Table of Contents
Macroscopic Anatomy of the Stomach
Position of the Stomach
The stomach is located in the upper left abdomen in the epigastric region and in the left hypochondriac region. While the position of most sections of this hollow muscular sack are variable, there are two sections, one oral and the other aboral, which have a fixed position: the entrance of the stomach (cardia), fixated by the lower esophageal sphincter, and the pylorus, which merges into the retroperitoneal duodenum and is therefore immobile.
External Shape of the Stomach
The stomach shows a large and a small curvature, which correspond to the anterior gastric wall (paries anterior) and the posterior gastric wall (paries posterior). The concave lesser curvature forms a well-marked notch (incisura angularis) at the junction to the pylorus, and the convexe greater curvature reaches from the fundus to the pyloric antrum. Furthermore, the stomach can be divided into four sections:
- Cardia (pars cardiaca), the entrance to the stomach: It connects the esophagus with the stomach, which is sealed with a functional sphincter.
- Fundus (fundus gastricus), a dome-shaped region: In an upright position, it is the highest point of the stomach. It is separated from the cardia through the cardiac notch (incisura cardiaca) and it usually contains swallowed air which makes it visible on radiographic images as the so-called gastric bubble.
- Body of the stomach (corpus gastricum): the main section of the stomach that extends from the fundus to the pylorus.
- Pylorus (pars pylorica): It consists of the wider pyloric antrum and the narrow pyloric canal. It ends in the pyloric orifice which consists of thick cylindrical muscles and forms the muscle of the pyloric sphincter connecting to the duodenum.
The external shape of the stomach is very variable and depends on different factors like the degree of filling (empty: anterior wall and posterior wall adjoin each other), body posture, gastric motility and physique. In x-ray examinations, a J-shaped stomach is most often found; tall and slim (asthenic) persons often have a long, saggy stomach (ptotic) and small, stocky (pyknic) persons a steer-horn stomach (almost horizontal).
Vascular Supply of the Stomach
The stomach is arterially supplied by the celiac artery (truncus coeliacus), the first unpaired branch of the abdominal aorta. It emits three arteries: the common hepatic artery (arteria hepatica communis), the left gastric artery (arteria gastrica sinistra) and the splenic artery (arteria splenica). The left gastric artery anastomoses with the right gastric artery (originating via the hepatic artery proper from the common hepatic artery) and they form the vascular arch of the lesser curvature. At the greater curvature, the right gastro-omental artery (from the gastroduodenal artery, which also originates from the common hepatic artery) and the left gastro-omental artery (from the splenic artery) anastomose and form another vascular arch.
Furthermore, the splenic artery emits branches that supply the fundus – the short gastric arteries (arteriae gastricae breves) – and the posterior wall of the stomach – posterior gastric artery (arteria gastrica posterior).
The veins of the stomach run alongside the arteries of the same name and lead the blood to the portal system, whereby the right and left gastric veins (venae gastricae dextra et sinistra) directly lead to the portal vein (vena portae), while the left gastro-omental vein (vena gastro-omentalis sinistra) leads to the splenic vein and the right gastro-omental vein (vena gastro-omentalis dextra) leads to the superior mesenteric vein (vena mesenterica superior).
Peritoneal Relations of the Stomach
The stomach is located intraperitoneally. From the lesser curvature, the omentum minus (or: lesser omentum; meaning “small net”) extends as a duplication of the peritoneum towards the liver. It originates in the ventral mesogastrium and has two portions, the hepatogastric ligament (ligamentum hepatogastricum) and the heptaduodenal ligament (ligamentum hepatoduodenale) which contains the portal triad. The greater omentum (omentum majus; “big net”), which develops from the dorsal mesogastrium, hangs down from the greater curvature and covers the large and small intestines like an apron. The following ligaments are also part of the greater omentum:
- Gastrophrenic ligament (ligamentum gastrophrenicum): between the greater curvature of the stomach and the bottom of the diaphragm
- Gastrosplenic ligament (ligamentum gastrosplenicum): between the stomach and spleen; contains the splenic artery including the short gastric arteries
- Gastrocolic ligament (ligamentum gastrocolicum): between the greater curvature and the large intestine (transverse colon); contains the right and left gastro-omental arteries
Relation of the Stomach to its Neighbouring Organs
With its location in the upper abdomen, the stomach has contact with different abdominal organs:
- Liver (facies hepatica): The left lobe of the liver covers the stomach on the right and ventral side.
