Anatomy of the Stomach

Gastric Digestive Function

• The four key components of gastric digestive function are:
  • Reservoir function
  • Acid secretion
  • Enzyme secretion
  • Role in gastrointestinal motility

Types of Stomachs

• Simple glandular stomach: found in carnivores
• Simple composite stomach: found in equines, has both glandular and non-glandular regions
• Complex composite stomach: found in ruminants, has four compartments (rumen, reticulum, omasum, and abomasum)

Surfaces of the Stomach

• Facies parietalis
• Facies visceralis

Borders of the Stomach

• Curvatura ventriculi major: convex and ventral border
• Curvatura ventriculi minor: concave and dorsal border

Regions of the Simple Stomach

• Pars cardiac (cardiac part)
• Fundus ventriculi (fundus)
• Corpus ventriculi (body)
• Pars pylorica (pyloric part)

Omentum

• A large, flat, adipose tissue layer that nestles on the surface of intraperitoneal organs
• Has key biological functions in immune-regulation and tissue regeneration
• Two parts: greater omentum and lesser omentum

Greater Omentum

• Attaches to:
  • Greater curvature of stomach
  • Left lobe of pancreas
  • Proximal end of descending colon
  • Distal end of ascending colon
  • Mesentric root
  • Spleen
• Ligaments that originate from the greater omentum:
  • Lig.phrenicolienale (phrenicosplenic lig.)
  • Lig.gastrolienale (gastrosplenic lig.)
  • Lig.gastrophrenicum
  • Lig.lienorenale (in horse)

Lesser Omentum

• Attaches to:
  • Lesser curvature of stomach
  • Cranial part of duodenum
  • Visceral surface of liver
• Ligaments that originate from the lesser omentum:
  • Lig.hepatogastricum
  • Lig.hepatoduodenale

Complex Composite Stomach in Ruminants

• Consists of four compartments: rumen, reticulum, omasum, and abomasum

Rumen

• Largest stomach compartment in ruminants
• Located on the left side of the abdomen
• Divided into several portions by inflections of the wall known as pila
• Function: stores food that is regurgitated, chewed again, and swallowed a second time
• Compartments:
  • Sulcus longitudinalis dextra (right longitudinal groove)
  • Sulcus longitudinalis sinistra (left longitudinal groove)
  • Saccus dorsalis (dorsal sac)
  • Saccus ventralis (ventral sac)
  • Saccus caecus caudodorsalis (caudodorsal blind sac)
  • Saccus caecus caudoventralis (caudoventral blind sac)
  • Saccus cranialis (atrium ruminis)

Reticulum

• Non-glandular part of the stomach
• Spherical shape, smallest compartment
• Located between the cranial surface of the rumen and the caudal surface of the diaphragm
• Two surfaces: diaphragmatic and visceral
• Feature: inner side of reticulum wall is honeycomb-like cellulae reticuli formed by crista reticuli in the reticula mucosa

Omasum

• Globe-shaped structure containing leaves of tissue (like pages in a book)
• Function: absorbs water and other substances from digestive contents
• Compartments:
  • Ostium reticulo-omasicum
  • Ostium omaso-abomasicum

Abomasum

• Simple columnar epithelium
• Gastric glands are present in the lamina propria of the mucosal layer in the pyloric region
• Similar to a non-ruminant stomach
• Located in the right front quadrant of the abdomen, just inside the seventh through 11th ribs
• Features:
  • Plicae spirales (large plica) in mucosal surface
  • Greater curvature: ventrally
  • Lesser curvature: dorsally
  • Fundus: in the xiphoid region
  • Body: in the midline
  • Pylorus: in the 9th-10th intercostal space
  • Torus pyloricus (in ruminant) is instead of the pyloric sphincter of the dog and horse