Which of the following structures develops first during the period of the embryo?
A) the neural tube
B) the primitive streak
C) the upper arms
D) the placenta

Question

Quizplus · Accepted Answer

The primitive streak is the first structure to appear during the period of the embryo, around day 15 of embryonic development. This marks the beginning of the process of gastrulation, in which the three germ layers (ectoderm, mesoderm, and endoderm) are formed. The neural tube and upper arms develop later in embryonic development, while the placenta develops from the outer layer of cells surrounding the embryo.

Which of the Following Structures Develops First During the Period