Location and structure of the stomach – Figure 1 shows a schematic drawing of the upper part of the digestive tract.
The oesophagus, which is usually 25-30 cm long, joins the stomach at the cardia, and the circular sphincter of the upper stomach lets food into the stomach.
Figure 1 Structure of the upper digestive tract:
oesophagus-stomach-duodenum (schematic drawing)
The stomach lies in the abdominal cavity, beneath the left side of the diaphragm. It is bordered above by the diaphragm and the liver, on the right by the liver, below by the transverse colon and the mesocolon (the double fold of peritoneum that attaches the transverse colon to the back wall of the abdominal cavity), on the left by the spleen, at the back by the pancreas, and at the front by the chest and abdominal walls.
The stomach the oesophagus and the duodenum, and it is a hollow organ that can be divided into several parts: the cardia, the fundus (the dome-shaped part of the stomach to the left of the cardia), the body (corpus), the horizontal section that follows it (antrum), and the pylorus.
Histologically, it consists of the following layers, from the inside outwards: the mucous membrane (tunica mucosa), covered by a single layer of columnar epithelium, beneath which lies the corium (lamina propria mucosae), in which the gastric glands are embedded.
In its lower part there is a thin layer of smooth muscle (lamina muscularis mucosae). Folds can be seen in the lining at the level of the fundus and the body, which allow the stomach to expand. The folds run lengthwise from the cardia to the angulus.
This is followed by the submucosa: a thick layer of loose fibrous connective tissue with a rich network of blood and lymph vessels. This is also where Meissner's plexus is found, which plays a role in autonomic innervation.
Next comes a complex muscle layer (tunica muscularis), made up of well-developed smooth muscle arranged in three layers (inner: oblique, middle: circular, outer: longitudinal). Auerbach's plexus lies between the outer and middle layers.
Finally, it is covered on the outside by the serosa (tunica serosa), i.e. the visceral peritoneum.
