Extra-embryonic mesoderm is derived from:
(A) Epiblast (B) Primary yolk sac (C) Secondary yolk sac (D) Hypoblast
(B) Ans: B. Primary yolk sac(Ref Gray's. 41/e p169, 40/e p167, 173, 186-189; Langmuir S 13/e p45,'Pe p54-55)Extra-embryonic mesoderm is derived from primary yolk sac.Formed by delamination of yolk sae cells - later by migration of cells through primitive streak during gastrulation.