Gastric juices

Gastric juices are a crucial component of the digestive system, responsible for the chemical breakdown of food in the stomach. Composed of water, hydrochloric acid, enzymes, and electrolytes, these juices play a pivotal role in digestion and absorption of nutrients.

Composition

Gastric juices are primarily made up of:

• Water - Serves as a medium for the substances in the juice.
• Hydrochloric Acid (HCl) - Creates an acidic environment (with a pH ranging from 1.5 to 3.5), which is necessary for the activation and function of the digestive enzyme pepsin. It also helps in killing bacteria and other pathogens ingested with food.
• Enzymes - The most important enzyme in gastric juice is pepsin, which breaks down proteins into smaller peptides. Other enzymes include gastric amylase and lipase, although they play a minor role in digestion within the stomach.
• Electrolytes - Such as sodium, potassium, calcium, and bicarbonate, are also present and play various roles in the digestive process and maintaining the pH balance.

Function

The primary function of gastric juices is to initiate the digestion of proteins by denaturing them and breaking them down into smaller peptides. This is facilitated by the enzyme pepsin, which is activated from its inactive form, pepsinogen, in the presence of hydrochloric acid. Gastric juices also help in:

• Making the food into a semi-liquid form, known as chyme, facilitating its movement into the small intestine.
• Killing harmful bacteria and pathogens ingested with food, thus preventing infections.
• Absorbing certain medications and nutrients, such as vitamin B12, directly through the stomach lining.

Regulation

The secretion of gastric juices is regulated by the nervous system and hormones. The sight, smell, or thought of food can trigger the vagus nerve to stimulate the secretion of gastric juices, a phase known as the cephalic phase. Once food enters the stomach, the gastric phase begins, further stimulating the production of gastric juices. Finally, the intestinal phase regulates the secretion as the chyme enters the small intestine, ensuring the proper balance of digestive juices for optimal digestion and absorption.

Clinical Significance

Disorders related to gastric juices, such as peptic ulcer disease and gastritis, can lead to significant discomfort and health issues. Excessive or reduced secretion of gastric juices can disrupt the digestive process, leading to symptoms like heartburn, nausea, and indigestion. Treatment for such conditions often involves regulating the production of gastric juices, either by medication that reduces acid production, such as proton pump inhibitors, or by lifestyle changes that can help manage the symptoms.