Stomach acid production begins with the anticipation of food and is further stimulated by the presence of food itself.
The Initial Phase: Anticipating Food
The process of stomach acid secretion starts even before food enters the stomach.
- Vagal Stimulation: The mere thought, smell, or taste of food triggers the vagus nerve, which stimulates gastrin-secreting G cells.
- Location of G cells: These G cells are located in the distal one third (antrum) of the stomach.
The Second Phase: Food in the Stomach
Once food arrives in the stomach, acid secretion is further increased.
- Protein Stimulus: Specifically, the presence of protein in the stomach further boosts the output of gastrin from the G cells.
Summary of the Process
| Stage | Trigger | Action |
|---|---|---|
| Initial | Thought, smell, or taste of food | Vagal stimulation of G cells in the stomach antrum |
| Secondary | Presence of protein in the stomach | Increased gastrin output from G cells |
In essence, stomach acid production is a two-step process. It's first initiated by the nervous system's response to food cues and then amplified by the physical presence of food, particularly protein, in the stomach.
