Which stomach compartment in ruminants is known as the true "stomach"?

The abomasum is referred to as the true "stomach" in ruminants because it functions similarly to the stomach of non-ruminant animals, such as humans. It is responsible for the secretion of gastric juices, including hydrochloric acid and digestive enzymes, which break down proteins and facilitate the digestion of food.

In ruminants, the digestive system is uniquely adapted for processing fibrous plant material, and it consists of four compartments: the rumen, reticulum, omasum, and abomasum. The rumen and reticulum are primarily involved in fermentation and the initial breakdown of food through microbial action, while the omasum acts to absorb water and some nutrients. However, it is the abomasum that is the site of enzymatic digestion, allowing for nutrient absorption similar to that found in simpler stomachs.

This distinction highlights the abomasum's crucial role in the overall digestive process of ruminants, where it serves the function necessary for nutrient breakdown and absorption following the fermentation in the earlier compartments.