Obstructive sleep apnea syndrome (OSAS) is referring to partial or complete cessation of airflow during sleep due to upper pharyngeal airway collapse. Snoring is often associated to such sleep-induced apnea as the result of the strong coupling and interaction between the respiratory airflow and the flexible tissue of the upper airway, resulting in self-excited oscillations of the soft tissue. It can occur at the level of the soft palate but also at the lower level of the pharyngeal airway. The knowledge of the tissue behavior subject to a particular airway flow is relevant for understanding the underlying physical mechanism of OSA. However, in-vivo measurements are usually not practical. A 3D fluid-structure interaction model for the human uvula-palatal system relevant to OSAS based on simplified geometries is utilized in the present study. Numerical simulations are performed to assess the influence of gravity and the rigidity of the soft tissue on the oscillatory dynamics. Meanwhile, the vortex dynamics and the structural modal frequency response are investigated for the coupled fluid-structure system as well.