GI Tract - Stomach Flashcards
Location?
Is the stomach a retroperitoneal or a intraperitoneal organ?
Located at approximately T11. It is located between the oesophagus and the duodenum.
Intraperitoneal organ.
Which region of the abdomen is the stomach located?
Primarily the epigastric and umbilical regions, although position may change from person to person and with respiration.
Anatomical structure
There are four anatomical divisions:
1) Cardia - surrounds the superior opening of the stomach at the T11 level.
2) Fundus - the rounded, and often gas filled portion superior to and left of the cardia.
3) Body - the large and central portion inferior to the fundus.
4) Pylorus - connects the stomach to the duodenum. It is divided into the pyloric antrum, pyloric canal, and pyloric sphincter. The pyloric sphincter marks demarcates the transpyloric plane at the level of L1.
Greater and lesser curvatures
Greater curvature - forms the long convex, lateral border of the stomach. Arising at the cardiac notch, it arches backwards and passes inferiorly to the left. It curves to the right as it continues medially to the reach the pyloric antrum. The short gastric arteries and the left and right gastro-omental arteries supply branches to the great 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 ligament and is supplied by the left gastric artery and the right gastric branch of the hepatic artery.
Anatomical relations
Superior - oesophagus and left dome of the diaphragm
Anterior - diaphragm, greater omentum, anterior abdominal wall, left lobe of liver, gall bladder
Posterior - lesser sac, pancreas, left kidney, left adrenal gland, spleen, splenic artery, transverse mesocolon
Sphincters of the stomach
There are two sphincters.
1) Inferior esophageal sphincter - the oesophagus passes through the diaphragm at the level of T10. It descends a short distance to the inferior oesophageal sphincter at the level of T11, which marks the transition between oesophagus and stomach (in contrast to the UES). It allows food to pass through the cardiac orifice and into the stomach - involuntary.
2) Pyloric sphincter - it lies between the pylotus and the 1st part of duodenum. It controls the exit of chyme from the stomach. In contrast to the IES this is an anatomical sphincter and contains smooth muscle. Emptying of the stomach occurs intermittently when intragastric pressure overcomes resistance of the pylorus. Gastric peristalsis pushes the chyme through the pyloric canal into the duodenum.
Neurovascular supply
The arterial supply originates from the celiac trunk and its branches.
Anastomoses are formed along the lesser curvature by the right and left gastric arteries. They are also formed along the greater curvature by the right and left gastro-omental arteries:
- Right gastric - branch of the common hepatic artery, which arises from the coeliac trunk.
- Left gastric - arises directly from the coeliac trunk.
- Right gastro-omental - terminal branch of the gastroduodenal artery, which arises from the common hepatic artery.
- Left gastro-omental - branch of the splenic artery, which arises from the coeliac trunk.
The veins run parallel to the arteries.
The right and left gastric vein drain into the hepatic portal vein.
The short gastric vein, left and right gastro-omental veins ultimately drains into the superior mesenteric vein.
Innervation
The stomach receives innervation from the autonomic nervous system.
Parasympathetic - supply arises from the anterior and posterior vagal trunks, derived from the vagal nerve.
Sympathetic - supply arises from T6-T9 spinal cord segment and passes to the coeliac plexus via the greater splanchnic nerve. It also carries some pain transmitting fibres.
Lymphatics
