During fertilization, two specific cells are involved in the process: the sperm and the egg. These two cells, also known as gametes, are essential for the formation of a new individual. The sperm is the male gamete, while the egg, or ovum, is the female gamete.
The journey of the sperm begins in the male reproductive system. It is produced in the testes and stored in the epididymis until ejaculation. When sexual intercourse occurs, the penis delivers the sperm into the female reproductive system through the vagina. The sperm then travel through the cervix, uterus, and into the fallopian tubes, where fertilization takes place.
On the other hand, the egg is produced in the female reproductive system. Each month, during the menstrual cycle, an egg is released from one of the ovaries. This process is called ovulation. The released egg is then captured by the fallopian tube, waiting for the sperm to arrive. If the egg is not fertilized within a specific period, it will disintegrate and be expelled from the body during menstruation.
When the sperm reaches the fallopian tubes, it undergoes a series of changes that allow it to penetrate and fertilize the egg. The outer layer of the egg, called the zona pellucida, needs to be penetrated by a single sperm to initiate fertilization. This process is facilitated by enzymes present on the sperm’s head, which help it break through the zona pellucida.
Once a sperm successfully penetrates the egg, a remarkable event occurs. The outer layer of the egg undergoes changes that prevent any other sperm from entering. This is crucial to ensure that only one sperm fertilizes the egg, preventing the formation of multiple embryos.
After the sperm enters the egg, their genetic material, contained within the sperm’s head, fuses with the genetic material of the egg. This fusion of genetic material from the sperm and the egg forms a single cell called a zygote. The zygote is now diploid, meaning it contains pairs of chromosomes from both the mother and the father. This marks the beginning of prenatal development.
The two cells used during fertilization are the sperm and the egg. The sperm, produced in the male reproductive system, travels to the fallopian tubes to meet the egg, which is released from the ovary during ovulation. Once the sperm penetrates the egg, their genetic material fuses, forming a diploid zygote. This zygote is the starting point for the development of a new individual.