Читать книгу Ridley's The Vulva - Группа авторов - Страница 21

The primordial germ cells, which are the antecedents of the male and female gametes, are present in the endoderm around the allantoic diverticulum (now a ventral outpouching of the hind gut) and are usually seen in the 17–20 day embryo, although possible primordial germ cells have been identified at 13 days [8]. The primordial germ cells are ectodermal in origin, having migrated to the allantoic diverticulum from the epiblast, and they retain two functional X chromosomes in contrast to the somatic cells, which possess only one functional X chromosome [9]. From here, they migrate through the mesoderm surrounding the hindgut and into the dorsal mesentery. The final destination is the gonadal ridge, which they reach at about 35 days (Figure 1.4).