- Diaphragm (facies phrenica): The fundus lies flat on the left diphragmatic cupola which divides the stomach from the pleural cavity.
- Spleen (facies splenica): The spleen is found on the left posterior half of the stomach in the area of the fundus. (Cave: Risk of injury in gastric surgeries!)
- Pancreas (facies pancreatica): Dorsal to the stomach runs the tail of the pancreas. The lesser sac (bursa omentalis) separates the two organs.
- Large intestine (facies colomesocolica): The transverse colon extends parallel to the pyloric part. The gastrocolic ligament connects the transverse colon with the greater curvature of the stomach.
- Kidney (facies renalis) and adrenal gland (facies suprarenalis): One part of the front surface of the left kidney and the adrenal gland makes contact with the gastric body.
Microscopic Anatomy of the Stomach
Structure of the Stomach Wall
The structure of the stomach wall resembles the structure of the entire gastrointestinal tract with its five typical layers: the mucosa (tunica mucosa), the submucosa (tela submucosa), the muscular layer (tunica muscularis), the subserosa (tela subserosa) and the serosa (tunica serosa). While, in the rest of the mid- and endgut, the muscular layer consists of a longitudinal muscular layer (stratum longitudinale) and of a circular muscular layer (stratum circulare), the stomach wall features a third innermost muscular layer with diagonal fibres (the oblique muscular layer).
The mucosa consists of firstly, an epithelial lamina with single-layered highly prismatic epithelium (columnar epithelium), which is sharply separated from the multilayer squamous epithelium of the esophagus by the gastroesophageal junction called z-line (historically: ora serrata); secondly, the lamina propria with the gastric glands; and thirdly, the lamina muscularis mucosae.
When the gastric body is empty, the mucosa lies in folds called rugae or gastric folds (Latin: plicae gastricae), which are most strongly developed on the lesser curvature. They stretch out when the stomach is filled. Furthermore, there are the gastric areas (area gastrica) on the surface of the mucosa with the gastric pits (foveolae gastricae) which merge with the gastric glands.
At the entrance of the stomach, there are the ramified cardiacglands with wide lumina, which primarily secrete mucus. The pyloric glands in the pyloric part also produce mucus. Furthermore, there are G cells which produce gastrin, thereby stimulating the parietal cells. The largest portion of the mucosa is covered by the fundic glands (glandulae gastricae propriae), which are located in the fundus and body of the stomach. They have a narrow lumen, have a few branches, are long and consist of the following cells:
- Chief cells: basophilic (because of a lot of rough endoplasmic reticulum); located in the bases of the glands; production of pepsinogen und lipase.
- Parietal cells: eosinophilic (because of a lot of mitochondria); located in the middle region of the glands; secretion of hydrochloric acid and intrinsic factor (needed for the absorption of vitamin B12 in the terminal ileum).
- Mucous neck cells: located in the neck of the glands; production of bicarbonate ions and mucus.
- Endocrine cells: located in the bases of the glands; production of histamine.
The protection of the stomach wall is ensured by a mucous coating, which is produced by the cardiac, pyloric and fundic glands (mucous neck cells) and the cells of the surface epithelium.
Function of the Stomach
The stomach serves as a reservoir, which means that it temporarily stores the food before it travels in small portions to the intestine. This is why a few large meals provide sufficient sustenance throughout the entire day. After a gastrectomy, however, meals have to be split up into various small portions throughout the day. The digestion process that started in the mouth continues in the stomach, aided by special digestive enzymes: The inactive enzyme precursor pepsinogen is converted into pepsin through contact with the gastric acid, which then helps with the pre-digestion of proteins by breaking them down into their components.
