Gastrointestinal System : The Classical World

Introduction

The gastrointestinal, or digestive, system is composed of 30 feet of intestinal tubes that make up the alimentary canal. Alimentum is the Latin word for nourishment (hence its metaphorical use for the intellectual nourishment provided by the Alma Mater to the Alumni). The canal extends from the mouth to the anus with various temporary stopping places along the way (the mouth, throat, esophagus, stomach, small and large intestine, rectum, and anus). Its function is to take in food (ingestion), break it down mechanically and chemically (digestion), to provide nutrients (absorption), and eliminate the waste or non-absorbable elements (elimination).

Food enters the mouth, where it is moved by the tongue and broken up by the teeth by chewing. Saliva produced by the salivary glands begins the process of digestion and facilitates swallowing. The epiglottis in the throat ensures that the food is passed into the esophagus, the 10” tube between the throat and the stomach, where the involuntary progressive wavelike movement (peristalsis) is initiated by the contraction and relaxation of circular muscular valves known as sphincters. The cardiac, or lower esophageal, sphincter controls the entry into the stomach, where the food is collected, mixed with gastric juices, and stored until it is released via the pyloric sphincter into the tri-part small intestine. Here most of the digestion and absorption takes place. The duodenum got its name from the fact that it was approximately 12 fingers breadth in its length. The jejunum (Latin = hungry or empty) was found to be empty on examination after death. The large intestine starts with a blind alley, the cecum (caecus = blind) which contains the vermicular (worm-shaped) appendix. The largest portion, the colon, rises, crosses, descends, then forms an S-shape (hence ascending, transverse, descending, and sigmoid) before straightening out at the rectum, and releases the stored feces through the anal sphincter.

Accessory organs are the liver, which produces bile, a substance necessary for digestion, processes nutrients, and aids in detoxifying harmful materials; the gallbladder (cholecyst), which stores the bile until needed; the pancreas, which secretes digestive enzymes.