process of breaking down food, with the jejunum and ileum being mainly responsible for the absorption of nutrients into the bloodstream.

Large Intestine (Colon) Stool, or waste left over from the digestive process, is passed through the colon. First in a liquid state and ultimately in solid form as the water is removed from the stool. A stool is stored in the sigmoid colon until a "mass movement" empties it into the rectum. The stool is mostly food debris and bacteria. These bacteria synthesize vitamins, process waste products and food, and protect against bacteria. When the descending colon becomes full, it empties its contents into the rectum to begin the process of elimination.

Rectum The rectum connects the colon to the anus. It receives stools from the colon, to hold the stool until evacuation happens. When anything enters the rectum, sensors send a message to the brain. The brain decides if the rectal contents can be released. If they can, the sphincters (muscles) relax and the rectum contracts, expelling its contents. If the contents cannot be expelled, the sphincters contract.

Anus It consists of the pelvic floor muscles and the two anal sphincters. The lining of the upper anus detects rectal contents. The pelvic floor muscle creates an angle that stops stool from coming out when it is not supposed to. The anal sphincters provide control of stool. The internal sphincter prevents us from going to the bathroom when we are asleep, or unaware. When we get an urge to go to the bathroom, we rely on our external sphincter to keep the stool in.

The Digestive System & Homeostasis Review: Homeostasis is the balance the body maintains to continue to function properly. The digestive system breaks down food into a chemical form (simpler molecules) that can be absorbed by the body. These molecules can be used to fuel cellular activities and regulate body temperature. The liver, which monitors the blood, is a very important organ of homeostasis. The liver breaks down toxic substances like alcohol and other drugs, and it produces urea, the end product of nitrogenous metabolism. The liver produces the plasma proteins and stores glucose as glycogen after eating. In between eating it releases glucose, thereby keeping the blood glucose concentration constant. The liver destroys old blood cells and breaks down hemoglobin--hemoglobin breakdown products are excreted in bile.

Digestive System Interaction with Other Systems Cardiovascular System Nutrients broken down from digested food absorbs into the bloodstream. The bloodstream carries the nutrients to all the other cells in the body. Endocrine system Sends chemical signals that control the speed of digestion Lymphatic System The lymphatic system is the absorbs fats and fat-soluble vitamins from the digestive system and transports these substances to the venous circulation. Blood capillaries absorb most nutrients, but the fats and fat-soluble vitamins are absorbed by the lacteals. Excretory System While the digestive system collects and removes undigested solids, the excretory system filters compounds from the bloodstream and collects them in urine.

Disorders and Diseases 1. Crohn’s Disease: A chronic disease that causes inflammation in the gastrointestinal tract. 2. Celiac Disease: A disorder where the individual cannot tolerate gluten because it harms the inner liner of the small intestine which prevents the absorption of nutrients.

Pathway of food in the digestive tract 1) Mouth 2) Esophagus 3) Stomach 4) Small Intestine 5) Large Intestine (Colon) 6) Rectum 7) Anus

Major Digestive Enzymes: Function and Location Salivary Amylase Salivary Glands in the Mouth Begins carbohydrate digestion by breaking down starch and glycogen to disaccharides Peptidase Small Intestine Breaks down peptides into amino acids Bile, also called gall Liver Released during digestion when fats enter the first part of the small intestine (duodenum). Bile emulsifies fats preparing them for further digestion and absorption in the small intestine. Intestinal Lipase Small Intestine Breaks down fats into fatty acids and glycerol Enterokinase Small Intestine Converts trypsinogen into trypsin Sucrase, Maltase, Lactase Small Intestine Breaks down disaccharides into monosaccharides

The Digestive System’s Interaction with the Circulatory System The digestive system works very closely with the circulatory system to get the absorbed nutrients distributed through your body. The circulatory system also carries chemical signals from your endocrine system that control the speed of digestion.

Villi Villi are small finger like objects that extends from the lining of the small intestine walls. The villi increases the absorption of nutrient molecules that are passing through the small intestine by creating more surface area for absorption. The absorbed nutrients can then enter the bloodstream through diffusion and are transported through the body to be used or stored.

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