Sperm or Spermatozoon; consists of 4 parts - Head, Neck, Middle Piece and Tail.
Tail is very long, slender and tapering, and is formed of cytoplasm (though less in quantity but outside). Axoneme or Axial Filament occurs throughout.
Tail is vibratile part of sperm.
Main function of Tail; is the propulsion system. It is the whip-like structure of the sperm tail which serves the important function of propelling the sperm cell forward with a snake-like motion. It is critical that sperm move forward and not laterally or in circles.