Anatomy

• The size of the Stomachand the length along with the hape

  Most dilated part of GIT between the esophagus and small intestine, It is 10 inches and J shaped.
• Functions of stomach


  • Specialized for the accumulation of ingested food, which it chemically and mechanically prepares for digestion and passage into the duodenum
  • Acts as a food blender and reservoir; its chief function is enzymatic digestion
  • Gradually converts a mass of food into a semiliquid mixture, chyme, which passes fairly quickly into the duodenum
  • Storage of food, digestion, mixing of food into chyme, acid secretion, enzyme secretion, hormone secretion, absorption, periodic release of chyme into the duodenum which is the first part of the small intestine
• Stomachlocation,length,shape and capacity


  • Located in the upper left part of abdomen - left hypochondriac, epigastric and umbilical regions of abdomen
  • 10 inches long
  • Having a capacity of 30 ml in the new born and 1½ to 2 liters in adults
  • When empty it looks 'J' shaped

  
• External features of stomach

  • Ends: cardiac and pyloric ends
  • Orifices: cardiac and pyloric orifices
  • Curvatures: lesser and greater
  • Surfaces: anterior and posterior
• Cardiac end


  Upper end, esophagus continuous with the stomach, located at the level of T11 vertebra, presents cardiac orifice
• Pyloric end


  Lower end, stomach continues as duodenum, located at the level of L1 vertebra, presents pyloric sphincter (pylorus) which has pyloric orifice
• Lesser curvature


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


  Convex, longer than the 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 which has 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
• Anterior relations of stomach

  • Anterior abdominal wall, diaphragm, left lobe of liver, left costal margin, left lung and left pleura

  
• Posterior relations of stomach

  • Lesser sac, diaphragm, left kidney, left suprarenal gland, splenic artery, splenic flexure of colon, pancreas, and transverse mesocolon, spleen

  
• Interior of stomach


  • Shows gastric rugae and gastric pits
  • Gastric rugae: Folds of mucous membrane, 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 the gastric canal to the pyloric canal 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
  • Hepatic artery
  • Coeliac trunk
  • Splenic artery
• Venous drainage of stomach

  • Superior mesenteric, splenic and portal veins

  
• 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
  • Lymph from right gastric, left gastric, right gastroepiploic nodes drains to hepatic nodes
  • Lymph from the pacreaticosplenic, hepatic nodes drains 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. As a result, food does not pass easily from the stomach into the duodenum and the stomach becomes 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
• Diet contains carbohydrates, fat and proteins
• They are high molecular weight complex compounds
• Must be digested for absorption
• Digestion of carbohydrates


  1. Polysaccharides (starch and glycogen) hydrolyzed to simple sugars through enzymes

  2. Salivary amylase hydrolyses α-1,4-glycosidic linkages of polysaccharide chain to produce mono and disaccharides

  3. Further digestion in small intestine by intestinal enzymes which hydrolyze terminal α-1,4-glycosidic linkage

  
• Entry of acidic contents of stomach into duodenum

  1. Stimulates mucosal cells to release secretin and cholecystokinin

  2. Secretin stimulates pancreas to release bicarbonate and water to neutralize acidic chyme

  3. Cholecystokinin stimulates production of digestive enzymes including pancreatic amylase

  4. Pancreatic amylase digests polysaccharides to maltose, isomaltose and limit dextrin

  5. Disaccharidases digest disaccharides into monosaccharides

  
• Humans do not produce β 1,4-endoglucosidase to digest cellulose

  
• Cellulose helps in easy peristalsis and provides bulk to feces
• Lactase deficiency leads to lactose intolerance
• Absorption of monosaccharides


  • Galactose and glucose absorbed rapidly by active process
  • Fructose and mannose absorbed by Na+ independent facilitative transport mechanism

  
• Digestion of proteins in stomach

  1. Protein does not undergo digestion in mouth

  2. Enters stomach and stimulates secretion of hormone gastrin

  3. Gastrin stimulates release of gastric juice containing HCl and pepsinogen

  4. HCl unfolds proteins and activates proteolytic enzyme pepsin

  5. Pepsin digests protein polypeptides into tripeptides, dipeptides and amino acids

  
• Digestion of proteins in intestine

  1. Entry of acidic contents from stomach into intestine triggers secretion of hormones cholecystokinin and secretin

  2. Secretin stimulates release of bicarbonate and pancreatic juice

  3. Cholecystokinin stimulates secretion of pancreatic endopeptidases and exopeptidases

  4. Endopeptidases (trypsin, chymotrypsin, elastase) cleave internal peptide bonds

  5. Carboxypeptidase and aminopeptidase hydrolyze peptide bonds from carboxyl and amino terminal ends respectively

  
• Trypsin

  Hydrolyzes peptide bonds whose carboxyl groups are contributed by lysine and arginine
• Chymotrypsin

  Specifically hydrolyzes peptide bonds involving carboxyl group of aromatic amino acids (phenylalanine, tyrosine, tryptophan) and also splits bonds of leucine, methionine, asparagine, histidine