Principles of Histological Differentiation of Stomach Regions
On a histological slide, the cardiac, fundic, and pyloric regions can be distinguished by three main diagnostic criteria. These are the key features to focus on when examining sections:
- Depth of gastric pits — the ratio of the pit depth to the total thickness of the mucosa.
- Degree of glandular branching — how extensively the terminal portions branch.
- Cellular composition — the ratio of main cell populations (chief cells, parietal cells, mucous cells, and enteroendocrine cells).
Cardia and the Esophageal Transition
The cardiac region represents the junction between the esophagus and the stomach. A sharp transition of tissue structures is clearly visible here on a histological slide.
The epithelial lining changes abruptly: the stratified squamous non-keratinized epithelium of the esophagus transitions into simple columnar glandular epithelium of the stomach. The surface relief becomes irregular due to the appearance of gastric pits, which occupy about 25% of the mucosal thickness in the cardia.
In the lamina propria of the gastric mucosa, cardiac glands are densely packed as simple, branched, tubular structures. Their exocrine cells are primarily represented by pale mucous cells producing a mucous secretion. The muscularis mucosae thickens from a single layer of myocytes (in the esophagus) to three. A crucial distinguishing feature: the submucosa of the stomach lacks glands (whereas the esophagus contains proper complex alveolar-tubular glands there). The muscularis externa of the stomach acquires a third, additional oblique layer.
Diagnostic Triad of the Pyloric Region
The pyloric part of the stomach has distinct morphological features that form a classic diagnostic triad:
- Deep pits: Unlike other regions, the gastric pits here are very deep, penetrating 50–70% into the thickness of the mucosa.
- Glandular morphology: Pyloric glands are located in the lamina propria. They are highly branched and resemble "clusters" of short tubules with wide lumens. Unlike fundic glands, they lie more sparsely and are separated by prominent connective tissue septa.
- Cytology: The glands are mucous. Terminal portions are formed by pale cells — mucous cells (mucocytes). The nuclei of these cells are dense, flattened, and displaced toward the basal pole. On a slide, the terminal portions appear pale.
Additionally, the internal surface of the organ is lined by simple columnar glandular epithelium. Intramural nerve plexuses are present in the wall, and the muscular layer contains three layers of smooth muscle tissue, where the circular layer forms a thick pyloric sphincter.
Endocrine Apparatus of the Stomach
Cardiac and pyloric glands contain specialized enteroendocrine cells (cells with dark cytoplasm) that secrete hormones regulating gastrointestinal motility and secretion.
In the cardiac region, EC cells (serotonin and melatonin) and G cells predominate.
The endocrine apparatus of the pylorus is more diverse, preparing the digestive system for the intestinal phase:
- G cells ("open" type): Activated by food intake and low acidity. They secrete gastrin (stimulating HCl production in the fundus and body via the bloodstream) and enkephalin (local analgesia).
- P cells: Produce bombesin. They stimulate HCl secretion, pancreatic juice release, and gallbladder motility.
- D cells: Produce somatostatin, which inhibits GI activity (suppressing endocrine and exocrine functions).
- D1 cells: Secrete vasoactive intestinal peptide (VIP). They act as somatostatin antagonists, stimulate the pancreas, and cause systemic vasodilation and decreased blood pressure.