The Stomach is a digestive organ located between the oesophagus and the duodenum,stomach is part of the gastrointestinal tract. It has a ‘J’ shape, and features a lesser and greater curvature. The anterior and posterior surfaces are smoothly rounded with a peritoneal covering.
The stomach is located in the superior aspect of the abdomen. It lies in the epigastric and umbilical regions, mostly protected by the lower portion of the rib cage.
It consist of four regions;
- body and
Cardia– this the superior part of the stomach which connects to oesphagus.
Fundus – the rounded portion superior to and left of the cardia. Cardia – surrounds the superior opening of the stomach.
Body – the large central portion inferior to the fundus.
Pylorus – connects the stomach to the duodenum. Greater and Lesser Curvatures The medial and lateral borders of the stomach are curved, forming the lesser and greater curvatures:
Greater curvature – forms the long, convex, lateral border of the stomach. Arising at the cardiac orifice, it arches backwards and passes inferiorly to the left.
It curves to the right as it continues medially to reach the pyloric antrum. The short gastric arteries and the right and left gastro-omental arteries supply branches to the greater curvature.
Lesser curvature – forms the shorter, concave, medial surface of the stomach. The most inferior part of the lesser curvature, the angular notch, indicates the junction of the body and pyloric region.
The lesser curvature gives attachment to the hepatogastric ligamentand is supplied by the left gastric artery and right gastric branch of the hepatic artery.
RELATIONS OF THE ORGAN TO THE STOMACH
||Head and neck of pancreas
||Greater omentum, abdominal wall, left lobe of liver, gall bladder
||Lesser sac, left kidney, left adrenal gland, splenic artery, common bile duct, gastroduodenal artery
Sphincters of the Stomach
There are two sphincter that controls movement or passage of substances entering and existing the organ.
- Esophageal spinchter and
- pyloric sphincter
Oesophageal sphincter: The inferior oesophageal sphincter is located between the oesophagus and the stomach (in contrast to the superior oesophageal sphincter, located in the pharynx). It is located to the left of the T11 vertebra.
Situated immediately superior is th eoesophageal hiatus, an opening in the diaphragm through which the oesophagus travels.
Histologically, the sphincter is marked by an abrupt change from stratified squamous epithelium to simple columnar.
It does not have any specific muscle. Instead, a number of extrinsic forces act to produce the sphincter:
pyloric sphincter: The pyloric sphincter lies between the pylorus and the duodenum. It controls of the exit of chyme(food and gastric acid mixture) from the stomach.
Greater and Lesser Omenta
- Greater omentum – hangs down from the greater curvature of the stomach. It drapes over the transverse colon and folds back upon itself before reaching the posterior abdominal wall. It features many lymph nodes, which contain macrophages to help combat infections of the GIT.
- Lesser omentum – continuous with peritoneal layers of the stomach and duodenum. These two layers combine at the lesser curvature, and ascend to attach to the liver. The main function of the lesser omentum is to attach the stomach and duodenum to the liver.
Blood Supply To Stomach
The arterial supply to the stomach comes from the celiac trunk and its branches. Anastomoses form along the lesser curvature by the right and left gastric arteriesand along the greater curvature by the right and left gastro-omental arteries:
- Right gastric – branch of the common hepatic artery, which arises from celiac trunk.
- Left gastric – arises directly from the celiac trunk.
- Right gastro-omental – terminal branch of the gastro-duodenal artery, which arises from the common hepatic artery.
- Left gastro-omental – branch of the splenic artery, which arises from the celiac trunk.
The veins of the stomach run parallel to the arteries. The right and left gastric veins drain into the hepatic portal vein. The short gastric vein, left and right gastro-omental veins ultimately drain into the superior mesenteric vein.
Innervation of the Stomach
The stomach receives innervation from the autonomic nervous system:
- Parasympathetic nerve supply comes from the posterior vagal trunks, derived from the vagus nerve.
- Sympatheticnerve supply from the T6-T9 spinal cord segments pass to the celiac plexus. It also carries some pain transmitting fibres.
The gastric lymphatic vessels travel with the arteries along the greater and lesser curvatures of the stomach.
Lymph fluid drains into the gastric and gastro-omental lymph nodes found at the curvatures.
Efferent lymphatic vessels from these nodes connect to the celiac lymph nodes, located on the posterior abdominal wall.
Disorder of the Stomach
This is a digestive disorder affecting the lower oesophageal sphincter.It refers to the movement of gastric acid and food into the oesophagus.
It is a common condition, affecting 5%-7% of the population. Symptoms include chronic heartburn, dysphagia, and an unpleasant sour taste in the mouth .There are three main causes of reflux
- Dysfunction of the lower oesophageal sphincter
- Delayed gastric emptying
- Hiatal hernia (see below)
Treatment involves lifestyle changes, medication, and as a last resort, surgery.
Hiatus hernia occurs when a part of the stomach protrudes into the chest through the oesophageal hiatus in the diaphragm. There are two main types of hiatal hernias, sliding and rolling:
- Sliding hiatus hernia – The lower oesophageal sphincter slides superiorly. Reflux is a common complication, as the diaphragm is no longer reinforcing the sphincter.
- Rolling Hiatus Hernia – The lower oesophageal sphincter remains in place, but a part of the stomach herniates into the chest next to it.