20 Questions
What are the components of the gastric mucosa?
The components of the gastric mucosa include epithelium, lamina propria, and muscularis mucosa.
What is the function of the parietal cells in the stomach?
Parietal cells secrete hydrochloric acid (HCL) and intrinsic factor for B12 absorption.
What do chief cells in the stomach secrete?
Chief cells secrete pepsinogen, which is activated to pepsin with the help of HCL.
Describe the organization of the muscularis externa in the stomach.
The muscularis externa consists of three layers of muscles: an inner oblique layer, a middle circular layer, and an outer longitudinal layer.
What is the main cell type found in the gastric glands?
The main cell type found in the gastric glands are simple columnar epithelial cells.
What is the role of the lamina propria in the stomach?
The lamina propria is a very cell-rich loose connective tissue that supports the mucosa with various cell types like fibroblasts, lymphocytes, and macrophages.
What are the three layers of muscles that make up the muscularis externa in the stomach?
Inner oblique layer, middle circular layer, outer longitudinal layer
What is the function of the simple columnar epithelium in the stomach mucosa?
Secrete bicarbonate-buffered mucus
What is the role of chief cells in the stomach glands?
Secrete pepsinogen (activated to pepsin with HCL)
Which stomach hormone stimulates chief cells to secrete pepsinogen?
Gastrin
Describe the appearance of the gastric pits on the mucosal surface of the stomach.
Small, funnel-shaped depressions
What is the main component of the lamina propria in the stomach?
Cell-rich loose connective tissue
What type of muscle cells are found in the muscularis mucosae of the stomach?
Both circular and longitudinal muscle cells
What is the function of parietal cells in the stomach glands?
Secrete HCL & Intrinsic factor (for B12 absorption)
Describe the structural features of the small intestine mucosa that increase the luminal surface area.
Plicae circulares and intestinal villi with microvilli
What is the role of plicae circulares in the small intestine?
Increase luminal surface area
How do microvilli contribute to the function of the small intestine?
Increase surface area for absorption
What is the function of enterocytes in the small intestine epithelium?
Absorption of degraded food components
Explain the importance of the simple columnar epithelium in the small intestine villi.
Forms the surface of the villi
How do the structural features of the small intestine mucosa support its main function?
By increasing the surface area for absorption
Study Notes
Stomach Wall Layers
- Histologically, most layers of the stomach wall appear similar in different parts, with regional differences mainly restricted to the gastric mucosa.
Mucosa
- The mucosa is thrown into longitudinal folds (gastric folds or rugae) that disappear when the stomach is fully distended.
- A network of shallow grooves divides the mucosa into gastric areas.
- The mucosal surface has small, funnel-shaped depressions (gastric pits).
- Almost the entire mucosa is occupied by simple, tubular gastric glands that open into the bottom of the gastric pits.
- Simple columnar epithelium secretes bicarbonate-buffered mucus.
Gastric Glands
- Parietal cells secrete HCL and intrinsic factor (for B12 absorption).
- Chief cells secrete pepsinogen (activated to pepsin with HCL) and are stimulated by gastrin, a stomach hormone.
Lamina Propria
- The lamina propria is formed by a very cell-rich loose connective tissue (fibroblasts, lymphocytes, plasma cells, macrophages, eosinophilic leukocytes, and mast cells).
Muscularis Mucosae
- The muscularis mucosae of the stomach contains both circular and longitudinal layers of muscle cells, with variable organization depending on the location in the stomach.
Muscularis Externa
- The muscularis externa consists of three layers of muscles: an inner oblique layer, a middle circular layer, and an outer longitudinal layer.
Small Intestine
- The small intestine is divided into duodenum (25-30 cm), jejunum (about first two-fifths of the rest), and ileum.
- The three segments have the same basic histological organization.
Small Intestine Mucosa
- The mucosa of the small intestine has structural features that increase the luminal surface area for absorption.
- Plicae circulares (of Kerckring) are macroscopically visible, crescent-shaped folds of the mucosa and submucosa.
- The entire intestinal mucosa forms intestinal villi (about 1 mm long), increasing the surface area by a factor of ~ ten.
- The surface of the villi is formed by a simple columnar epithelium.
- Each absorptive cell or enterocyte of the epithelium forms numerous microvilli (1 µm long and about 0.1 µm wide), increasing the surface area by a factor of ~ 20.
Test your knowledge on the histological features of the different layers of the stomach wall, focusing on the regional differences in the gastric mucosa. Explore the structure of the mucosa including epithelium, lamina propria, and muscularis mucosa.
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