De la totipotencia del cigoto a las células troncales maduras y de reserva

Zusammenfassung

In the process of life-transmission, when could we say that we are in the presence of a developing human body? A new human being starts with conception, after the specific gametes of father and mother recognize and fuse with each other; inherited genetic information is fed back reciprocally between the two «pronuclei», during a number of hours, and the resulting egg cell is more than the sum resulting from the fusion of the gametes. It is a living being in its totipotent unicellular stage, a body indeed, with corporal axes assigned, and ready to develop following a «continuum», a marked-out sequence. Divisions initiated in the totipotent fertilized egg give rise to diverse stemcells: pluripotent, multipotent and germinating cells; these latter cells maturing in special niches. Space-cellular organization of each organ and tissue has a precise site in the early, developing organism following a process with precise starting and finishing times and always preserving the individual as a unit. At precisely linked stages the individual temporarily activates potentialities proper of his biological identity. The fact, being tracked through human biology, that each human body is a manifestation of its owner, offers a clear response to the debated question of the connection between the temporal beginning of each man as a zygote or fertilized egg and the origin of his specifically human capacities