The location and shape of the stomach
Most of the stomach is located in the left quadrant of the rib cage, and a small part of it is located in the upper abdomen. The location of the stomach often changes depending on body type, body position, the amount of stomach contents and breathing, and sometimes the greater curvature of the stomach can reach the umbilicus or even the pelvis. Generally, the stomach is divided into five regions:
Gastric body: the part of the stomach below the fundus is the gastric body, the left boundary of which is the greater curvature of the stomach, the right boundary is the lesser curvature of the stomach; the lesser curvature of the stomach turns vertically and abruptly to the right, the junction of which is the gastric angle cut, the gastric angle cut to the corresponding line of the greater curvature of the stomach is its lower boundary. The stomach body occupies the largest area and contains most of the wall cells.
1.Plasma layer The peritoneum covering the surface of the stomach, forming various ligaments of the stomach, connected with neighboring organs, and forming the greater omentum at the greater curvature of the stomach.
2, muscle layer The thicker intrinsic muscle layer under the plasma membrane, consisting of three layers of smooth muscle in different directions. The outer longitudinal layer is connected to the outer longitudinal smooth muscle of the esophagus, thicker at the large and small curves of the stomach, and the middle circular muscle, thickened at the pylorus to form the pyloric sphincter. The inner layer of oblique muscle, the gastric muscle layer contains the Auerbach plexus.
This layer is the most supportive structure in the entire gastric wall. The submucosal layer should be penetrated when suturing the gastric wall, while the submucosal vessels should be ligated first during gastrectomy to prevent postoperative anastomotic bleeding.
4.Mucosal layer The mucosal layer includes surface epithelium, lamina propria and mucosal muscle layer. The mucosal muscle layer makes the mucosa form many folds, which mostly flatten and disappear when the stomach is filled, thus increasing the surface epithelial area. There are 2-4 constant longitudinal folds in the lesser curvature of the stomach, and the intermural groove formed by them is called the gastric tract, which is the pathway of the esophagus into the stomach. The intrinsic layer is a thin layer of connective tissue containing capillaries, lymphatics and nerves that innervate the surface epithelium.
The gastric mucosa is composed of a layer of columnar epithelial cells with a dense surface of small depressions called gastric pits, which are the openings for the glandular ducts. Columnar epithelial cells secrete large amounts of mucus to protect the gastric mucosa. Different parts of the gastric mucosa have different glands and cells. The lytic glands are located in the fundus and body of the stomach and consist of primary and mural cells. The cardia glands are in the cardia and are dominated by mucus cells, and the pyloric glands are in the gastric sinus and pyloric region and are dominated by mucus and endocrine cells.
There are five cell types in the gastric glands;
①Mural cells: secrete hydrochloric acid and endocrine factors, mainly in the fundus and body of the stomach. A small amount is found in the proximal pyloric sinus.
(ii) Mucus cells, which secrete mucus.
③Main cells, secreting pepsinogen, mainly in the fundus or gastric body.
④Endocrine cells: G cells secrete gastrin, D cells secrete growth inhibitory hormone, EC cells release 5-hydroxytryptamine in a silvery or silvery stain.
⑤ Undifferentiated cells.
The gastric horn notch is an anatomical landmark at the junction of the body of the gastric sinus, and its histological demarcation is not consistent with anatomy and varies according to age. The histological demarcation is often located proximal to the gastric horn notch and can be as high as the cardia with age, where acid resistance is poor and is the site of gastric ulcers. During pyloric sinus resection, the line of resection of the gastric lesser curvature should reach the subcardia in order to completely remove the gastrin-secreting mucosa of the pyloric sinus.
The anterior wall of the stomach is adjacent to the left half of the liver on the left side and to the diaphragm on the right side, and its posterior wall is adjacent to the pancreas, the left adrenal gland, the left kidney, the spleen, the transverse colon and its ligament, and the anterior and posterior walls of the stomach are covered with peritoneum, which migrates from the greater and lesser curves of the stomach to the nearby organs, namely the ligament and the omentum.
1, hepatogastric ligament and hepatoduodenal ligament The hepatogastric ligament connects the lower transverse sulcus of the left lobe of the liver and the lesser curvature of the stomach, and the hepatoduodenal ligament connects the hepatic portal and duodenum, together forming a small omentum, which is a double-layer peritoneal structure. The hepatoduodenal ligament contains the common bile duct, hepatic artery and portal vein.
2, gastrocolic ligament connecting the stomach and transverse colon, extending downward to the greater omentum, a four-layer peritoneal structure. The posterior layer of the greater omentum is connected to the upper layer of the transverse colonic mesentery. In the hepatic and splenic regions of the transverse colon, the two are loosely connected and can be easily dissected and separated; in the middle, the two are tightly connected, so when dissecting the gastrocolic ligament, attention should be paid to avoid injuring the middle colonic artery in the transverse colonic mesentery.
