[From the totipotence of the zygote to mature stem cells and reserve cells].
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 stem cells: 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.
Universidad Católica de Murcia Campus Los Jerónimos, 30107 Guadalupe, Murcia, Spain. gtomas@pdi.ucam.edu
Gloria María
GM
Tomás Y Garrido
Natalia
N
López Moratalla
D033421:Beginning of Human Life; D002118:Calcium / Q000502:physiology; D019070:Cell Lineage; D047108:Embryonic Development; D053595:Embryonic Stem Cells / Q000166:cytology*; D005260:Female; D005306:Fertilization; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007206:Individuality; D008297:Male; D039902:Multipotent Stem Cells / Q000166:cytology; D009432:Neural Crest / Q000502:physiology; D028723:Personhood; D039904:Pluripotent Stem Cells / Q000166:cytology; D011247:Pregnancy; D039901:Totipotent Stem Cells / Q000166:cytology*; D014430:Twins, Monozygotic; D015053:Zygote / Q000166:cytology*
D002118:Calcium