Glossary of terms

      Ovules are female gametes of animals, higher plants, and many algae and other protozoa characterized by oogamy. As a rule, eggs are haploid cells, but can have other ploidy in polyploid organisms. The human egg has a diameter of approximately 150 microns.

     The cytoplasm of eggs (ooplasm) contains nutrient inclusions - yolk. Eggs are formed as a result of ovogenesis. After fertilization, an embryo develops from a fertilized egg (zygote). In parthenogenesis, the embryo, and later a new organism, develops from an unfertilized egg.

 

     The human egg was first described in 1827. It differs from the sperm by:

    * its predominant immobility;

    * its characteristic more or less spherical shape

    * presence of various protective and nutrient-supplying membranes

    * absence of functional organelles or structures inherent in the spermatozoon: tail, specialized mitochondrial complex, acrosome, etc;

    * genetic information (sex chromosomes - XX);

    * peculiarities of formation and development, life span;

    * a much smaller number of eggs in the body (during life, about 400 eggs are formed in a woman's body, while hundreds of millions of sperm are formed in a man's body)

    * A supply of nutrients for the development of the future embryo, localized in the cytoplasm;

    * significantly larger size (a human egg is 85,000 times larger than a sperm).

 

      A characteristic property of the egg is blocking the permeability of the membranes after contact with the acrosome of the first sperm and its activation, i.e. the transition from dormancy to development. The eggs of certain species of organisms can also be self-sufficient units of sexual reproduction (they do not need sperm for activation) - such reproduction is called parthenogenesis.