4.Gastro-diaphragmatic ligament is connected to the diaphragm by the fundus of the upper part of the greater curvature of the stomach, and this ligament needs to be cut when freeing the cardia and the lower part of the esophagus during total gastrectomy.
5.Gastro-pancreatic ligament The posterior wall of the gastric sinus connects to the peritoneal fold of the neck of the head of the pancreas, in addition, the peritoneal fold from the cardia of the lesser curvature of the stomach to the pancreas, which contains the left gastric vein. In the case of portal hypertension, blood can flow into the superior vena cava through the left gastric vein to the esophageal vein and the odd vein, and varices of the esophagogastric fundus can occur.
1.Arteries of stomach The stomach is the most abundant organ of blood supply in the gastrointestinal tract, which comes from the abdominal artery and its branches. Two arterial arches are formed along the major and minor curves of the stomach, and then many branches are issued to the anterior and posterior walls of the stomach.
(1) The left gastric artery originates from the celiac artery and is the smallest branch of the celiac artery, but the largest artery of the stomach. It reaches the cardia via the gastro-pancreatic peritoneal folds on the upper left, and then branches upward to the esophageal and cardia branches, and then branches downward along the lesser curvature of the stomach in the hepatogastric ligament to the anterior and posterior walls of the stomach, where it coincides with the right gastric artery at the gastric horn notch to form the lesser curvilinear arterial arch.
15-20% of the left hepatic artery may originate from the left gastric artery and, together with the hepatic branch of the left vagus nerve, reach the liver, which is occasionally the only arterial flow in the left hepatic lobe. Ligation of the left gastric artery at the root can lead to acute left hepatic necrosis and should be observed during surgery.
(2) Right gastric artery Originates from the innominate hepatic artery or gastroduodenal artery, travels to the superior border of the pylorus, turns to the left, and branches in the hepatogastric ligament along the lesser curvature of the stomach, from left to right, along the way to the anterior and posterior walls of the stomach, to anastomose with the left gastric artery at the gastric angle notch.
(3) The left gastroretinal artery starts from the end of the splenic artery, enters the anterior lobe of the greater omentum between two layers of the peritoneum through the splenogastric ligament from the splenic portal, travels left along the greater curvature of the stomach, branches to the anterior and posterior walls of the stomach and the greater omentum, distributes to the lower left side of the greater curvature of the gastric body, anastomoses with the right gastroretinal artery, and forms the greater curvilinear arterial arch of the stomach. Major gastrectomy is often performed by cutting the gastric wall from the first short gastric artery at the side of the greater curvature.
(4) The right gastroretinal artery originates from the gastroduodenal artery and runs from right to left along the greater curvature of the stomach between the two peritoneal layers of the anterior lobe of the greater omentum, branching along the way to the anterior and posterior walls of the stomach and the greater omentum, anastomosing with the left gastroretinal artery and distributing to the left half of the greater curvature of the stomach.
(6) Posterior gastric artery It is a branch of the splenic artery, usually 1-2 branches, from the upper edge of the pancreas through the gastric diaphragmatic ligament and reaches the posterior wall of the stomach base.
(7) Left inferior diaphragmatic artery It branches out from the abdominal aorta, follows the diaphragmatic ligament, and is distributed in the upper part of the fundus and the cardia. The left inferior diaphragmatic artery has a role in the blood supply to the remnant stomach after major gastrectomy. There are extensive anastomotic branches between the arteries of the stomach. If any three of the four arteries, the left gastric artery, the right gastric artery, the left gastroretinal artery and the right gastroretinal artery, are ligated, the stomach can still receive a good blood supply as long as the arch of the greater and lesser curvatures of the stomach is not damaged. (Figure 27-1-2)
2. Veins of the stomach The veins of the stomach accompany each eponymous artery and all converge into the portal venous system. The distal splenorenal vein anastomosis can effectively decompress the varices of the gastroesophagus, which is enough to prove the extensive venous anastomosis network in the stomach.
(2) The right gastric vein en route receives the anterior pyloric vein, which is located in front of the junction between the pylorus and duodenum and goes up into the portal vein, and the anterior pyloric vein is the marker to identify the pylorus.
The layers of the gastric wall are rich in capillary lymphatics, starting from the lamina propria of the gastric mucosa. They are interwoven into a network in the submucosal, muscular and subplasmic layers and flow into the perigastric lymph nodes, which are finally incorporated into the abdominal lymph nodes and reach the thoracic duct. The lymphatic drainage generally accompanies the blood vessels and converges into the corresponding four perigastric lymph node areas.
