Which cell type is not found in gastric pits?
a) Mucous
b) Brush border
c) Zymogen
d) Parietal
The Correct Answer and Explanation is:
The correct answer is b) Brush border.
Explanation:
Gastric pits are small invaginations found in the lining of the stomach that contain various types of cells responsible for gastric secretions. These cells include mucous cells, zymogen cells (also known as chief cells), and parietal cells, each contributing to the digestive process in the stomach.
- Mucous Cells: Located in the gastric pits, mucous cells secrete mucus, which plays a crucial role in protecting the stomach lining from the acidic environment created by gastric acid (hydrochloric acid). The mucus forms a protective barrier that prevents erosion of the gastric epithelium and helps lubricate food as it passes through the stomach.
- Zymogen Cells (Chief Cells): These cells are responsible for the secretion of digestive enzymes, specifically pepsinogen, which is an inactive precursor of the enzyme pepsin. Once pepsinogen is secreted into the gastric lumen, it is activated by the acidic environment of the stomach into pepsin, facilitating protein digestion.
- Parietal Cells: Found in the gastric pits, parietal cells are crucial for the secretion of hydrochloric acid (HCl) and intrinsic factor. HCl creates an acidic environment necessary for enzyme activation and helps in the breakdown of food. Intrinsic factor is essential for the absorption of vitamin B12 later in the digestive tract.
- Brush Border Cells: In contrast to the aforementioned cell types, brush border cells are not found in gastric pits. Instead, they are located in the small intestine, specifically in the microvilli of the intestinal epithelium. Brush border cells are characterized by their microvilli, which increase the surface area for absorption and contain enzymes that aid in the final stages of digestion, such as disaccharidases and peptidases.
In summary, while gastric pits contain mucous, zymogen, and parietal cells, they do not contain brush border cells, which are specific to the small intestine and play a different role in digestion.