The gastric mucosa is the innermost layer of the stomach lining, composed of epithelial cells that secrete mucus, enzymes, and gastric acid. This layer plays a crucial role in digestion by protecting the stomach walls from the harsh acidic environment and aiding in the breakdown of food. Additionally, the gastric mucosa contains specialized cells, such as parietal cells, which produce hydrochloric acid, and chief cells, which secrete digestive enzymes. The health of the gastric mucosa is vital for proper digestion and overall stomach function, as damage to this layer can lead to conditions like gastritis or ulcers.