1. Left lymph node area of the stomach The cardia, the left half of the lesser curvature of the stomach and the right half of the anterior and posterior walls of the fundus of the stomach are injected into the paracolic lymph nodes, the epigastric lymph nodes and finally the abdominal lymph nodes.
2. The right lymph node area of the stomach The anterior and posterior walls of the pylorus, the right half of the gastric lesser curvature, drain into the suprapyloric lymph node, thus through the lymph node of the common hepatic artery, and finally into the lymph node of the abdominal cavity.
3.Left lymph node area of the gastric omentum The left half of the fundus and the left half of the greater curvature of the stomach flow into the left inferior gastric lymph node, splenic hilar lymph node and pancreatic-splenic lymph node respectively, and then into the abdominal lymph nodes.
The right lymph node area of the gastric omentum flows into the right half of the gastric curvature and the pylorus, into the subpyloric lymph node of the stomach, and then along the lymph node of the common hepatic artery and into the lymph nodes of the abdominal cavity.
Lymph node metastasis usually starts from the lymph node area adjacent to the primary focus, and then shifts to the next station in order from near to far. Sometimes cancer from any part of the stomach can metastasize to any group of lymph nodes around the stomach, and about 30% of cancer in the gastric sinus can metastasize to the splenic lymph nodes.
Parasympathetic nerve The parasympathetic nerve of stomach comes from the vagus nerve. The nucleus of vagus nerve is located at the base of the fourth ventricle through the carotid sheath of the neck into the mediastinal barrier, forming several branches around the esophagus and fusing into the left and right vagus nerves above the diaphragmatic esophageal fissure, before the left vagus nerve position at the cardia, about the deep surface of the plasma membrane near the midline of the esophagus, which needs to be cut open during surgery to reveal. The right vagus nerve is located posteriorly and descends in the right posterior part of the esophagus.
The anterior trunk divides into the hepatic and anterior gastric branches (anterior Latarget nerve) in front of the cardia. The hepatic branch travels right into the liver in the lesser omentum, and the anterior gastric branch travels right with the left gastric artery in the lesser omentum about 1 cm from the lesser curvature of the stomach, generally sending 4-6 branches to the anterior wall of the stomach, forming a terminal branch at the angular notch called the claw branch, which is distributed in the pyloric sinus and anterior wall of the pyloric duct. The posterior trunk divides into the ventral branch and the posterior gastric branch at the dorsal aspect of the cardia. The ventral branch enters the ventral plexus with the beginning segment of the left gastric artery.
The posterior gastric branch (posterior Latarget nerve) travels along the lesser curvature of the stomach and branches to the posterior gastric wall, with its terminal branches also distributed in a crow’s claw pattern to the posterior wall of the pyloric sinus and pyloric duct. The posterior vagus nerve has branches distributed on the side of the greater curvature of the gastric fundus called Grassi’s nerve or sinus nerve, which should be cut during mural cell vagotomy to reduce recurrence.
Most of the fibers of the vagus nerve are of afferent type, which transmits stimuli from the intestine to the brain, and the pulling sensation and hunger impulses of the stomach are transmitted from the vagus nerve to the medulla oblongata, and excessive pulling and strong stimulation of the vagus nerve during surgery can cause cardiac arrest. Each gastric branch of the vagus nerve transmits postganglionic fibers within the plexus of the gastric wall, innervates the gastric glands and muscles, and enhances gastric motility and promotes gastric acid and pepsin secretion through acetylcholine as transmission.
Selective vagotomy is a vagotomy that preserves the hepatic and ventral branches. Mural cell vagotomy preserves the hepatic, ventral and anterior and posterior ravenous claw branches, and cuts only the anterior and posterior gastric branches that innervate the mural cells and all their gastric wall branches. It can reduce the secretion of gastric acid and achieve the purpose of treating ulcers, while preserving the emptying function of the stomach and avoiding the dysfunction of liver, bile and pancreas.
2, sympathetic nerve Gastric sympathetic nerve preganglionic fibers from the spinal cord T5-T10, through the sympathetic nerve to the celiac nerve from the internal celiac ganglion, postganglionic fibers along the celiac artery system distributed in the stomach wall, its role is to inhibit gastric secretion and peristalsis, enhance the tension of the pyloric sphincter, and make the gastric vasoconstriction.
Mural cell vagotomy, which necessarily cuts off the blood supply to the gastric lesser curvature, cannot preserve sympathetic innervation, and the painful impulses of the stomach follow the sympathetic nerves and enter through the sympathetic trunk of the ventral plexus