photo.jpg

## Gametogénesis: Conversion of Germ Cells Into Gametes ### Germ Cells The development starts with fertilization, the process by which the male gamete, sperm, and the female gamete, the oocyte, combine to create a zygote. Gametes originate from **primordial germ cells** (PGCs) that form in the epi...

## Gametogénesis: Conversion of Germ Cells Into Gametes ### Germ Cells The development starts with fertilization, the process by which the male gamete, sperm, and the female gamete, the oocyte, combine to create a zygote. Gametes originate from **primordial germ cells** (PGCs) that form in the epiblast during the second week. During gastrulation, they migrate through the primitive streak and into the yolk sac wall. By the fourth week, PGCs migrate from the yolk sac to the developing gonads, arriving by the end of the fifth week. The frequency of mitotic divisions increases during their migration and once they reach their final location. In preparation for fertilization, germ cells undergo the process of **gametogenesis**, which includes **meiosis** to reduce the number of chromosomes and **cytodifferentiation** to allow maturation. ### Clinical Correlations **Teratomas** are tumors that originate from pluripotent cells capable of differentiating into many tissue types, including bone, hair, muscle, and intestinal epithelium. They are thought to arise from the **pluripotent germ cells**, which are capable of differentiating into any of the three embryonic germ layers. While evidence suggests that PGCs that have migrated incorrectly could be involved, another possible origin is from **epiblastic cells**, which form the three germ layers during gastrulation. ### Diagram This diagram shows an embryo at the end of the third week, with PGCs located in the yolk sac wall. By this point, the umbilical cord will attach near the site where the PGCs are located. The diagram clearly shows that these cells then migrate to the gonads, where they will continue their development.