The spermatozoon is a highly specialized cell that is formed through a complex cellular program of differentiation during spermatogenesis. It has a unique structure and chromatin that reflects its vital function. Morphologically it comprises a head, a midpiece and a tail. The sperm DNA is confined to the nucleus of the head and it has a characteristic protamine-based chromatin that makes it the most condensed eukaryotic DNA. This super compaction of sperm chromatin enhances the protection of DNA from damage since this cell type do not possess robust repair mechanisms. The midpiece is considered the “source of power” of spermatozoa, since it contains many mitochondria, which are responsible for the energy production required for motility. The tail, also known as flagellum, is crucial for spermatozoa movement and transit until they reach the female gamete. The morphological integrity of spermatozoa is of extreme importance for their responsiveness to testicular and epididymal factors involved in maturation. One of the main features that spermatozoa acquire during the maturational process is their motility capacity. This characteristic is not only dependent on the communication of spermatozoa with their surroundings, but also on sperm intrinsic factors, such as adenosine triphosphate (ATP) and specific membrane and secretory proteins. In recent years, sperm epigenome has been a matter of debate among researchers. Its importance is related to its impact on the embryo fate and offspring development. This chapter will discuss the significance of spermatozoa exclusive structure and function for human reproduction and the preservation of generations.
Keywords: Activated motility, Assisted Reproductive Technologies, DNA damage, Epigenetics, Fertilization, Histone, Hyperactivated motility, Protamine, Offspring, Sperm Chromatin, Sperm DNA, Spermatozoa morphology.