Puberty and the reproductive systems · Biology Class 9–10 | StemPy Lab
Course 6.2·Lesson 1 of 3
Puberty and the reproductive systems
In human beings, sexual reproduction needs special cells made by the reproductive organs, which become active at puberty. In males the testes make sperm and the hormone testosterone; tubes and glands carry the sperm out of the body. In females the ovaries release one egg each month, and the oviduct carries it to the uterus.
about 25 min1 simulation1 practice question1 Python program5 questions to check yourself
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Two parents, new combinations
Many simple organisms reproduce on their own, from one parent. Human beings, like most animals, reproduce sexually: a cell from a male joins a cell from a female. Each child gets a mix of the two parents' DNA, so each child is a new combination.
These special cells are called germ cells or gametes. The male gamete is the sperm. The female gamete is the egg, or ovum. The organs that make them are the reproductive organs.
Puberty: the body gets ready
A newborn baby has reproductive organs, but they are not active. They start to work at puberty, usually between about ten and fifteen years of age. The age differs from person to person, and that is normal.
Some changes happen in both boys and girls:
thick hair grows in the armpits and in the genital area;
thinner hair may appear on the legs, arms and face;
the skin becomes oily, and pimples may appear;
they become more aware of their own bodies and of others.
Other changes differ.
In girls, the breasts begin to grow, and menstruation begins.
In boys, hair grows on the face, the voice begins to crack and deepen, and the penis grows.
These changes take place slowly, over months and years. They show that the body is becoming able to reproduce. Being able to reproduce is not the same as being ready for it: the mind and body go on developing for years after puberty.
The male reproductive system
A labelled plan of the male reproductive system, not to scale. Two oval testes hang in the scrotum, outside the body cavity; the label says that a testis makes sperm and the hormone testosterone. From each testis a tube, the vas deferens, carries the sperm up and over the urinary bladder. Near the bladder the seminal vesicle and the prostate gland add their secretions. The tube joins the urethra, the shared path for sperm and urine, which runs down through the penis.
The two testes make the sperm. They also make the hormone testosterone, which causes the changes of puberty in boys.
The testes lie in a bag of skin, the scrotum, outside the body cavity. Making sperm needs a temperature a little lower than the normal body temperature.
Each sperm is a single cell with a long tail, which helps it swim towards the egg. It carries the father's DNA.
A tube, the vas deferens, carries the sperm up from each testis.
It joins the urethra, the tube that also carries urine. So the urethra is a common path for sperm and urine.
Glands such as the seminal vesicles and the prostate gland add their secretions. The fluid makes it easier for the sperm to travel and gives them nutrition.
The female reproductive system
A labelled plan of the female reproductive system, not to scale. In the middle is the uterus, shaped like an upside-down pear, where the embryo grows. Two oviducts curve out from its upper corners towards two oval ovaries; the label says that an ovary holds the eggs and releases one a month, and that fertilisation happens in the oviduct. The narrow lower end of the uterus is the cervix, which opens into the vagina.
The two ovaries hold the eggs. A girl is born with thousands of immature eggs in her ovaries. They also make hormones.
From puberty, some eggs begin to mature. One egg is released each month, by one of the two ovaries.
A thin tube, the oviduct or fallopian tube, carries the egg from the ovary to the uterus.
The two oviducts join the uterus, a muscular, bag-like organ. A baby grows here.
The uterus opens into the vagina through a narrow neck, the cervix.
Step through the six stages. You should see that the sperm's path ends outside the body, while the egg's path ends in the uterus.
Try it in Python
The program lists the two paths and finds where the egg and a sperm can meet.
You should see the two paths joined by arrows, and the oviduct as the meeting place.
Practise with new numbers
Common mistakes
Thinking both ovaries release an egg every month. Usually one egg is released each month, by one of them.
Placing the testes inside the abdomen. They hang in the scrotum, where it is a little cooler.
Calling the urethra a tube for sperm only. In males it carries both sperm and urine, though not at the same time.
Thinking puberty comes at the same age for all. It comes earlier for some and later for others.
Remember these
Germ cells: the sperm (male) and the egg (female). Each carries half of the parent's DNA mix.
Puberty is when the reproductive organs become active.
Male: testes in the scrotum, vas deferens, urethra, and glands that add fluid. The testes make testosterone.
Female: ovaries, oviducts, uterus, cervix and vagina. One egg is released each month.
Check yourself
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
Name the hormone made by the testes.
Why do the testes lie outside the body cavity?
Which tube carries the egg from the ovary to the uterus?
Give two changes of puberty that happen in both boys and girls.
What do the seminal vesicles and the prostate gland add, and why?
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