20.1: Introduction

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Rosanna Hartline
West Hills College Lemoore

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Introduction

The digestive system consists of the gastrointestinal tract (also known as the alimentary canal), a hollow muscular tube extending from the mouth to the anus, and accessory organs, including the liver and pancreas. Nutrient absorption primarily occurs in the small intestine. To promote absorption of nutrients, the intestines have circular folds (large folds in the tissue), villi (small fold in the tissue) and microvilli (folds in the cell membranes) along the inner surface to increase surface area, thereby maximizing the potential for absorption. Like the alveoli of the lungs, microvilli substantially increase the surface area of the intestines to between 180 to 300 m²(the size of the average American home). Major structures of the gastrointestinal tract include the oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus. These structures and organs form a hollow space from mouth to anus and function to chemically and mechanically catabolize and absorb nutrients. Along the way, organs such as the salivary glands, liver, gallbladder and pancreas release enzymes to aid digestion and are known collectively as accessory structures.

Overview of digestive system anatomy. Mouth Oral cavity Pyloric sphincter Duodenum Hepatic flexu Ascending colon Jejunum Ce Ileocecal valve Rectum Oropharynx Laryngopharynx Upper esophageal sphincter Esophagus Lower esophageal sphincter Stomach Splenic flexure Transverse colon Descending colon Sic moid flexure Sigmoid colon Sigmoid flexure

Above: Overview of the anatomy of the digestive system.

Attributions

"Anatomy 204L: Laboratory Manual (Second Edition)" by Ethan Snow, University of North Dakota is licensed under CC BY-NC 4.0
"Human Anatomy Lab Manual" by Malgosia Wilk-Blaszczak, Mavs Open Press, University of Texas at Arlington is licensed under CC BY 4.0