Põhirakud

Põhirakud, also known as chief cells, are a type of cell found in the gastric glands of the stomach. Their primary function is to secrete pepsinogen, which is an inactive precursor to the enzyme pepsin. Pepsin is crucial for the digestion of proteins in the stomach. Põhirakud are typically located in the deeper portions of the gastric glands, often in the lower half. They are characterized by their basophilic cytoplasm, which is due to the abundant ribosomes involved in protein synthesis. The cells contain prominent granules that store pepsinogen.

When stimulated, põhirakud release pepsinogen into the stomach lumen. In the acidic environment of the stomach, pepsinogen is converted into its active form, pepsin. This conversion is initiated by the presence of hydrochloric acid, which is secreted by parietal cells, another cell type in the gastric glands. Pepsin then begins the process of breaking down large protein molecules into smaller peptides.

The secretion of pepsinogen by põhirakud is regulated by various factors, including hormonal signals and neural pathways. For example, the hormone gastrin stimulates both acid secretion by parietal cells and pepsinogen secretion by põhirakud. Vagal stimulation also plays a role in regulating their activity. The continued production and secretion of pepsinogen by põhirakud are essential for efficient protein digestion and overall gastrointestinal health.