Final answer:
Fertilization is the process where a sperm and an oocyte (egg) fuse in the Fallopian tube, forming a zygote. The zygote then divides several times, becomes a blastocyst, and implants in the uterus to begin gestation.
Step-by-step explanation:
Fertilization occurs when a sperm and an oocyte (egg) combine and their nuclei fuse, typically taking place in the Fallopian tube.
The journey of the sperm to reach the egg is a feat that involves overcoming various obstacles, including the acidic environment of the vagina and immune defenses of the uterus. Successful fertilization results in the formation of a zygote, a single diploid cell containing a complete set of genetic information. After fertilization, the zygote undergoes a series of mitotic cell divisions as it travels towards the uterus, transforming into a blastocyst ready for implantation.
The entire process of fertilization is crucial for the start of a new human life, enabling the combination of genetic material from both parents. It begins when sperm enters the Fallopian tube where it may encounter and fertilize an oocyte, a process supported by cellular signals and mechanisms including chemotaxis and adhesion.
The resulting zygote then divides several times through a process called cleavage, and eventually forms a blastocyst which implants in the uterus, marking the beginning of gestation.