Stomach

Summary

  • Function
  • Anatomical relations
  • Structure
  • Neurovascular supply

Functions

  • Enzymatic digestion – formation of chyme from food
  • Mechanical digestion

Location & Anatomical Relations

  • Position varies greatly depending on diaphragmatic movement and positional changes
  • Anatomical relations:
    • Anteriordiaphragm, left lobe of liver
    • Posterioromental bursa, pancreas
      • The stomach makes up the anterior border of the omental bursa
    • Superior – left hemidiaphragm, lesser omentum
    • Inferiortransverse colon
  • The stomach bed is the resting place of the stomach when supine
    • Diaphragm
    • Spleen
    • Left kidney/adrenal
    • Splenic artery
    • Pancreas
    • Transverse Colon

  • Surface anatomy
    • Most commonly between the ribs in the supine position
  • Position can change with increased/decreased body habitus

    Changes in stomach position with large vs small (left vs right) body habitus.

Peritoneal relations
  • Most of the stomach is intraperitoneal
    • Covered by the greater and lesser omentum
  • Lesser omentum:
    • Extends from the lesser curvature around to the greater curvature of the stomach
  • Greater omentum:
    • Extends from the greater curvature
    • Folds back to become continuous with the transverse mesocolon
    • Contains the left and right gastroepiploic arteries (which anastomose to form the epiploic arterial arc)

Structure

  • 2 sphincters
    • Superior muscular sphincter = oesophageal sphincter
    • Inferior muscular sphincter = pyloric sphincter
  • 4 separate parts:
    1. Cardia – surrounds the cardial orifice (where oesophagus enters)
    2. Fundus
      • Dilated superior part
      • Related to the left hemidiaphragm just under the 5th ICS
      • Separated from oesophagus by the cardial notch
      • Separated by body by the horizontal plane of cardial orificie
    3. Body
      • Lies between fundus and pyloric antrum
    4. Pyloric part
      • Funnel at the end of the stomach
      • Separated from the body by the angular incisure 2/3rds down the lesser curvature
      • It has several sub parts
        • Pyloric antrum – wide part coming from the body
        • Pyloric canal – narrowing after the antrum
        • Pylorus/pyloric sphincter – thickened, distal sphincteric area
          • This controls discharge of chyme into the duodenum via tonic contractions
        • Pyloric orifice – border with duodenum
      • Cardial notch Esophagus Pylorus Duodenum Fundus Cardia Angular incisure Body Pyloric canal Pyloric

  • 2 curvatures:
    1. Lesser curvature (the superior concave border)
      • Attachment of lesser omentum
    2. Greater curvature (inferior convex border)
      • Attachment of greater omentum

Layers

 

  • Various layers
    1. Mucosal layer
    2. Submucosal layer
    3. External muscular layer (muscularis externa)
      • This itself is made up of 3 muscle layers
      1. Outer longitudinal muscle
      2. Middle circular muscle
      3. Inner oblique layer
    4. Adventitial layer (linked to the parietal peritoneum)
  • The stomach is highly distensible to accommodate up to 3 litres of food
  • When contracted, the mucosal/submucosal layers form longitudinal folds (rugae)
  • The gastric canal is a furrow formed along the lesser curvature during swallowing and communicates fluids
    • Develops due to absence of the oblique layer here


Neurovascular supply


Arteries
  • Many arteries supply the stomach – all are linked to the celiac trunk which lies superomedial to the lesser curvature
    • 2 arteries supply lesser curvature (Gastric Arteries)
    • 2 arteries supply greater curvature (Gastroepiploic arteries)
Table summarising the three different segments of arterial supply of the stomach.
  1. Left gastric artery
    • One of the 3 branches directly off the coeliac trunk
    • Runs in the lesser omentum until the cardia where it turns back along the lesser curvature
    • Anastomoses with the right gastric around the lesser curvature
  2. Right gastric artery
    • Comes off the common hepatic artery (branch of the celiac)
    • Anastomoses with the left gastric
  3. Right gastroepiploic (gastro-omental) artery
    • One of the 2 terminal branches of the gastroduodenal artery (along with superior pancreaticoduodenal)
    • Runs along the greater curvature and anastomoses with left GE artery
  4. Left gastroepiploic artery
    • Arises from splenic artery
    • Runs along the greater curvature and anastomoses with right GE artery
  5. Short gastric arteries
    • A group of 4/5 arteries which supply around the fundus of the stomach
    • Arise from splenic a.

 

Arterial supply of stomach (taken from Wikipedia)

Veins
  • Gastric veins follow the arteries in position and course but drain into various larger veins
    • Directly or indirectly will enter the HPV
  1. Left and right gastric veins drain directly into the portal vein
  2. Short gastric and left gastroepiploic drain into the splenic vein (=> portal vein)
  3. Right gastroepiploic drains into the SMV
  4. There is also a small prepyloric vein which ascends over the pylorus and drains into the right gastric vein
    • Large in living patients – useful to surgeons identifying the pylorus
Venous supply of the stomach (Moore & Dalley).

Lymphatic Drainage
  • Accompanies arteries
  • Ultimately drains into 2 nodes at the stomach curvatures
  1. Gastric nodes – at the lesser curvature
    • Take lymph directly from the superior 2/3s of the stomach via vessels accompanying the gastric arteries
    • Also via other nodes
      1. Pancreaticosplenic nodes
        • Drain the fundus along the short gastric and left gastroepiploic arteries
  2. Gastro-omental nodes
    1. Pyloric lymph nodes
      • Drain the right 2/3s of the greater curvature
    2. Pancreaticoduodenal nodes
      • Drain the left 1/3 along the short gastric and splenic vessels
  • These nodes all drain into the coeliac lymph nodes

Nerves
  • Parasympathetic supply is via direct branches of the anterior/posterior vagal trunks as well as the celiac plexus
    • Anterior:
      • Comes mainly from the left CNX which runs along the anterior oesophagus and lesser curvature where it gives off anterior gastric branches
    • Posterior:
      • Comes from the right CNX and runs along the posterior oesophagus.
      • Gives off 2 branches
        • Gives off a celiac branch which meets the celiac artery and then continues along the lesser curvatures
        • Posterior gastric branches
  • Sympathetic supply is via the Greater Splanchnic Nerve (T6-T9)
    • Via the Celiac Plexus
    • Fibres are distributed around the gastric/gastroepiploic arteries

Nerve supply of the stomach (Moore & Dalley).