How do babies get inside mummy?
Every baby starts life as a single cell, which is formed from the joining together or union of two cells called germ cells and this union is called fertilization. The germ cell from the mother is called the egg and the germ cell from the father is called the sperm. The egg and the sperm must meet to start a new baby.
Animals, which live in water: lakes and rivers will just spill their sperms and eggs into the water where fertilization occurs. It is a little difficult for land animals because some amount of warmth and moisture is required for the germ cells to survive. Therefore the sperms are spilled inside the warm body of the mother in a passage just below the uterus called the vagina. At the upper end of the vagina is the opening to the mouth of the uterus and the lower end opens outside in between the opening of the urinary tube and the rectal tube.
The specialized structure by which sperms can be placed in the vagina is called the penis. This is a tube like organ lying just in front of the scrotal sacs, which house the two testes. From the testes, where the sperms are made, the sperms are carried in a small pipe, which lies in the center of the penis. This pipe or the urethra also carries the urine outside. For the male to be able to place its sperm load at the topmost part of the vagina, near the uterus, the penis needs to be stiffened. For this, due to nervous excitement at the time of sexual intercourse, the spongy tissue inside the penis gets filled with blood. This makes the penis stiff and makes the entry into the vagina easier. This thickening, lengthening, and straightening of the penis is called erection. After sexual intercourse, the erection subsides and the urethra is now ready to resume its other function of carrying urine from the urinary bladder to the outside.
This is the only way babies are made, though of course, sperms spilled even at the entry to the vagina, not inside, can lead to a pregnancy. This is because sperms have a tail and they move or swim up in order to reach the egg. But certainly, pregnancy cannot be caused if boys and girls use the same swimming pool or drink from the same glass or even kiss.
Only one egg is released in one month whereas millions of sperms are ejected out during each intercourse. The sperms begin their journey from the top of the vagina through the uterus and in the tube where one sperm will fertilize the egg-giving rise to a new individual. Sometimes two eggs may be released at the same time, which get fertilized to form twins. Since these come from two different eggs and two different sperms they are not identical. However, division of one fertilized egg and separation to two groups can form twins, which are identical.
But how does that single fertilized cell know what to do and is able to form a complete baby by itself? This is because each egg and sperm carry coded instructions which tell it what to do. These instructions are packaged in a set of microscopic ribbons called chromosomes. The fertilized egg of the human contains forty-six of these. Twenty-three have been provided by the father and twenty-three by the mother and they contain the entire information in code form to develop the human being from an egg, including information like colour of hair, shape of nose and any diseases which may come from either parent to the child. However, only two chromosomes out of the entire set of forty-six chromosomes determine the sex of the baby. These chromosomes are called the sex chromosomes and the baby gets one from each parent. The egg from the mother has only the X chromosome but the father’s sperms may carry either the X or the Y chromosome. If the sperm carrying the X chromosome fertilizes the egg, the baby will have XX (double X) sex chromosomes and therefore will be a girl. On the other hand, if the sperm carrying the Y chromosome unites with the egg, the baby’s sex chromosomes will be XY. This baby will be a boy. The sex of the newborn baby is decided at the time of fertilization itself, and no amount of prayers can change it. Not only that, the sex of the baby depends upon which sperm of the father is more active and able to survive: the X sperm or the Y sperm.
So now, a baby boy or a girl is born. Even at birth, the baby has kept aside it’s own germ cells to be used once it is grown into adulthood. Before that however, many growth and developmental changes have to occur. By the time this baby has grown physically, matured mentally and completed education, it is time to have a baby of one’s own so that the human race does not become extinct.