The stomach plays a crucial role in the digestive process of animals. It acts as a storage organ for food and releases several substances that aid in digestion. When food enters the stomach, it undergoes mechanical and chemical digestion before being further broken down in the small intestine.

**Gastric Juice:**

The stomach lining contains gastric glands that secrete gastric juice, a mixture of various substances that aid in digestion. Gastric juice is composed of hydrochloric acid, pepsinogen, mucus, and intrinsic factor.

- Hydrochloric Acid: The stomach releases hydrochloric acid, which helps to break down food and creates an acidic environment in the stomach. It activates pepsinogen, an inactive enzyme, to its active form called pepsin. Hydrochloric acid also kills harmful bacteria that may be present in the food.
- Pepsinogen: Pepsinogen is an inactive enzyme that is converted into pepsin by hydrochloric acid. Pepsin is responsible for the digestion of proteins into smaller peptide fragments.
- Mucus: The stomach lining secretes mucus, which forms a protective layer to prevent the stomach from being damaged by the acidic gastric juice.
- Intrinsic Factor: Intrinsic factor is a glycoprotein that is essential for the absorption of vitamin B12 in the small intestine.

**Gastrin:**

Gastrin is a hormone released by the stomach in response to the presence of food. It stimulates the release of gastric juice and promotes the contraction of the stomach muscles, aiding in the mechanical digestion of food.

**Chyme:**

The stomach mixes the food with gastric juice, resulting in the formation of a semi-fluid mass called chyme. Chyme is then gradually released into the small intestine for further digestion and absorption.

**Conclusion:**

In summary, the stomach releases gastric juice, which contains hydrochloric acid, pepsinogen, mucus, and intrinsic factor. These substances aid in the digestion of food, particularly proteins, and create an acidic environment in the stomach. Additionally, the stomach releases the hormone gastrin, which stimulates the release of gastric juice and promotes muscle contractions. The resulting chyme is then passed into the small intestine for further digestion and absorption of nutrients.

Hydrochloric acid