Petesejté

Petesejté is a term used in biology to refer to the process by which a sperm cell fertilizes an egg cell. This is a fundamental event in sexual reproduction, occurring in a wide range of organisms from humans to plants and fungi. The fusion of the male gamete (sperm) and the female gamete (egg) results in the formation of a zygote, which is the first diploid cell of a new organism.

The process of petesejté typically involves several stages. First, sperm must reach the vicinity of the egg. This may involve complex signaling mechanisms, especially in motile sperm. Once in proximity, the sperm undergoes a process called the acrosome reaction, where enzymes are released from a cap-like structure on the sperm's head. These enzymes help to break down the outer layers of the egg, allowing the sperm to penetrate. Following penetration, the plasma membranes of the sperm and egg fuse, and the sperm nucleus enters the egg's cytoplasm.

A crucial aspect of petesejté is the prevention of polyspermy, the fertilization of an egg by more than one sperm. Mechanisms such as the cortical reaction, where granules within the egg release substances that alter the egg's outer layers, are activated upon the first sperm's entry to block further sperm penetration. The fusion of sperm and egg nuclei then restores the diploid chromosome number, initiating embryonic development.