Name the 2 sphincters of the stomach
- LES
2. Pyloric
What are the 4 main regions of the stomach?
- Cardia
- Fundus
- Body
- Pylorus (Pyloric antrum + Pyloric canal)
What are the 3 layers of the Muscularis Mucosa
- Outermost Longitudinal Layer
- Middle Circular Layer
- Innermost Oblique Layer
What is the role of Prostaglandins?
They play an important role in protecting the stomach mucosa from injury by enhancing mucus production
The stomach lining or mucosa is usually impermeable to what? Why is this important?
To the gastric juices it secretes, a property that allows the stomach to contain acid and enzymes without having its wall digested.
What is the most important factor contributing to the protection of the stomach lining or gastric mucosa
The layer of alkaline mucous –> Gastric Mucosal Barrier
What type of epithelium makes up the mucosal surface of the stomach?
Simple Columnar Epithelium
What do Mucous neck cells do?
Secrete alkaline mucous
What do parietal cells do?
Secrete HCl & Intrinsic Factor (IF)
What do Chief cells do?
Secrete Pepsinogen & Gastric Lipase
What do endocrine cells do in the stomach mucosa
Some secrete gastrin (G cells)
Others secrete histamine (ECL cells)
How much gastric juice is released daily by gastric glands?
2500 mL
What 3 roles does the HCl have when secreted by the Parietal cells
- Kills many ingested bacteria
- Aids protein digestion
- Stimulates the flow of bile and pancreatic juice
Name 4 things that may disrupt the stomach barrier and cause gastric injury/irritation
- Ethanol
- Bile salts
- NSAIDS
- H. pylori
4 main functions of the stomach
- Temporarily stores ingested liquids and solids until they are released into the small intestines
- Mechanical Digestion - Stomach churns food into chyme
- Secretes gastric juice that is involved in chemical digestion
- Secretes hormones gastrin and histamine
What nerve stimulates gastric juice secretion and what action causes the nerve to work?
Vagus nerve
When food is being chewed in the mouth or with the sight, smell or thought of food
What three actions make up the cephalic phase of the regulation of gastric secretion and motility?
- Vagus nerve weakly stimulates gastric juice secretion when food is chewed in mouth or with sight, smell, or thought of food
- Vagus nerve stimulates gastrin secretion from the enteroendocrine cells of the gastric glands
- Gastrin further stimulates secretion of gastric juice
Vagus nerve stimulates gastrin secretion from what cells?
Enteroendocrine cells of gastric glands
What does gastrin do?
Further stimulates secretion of gastric juice
When does the gastric phase in regulation of gastric secretion and motility?
Begins when food reaches the stomach
What three actions make up the gastric phase os the regulation of gastric secretion and motility?
- Distention of the stomach and protein digestion products (AA) stimulate gastrin secretion and hence more gastric juice secretion (positive feedback loop)
- Vagus nerve also continues to stimulate gastrin release and gastric motility
- Elevated levels of gastrin stimulate the release of histamine, which in turn increases HCl secretion from parietal cells.
When acidic chyme enters the duodenum it stimulates the secretion of what 3 hormones?
Cholecystokinin
Secretin
Gastric inhibitory peptide
What do the 3 hormones that are stimulated as chyme enters the duodenum do?
They inhibit gastric juice secretion
GIP also inhibits gastric motility
Why is the control of chyme leaving the stomach and entering the duodenum critical? (2)
- So that the duodenum does not become too full (especially with acid)
- So that the small intestine can adequately process the incoming chyme
