Embryology Practice Questions With Answers Study Guide Rated A+

29. Chorionic villi are designated as secondary chorionic villi when they: A. contact the decidua basalis B. are covered by syncytiotrophoblast C. develop a mesenchymal core D. give rise to branch villi E. none of the above {Ans: C. is correct. All chorionic villi possess an outer layer of syncytiotrophoblast. The cytotrophoblast shell is a feature of the mature chorion. Extraembryonic somatic mesoderm forms the core of secondary villi, becoming tertiary with vascular development. Primary villi, at 14 days, are syncytial processes with a core of cytotrophoblast.}52. The foramen cecum of the adult tongue: A. marks the point of embryonic evagination of the thymus gland B. divides the tongue into two parts, an anterior one-third and a posterior two-thirds C. marks the point of embryonic evagination of the thyroid gland D. develops into taste buds E. has no embryologic significance {Ans: C. is correct. The foramen cecum on the tongue is the point from which the thyroid gland evaginated and began its journey down into the neck. It lies at the apex of the V-shaped terminal sulcus, which divides the tongue into anterior 2/3rds, from the lateral lingual swellings and truberculum impar, and posterior 1/3rd, from the copula.}77.