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Multiple Choice
In the context of early embryonic development, which embryonic structure develops first?
A
Blastocyst
B
Zygote
C
Gastrula
D
Morula
Verified step by step guidance
1
Step 1: Understand the sequence of early embryonic development. The process begins with the formation of a zygote, which is the single-celled organism formed after the fertilization of an egg by a sperm.
Step 2: Recognize that the zygote undergoes a series of mitotic divisions, a process called cleavage, to form a solid ball of cells known as the morula.
Step 3: Learn that the morula continues to develop and forms a hollow structure called the blastocyst. The blastocyst is characterized by an inner cell mass and an outer layer of cells.
Step 4: Note that the blastocyst eventually undergoes further differentiation and forms the gastrula, which is the stage where the three germ layers (ectoderm, mesoderm, and endoderm) are established.
Step 5: To answer the question, identify the correct chronological order of development: Zygote → Morula → Blastocyst → Gastrula. The zygote is the first structure to develop in this sequence.