23 Chapter 23 The Digestive System
Motivation.
Diabetes is a disorder of pancreas which is an accessory organ of the digestive system. In diabetes the pancreas is unable to regulate the level of sugar in our blood. Diabetes prevalence is disparately high in African-American populations in the U.S. compared to other racial groups.
The pancreas is an associated part of the digestive system that consists of the mouth, pharynx, esophagus, stomach, small and large intestine. Other associated components of the digestive system are the liver and gall bladder. The digestive system functions to process food that is eaten and to convert it into useable energy by metabolism and therefore the digestive system is important in our lives for survival. Diabetes is a disorder that can be managed with a proper diet and exercise. In this chapter, you will learn the parts of the digestive system and its associated organs and their functions.
Learning Objectives
Upon completion of the work in this chapter students should be able to:
- Identify the structures of the digestive system and associated parts.
- Describe the histology of the esophagus, stomach, small and large intestine.
- Explain the function of the stomach, small and large intestine.
- Describe the function of the liver, gall bladder and pancreas.
- Explain carbohydrate metabolism.
Background.
The digestive system consists of the mouth, pharynx, esophagus, stomach, small intestine and large intestine. The organs associated with the digestive system are the liver, gall bladder and pancreas and several glands (Figure 23.2). Each organ of the digestive system is made up of specialized tissues with specific functions (Figure 23.3).
The digestive system is mostly suspended in the abdominal cavity. Food goes through the digestive canal or alimentary canal (Figure 23.2) and is processed as it moves down the lumens of a set of digestive organs starting with the mouth.
The mouth is a cavity with teeth, tongue and salivary glands. The pharynx is a hollow tube that connects with the esophagus (Figure 23.4). (The pharynx is also connected with the respiratory system.)
The tubular esophagus passes through an opening in the diaphragm (muscular organ that divides the thoracic and abdominal cavity.) It leads to a curved stomach which is essentially a holding bag that is a muscular organ (Figures 23.4 and 23.5).
The stomach is connected to the small intestine which is approximately 671 cm., long. Most of digestion and absorption occur in the small intestine. Between the stomach and the small intestine is a pyloric sphincter. It is a valve that prevents the backflow of food once it passes from the stomach into the small intestine (Figure 23.6).
Undigested food passes from the small intestine into the large intestine. The large intestine is 213 cm long (Figure 23.7). The large intestine stores waste such as feces and water.
The pancreas is an organ located in the bend between the stomach and small intestine (Figure 23.8). I