Sperm changes enabling fertilization in mammals

In order to acquire the potential to fertilize an egg, mammalian sperm have to undergo a series of molecular events that make the sperm capacitated. The capacitated state apparently enables sperm to detach from the oviductal epithelium, to be recruited by chemotaxis to the egg environment, to penetrate through the cumulus oophorus, to bind to the zona pellucida (the extracellular coat of the egg), and to undergo the acrosome reaction (in which hydrolytic enzymes that enable the penetration of the sperm to the egg are released). It is given that the life span of the capacitated state is short. A clever solution of nature is the turnover of capacitated cells within a sperm population, thus prolonging the period of time that a sperm population, as a whole, maintains its fertilizing potential. All these physiological events point at the key role of capacitation in fertilization.