This brief investigates the spectral efficiency of multiuser massive multiple-input multiple-output systems with a very large number of antennas at a base station serving single-antenna users. A practical physical channel model is proposed by dividing the angular domain into a finite number of distinct directions. A lower bound on the achievable rate of uplink data transmission is derived using a linear detector for each user and employed in defining the spectral efficiency. The obtained lower bound is further modified for the maximum-ratio combining and zero-forcing receivers. A power control scheme based on the large-scale fading is also proposed to maximize the spectral efficiency under peak power constraint. Experiments are conducted to evaluate the obtained lower bounds and the performance of the proposed method. The numerical results show a comparison between the performances of both receivers along with the advantage of the proposed power control scheme in terms of the spectral efficiency.