THE DIGESTIVE SYSTEM

Your digestive system is uniquely designed to turn the food you eat into nutrients, which the body uses for energy, growth and cell repair. here's how it works.

MOUTH- food enters the digestive tract

 through the mouth or oral cavity.

PHARYNX- from the mouth, food passes posteriorly into the oropharynx and laryngopharynx, both of which are common passageways for food, fluids and air. The pharynx is subdivided into the nasopharynx, part of the respiratory passageway; the oropharynx, posterior to the oral cavity; and the laryngopharynx, which is continuous with the esophagus below.

ESOPHAGUS- the esophagus or gullet runs from the pharynx through the diaphragm to the stomach. About 25cm (10 inches) long, it is essentially a passageway that conducts food to the stomach.

STOMACH-The stomach is a muscular organ located on the left side of the upper abdomen. The stomach receives food from the esophagus. As food reaches the end of the esophagus, it enters the stomach through a muscular valve called the lower esophageal sphincter. The stomach secretes acid and enzymes that digest food. Ridges of muscle tissue called rugae line the stomach. The stomach muscles contract periodically, churning food to enhance digestion. The pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.

SMALL INTESTINE- the small intestine is the body’s major digestive organ. Within its twisted passageways, usable food is finally prepared for its journey into the cells of the body. The small intestine is a muscular tube extending from the pyloric sphincter to the ileocecal valve. It is the longest section of the alimentary tube, with an average length of 2.5 to 7 meters (8-18 feet) in a living person. Except for the initial part of the small intestine (the duodenum), which mostly lies in a retroperitoneal position, the small intestine hangs in sausage like coils in the abdominal cavity, suspended from the posterior abdominal wall by the fan-shaped mesentery. The large intestine encircles and frames it in the abdominal cavity.

LARGE INTESTINE- the large intestine is much larger in diameter than the small intestine (thus its name, the large intestine) but shorter in length. About 1.5 meters (5 feet) long, it extends from the ileocecal valve to the anus. Its major function is to dry out the indigestible food residue by absorbing water and to eliminate these residues from the body as feces. 

RECTUM- The rectum (Latin for "straight") is an 8-inch chamber that connects the colon to the anus. It is the rectum's job to receive stool from the colon, to let you know there is stool to be evacuated, and to hold the stool until evacuation happens. When anything (gas or stool) comes into the rectum, sensors send a message to the brain. The brainthen decides if the rectal contents can be released or not. If they can, the sphincters (muscles) relax and the rectum contracts, expelling its contents. If the contents cannot be expelled, the sphincters contract and the rectum accommodates, so that the sensation temporarily goes away.

ANUS-The anus is the last part of the digestive tract. It consists of the pelvic floor muscles and the two anal sphincters (internal and external muscles). The lining of the upper anus is specialized to detect rectal contents. It lets us know whether the contents are liquid, gas, or solid. The pelvic floor muscle creates an angle between the rectum and the anus that stops stool from coming out when it is not supposed to. The anal sphincters provide fine control of stool. The internal sphincter keeps us from going to the bathroom when we are asleep, or otherwise unaware of the presence of stool. When we get an urge to go to the bathroom, we rely on our external sphincter to keep the stool in until we can get to the toilet.

PREPARED BY: JOSE CARLO D. RAMORES MW 2:30-4:00