Exam #5: Gastric Secretions Flashcards
What are the secretory products of parietal cells? Where are these cells located?
Parietal cells secrete HCl & Intrinsic Factor
- HCl functions in protein digestion, sterilization, nutrient absorption
- Intrinsic Factor= Vitamin B absorption
**Parietal cells are located in the body of the stomach
What is the secretory product of chief cells? Where are these cells located?
Chief cells secrete pepsinogen, which functions in protein digestion
*****Chief cells are located in BOTH the body & antrum of the stomach
What are ECL cells? Where are these cells located? What is their product?
ECL, or “enterochromaffin-like” cells produce histamine, which promotes HCl secretion
*****ECL cells are located in the body of the stomach
What is the secretory product of G-cells? Where are these cells located?
G-cells produce gastrin, which promotes HCl secretion
What is the secretory product of D-cells? Where are these cells located?
D-cells produce somatostatin, which suppress HCl secretion
*****antrum of the stomach
What is the secretory product of superficial epithelial/ neck cells? Where are these cells located?
Mucous
Bicarbonate
*****Both are gastroprotective & cells are located throughout the entire stomach
How do neuronal pathways regulate acid secretion in the stomach?
ACh secretion
- promotion of mucous, bicarbonate, and HCl secretion
How do paracrine pathways regulate acid secretion in the stomach?
Histamine binding to receptors on parietal cells stimulates acid secretion
How do endocrine pathways regulate acid secretion in the stomach?
Gastrin binding to receptors on parietal cells stimulate acid secretion
What are the functions of gastric acid?
1) Protein digestion & conversion of pepsinogen to pepsin (for protein digestion)
2) Provide sterile environment
3) Prevent bacteria and fungal growth
4) Facilitate absorption
5) Promote bile and enzyme flow
What are the positive and negative regulators of gastric acid secretions?
Positive=
- ACh (neural)
- Histamine (ECL)
- Gastrin (G-cells)
Negative=
- Somatostatin (D-cells)
What cells release the positive regulators of gastric acid secretion?
Histamine= ECL Gastrin= G Neural= ACh
What cells release the negative regulators of gastric acid secretion?
D-cell secretion of somatostatin
Prostaglandins
Describe the steps of how pepsinogen is converted in lumen of the stomach to the active protease pepsin.
- Pepsinogen is secreted by chief cells in the body & antrum of the stomach.
- HCl converts pepsinogen into pepsin (active) i.e. lower pH
- This is protective and ensure that pepsinogen is activated once it is in the lumen of the stomach
- Higher pH inactivates the enzyme
*****ACh is a key stimulus in the secretion of pepsinogen
What is the site of intrinsic factor secretion?
Parietal cells secrete intrinsic factor in the body of the stomach
I.e. damage to parietal cells & the gastric epithelium will result in an inability to absorb Vitamin B12