Answer
The stomach is often described as a "j-shaped" organ, but this is a generalization and probably an oversimplification --the stomach may have variations on this shape. The organ is located in the upper left abdominal cavity, inferior to the diaphragm. It and may be analyzed as having 4 anatomical regions: these include the cardiac region( cardia), the fundus, the body, and the pyloric region.
1. The cardiac region is the small section of the stomach ( about 1.25'' long) just caudal to the cardiac
orifice( the opening of the esophagus into the stomach).
2. The fundus is the semi-spheroid region of the stomach that bulges up above the esophageal
attachment
to the stomach
3. The body ( corpus) of the stomach is the largest part of the stomach; it is the section caudal of
cardiac orifice.
4. The pyloric region of the stomach is at the inferior end of the organ, and consists of the antrum and the pyloric canal. The funnel shaped antrum connects the pyloric region with the body, and the pyloric canal is a narrow passage that leads into the duodenum.
The two curvatures of the stomach are conspicuous features. They are the greater curvature --suspended by the greater omentum--, and the lesser curvature attached to the lesser omentum. The greater curvature, located below and on the left side, is about 16 inches around ; the distance is about four inches along the superior lesser curvature which faces the liver, medially.
The stomach begins , anatomically below the esophageal sphincter, and ends at the pyloric sphincter which controls the movement of chyme from stomach to the duodenum of the small intestine. Between these boundaries the stomach is displayed, but the appearance of size varies , dependent on whether the organ is full, half-full, or empty.
Fully expanded, the volume of the stomach may be as great as 4,000 ml. However,the cavity of an empty stomach may be no more than 50 ml. After an ordinary meal, this volume may increase twenty-fold or even thirty-fold
Work Step by Step
The stomach performs several functions. These include storage of partially-digested food; mechanical break up of food; liquefaction of food; initiation of digestion of proteins and fats , and passage of chyme to the small intestine. Sometimes storage, and sometimes digestion, is considered the most important function of the stomach. However, the secretion of intrinsic factor(IF)-- important in absorption of Vitamin B1-- is the only indispensable function of the stomach
The walls of the stomach have the following layers:
1. The internal mucosa of epithelial cells (endothelium) sitting on a lamina propria ( with tubular glands), followed by the muscularis mucosae.
2. The submucosal layer, external to the muscularis mucosae; the latter consists primarily of loose connective tissue.
3. The muscularis externa; its three layers ( internal to external) are the oblique layer, the circular muscles, and the longitudinal layer. These smooth muscle layers are vital in the performance of the mechanical mixing, and transportation activities of the stomach.
4.The most external layer of the stomach wall is the serosa ( simple squamous epithelium, over connective tissue)
