Understand the pre-embryonic period: This is the stage of human development that occurs from fertilization to implantation in the uterus. It involves several sequential processes that transform a single fertilized cell into a structure capable of implantation.
Step 1: Fertilization occurs when a sperm cell successfully penetrates an egg cell, forming a zygote. This marks the beginning of the pre-embryonic period.
Step 2: Cleavage is the process of rapid mitotic cell divisions of the zygote, resulting in smaller cells called blastomeres. This does not increase the overall size of the structure but increases the number of cells.
Step 3: Morula formation occurs as the cleavage continues, forming a solid ball of cells known as the morula. The morula is an early stage in embryonic development.
Step 4: Blastocyst formation follows, where the morula develops into a hollow structure with an inner cell mass and an outer layer. This blastocyst is the structure that will implant into the uterine wall during the final step, implantation.