21: Digestive System
- Page ID
- 22407
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Thumbnail Image Credit: "Digestive System Diagram" by Mariana Ruiz is in the Public Domain CC0.
- 21.1: Introduction to the Digestive System
- The digestive system is continually at work, yet people seldom appreciate the complex tasks it performs in a choreographed biologic symphony. This chapter examines the structure of the organs that allow you to use food you eat to keep you going.
- 21.2: Organs of the Digestive System
- The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process.
- 21.3: Digestive System Processes and Regulation
- The digestive system uses mechanical and chemical activities to break food down into absorbable substances during its journey through the digestive system. The processes of the digestive system include seven activities: ingestion, propulsion, mechanical digestion or physical break down, chemical digestion or break down, secretion, absorption, and defecation.
- 21.4: Mouth, Pharynx, and Esophagus
- In this section, you will examine the anatomy and functions of the three main organs of the upper alimentary canal—the mouth, pharynx, and esophagus—as well as three associated accessory organs—the tongue, salivary glands, and teeth.
- 21.5: Stomach
- Although a minimal amount of carbohydrate digestion occurs in the mouth, chemical digestion really gets underway in the stomach. An expansion of the alimentary canal that lies immediately inferior to the esophagus, the stomach links the esophagus to the first part of the small intestine (the duodenum) and is relatively fixed in place at its esophageal and duodenal ends. In between, however, it can be a highly active structure, contracting and continually changing position and size.
- 21.6: Small and Large Intestines
- The word intestine is derived from a Latin root meaning “internal,” and indeed, these two organs together nearly fill the interior of the abdominal cavity. In addition, called the small and large bowel, or colloquially the “guts,” they constitute the greatest mass and length of the alimentary canal and, with the exception of ingestion, perform all digestive system functions.
- 21.7: Accessory Organs in Digestion- Liver, Pancreas, and Gallbladder
- Chemical digestion in the small intestine relies on the activities of three accessory digestive organs: the liver, pancreas, and gallbladder (Figure 23.6.1). The digestive role of the liver is to produce bile and export it to the duodenum. The gallbladder primarily stores, concentrates, and releases bile. The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.