What is the stomachs job?
1. Food Storage: The stomach acts as a temporary storage container for ingested food. As food enters the stomach from the esophagus, it begins to expand to accommodate the incoming volume.
2. Mechanical Digestion: The stomach initiates mechanical digestion by churning and mixing the food thoroughly. This process is made possible by the strong muscular walls of the stomach. The contractions of these muscles create a churning motion that physically breaks down the food into smaller pieces.
3. Secretion of Gastric Juices: The stomach secretes various digestive juices, primarily gastric juice, to aid in chemical digestion. These juices contain important components such as hydrochloric acid (HCl) and enzymes, including pepsin.
a. Hydrochloric Acid (HCl): HCl creates an acidic environment in the stomach. This acidic pH is necessary for the activation of pepsin and also helps to kill most ingested bacteria, providing an important antibacterial function.
b. Pepsin: Pepsin is the primary enzyme secreted by the stomach. It becomes active in the acidic environment and plays a major role in breaking down proteins into smaller peptides.
4. Gastric Mixing and Motility: The stomach muscles not only help with physical breakdown but also mix the food with the digestive juices. This constant mixing creates a semi-liquid substance known as 'chyme,' which contains partly digested food particles.
Peristaltic contractions then occur, which are wave-like muscle movements that propel the chyme toward the small intestine.
5. Absorption: Although absorption primarily occurs in the small intestine, a small amount of water, certain drugs, and alcohol can be absorbed through the stomach directly into the bloodstream.
As the food is continuously mixed and broken down in the stomach, it gradually moves towards the pyloric valve, which is a muscular ring at the lower end of the stomach. When the chyme reaches a suitable consistency and composition, the pyloric valve opens, allowing it to pass into the small intestine for further digestion and absorption of nutrients.