Your digestive tract is essentially a series of hollow tubes and organs. As food mixes with digestive juices, it travels along your digestive tract. Throughout the journey, large molecules of food are broken down into smaller molecules that can be used by your body as fuel. Digestion generally begins when food enters your mouth and ends in the small intestine. Waste materials exit your body through the anus. Below is an outline of each of the major components of your digestive system.

Esophagus

Muscular tube that transports food by peristalsis from the pharynx to the stomach. Both ends are closed off by sphincters (muscular constrictions), which relax to let food through and close to keep food from backing up.

Liver and Biliary System

The liver is the body's largest internal organ, weighing about 1.5 kg or 2.5% of body weight. The liver and biliary system produce bile and transport it to the small intestine, where it breaks up fats and other components of diet, and aids the digestion and absorption of nutrients. Approximately 1 L of bile is produced daily and enters the small intestine.

Stomach

The stomach is a digestive sac in the left upper abdominal cavity, which expands or contracts with the amount of food in it. It has four regions: the cardia leads down from the esophagus; the fundus curves above it; the body is the largest part; and the antrum narrows to join the duodenum at the pyloric valve. Iron and very fat-soluble substances (e.g., alcohol and some drugs) are absorbed in the stomach. Peristalsis mixes food with enzymes and hydrochloric acid from glands in its lining and moves the resulting chyme toward the small intestine. The vagus nerve and sympathetic nervous system control the stomach's secretions and movements.

Pancreas

The pancreas is a digestive and endocrine organ located behind the stomach in the upper abdomen. The pancreas secretes digestive juices containing enzymes into the duodenum to help break down food into smaller molecules that can be absorbed. It also secretes insulin into the bloodstream to maintain the appropriate concentration of glucose in the blood.

Colon

The colon, also known as the large intestine, is the final organ of the digestive process. It is responsible for drying out indigestible food residues by absorbing fluid and producing solid waste (feces) for elimination. Approximately 1.5 m long, the colon has six distinct regions leading from the join with the small intestine (ileocaecal valve): cæcum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum.

Small Intestine

The small intestine is the longest section of the digestive tract, with an average length of about 6 m. Although only 2.5cm in diameter, its surface area for absorption covers the size of a tennis court. Large quantities of nutrients and water can be absorbed in the small intestine. Daily, it is capable of absorbing: several kg of carbohydrate; up to 1 kg of fat; 500 g of proteins; and 20 L of water. The surface cells of the small intestine are highly specialized for digestion and absorption of nutrients. Almost all of the body's nutrient absorption occurs in the small intestine along its three sub divisions: the duodenum, the jejunum and the ileum.

Appendix

The appendix is a small, 2- to 4-inch pouch located near where the large and small intestines meet. Doctors have debated the exact function of the organ for years as removal causes no noticeable symptoms. New research suggests that the appendix may provide a safe haven for good bacteria to live undisturbed until they are needed to repopulate the digestive system and keep you healthy following an infection of the intestines.

Rectum

The rectum is about eight inches long. It links to the sigmoid colon at the top and the anal canal at the base. It's primary purpose is to serves as a warehouse for feces before it enters the rectum.

Anus

The anus is the located at the end of our digestive tract. During defecation, waste passes from the rectum and out through the anus. The internal anal sphincter, located at the top of the anus, is an involuntary muscle helps keep waste from leaving the body. The external anal sphincter, located at the bottom of the anus, is a voluntary muscle that allows us to control when we defecate.

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