How does fertilization occur in humans? to understand this topic you need to go through the below article So first the woman’s menstrual cycle prepares the body for the fertilization… it does this by releasing an egg from the ovary into the fallopian tube….
After sexual intercourse… the man ejaculates into the woman’s vagina where there are millions of sperm…. so they start their journey (takes..12–48 hrs or else they die) to the egg by swimming through.. using their tail…
Its all upon the sperms decision on which fallopian tube to chose…as there are two and only one of them have the egg…..One successful sperm reaches first and its head contains an enzyme (acrosome) that digest through the wall of the egg…. as soon as the nucleus of ONE sperm enters leaving the tail outside…. the egg forms an impermeable membrane on the outside to prevent any more sperms from entering.
The two nucleus fuse together to form a zygote… this now moves through the fallopian tube… and it already started dividing by mitosis… and when by the time it leaves the fallopian tube it is now a hollow ball of cells…. called a blastocyst
This blastocyst now implants onto the wall of the uterus and gradually starts forming into an embryo where it attaches itself to the placenta.
The Sperm Cell Delivery Vehicle
uring sexual intercourse, when a male human ejaculates, he ejects a viscous mixture of semen and sperm cells that act as a delivery vehicle in the fertilization process. Ideally, when a human male ejaculates inside a human female vagina, the semen and sperm mixture are thrust inward. The sperm cells then swim towards the egg cell to fertilize it.
The Role of the Sperm Cell
The sperm cell approaches the egg head-first, using a specialized organelle called the acrosome to penetrate the proteins in the egg’s cell aided by specialized enzymes called hyaluronidase and acrosin. When the sperm cell successfully penetrates the cell wall during this acrosome reaction, the sperm cell then enters the egg to complete the fertilization process. Following fertilization by the sperm cell, the egg cell undergoes what is known as a cortical reaction, which alters the egg cell’s zona pellucida – the outer shell of the egg — and prevents more than one sperm cell from penetrating the egg’s cell wall, which is a condition known as polyspermy.
The Role of the Egg Cell
During the female reproductive cycle, usually, one egg cell is released from a small, fluid-filled sac within either of the two ovaries, known as a follicle. This release is accomplished via activation by the follicle stimulating hormone and the luteinizing hormone. Once the egg is released from the follicle, the follicle becomes the corpus luteum, which releases a hormone that helps thicken the lining of the uterus, preparing it for the egg. The egg remains in the fallopian tube for approximately 24 hours; however, once it is fertilized by a human male sperm cell, the egg forms into a zygote and quickly drops down into the uterus and implants in the uterine wall.