Final answer:
The initial event following fertilization and implantation is the beginning of embryonic development, which starts with the zygote formation, proceeds to the morula stage, and eventually becomes a blastocyst that implants in the uterus to receive nutrients and develop further.
Step-by-step explanation:
Understanding Fertilization and Implantation
The initial event that occurs following fertilization and implantation is the start of embryonic development. Fertilization usually takes place in a Fallopian tube when an egg (oocyte) is fertilized by a sperm, forming a zygote. This marks day 0 of embryonic development.
The zygote then begins to divide, forming a solid ball of cells known as a morula around days 3-4. By days 5-7, the morula transforms into a blastocyst, a hollow ball of cells prepared for implantation. Implantation in the endometrium of the uterus occurs around days 8-9. After implantation, the blastocyst is referred to as an embryo and starts to receive nutrients for further development.
The Phases of Menstrual Cycle Related to Fertilization
The menstrual cycle includes a phase after ovulation where the endometrium continues to build up, ready for the potential of a fertilized egg to implant. If the egg is fertilized, the events preceding implantation include the changes from a zygote to a morula and eventually to a blastocyst that implants in the uterus to continue into embryonic development.