Saliva — the gatekeeper at the entrance to the gastrointestinal tract — a remarkable biofluid, its proteins, and the upper part of the alimentary tract

Saliva, a seemingly unpretentious secretion, is actually a multifaceted and multipurpose biofluid. Performing numerous functions, far exceeding only lubrication of oral mucosa, it is essential for general health. Saliva's remarkable properties are primarily due to its constituents, mainly peptides and proteins. Excreted at the entrance to the gastrointestinal tract, this biofluid-active in the oral cavity-also affects other sections of the canal alike, particularly esophagus, where its active components do not undergo degradation. Animal models employing sialoadenectomy consistently with clinical data of patients afflicted with issues related to insufficient salivation, clearly demonstrate how indispensable proper saliva secretion is. In this paper we briefly summarize current perspectives on saliva, with a focus on its protein components and its impact on the upper part of the alimentary tract, particularly on oral and esophageal mucosa. The practical aspects of the modern proteomic research of saliva being at the forefront of salivaomics progress are also discussed, and the current state-of-the-art proteomic methodology is outlined.