The wall of the stomach is made of the same four layers as most of the rest of the alimentary canal, but with adaptations to the mucosa and muscularis for the unique functions of this organ. ![]() The stomach is held in place by the lesser omentum, which extends from the liver to the lesser curvature, and the greater omentum, which runs from the greater curvature to the posterior abdominal wall. The convex lateral surface of the stomach is called the greater curvature the concave medial border is the lesser curvature. The addition of an inner oblique smooth muscle layer gives the muscularis the ability to vigorously churn and mix food. Figure 23.4.1 – Stomach: The stomach has four major regions: the cardia, fundus, body, and pylorus. In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into large folds called rugae. The smooth muscle pyloric sphincter is located at this latter point of connection and controls stomach emptying. The narrower end is called the pyloric canal, which connects to the duodenum. The wider end of the funnel, the pyloric antrum, connects to the body of the stomach. The funnel-shaped pylorus connects the stomach to the duodenum. Below the fundus is the body, the main part of the stomach. Located inferior to the diaphragm, above and to the left of the cardia, is the dome-shaped fundus. The cardia (or cardiac region) is the point where the esophagus connects to the stomach and through which food passes into the stomach. There are four main regions in the stomach: the cardia, fundus, body, and pylorus ( Figure 23.4.1). Little if any absorption occurs in the stomach, with the exception of lipid soluble substances such as alcohol and aspirin. Foods are not processed in the order they are eaten rather, they are mixed together with digestive juices in the stomach until they are converted into chyme, which is released into the small intestine.Īs you will see in the sections that follow, the stomach plays several important roles in chemical digestion, including the continued digestion of carbohydrates until salivary amylase is inactivated by stomach acid, and the initial digestion of proteins and triglycerides. Thus, the stomach holds food and parses only small amounts into the small intestine at a time. You can ingest a meal far more quickly than it can be digested and absorbed by the small intestine. An important function of the stomach is to serve as a temporary holding chamber. Popular culture tends to refer to the stomach as the location where all digestion takes place. Rather, when you eat greater quantities of food-such as at holiday dinner-you stretch the stomach more than when you eat less. Although you might think that the size of a person’s stomach is related to how much food that individual consumes, body weight does not correlate with stomach size. The empty stomach is only about the size of your fist, but can stretch to hold as much as 4 liters of food and fluid, or more than 75 times its empty volume, and then return to its resting size when empty. ![]() These contractions provide mechanical assistance to digestion. In between, however, it can be a highly active structure, contracting and continually changing position and size. 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. Describe any absorption that happens in the stomachĪlthough a minimal amount of digestion occurs in the mouth, chemical digestion really gets underway in the stomach, primarily as the initial site of protein digestion.Describe the mechanical and chemical digestion of food entering the stomach.Explain why the stomach does not digest itself.Identify the four main types of secreting cells in gastric glands, and their important products. ![]() Describe the functional anatomy of the stomach.By the end of this section, you will be able to:
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