[en] The nature of phase transitions in hot and dense nuclear matter is discussed in the framework of the effective SU(2) Nambu – Jona-Lasinio model with a Polyakov loop with two quark flavor — one of a few models describing the properties of both chiral and confinement-deconfinement phase transitions. We consider the parameters of the model and examine additional interactions that influence the structure of the phase diagram and the positions of critical points in it. The effect of meson correlations on the thermodynamic properties of the quark-meson system is examined. The evolution of the model with changes in the understanding of the phase diagram structure is discussed.