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Anatomy - Gastrointestinal anastomosis technique – Roux-en-Y esophagojejunostomy
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Surgical anatomy of the stomach
In terms of function, the stomach mixes and stores food and is an expansion of the alimentary tract between the esophagus and the duodenum. This muscular hollow viscus produces acidic gastric juice (mucus and HCl) and enzymes, which predigest some elements of the ingested food, and portions the chyme into the duodenum.
Usually, the stomach is located immediately inferior to the diaphragm in the left upper quadrant and epigastrium. Location, size and shape of the stomach vary from person to person and may differ substantially, depending on age, filling condition and body position. The moderately filled stomach has a mean length of 25-30 cm and can hold 1.5 liters, in extreme cases up to 2,5 liters.
Within the abdominal cavity the stomach is held in position and stabilized by ligaments inserting at the liver and spleen Its convex aspect forms the major curvature (curvatura major gastrica) and its concave aspect the lesser curvature (curvatura minor gastrica). Its anterior wall is termed paries anterior gastrica and its posterior aspect paries posterior gastrica.
Since the stomach is an intraperitoneal viscus, it is covered by the gastric serosa (tunica serosa gastrica), and only the posterior aspect of the cardia is free of serosa. Stomach rotation shifts the embryonic mesogastrics from their former sagittal position to a frontal location. The lesser omentum originates at the lesser curvature and extends to the hepatic portal, while the greater omentum originates at the greater curvature and courses to the transverse colon, spleen and diaphragm.
The stomach displays the following portions:
- Entrance of stomach / Cardia / Ostium cardiacum:
The superior opening of the stomach, where the esophagus enters the stomach, is 1-2 cm long. It is characterized by a marked transition from the mucosa of the esophagus to that of the stomach.
- Gastric fundus / fundus gastricus:
Superior to the level of entrance of the esophagus the fundus arches cephalad, which then is called gastric fornix (fornix gastricus). Usually, the fundus is full of air which is swallowed automatically when ingesting food. In the erect position the fundus is the highest point of the stomach, and on abdominal films its trapped air is evident as the “gastric bubble”. A notch (incisura cardialis) clearly delimits the fundus from the entrance of the stomach.
- Body of the stomach / Corpus gastricum
The main portion of the stomach is taken up by the gastric body. The deep mucosal folds (plicae gastricae) found here extend from the cardia to the pylorus and are also known as “magenstrasse”.
- Pylorus / Pars pylorica:
This portion begins with the extended pyloric antrum, followed by the pyloric canal, and terminates at the actual pylorus. It is formed by the pyloric sphincter (m. sphincter pyloricus), a strong circular layer of muscle which closes off the inferior gastric orifice (ostium pyloricum). The pylorus closes off the gastric outlet and periodically lets some of the chyme pass into the adjacent duodenum.
- Entrance of stomach / Cardia / Ostium cardiacum:
The stomach acts as a reservoir for ingested food. Since it may store food for hours, it ensures that we can meet our daily nutritional requirements with a few major meals. Peristalsis thoroughly mixes the chyme with the gastric juice, the food is broken up chemically, predigested and then portioned into the duodenum.
The first (or superior) portion of the duodenum, also known as the duodenal bulb or cap, starts at the end of the stomach pylorus and is followed by the second (or vertical or descending) portion. The third (or horizontal or transverse) portion starts at the duodenal angulus (“knee”), while the fourth (or oblique or ascending) portion terminates in the jejunum at the duodenojejunal flexure, where the suspensory ligament of the duodenum (ligament of Treitz) attaches. The arterial supply of the duodenum derives from the gastroduodenal, pancreaticoduodenal and supraduodenal arteries, which are branches of the celiac trunk and the superior mesenteric artery.
- The jejunum is one of three sections of the small intestine. It extends from the duodenum to the ileum.
- Its colloquial German term of “Leerdarm” or “empty bowel” stems from the fact that in most dead patients it is empty. *
The jejunum is plicated in numerous loops and with its mesentery attaches to the posterior abdominal wall. The corresponding segment of the mesentery is called mesojejunum. When considered together with the ileum, which begins at the jejunum and terminates at the cecum, the radix mesenterii or root of the mesentery extends from the duodenojejunal flexure to the ileocecal valve.
- Since the loops of the jejunum are quite mobile, they shift their positions. While the beginning of the jejunum is well defined by the duodenojejunal flexure at the level of the second lumbar vertebra, the boundary between the jejunum and ileum is not well defined.
Like any other hollow viscus, the jejunum is lined with a mucous membrane (tunica mucosa). On the outside the mucous membrane is enclosed by a double layer of smooth muscle (tunica muscularis), while the serosa is a reflection of the peritoneum over the exterior of the jejunum.
- The superior mesenteric artery supplying the jejunum, ileum, appendix, ascending colon and the proximal two thirds of the transverse colon courses in the proximal section of the mesenteric root.
- The arterial supply of the jejunum derives from the jejunal arteries, which are branches of the superior mesenteric artery. The veins of the jejunum drain into the superior mesenteric vein which parallels the superior mesenteric artery on the right and then courses posterior to the head of the pancreas to the portal vein.
- The jejunum is primarily innervated by the enteric nervous system. Peristalsis is controlled by the mesenteric plexus (Auerbach plexus), while the mucous membrane is innervated by the submucous plexus (Meissner plexus). In addition, the jejunum is also regulated by the sympathetic and parasympathetic nervous systems (in particular the vagus nerve).
Jeiunus is Latin for fasting, hungry, meager *