ANATOMY

• Stomach


  Specialized for the accumulation of ingested food, which it chemically and mechanically prepares for digestion and passage into the duodenum
• Functions of stomach


  • Storage of food
  • Digestion
  • Mixing of food into chyme
  • Acid secretion
  • Enzyme secretion
  • Hormone secretion
  • Absorption
  • Periodic release of chyme into the duodenum
• Chyme


  Semiliquid mixture that the gastric juice gradually converts the mass of food into, which passes fairly quickly into the duodenum
• Gross anatomy of stomach

  • Location - upper left part of abdomen
  • Shape - 'J' shaped when empty
  • Size - 10 inches long
  • Capacity - 30 ml in newborn, 1.5-2 litres in adults
  • Ends - cardiac and pyloric
  • Orifices - cardiac and pyloric
  • Curvatures - lesser and greater
  • Surfaces - anterior and posterior

  
• Cardiac end


  Upper end where esophagus continuous with stomach, located at T11 vertebra, presents cardiac orifice

  
• Pyloric end


  Lower end where stomach continues as duodenum, located at L1 vertebra, presents pyloric sphincter (pylorus) with pyloric orifice
• Lesser curvature


  Concave, shorter than greater curvature, presents angular notch, gives attachment to lesser omentum, related to right and left gastric vessels
• Greater curvature


  Convex, longer than lesser curvature, gives attachment to greater omentum, gastrosplenic and gastrophrenic ligaments, related to right and left gastroepiploic vessels
• Parts of stomach


  • Cardia
  • Fundus
  • Body
  • Pyloric part (pyloric antrum and pyloric canal)

  
• Cardia


  Part surrounding the cardiac orifice
• Fundus


  Dome shaped part, situated above the level of cardiac orifice, contains undigested food and filled with gas
• Body


  Largest part lies between fundus and pyloric antrum
• Pyloric antrum


  Situated between body and pyloric canal
• Pyloric canal


  Narrow, tubular part, at its right end presents pyloric sphincter (pylorus) which guards pyloric orifice
• Relations of stomach


  • Anterior surface - related to anterior abdominal wall, diaphragm, left lobe of liver, left costal margin, left lung and left pleura
  • Posterior surface - related to lesser sac, diaphragm, left kidney, left suprarenal gland, splenic artery, splenic flexure of colon, pancreas, and transverse mesocolon

  
• Gastric rugae


  Folds of mucous membrane that disappear when the stomach is distended
• Gastric pits


  Depressions which open into the lumen of stomach, each receives openings of 2 to 3 gastric glands
• Gastric canal


  Groove formed temporarily by the gastric rugae along the lesser curvature during swallowing, saliva, small quantities of masticated food and other fluids drain along it when the stomach is mostly empty
• Arterial supply of stomach

  • Left gastric artery (splenic)
  • Right gastric artery (hepatic)
  • Right gastroepiploic artery (gastroduodenal)
  • Left gastroepiploic artery (splenic)
  • Short gastric artery

  
• Venous drainage of stomach

  • Superior mesenteric vein
  • Splenic vein
  • Portal vein

  
• Nerve supply of stomach

  • Parasympathetic nerves - anterior and posterior vagal trunks
  • Sympathetic nerves - arise from T6 to T9 spinal segments and distributed via coeliac plexus, hepatic plexus and greater splanchnic nerves
• Lymphatic drainage of stomach

  • Right gastric, left gastric, right gastroepiploic, left gastroepiploic, short gastric nodes
  • Left gastroepiploic and short gastric nodes drain into pancreaticosplenic nodes
  • Right gastric, left gastric, right gastroepiploic nodes drain to hepatic nodes
  • Pancreaticosplenic, hepatic nodes drain into coeliac nodes

  
• Development of stomach


  1. Appears as a fusiform dilation of the foregut in week 4

  2. Has dorsal mesogastrium and ventral mesogastrium

  3. Rotates 90⁰ around its longitudinal axis - results in the left side facing anteriorly and its right side facing posteriorly

  4. Cranial and caudal ends originally lie in the midline

  5. Stomach rotates around an anteroposterior (a-p) axis - caudal end moves to the right and upward, cranial end moves to the left and slightly downward

  
• Gastric canal along lesser curvature is a common site for occurrence of peptic ulcer because this area is irritated most by the swallowed liquids and has more number of secretomotor supply from vagal trunks
• Gastric pain is referred to the epigastric region (due to the nerve supply from T6 to T9 spinal segments)
• A hiatal (hiatus) hernia is a protrusion of part of the stomach into the thorax through the esophageal opening of the diaphragm
• Pylorospasm is characterized by failure of the smooth muscle fibers encircling the pyloric canal to relax normally, resulting in food not passing easily from the stomach into the duodenum and the stomach becoming overly full, usually resulting in discomfort and vomiting
• A posterior gastric ulcer may erode through the stomach wall into the pancreas, resulting in referred pain to the back. In such cases, erosion of the splenic artery results in severe hemorrhage into the peritoneal cavity
• Esophagus


  Muscular tube, 10 inches in length

  
• Origin of esophagus


  Continuation of pharynx (pharyngo-esophageal junction) at the level of C6 vertebra

  
• Course of esophagus


  1. Runs down in the lower part of neck

  2. Enters thorax by passing through thoracic inlet

  3. Descends in the superior mediastinum and then in the posterior mediastinum

  4. Passes through esophageal opening of diaphragm (T10 vertebra)

  5. Enters abdomen

  
• Termination of esophagus


  Joins the cardiac end of stomach (T11 vertebra)

  
• Parts of esophagus

  • Cervical
  • Thoracic
  • Abdominal

  
• Cervical part of esophagus

  • Anterior – trachea, recurrent laryngeal nerves
  • Posterior – vertebral column
  • Lateral – carotid sheath, lobe of thyroid gland
• Thoracic part of esophagus

  • Anterior relations - trachea, left principal bronchus, pericardium, heart
  • Posterior relations - vertebral column
  • Right relations - right lung, right pleura, arch of azygos vein
  • Left relations – left lung, left pleura, arch of aorta, descending thoracic aorta

  
• Abdominal part of esophagus

  • Anterior – left lobe of liver
  • Posterior – diaphragm

  
• Constrictions of esophagus


  • First constriction – at its beginning (15 cm from incisor teeth) caused by cricopharyngeus muscle (inferior constrictor)
  • Second constriction – where it is crossed by arch of aorta (22.5 cm from incisor teeth)
  • Third constriction – where it is crossed by left principal bronchus (27.5 cm from incisor teeth)
  • Fourth constriction – where it pierces diaphragm (40 cm from incisor teeth)

  
• No constrictions are visible in the empty esophagus. As it expands during filling, the structures mentioned above compress its walls

  
• Blood supply of esophagus

  • Cervical part – inferior thyroid artery and vein
  • Thoracic part –descending thoracic aorta, azygos, hemiazygos and accessory hemiazygos veins
  • Abdominal part – left gastric artery and vein

  
• Nerve supply of esophagus

  • Parasympathetic nerves - vagus, recurrent laryngeal nerve
  • Sympathetic nerves – middle cervical sympathetic ganglia and upper 4 thoracic sympathetic ganglia