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By
Michael Bartel
, MD, PhD, Fox Chase Cancer Center, Temple University
Reviewed/Revised Oct 2022 | Modified Feb 2023
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Overview of the Digestive System
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The digestive system, which extends from the mouth to the anus, is responsible for receiving food, breaking it down into nutrients (a process called digestion), absorbing the nutrients into the bloodstream, and eliminating the indigestible parts of food from the body. The digestive tract consists of the
Mouth Biology of the Mouth The mouth is the entrance to both the digestive and the respiratory systems. The inside of the mouth is lined with mucous membranes. When healthy, the lining of the mouth (oral mucosa) ranges... read more
Throat and esophagus Throat and Esophagus The throat (pharynx) lies behind and below the mouth. When food and fluids leave the mouth, they pass through the throat. Swallowing of food and fluids begins voluntarily and continues automatically... read more
Stomach Stomach The stomach is a large, bean-shaped, hollow muscular organ consisting of four regions: Cardia Fundus Body Antrum read more
Small intestine Small Intestine The duodenum is the first segment of the small intestine, and the stomach releases food into it. Food enters the duodenum through the pyloric sphincter in amounts that the small intestine can... read more
Large intestine Large Intestine The large intestine consists of the Cecum and ascending (right) colon Transverse colon Descending (left) colon Sigmoid colon (which is connected to the rectum) read more
Rectum and anus Rectum and Anus The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus ( Home.see also page Overview of the Anus and Rectum). Ordinarily... read more
The digestive system also includes organs that lie outside the digestive tract:
The pancreas Pancreas The pancreas is an organ that contains two types of glandular tissue: Pancreatic acini Islets of Langerhans (See also Overview of the Digestive System.) The acini produce digestive enzymes.... read more
The liver Liver The wedge-shaped liver is the largest—and, in some ways, the most complex—organ in the body. It serves as the body's chemical factory, performing many vital functions, from regulating the levels... read more
The gallbladder Gallbladder and Biliary Tract The gallbladder is a small, pear-shaped, muscular storage sac that holds bile and is interconnected to the liver by ducts known as the biliary tract. (See also Overview of the Liver and Gallbladder... read more
The salivary glands Biology of the Mouth The mouth is the entrance to both the digestive and the respiratory systems. The inside of the mouth is lined with mucous membranes. When healthy, the lining of the mouth (oral mucosa) ranges... read more
The digestive system is sometimes called the gastrointestinal system, but neither name fully describes the system’s functions or components. The organs of the digestive system also produce blood clotting factors and hormones unrelated to digestion, help remove toxic substances from the blood, and chemically alter (metabolize) drugs.
The abdominal cavity is the space that holds most of the digestive organs. It is bordered by the abdominal wall (composed of layers of skin, fat, muscle, and connective tissue) in front, the spinal column in back, the diaphragm above, and the pelvic organs below. It is lined by a membrane called the peritoneum. The peritoneum lines most of the outer surfaces of the digestive organs.
Experts have recognized a powerful connection between the digestive system and the brain. For example, psychologic factors greatly influence contractions of the intestine, secretion of digestive enzymes, and other functions of the digestive system. Even susceptibility to infection, which leads to various digestive system disorders, is strongly influenced by the brain. In turn, the digestive system influences the brain. For example, long-standing or recurring diseases such as irritable bowel syndrome Irritable Bowel Syndrome (IBS) Irritable bowel syndrome is a disorder of the digestive tract that causes recurring abdominal pain and constipation or diarrhea. Symptoms vary but often include lower abdominal pain, bloating... read more , ulcerative colitis Ulcerative Colitis Ulcerative colitis is a chronic inflammatory bowel disease in which the large intestine (colon) becomes inflamed and ulcerated (pitted or eroded), leading to flare-ups (bouts or attacks) of... read more , and other painful diseases affect emotions, behaviors, and daily functioning. This two-way association has been called the brain-gut axis.
Aging may also affect how the digestive system functions (see Effects of Aging on the Digestive System Effects of Aging on the Digestive System Because the digestive system has a lot of reserve built into it, aging has less effect on its function than it does on the function of other organ systems. Nonetheless, aging is a factor in... read more ).
The Digestive System
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