Reproduction is a process through which organisms make more organisms like themselves. In the reproductive cycle in humans, two kinds of sex cells (gametes) are involved: the sperm (male gamete) and the egg/ ovum (female gamete).
If the reproduction process seems simple, know that it is not so…it is a complex mechanism!
In schools, we have been taught that pregnancy occurs when the sperm and ovum come into contact, but it is not as simple as that. Biology textbooks explain great details, but the teachers in many schools may shy from having open discussions on this subject.
So, topics beyond reproduction like those related to sexuality and reproductive health are a far cry! This makes students lean on unauthentic and irrelevant places to educate themselves. A large majority of adolescents and youth in India rely on porn and conversations with friends to get important information on the sexual health and reproduction system.
In girls or females, the reproduction system consists of a vagina and uterus, two ovaries containing ovarian follicles. These ovarian follicles are immature ovum which stays dormant till the girl reaches an appropriate age for procreation (yes! this may be as early as 14 years as per nature).
In the female reproductive system, during each menstruation cycle, one of those eggs develops and is released by the ovaries into one of the fallopian tubes. The egg starts slowly moving through the fallopian tube. During this cycle, other processes are simultaneously going on. First, the cervical mucus – the fluid around the cervix- becomes very watery and stretchy. Second, the opening of the cervix gets softer and more open. These processes are for the sperm cells to have a greater probability of reaching the egg.
While all of this is happening, someone with a penis must ejaculate (“semen or seminal fluid”) inside the vaginal opening or directly onto the vulva.
A few reasons why a pregnancy may not take place is: during some periods in the fertility cycle, the cervical mucus is too thick for the sperm cells to penetrate, or the opening to the cervix is not enough for them to get inside of it. So, the sperm cells remain in the vagina where they die. At other times, there is not just enough semen or viable sperm cells due to low sperm count for the steps of pregnancy to take place.
When they can get through the vagina and the cervical opening, the healthy viable sperm cells will go to either of the fallopian tubes- some to one, some to the other. Once inside the tube, these sperm cells are helped by the uterus and fallopian tube mechanisms of contractions to keep moving towards that egg cell. Chemicals (Hormones) inside the female reproductive system also help by providing the sperm cells with more energy and making the egg more favourable to receive the sperm.
Millions of sperm are needed to fertilize one egg! The sperms that went to the tube with a live egg, surround it and try to enter the sac. If the ovum is healthy, the healthiest sperms will try to push into the protective layers and enter the egg or ovum. Some sperms die on the way, some die trying to enter. Then it is just a matter of which one of the viable sperm cells is the healthiest to fertilize it, with the egg also taking part by pulling the sperm cell inside. The egg then releases special enzymes that lock out any other sperm cells left trying to get in. This is what is called the fertilization of the egg. However, this does not always lead to a viable pregnancy.
About five or six days after fertilization, the egg cell and sperm cell become something new: a zygote. The zygote starts moving together towards the uterus, its cells dividing all the time. It then becomes a hollow ball of cells called a blastocyst (pronounced BLAS-toe-sist); this is implanted in the uterine wall, attaching to the endometrium (the uterine lining, the same ling which is shed during a period) and then becomes an embryo. This process is called conception or implantation.
After about eight weeks, the embryo has developed, and most of its parts- the brain, nerves, heart, blood, stomach and intestines, and the muscles and skin have been formed.
During the foetal stage, which starts nine weeks after fertilization to birth, the development continues as cells multiply, move and change. The foetus floats in amniotic fluid inside the amniotic sac, and it gets oxygen and nourishment from the mother’s blood via the placenta. The placenta is a disk-like structure stuck to the inner lining of the uterus and connects to the foetus via the umbilical cord.
Pregnancy lasts for an average of 280 days (about 9 months!). When the baby is ready for birth, its head presses on the cervix, which begins to relax and widens to get ready for the baby to pass through the vagina.