We calculate the transient dynamic response of human finger skin and the distribution of the strain energy density at the tactile receptors focusing on the effect of epidermal ridges on tactile sensation. Using a FE (finite element) model which we create from geometric and material properties measured from an actual human index finger, we introduce a method of dynamic contact analysis which we use to analyze the dynamic contact between a finger with/without epidermal ridges and an object with/without surface roughness. It is found that the epidermal ridges increase the sensitivity of the tactile receptors. The presence of epidermal ridges change either the distribution pattern or the amplitude of the strain energy density at the tactile receptors. It is also found that the Meissner's corpuscles are relatively sensitive for detecting the surface roughness, whereas Merkel's discs are relatively sensitive for detecting indentations in objects.