Another important task is the production of one to three litres of gastric juice per day. The gastric juice is a mixture of hydrochloric acid, intrinsic factor (coming from the parietal cells), mucus and enzymes. Because of the hydrochloric acid, the pH level of the stomach is acidic, which prevents infections of the intestines by killing off most of the bacteria (except: Helicobacter pylori).
Diseases of the Stomach
The functional dyspepsia (irritable bowel) is characterized by nausea, vomiting, a postprandial feeling of fullness and early statiety, and a diffuse pain in the upper abdomen. In order to confirm a diagnosis of functional dyspepsia, the symptoms have to persist for more than three months and it is important to exclude other organic causes (diagnosis by exclusion). Diagnostic measures include gastroscopy, sonography and laboratory tests. The disease is harmless and is often accompanied by psychological symptoms. A symptomatic treatment is sufficient.
Acute gastritis is a sudden inflammation of the gastric mucosa whereby this barrier of mucous tissue is destroyed and mucosal bleeding can occur. Causes might be exogenous and endogenous. Exogenous factors include alcohol, pharmaceuticals (acetylsalicylic acid, cytostatics) and bacteria (staphylococcus and salmonella). Symptoms are epigastric pressure pain, nausea and vomiting, and loss of appetite. A dangerous complication is gastric bleeding which is called erosive gastritis. Treatment includes temporarily reduced food intake and no consumption of alcohol and nicotine. Symptomatic treatment is possible with acid inhibitors (e.g., proton pump inhibitors) and antiemetic drugs.
In contrast to acute gastritis, patients with a chronic inflammation of the gastric mucosa are normally symptom-free. Only a few patients have unspecific pain in the upper abdomen. Chronic gastritis can be divided into the following types.
- Type A (autoimmune gastritis): This form only affects cardia and the body of the stomach. Antibodies against parietal cells and intrinsic factors can be found. The increasing loss of parietal cells leads to achlorhydria, and the lack of intrinsic factor to a disturbed absorption of vitamin B12 in the terminal ileum results in pernicious anemia. Some patients also present with an additional autoimmune disease and they are more likely to develop gastric carcinoma.
- Type B (bacterial gastritis): Type B gastritis mostly manifests in the antrum and is caused by an infection of the gastric mucosa with the bacterium Helicobacter pylori. The infection is likely to ascend to the gastric body, which leads to a decrease in the number of parietal cells and hypochlorhydria.
- Type C (chemical gastritis): This kind of gastritis is mostly caused by bile reflux from the gall bladder or use of NSAIDs, like ibuprofen or diclofenac.
For a diagnosis, biopsies of the gastric mucosa are taken by means of a gastroscopy. Furthermore, a colonization with Helicobacter pylori can be tested in two different ways, invasive (rapid urease test) and non-invasive (13C urea breath test). In cases of type A gastritis, autoantibodies (against parietal cells and intrinsic factor), as well as a diminished level of vitamin B 12, can be found in the serum.
Therapeutically, a first step would be to treat any existing symptoms. Furthermore, in cases of type B gastritis with corresponding indication (e.g. ulcerative disease); can be treated with eradication of Helicobacter pylori by means of a triple therapy (proton pump inhibitor + clarithromycin + amoxicillin or metronidazole). A lack of vitamin B12, due to an autoimmune gastritis, can be remedied through substitution. In addition, because of the increased risk for gastric carcinoma, a monitoring gastroscopy is recommended once a year.
A gastric ulcer (ulcus ventriculi) is a defect of the mucosa, extending deep into its muscular layer. In most cases, it is located in the lesser curvature and the antrum. It can be attributed to different causes whereby a decline in defensive factors (protection through mucus) and the reinforcement of aggressive factors (gastric acid) would have to be a focus.
The majority of gastric ulcers is caused by a colonization with Helicobacter pylori and thus, develops from a chronic gastritis. However, the ingestion of non-steroidal anti-inflammatory drugs (NSAID) as well as smoking (inhibiting the secretion of physiologically active prostaglandins), can lead to an ulcer. Clinically, an ulcer is often asymptomatic; some patients have left paraumbilical pain, which can be either independent of nutrition or be reinforced through food intake. Typically, however, the first symptoms appear only when complications occur. These include primarily bleeding, perforation and penetration.
