Principles of histological differentiation of the regions
On a histological slide, the cardia, fundus, and pylorus can be distinguished by three main diagnostic criteria. These are what should be focused on when examining sections:
- Depth of gastric pits — the ratio of the pit depth to the total mucosal thickness is assessed.
- Degree of branching of the glands — how extensively the terminal portions branch.
- Cellular composition — the ratio of the main cell pools (chief cells, parietal cells, mucous mucocytes, and endocrinocytes).
Cardia and the esophagogastric junction
The cardiac zone represents the junction between the esophagus and the stomach. On a histological slide, the boundary of an abrupt shift in tissue structures is clearly visible here.
The epithelial lining changes abruptly: the stratified squamous non-keratinized epithelium of the esophagus transitions into the simple columnar glandular epithelium of the stomach. The surface relief becomes uneven as gastric pits appear, which in the cardia occupy approximately 25% of the mucosal thickness.
In the lamina propria of the gastric mucosa, cardiac glands are densely packed as simple, branched, tubular structures. Their exocrinocytes are represented mainly by light mucocytes 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 in the esophagus it contains proper compound alveolar-tubular glands). The muscular coat 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 the classic diagnostic triad:
- Deep pits: Unlike other regions, the gastric pits here are very deep and penetrate 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 are spaced more sparsely and separated by prominent connective tissue septa.
- Cytology: The glands are mucous. The terminal portions are formed by light cells — mucocytes. The nuclei of these cells are dense, flattened, and displaced to the basal pole. On the slide, the terminal portions appear light.
In addition, the internal surface of the organ is lined with a simple columnar glandular epithelium. Intramural nerve plexuses are present in the wall, and the muscular coat contains three layers of smooth muscle tissue, where the circular layer forms a powerful pyloric sphincter.
Endocrine system of the stomach
In the cardiac and pyloric glands, specialized endocrinocytes (cells with dark cytoplasm) are present, which secrete hormones regulating gastrointestinal motility and secretion.
The cardiac region is dominated by EC cells (serotonin and melatonin) and G cells.
The endocrine system of the pylorus is more diverse and prepares the digestive system for the intestinal phase:
- G cells ("open" type): Activated upon food intake and low acidity. They secrete gastrin (stimulating HCl production in the fundus and body of the stomach via the bloodstream) and enkephalin (local analgesia).
- P cells: Produce bombesin. They stimulate HCl secretion, pancreatic juice secretion, and gallbladder motility.
- D cells: Produce somatostatin, which inhibits GI tract activity (suppressing endocrine and exocrine functions).
- D1 cells: Secrete vasoactive intestinal peptide (VIP). They act as antagonists to somatostatin, stimulate the pancreas, and cause systemic vasodilation and a drop in blood pressure.
Briefly: answers to topical questions
What is the morphological difference between pyloric and fundic glands?
The morphological difference between pyloric and fundic glands lies in the shape of their terminal portions, their packing density, and their cellular composition.
| Characteristic | Pyloric glands | Fundic glands |
|---|---|---|
| Shape | Highly branched ("clusters" of short tubules) | Simple tubular, virtually unbranched (long straight tubules) |
| Lumen | Wider | Narrow |
| Organization | Separated by connective tissue layers, spaced more sparsely | Packed densely |
| Cellular composition | Mucous (mucocytes), chief cells almost absent, parietal cells absent | Contain all cell types (including chief and parietal) |
| Staining on the slide | Pale | Basophilic and oxyphilic |
What is the function of chief and parietal cells of the stomach?
The function of chief and parietal cells is to secrete the components of gastric juice.
- Chief cells — synthesize pepsinogen (an inactive form that converts into pepsin), and also produce chymosin and lipase.
- Parietal cells — secrete hydrochloric acid components (H⁺ and Cl⁻ ions) and produce intrinsic factor (Castle's intrinsic factor), which is necessary for vitamin B₁₂ absorption.
For rapid identification of the region on a histological slide: "Cardia — shallow pits (1/4), pylorus — deep pits (greater than 1/2)".
Class and exam questions
How does the esophageal epithelium differ from the gastric epithelium at the transition zone?
In the cardiac zone, an abrupt change in the lining occurs: the stratified squamous non-keratinized epithelium of the esophagus borders the simple columnar glandular epithelium of the stomach.
Where are glands located in the esophagus and the stomach?
Proper compound mucous glands of the esophagus lie in its submucosa. In the stomach (both in the cardia and the pylorus), the glands are located strictly within the lamina propria of the mucosa.
What is the function of G cells and where are they located?
G cells are found in the cardiac and pyloric glands. They produce gastrin, which is delivered via the bloodstream to the glands of the gastric body and stimulates the production of hydrochloric acid (HCl).
What is the morphological appearance of mucous cells in the pyloric glands?
These are light cells with wide lumens in their terminal portions. Their nuclei are dense, strongly flattened, and displaced to the basal pole of the cell by the accumulating mucous secretion.
What else to study on this topic
- Cytophysiology of mucocytes: synthesis and secretion of mucus
- Histoarchitectonics of the muscular coat and formation of the pyloric sphincter
- Organization of intramural nerve plexuses of the stomach
- Differences between cardiac glands of the stomach and cardiac glands of the esophagus
- Mechanism of action of gastrin on parietal cells of fundic glands
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