The Fermi Gamma-Ray Space Telescope observations of blazars show a strong correlation between the spectral index of their -ray spectra and their synchrotron peak frequency synpk ;additionally, the rate of Compton dominance of these sources also seems to be a function of synpk .In this work, we adopt the assumption that the non-thermal emission of blazars is primarily due to radiation by a population of Fermi-accelerated electrons in a relativistic outflow (jet) along the symmetry axis of the blazar's accretion disc. Furthermore, we assume that the Compton component is related to an external photon field of photons, which are scattered from particles of the magnetohydrodynamic wind emanating from the accretion disc. Our results reproduce well the aforementioned basic observational trends of blazar classification by varying just oneparameter, namely the mass accretion rate on to the central black hole.