Primordial germ cells are seen in ------ by 3rd week of development?: (A) Neural crest, (B) Splanchnic mesoderm, (C) Genital ridge, (D) Yolk sac
Answer is D. Primordial germ cells originate in the epiblast, migrate through the primitive streak, and by the third week reside among endoderm cells in the wall of the yolk sac close to the allantois. Germ cells do not appear in the genital ridges until the sixth week of development Ref: Langman's embryology; Chapter 16; Pg no 243