Human reproduction

Every human once started as a single cell, smaller than the dot at the end of this sentence. In reproduction a new human is formed from two special cells. This process is completely natural and follows the same pattern in all humans.

Egg cell and sperm cell

For a new human two kinds of cells are needed. The egg cell comes from the mother and is the largest cell in the human body. The sperm cell comes from the father, is very small, and can move itself with a tail. Together they each bring half of the genetic information.

Fertilization

When a sperm cell reaches the egg cell and merges with it, this is called fertilization. This happens in the fallopian tube, a narrow passage between the ovary and the uterus. Two cells become one single new cell. This cell now holds the complete genetic information, half from the mother and half from the father. This is exactly why a child often resembles both parents.

One cell becomes many

The fertilized cell divides again and again: one becomes two, two become four, and so on. The tiny cluster of cells travels into the uterus and settles into its lining about a week after fertilization. There it is protected and gets everything it needs to grow.

Growing in the womb

In the womb the small cluster of cells grows into a baby over about nine months. Through the umbilical cord it gets food and oxygen from the mother's blood. The cord leads to the placenta: there the mother's blood and the baby's blood come very close without ever mixing. Step by step the heart, brain, arms, and legs form. At the end of this time the baby is ready to be born.