When a sperm cell successfully fertilizes an egg, it's called fertilization or conception. This marks the beginning of pregnancy.
The Fertilization Process
The process begins when a sperm penetrates an egg. This causes a change in the egg's surface, preventing other sperm from entering. The genetic material from the sperm (23 chromosomes) then combines with the genetic material from the egg (23 chromosomes), forming a single cell with 46 chromosomes—a zygote. This zygote contains all the genetic information needed to develop a new human being. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Post-Fertilization: The Journey Begins
The zygote begins to divide rapidly, starting with two cells, then four, and so on. This process of cell division is called cleavage. Approximately one week after fertilization, the zygote, now a mass of cells, travels from the fallopian tube to the uterus. [1, 3, 7]
Time Constraints
It's important to note that sperm can survive up to six days in the female reproductive tract. Fertilization typically occurs within 24 hours of the egg being released from the ovary. [1, 5]
The Result: A New Life
The resulting zygote is the first stage of embryonic development, initiating the development of a new, unique individual. The successful union of egg and sperm is the cornerstone of human reproduction. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[1] Planned Parenthood: How Does Pregnancy Happen? | Pregnancy Symptoms & Signs https://www.plannedparenthood.org/learn/pregnancy/how-pregnancy-happens
[2] Cleveland Clinic: Conception: Fertilization, Process & When It Happens https://my.clevelandclinic.org/health/articles/11585-conception
[3] MyHealth.Alberta.ca: How Pregnancy (Conception) Occurs https://myhealth.alberta.ca/Health/pages/conditions.aspx?hwid=tw9234
[4] Merck Manual: Stages of Fetal Development https://www.merckmanuals.com/home/women-s-health-issues/normal-pregnancy/stages-of-fetal-development
[5] WebMD: Conception Pictures: From Egg to Embryo https://www.webmd.com/baby/ss/slideshow-conception
[6] King County: Pregnancy - Elementary FLASH Grades 4-6 https://cdn.kingcounty.gov/-/media/king-county/depts/dph/documents/health-safety/health-programs-services/sexual-health-education/elementary/es13-pregnancy.pdf?rev=bcdb0416b52947289d78a5851774a288&hash=EA95B38EAB5EC7E444C29A9352E564C4
[7] University of Rochester Medical Center: Anatomy of the Uterus https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=34&ContentID=17114-1
[8] ColumbiaDoctors: How Pregnancy (Conception) Occurs Information https://www.columbiadoctors.org/health-library/article/how-pregnancy-conception-occurs/
[9] Urology Care Foundation: Male Infertility: Symptoms, Diagnosis & Treatment https://www.urologyhealth.org/urology-a-z/m/male-infertility
[10] Learn.Genetics.Utah.edu: Mitosis, Meiosis, and Fertilization https://learn.genetics.utah.edu/content/basics/diagnose/
