Chapter 15. The Digestive System
15.0 Introduction
Learning Objectives
After studying this chapter, you will be able to:
- describe the functional histology of the alimentary canal;
- describe the processes and control of ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation;
- describe the digestive processes of the mouth, pharynx, and esophagus;
- describe the digestive processes of the stomach;
- describe the digestive processes of the liver, pancreas, and gall bladder;
- describe the digestive processes of the small and large intestines; and
- describe the digestion and absorption of carbohydrates, proteins, lipids, nucleic acids, minerals, vitamins, and water.
The digestive system is continually at work, yet people seldom appreciate the complex tasks it performs in a choreographed biologic symphony. Consider what happens when you eat an apple. Of course you enjoy the apple’s taste as you chew it, but in the hours that follow, unless something goes amiss and you get a stomachache, you don’t notice that your digestive system is working. You may be taking a walk or studying or sleeping, having forgotten all about the apple, but your stomach and intestines are busy digesting it and absorbing its vitamins and other nutrients. By the time any waste material is excreted, the body has appropriated all it can use from the apple. In short, whether you pay attention or not, the organs of the digestive system perform their specific functions, allowing you to use the food you eat to keep you going. This chapter examines the structure and functions of these organs and explores the mechanics and chemistry of the digestive processes.
This work, Human Physiology, is adapted from Anatomy & Physiology by OpenStax, licensed under CC BY. This edition, with revised content and artwork, is licensed under CC BY-SA except where otherwise noted.
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