  The orbital angular momentum ($L_q$) of the proton is studied by employing
the extended constituent quark model. Contributions from different flavors,
namely, up, down, strange, and charm quarks in the proton are investigated.
Probabilities of the intrinsic $q\bar{q}$ pairs are calculated using a
$^{3}P_{0}$ transition operator to fit the sea flavor asymmetry
$I_a=\bar{d}-\bar{u}=0.118\pm0.012$ of the proton. Our numerical results lead
to $L_q=0.158 \pm 0.014$, in agreement with $4/3I_a=0.157 \pm 0.016$, and
consistent with findings based on various other approaches.
