They provide the apicobasal polarity of tubular cells and regulate the paracellular flux of molecules between urine and interstitium.

A lexicon can therefore be said to correspond more to a dynamic system of relations: a) syntagmatic sense relations between lexical units in the same string, ie philonymy, xenonymy, tautonymy; b) paradigmatic sense relations between lexical units occurring in a given combination, and a set of possibilities provided by the language...

Why then is this thin slice of something wedged between volumes of nothing called a something instead of a nothing sandwich?

This is not an unusual situation since some acquisition vehicles are newcos that have not conducted any business activities prior to the acquisition.