Anatomy of the Stomach

Overview

• Location: Upper left quadrant of the abdominal pelvic region
• Main Function: Temporary storage of food, minimal digestion leading to kime formation

Gross Anatomy

• Regions of the Stomach:

  • Cardia: Area where esophagus meets the stomach
  • Fundus: Dome-shaped region beneath the diaphragm
  • Body: Central region of the stomach
  • Pyloris: Terminal region leading to the small intestine
    • Antrum: Superior part with folds called rug for stretchability
    • Pyloric Canal: Leads to the pyloric sphincter

• Curvatures of the Stomach:

  • Greater Curvature: Lateral surface
  • Lesser Curvature: Concave region

• Mesenteries:

  • Lesser Omentum: From liver to lesser curvature
  • Greater Omentum: Covers small intestines, spleen, transverse colon

Functionality & Physiology

• Stomach Capacity: Holds up to 4 liters due to tissue compliance
• Gastric Movement: Controlled release to duodenum via rhythmic contractions
• pH Environment:
  • Stomach: Highly acidic
  • Duodenum: Neutral pH for enzyme activity

Microscopic Anatomy

• Stomach Layers: Four basic tunics

  • Muscularis Externa: Unique third oblique layer for mechanical breakdown
  • Mucosa: Alkaline mucus secretion to protect against acid

• Gastric Pits & Glands:

  • Parietal Cells: Secrete HCl, denature proteins, activate pepsinogen
  • Chief Cells: Secrete pepsinogen and lipases
  • Enteroendocrine Cells: Secrete hormones like serotonin, histamine, gastrin

Defense Mechanisms

• Mucosal Barrier: Thick bicarbonate-rich mucus layer
• Epithelial Protection: Tight junctions and rapid cell turnover every 3 to 6 days

Pathologies

• Gastritis: Inflammation due to mucosal breaches
  • Causes:
    • Bacterial Infection: Helicobacter pylori disrupting mucosal layer
    • Medication Overuse: NSAIDs like ibuprofen

Autonomic Nervous System & Blood Supply

• Sympathetic & Parasympathetic Inputs
• Blood Supply: Celiac trunk, gastric, and splenic branches
• Venous Drainage: Hepatic portal system

These notes provide an overview of the stomach's gross and microscopic anatomy, explaining its main functions, structural components, and its protective mechanisms against the harsh acidic environment.