Effect of electric current through the vital parts of human body depend on the duration, magnitude and frequency of this current. Most dangerous consequence could be ventricular fibrillation, a condition of inordinate action of main chambers of the heart, resulting in immediate arrest of blood circulation.
Currents at 50 Hz about 0.1 A can be lethal. But human can sustain larger currents at 25 Hz or DC or at frequencies in the range of 3,000 - 10,000 Hz.
Current depends on voltage applied and body resistance. Resistance is mainly offered by skin. Skin resistance increases with thickness and diminishes with moisture / perspiration. Except for skin; blood vessels, intravascular spaces etc. offer conduction system.