Abdomen Anatomy and Digestive System

Peritoneal Cavity Algorithm

  • Parietal Peritoneum: Lines the abdominal wall.
  • Mesentery: Fold back and creates attachments, connecting organs to the posterior abdominal wall (mesentric proper).
    • Contains blood vessels and nerves that supply the intestines.
    • The mesentery proper specifically supports the small intestine.
  • Greater Omentum: Doesn't cover any structure, nor does it attach to the posterior abdominal wall (not visceral or parietal).
    • Rich in fat and immune cells.
    • Contributes to immune response within the peritoneal cavity.

Abdominal Exploration

  • Upon opening the abdomen, the small intestine is initially covered by a sheath-like structure (greater omentum) hanging from the transverse colon.
    • The greater omentum can vary in size and fat content among individuals.
  • To view the small intestine, the greater omentum must be lifted.
  • The mesentery proper attaches the small intestine to the posterior abdominal wall.

Greater Omentum

  • The greater omentum doesn't line the abdominal wall (not parietal).
  • It also doesn't cover the structures (not visceral) in the way a visceral peritoneum would.
    • Can move within the peritoneal cavity to areas of inflammation or injury.

Esophagus and Sphincters

  • Esophagus passes the diaphragm through the esophageal hiatus.
  • Upper Esophageal Sphincter: Located between the pharynx and esophagus.
    • Prevents air from entering the esophagus during breathing.
  • Lower Esophageal Sphincter: Located at the distal end of the esophagus.
    • Prevents stomach acid from refluxing into the esophagus.

Sphincters

  • Upper esophageal sphincter is found at the junction of the pharynx and esophagus.
    • Consists of cricopharyngeus muscle.
  • Lower (or inferior) esophageal sphincter is the lower end of the esophagus.
    • Not a true anatomical sphincter but a physiological one.
  • Pyloric canal leads to the pyloric orifice.
  • Pyloric orifice contains a pyloric sphincter.
    • Controls the emptying of chyme from the stomach into the duodenum.

Stomach Expansion

  • When food accumulates in the stomach (antrum), expansion primarily occurs towards the left side.
  • The liver, located on the right side, is a large, solid organ that resists being pushed.