Washington Master Esthetics Practice Exam

What is an embryo called after 100 cells have been produced following conception?

1. Gastrula

2. Morula

3. Blastula

4. Zygote

The correct answer is: Blastula

After conception, the early stages of embryo development involve several key phases. When the embryo reaches the stage where it consists of approximately 100 cells, it is identified as a morula. This stage is characterized by a solid ball of cells formed from the division of the fertilized egg, which is also known as a zygote. Following the morula stage, which occurs usually around the third to fourth day after fertilization, the next phase is the blastula stage. During the blastula stage, the solid morula transforms into a hollow ball of cells, known as a blastocyst, that will eventually implant in the uterine lining. The gastric stage refers to a further development where the blastula undergoes shaping and cell differentiation, which leads to the formation of the three primary germ layers. The zygote is the very first stage, comprising just a single fertilized egg cell, not a multicellular structure. Understanding these developmental stages is crucial for recognizing how the embryo grows and changes immediately following conception. The key takeaway is that the correct answer, morula, precisely describes the early state of the embryo after about 100 cells have formed.