Metabolic pathways are defined for groups of substances (metabolites) that are interconverted by a corresponding group of enzymes. Conceptually, they start with one substance (glucose, say) and end with another (carbon dioxide). However, there is no reason why they shouldn't be connected in a circle rather than an arrow, as is the case for the TCA cycle.

A  -> B ->  C -> D -> E pathway

            F   <-   E <
          /              \
           A            D
         \               / 
            B  -> C     

Naturally, the whole of the cell is part of one large metabolic net consisting of many pathways that intertwine and mix. This is the basis behind the concept of autopoesis - that the cell is catalytically closed. One large cycle.