The stomach plays a crucial role in digestion, with four primary functions that facilitate the breakdown of food.
Here's a breakdown of the stomach's four key functions:
-
Reservoir Function: The stomach acts as a temporary storage area for ingested food, allowing us to eat meals at intervals rather than constantly. It gradually releases the contents into the small intestine at a controlled rate, preventing the small intestine from being overwhelmed.
-
Acid Secretion: Specialized cells in the stomach lining, called parietal cells, secrete hydrochloric acid (HCl). This acidic environment (pH 1.5 to 3.5) is essential for several reasons:
- It denatures (unfolds) proteins, making them more accessible to digestive enzymes.
- It kills many bacteria and other microorganisms ingested with food, protecting the body from infection.
- It activates pepsinogen into pepsin, a key enzyme for protein digestion (explained below).
-
Enzyme Secretion: The stomach secretes various enzymes, most notably pepsin, which is secreted as an inactive zymogen called pepsinogen. Pepsin is crucial for breaking down proteins into smaller peptides. Other enzymes, such as gastric lipase, play a minor role in fat digestion.
-
Gastrointestinal Motility (Mixing and Emptying): The stomach's muscular walls contract and churn the food, mixing it with gastric juices to form a semi-liquid mixture called chyme. These contractions also help to propel the chyme towards the pyloric sphincter, which regulates the emptying of the stomach contents into the duodenum (the first part of the small intestine). The rate of gastric emptying is carefully controlled to allow for proper digestion and absorption in the small intestine.
| Function | Description | Importance |
|---|---|---|
| Reservoir | Stores ingested food temporarily. | Allows for intermittent eating patterns and controlled release of food into the small intestine. |
| Acid Secretion | Secretes hydrochloric acid (HCl). | Denatures proteins, kills bacteria, and activates pepsin. |
| Enzyme Secretion | Secretes enzymes like pepsin (as pepsinogen) and gastric lipase. | Pepsin breaks down proteins; gastric lipase assists in fat digestion. |
| Gastrointestinal Motility | Mixes food with gastric juices and propels chyme into the small intestine through controlled contractions. | Facilitates digestion and absorption by creating chyme and regulating the rate at which it enters the small intestine. |
In summary, the stomach serves as a reservoir, secretes acid and enzymes, and utilizes gastrointestinal motility to efficiently digest food before it enters the small intestine.
