Human Anatomy of Stomach
The stomach is the muscular organ located on the left side of the upper abdomen. It acts as a storage bag for food and thus delays the continuous eating patterns. It is an elastic organ and can expand to about 2 L storing the food in it. It receives food from the esophagus through its upper valve that is known as cardiac sphincter. It secretes gastric juice to digest the protein content of food. It undergoes the process of churning that is muscular movement to mix the food with gastric juice. At its other end, near to small intestine there is another sphincter known as the pyloric sphincter that allows the slow passage of food from the stomach. In this article, the discussion will be only about the stomach anatomy and structure not its function.
Structure of Stomach:
In humans, the stomach lies between the esophagus and the duodenum on the upper left side of the abdominal cavity. Behind the stomach, there is pancreas and two sphincters that are:
Lower esophageal sphincter
Pyloric sphincter; that leads to duodenum,
Keep the stomach contents confined to its internal body. Stomach is surrounded by the parasympathetic and sympathetic plexuses that regulate the secretory and motor activity of stomach muscles.
Sections of stomach:
Human stomach is divided into four sections. These are:
The cardia is the region of the esophagus from where food enters into the stomach.
The fundus is formed in the upper part that is curved.
The body is the main, central region of the stomach.
The pylorus that literally means the ‘gatekeeper’ is the lower section of the stomach that empties food contents into the duodenum.
Epithelium of the stomach mucosa:
The cardia is the point where the stratified squamous epithelium of esophagus mucosa changes into the simple columnar ciliated epithelium. The epithelium is modified into long tubular gastric glands that secrete gastric juice.
Micro anatomy of stomach walls:
Like other parts of GIT, human stomach is also composed of four layers that are:
The gastric mucosa consists of epithelium and lamina propria (that is a layer of loose connective tissue with many lymphocytes) with a thin layer of muscularis mucosae that separates the mucosa from the submucosa. Muscularis mucosae is blessed with blood vessels and nerve plexus.
Submucosa lies beneath the mucosa and separates the mucosa from the muscularis externae.
It lies beneath the submucosa and is readily involved in the muscle movement of stomach. It consists of three layers:
The inner oblique layer: This layer is responsible for movement that assists in the process of churning that undergoes the break down of food. It is the layer present only in stomach and not in other digestive organs.
The middle circular layer: At this layer, the pylorus is surrounded by a thick circular muscular wall, forming a functional pyloric sphincter, which controls the passage of chyme into the duodenum. This layer is concentric to the longitudinal axis of the stomach.
Auerbach’s plexus (myenteric plexus) is found between the outer longitudinal and the middle circular layer and is responsible for causing peristalsis and mixing movements.
The outer longitudinal layer is responsible for moving the bolus towards the pylorus through muscular contraction.
Serosa is the outer most layer of the stomach and has simple squamous epithelium with loose connective tissue of peritoneal covering.
In gastric glands, different types of glandular cells are found. Three types of glands usually exist in the gastric mucosa of stomach at different sites. These are:
Cardia glands: that are found in only the cardia region and secretes mainly mucous. Only cardia glands are found here in the cardia region. They are fewer in number and are shallowly positioned in the mucosa.
The fundic glands are found in the fundus and body of the stomach. They are almost straight tubes which open into a single duct. They secrete hydrochloric acid (HCl) and intrinsic factor. Chief cells are also found in this region that secretes pepsinogen.
The pyloric glands are located in the antrum of the pylorus. They secrete gastrin produced by G- cells.
So, in the light of above discussion, stomach is a very important or vital organ responsible for digestion. The stomach anatomy is in such a way to assist its function in a best way.
Human Anatomy of Stomach