The diagnosis of an ulcer can be made endoscopically where a tissue sample should be taken for excluding a gastric carcinoma. In cases of an infestation with Helicobacter pylori, the above-mentioned triple therapy can be administered. For the treatment of ulcers that test negative for Heliobacter, proton pump inhibitors are the first choice as a treatment with medication. In addition, noxious agents such as alcohol and nicotine should be avoided. Surgical interventions are unstoppable bleedings, open perforations, gastric outlet stenosis and carcinoma.
The frequency of carcinoma ventriculi peaks between the ages of 50 and 60 years and has a decreasing incidence. Most often, a carcinoma is found in the area of the lesser curvature and the pyloric part. Symptoms are unspecific and can range from pressure in the upper abdomen to nausea and a decrease in performance. Only in the progressed stages of the disease, it can result in weight loss, iron deficiency anemia, vomiting and dysphagia. For the diagnosis, a gastroscopy, with multiple biopsies, is performed. Here, an early diagnos is is crucial as it considerably improves the prognosis. For curative treatment, only an operation with subtotal or total gastrectomy comes into question. If the cancer is inoperable, palliative measures, that improve the quality of life, can be taken.
Examination of the Stomach
|Percussion||Because of the gas bubble in the fundus, there is a tympanitic resonance (different from the sonorous sound of the lung and damped sound of liver and spleen). The differentiation of the large intestine proves to be difficult because the sound of the transverse colon is similar to the sound of the stomach.|
|Sonography||The alternating hyperechoic and anechoic layers of the intestinal wall can be recognized; however, the presentation of the stomach through sonography is often difficult or incomplete due to the presence of air.|
|Gastroscopy (endoscopy of the stomach)||The gastroscope is inserted through the mouth into the esophagus and pushed into the stomach. It allows for assessing the gastric mucosa. Also the extraction of tissue samples and therapeutic interventions (e.g., stopping a bleeding) are possible.|
|Upper gastrointestinal tract radiography (upper GI)||This examination should be performed in the early morning. The patient is orally given a positive contrast agent (barium sulfate) and a negative contrast agent (carbon dioxide). Using fluoroscopy, images of the gastric mucosa are produced. A disadvantage of the upper GI is the exposure to radiation.|
Solutions can be found below the references.
1. Which statement about the blood supply of the stomach is correct?
- The lesser curvature is supplied by the right and left gastro-omental arteries.
- The left gastro-omental vein leads into the superior mesentery vein and the right gastro-omental vein leads into the splenic vein.
- The fundus is supplied by the splenic artery.
- The vascular arch of the greater curvature is made of branches of the left gastric artery.
- The venous blood of the stomach is led to the inferior vena cava.
2. Which statement about the peritoneal relations of the stomach is incorrect?
- The greater omentum emerges from the dorsal mesogastrium.
- The lesser omentum contains the hepatogastric ligament.
- The gastrocolic ligament contains the posterior gastric artery.
- The lesser omentum emerges, amongst other things, from the ventral mesogastrium.
3. The following statement about the histology of the stomach is correct:
- The muscular layer of the mucosa consists of two layers, the stratum longitudinale and the stratum circulare.
- The columnar epithelium of the esophagus merges at the z-line junction with the multi-layered squamous epithelium of the stomach.
- The chief cells of the gastric glands are eosinophilic, located at the base of the glands and produce enzymes like pepsinogen and lipase.
- The parietal cells are, amongst other things, responsible for the secretion of intrinsic factor.
- The gastric glands lead into the gastric areas.
4. Which statement is incorrect? Chronic gastritis…
- …can be divided in type A, B and C.
- …is diagnosed mostly through clinical tests.
- …is symptom-free in most patients.
- …in its type A form can lead to pernicious anemia.
- …in its type B form can be treated with a triple therapy involving the eradication of Helicobacter pylori.