Sexual reproduction - how babies are made
sperm; sexual; uterus; pregnant; placenta; umbilical; cord; reproduction; sex; baby; babies; foetus; fetus; embryo; intercourse; fertilisation; sperm; egg; ovum; cell; womb; chromosome; gene; DNA; twins ;
When girls and boys reach puberty, their bodies start to change and become more mature. From this time, if a male and a female have sexual intercourse (often called 'making love', or 'sleeping with someone'), it is possible that the girl could get pregnant, ie. a baby could start to grow.
a baby is started
Sperm are the male 'seeds' that contribute to starting a new life - living sperm look a lot like tadpoles (under a microscope).
When sperm are ejaculated (say ee-jak-u-lay-ted) from the penis during sexual intercourse, they swim up the vagina (vaj-eye-na), through the cervix (sir-vix), into the uterus (you-ter-us) and then into the fallopian (fal-o-pe-an) tubes of the female. These sperm are looking for an ovum (or egg) to fertilise.
When a female is born she carries thousands of ova or eggs ready to use when she becomes adult. These are the female 'seeds' that, along with sperm, contribute to creating a new life.
Once a month, the female releases an ovum (one egg) .
If an ovum has been released, a sperm can unite with it, fertilise it and make the first cell of a new baby.
Once one sperm has fertilised the ovum, no other sperm can get in.
For the sperm it's like a race and there is only one winner.
A female becomes physically 'adult' when menstruation starts (when she starts having periods). Periods can begin as early as 9 years for some females, but usually start a few years older than this. Have a look at this topic on Periods.
This fertilised ovum immediately divides into two cells, these cells then divide again and again over the next couple of days as the cluster of cells makes its way to the uterus (womb). Here it is planted in the lining of the uterus and continues dividing its cells to make billions of new cells. The female is now pregnant.
The amazing thing is that each one of these cells contains the same set of chromosomes or 'plans' that were created at fertilisation!
Over 9 months, these cells will grow into a new person - a baby.
Doctors have different names for this developing baby.
- 1 day - 'zygote'
- first 2 months - 'embryo'
- 3rd month to birth - 'fetus'
When your dad's sperm and mum's egg (ovum) got together, they each brought a set of 'plans' for what the new baby would be like.
When the ovum was fertilised and became your first cells, these 'plans' or genes helped to decide lots of things about you, eg. boy or girl, colour of skin, eyes, hair, etc.
Genes are made of DNA ('de-ox-y-ri-bo-nu-cle-ic acid', if you want the full name).
If you could see your genes they would look like beads on a necklace of DNA. These strands are called 'chromosomes'.
Usually each cell in a human body has 46 chromosomes.
That first single cell has 23 chromosomes from mum and 23 from dad, which is why you might look like mum or dad (or grandparents) and have similar traits, eg. you and dad may have pointy ears, or you and mum can both wiggle your noses!
The chromosomes in a male are slightly different to those in a female. This is a picture of chromosomes in a male.
(Isn't it annoying when people who haven't seen you for a while say things like, "He's got his dad's chin", or "she's got grandma's eyes!")
Remember, any one sperm can only fertilise one ovum, so if 2 ova (eggs) leave the ovaries at the same time and are both fertilised then 'non-identical' twins are born. They may look alike or they may not, just like any brothers or sisters.
If an ovum splits after it has been fertilised, then you get identical twins because they have the same set of genes.
It is called a multiple birth if two or more babies are born at the same birth. Do you know what we call a set of three babies who are born at the same time?
sex you are
What sex a baby will be is decided when the egg and sperm unite.
Each egg and each sperm have one sex chromosome.
There are two kinds of sex chromosomes - X and Y. Can you see why they are called x and y chromosomes? (Hint - look at the picture.)
Eggs carry only an X and sperm carry either an X or a Y
X+X means the cell will develop into a baby girl.
X+Y means that it will develop into a boy.
Once you are born, you will grow up into a unique human being - there's no-one else like you in the world. Even identical twins are not exact copies of each other - they each have their own personalities.
You may look a bit like someone in your family, but there is only one of you!
You are a completely unique and wonderful person.
the uterus (womb)
The place where the embryo plants itself is inside the uterus. The baby starts to grow, and other tissue grows into a placenta (say pla-sent-a).
During pregnancy (the time when the baby is growing in mum's uterus), the placenta provides oxygen from the air that mum breathes, and nutrients (say new-tree-ents) from the food she eats.
This is why it is important that mum gets good food and takes care not to smoke, drink alcohol or take drugs, because the developing baby gets those too and he or she cannot say, "No".
Some of the nutrients from what mum eats or drinks, and oxygen from the air she breathes, goes through the umbilical cord to the fetus. Any waste from the growing baby goes back through the cord into the mother's bloodstream and passes out of her body.
The umbilical cord is a soft 'bendy' tube from the placenta to the navel (or tummy button) of the fetus.
There is a sac (like a bag of thin skin) filled with fluid protecting the skin of the developing baby. The baby can move around safely inside the mother for 9 months until he or she is ready to be born into our world.
"When a girl starts menstruating (gets her period), that means that she is able to conceive (get pregnant). Having a baby means that the mum and dad have to be ready to look after their child until that child becomes an adult. It is a big decision that will affect the rest of their lives and that of their baby."
In Australia it is against the law to have sexual intercourse when you are under 17 years old or with someone who is under 17. These laws are to protect young people from getting hurt by situations that they are not old enough or experienced enough to manage.
"My sister got pregnant when she was 15. My mum and dad were very upset but they helped her. She had the baby and he lives with us now. Some people said mean things to my sister and to our family. It is still hard for our family, and my sister had to leave school. She wants to go back to school when her baby is older. My sister told mum that there was another girl in the hospital who had to let her baby be adopted by another family because she didn't have a mum and dad who would help her."
We've provided this information to help you to understand important things about staying healthy and happy. However, if you feel sick or unhappy, it is important to tell your mum or dad, a teacher or another grown-up.