What part of the digestive system is part of the first line of defence against attack by pathogens? Give the full name, not the symbols.

The part of the digestive system that serves as the first line of defense against attacks by pathogens is the stomach.

The stomach plays a crucial role in the digestive process, but it also has significant protective functions. Its acidic environment, with a pH typically between 1.5 and 3.5, creates a hostile environment for many microorganisms that may enter the body through ingested food or liquids. This high acidity helps to kill bacteria and other pathogens before they can enter the intestines, where they could potentially cause infection or disease. Additionally, the stomach produces digestive enzymes that further aid in breaking down food and neutralizing harmful substances.

Furthermore, the stomach's mucosal lining secretes mucus, which helps protect its walls from the harsh acidic environment while also providing an additional barrier against pathogens. Overall, the stomach is a vital component of both the digestive and immune systems, acting as a barrier to infection in the gastrointestinal tract.