Puberty

During some part of their life, animals and humans change from being young animals or children to being adults. In higher animals, and humans, adults are able to reproduce, by sexual reproduction. The time when a child changes to an adult is called **puberty**. Puberty is marked by a set of changes in the body. Girls go through puberty between the age of about 10, to about 16 years. Boys go through puberty about two years later, from about age 12 to about age 18. During that time, secondary sex characteristics start to show: hair will start to grow. Girls will develop a more marked breast, and they will start to have menstruation. A sex drive, called libido will set in. At the end of puberty, both sexes will be different: Men will be more muscular than women, they will also be heavier. In both sexes, the voice will deepen, in men this change is more marked than in women. is shown in orange. The gland makes hormones that cause males' and females' bodies to start puberty.]]

## How the body controls puberty 
Puberty is started and carried on by different hormones. Hormones are chemicals that tell parts of the body to do things. Hormones are made by glands in the body. Glands are organs (special parts) of the body that make hormones.

This is what happens during puberty:

#A gland at the bottom of the brain called the hypothalamus sends gonadotropin-releasing hormone (GnRH) into a nearby gland called the pituitary gland.
#GnRH causes cells in the pituitary gland to make two hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH). LH and FSH are types of hormones called gonadotropins. The bloodstream carries these hormones around the body.
#LH and FSH make the gonads grow larger and start producing their own hormones, estradiol and testosterone. A girl's gonads are her ovaries, and a boy's gonads are his testicles (also called testes). Both ovaries and testicles produce estradiol and testosterone, but ovaries produce more estradiol and testicles produce more testosterone. Estradiol and testosterone are types of hormones called steroid hormones. Steroid hormones are also made by the body's two adrenal glands, which sit on top of the two kidneys.
#When the amount of estradiol and testosterone in the body increases, various parts of the body change.

## Common changes 
Both sexes have a set of changes:

* Gonads (testicles in males, the vagina in females) grow bigger
* Pubic hair starts to grow
* Hair on the legs, and in the armpits
* Acne, mainly caused by hormonal change
* Growth spurt
* Voice deepens

## Male puberty changes  
Boys go through puberty betweenthe age of about 12, to about 18.

* Wet dreams
* Development of facial hair

## Female puberty changes  
For females, puberty generally begins at around 10 and ends around 15 In addition to the signs cited above, females have the following:

* Breasts begin to grow bigger
* Menstrual periods

## When puberty starts and ends 
On average, girls begin puberty around age 10 and ends at around 15 while boys  the average age is around 11 and ends around 16.   https://pmc.ncbi.nlm.nih.gov/articles/PMC3666985/ https://pubmed.ncbi.nlm.nih.gov/23640021/

It said that for girls, puberty begins around 10 years of age and ends around age 15. It said that boys usually start puberty around 11 years of age and it lasts until around age 16." Girls usually complete puberty by ages 15, while boys usually complete puberty by ages 16. The major landmark of puberty for females is menarche, the onset of menstruation, which occurs on average between ages 12–14; for males, it is the first ejaculation, which occurs on average at age 12-14. If puberty starts much later than average, the person is sometimes called a **late bloomer**. 

For most boys, puberty takes about a few years,  Male teenagers are usually about  taller and  heavier than female ones. They are also stronger. After puberty, a male teenager can make a woman pregnant (have a baby).

In rich countries in the 21st century, the average age at which children, especially girls, reach puberty is lower compared to the 19th century, when it was 15 for girls and 16 for boys. This can be due to improved nutrition resulting in rapid body growth, increased weight and fat deposition, or eating meat from animals which have been dosed up with estrogen.

This is the general picture, but people around the world may start puberty at different ages. This is because their environment (things around them) may differ quite a bit. Here are some of the things that make puberty happen at different ages in people:

***Genetics**. Genetics is the study of how parents pass on to their children some of the ways they are through their genes. Half of a person's genes come from the mother. The other half come from the father. Some studies have found that mothers and daughters tend to start puberty at about the same age.
***Diet**. Boys and girls who have a good diet – who eat healthy food – tend to start puberty earlier. This may be because people have better food to eat today.
***Exercise**. Young people who exercise a lot, such as athletes and gymnasts, may start puberty later. It may also happen more slowly for them. This is thought to be because their bodies use up the food that they eat faster. This causes them to have less body fat, so there is less leptin to tell their brains to start puberty.
***Obesity**. Obesity is the state of being very overweight. A scientific study seems to say that girls who are obese start puberty early. Some obese girls have started growing breasts before the age of nine years and have had their first period before 12 years. This could be because a woman who is pregnant needs more nutrients (chemicals the body needs to stay alive) to support her baby. Therefore, if a girl is obese, her body fat sends signals to her brain that she is ready to become pregnant. Girls who have early puberty can have health problems later on in life.
***Illness**. Boys and girls who are sick for a long time, especially with illnesses that cause them to have a poor diet, tend to start puberty late. For example, this often happens to people who suffer from anorexia nervosa. Anorexia nervosa, often called "anorexia" for short, is an eating disorder. People with anorexia think that they are fat, or are very afraid of becoming fat. They try to lose weight by eating too little and doing too much exercise. To avoid gaining weight, they do not eat the amount of food their body needs. This causes them to stay at a weight that is not normal for their age and height.
***Stress**. It is thought that people who are under a lot of stress start puberty later. Some research seems to show that girls have their first period a bit later when their fathers are not around when they are young when they have a stepfather if they have been sexually abused for a long time, or if they were adopted by their parents from another country at a young age. On the other hand, the first period may happen a bit later when a girl grows up in a large family with her natural father around. However, scientists are not sure how correct these studies are. Not many studies have been done to find out if stress also causes boys to start puberty later.
***Chemicals**. Some scientists think people may start puberty earlier because their bodies are affected by chemicals such as estrogens and progestogens that are put in the environment by humans. Another chemical that may cause early puberty is Bisphenol A (BPA). It is used to make plastics, such as some types of baby bottles, water bottles, and sports equipment.

Girls usually reach their adult height and become sexually mature (able to have babies) about four years - five years after puberty starts. Boys keep growing for about four to five years after puberty starts. Puberty in boys starts off more slowly than in girls, but then speeds up later on. Although boys are usually about  shorter than girls before puberty begins, men on average end up about  taller than women.

## Emotional changes in males and females
The large amounts of hormones in the bodies of boys and girls during puberty can also affect their emotions. Young people begin to be attracted by (drawn to) each other and thinking about what it is like to have sex. They are often worried about what other people think about them. They can also feel the urge to do things that are dangerous, such as taking drugs or too many alcoholic drinks, or smoking. They sometimes want more independence – more power to decide things for themselves – and can get angry when their parents do not allow them to do things. The brains of teenagers are still growing, and it may take a while before they are mature enough to know how to make good choices about their lives. Therefore, it may be helpful for them to follow the advice of adults they trust, even if it does not make much sense to them at the time.

## Culture
 photographed some time before 1911]]

Puberty is the time in a child's life when he or she becomes able to make children, this is seen as very important. Therefore, people in many countries around the world practice Rites of passage to mark this change.

### Males
***Australia**. Among some aboriginal tribes in Australia, when young men go through puberty, their penises are cut or pierced (something sharp is used to poke through the skin), or they may be circumcised. Circumcision is cutting off the foreskin of the penis (the piece of skin that covers the glans penis or head of the penis). Young men are also sent away from home to go on a long trip on foot called a walkabout. During this trip, they learn how to hunt animals and survive in the open.

### Females
***America**. Among the Navajo (, ), who are a Native American people, a young woman who has had her first period goes through a four-day ceremony called *Kinaalda* which shows that she has changed from being a girl to a woman. The young woman's mother combs her hair and ties it into a ponytail. The young woman's family then sings a prayer, after which she puts on a dress made of a rug and jewelry made of turquoise and seashells. The young woman then runs as fast as she can towards the east, and turns around and runs home. She usually does this once in the morning and once in the evening every day during the ceremony. On the first night, the young woman does not go to sleep but stays awake while more prayers are sung. During the ceremony, the young woman also stands straight or lies on the ground in front of her mother, and her mother passes her hands over the young woman's body to make sure that she grows up beautiful. On the last day of the ceremony, the young woman does a final run; her mother passes her hands over her body one last time; and the young woman gives *alkaan*, a large cake made of maize (corn) that she has made, to her whole tribe to eat.
***Brazil**. Among the Urubu-Kaapor people of Brazil, South America, when a young woman has had her first period, she goes into a room in her home covered with palm leaves to spend time alone for a month. She only eats cooked white cassava flour and white tortoise meat. She sleeps in a hammock (a type of bed made of rope that is hung above the floor) as it is believed that some magic will escape if her feet touch the ground. On the seventh day of her time alone, the young woman's father cuts her hair very short. Her legs are scratched with the tooth of an agouti, which is an animal that looks like a guinea pig. Pieces of cloth are wrapped around the woman's forehead and abdomen, and large ants are put inside the cloth. After the woman has been bitten by the ants a few times, the cloth is removed. The Urubu-Kaapor people believe that the woman will learn how to be strong if she suffers some pain. After the young woman has finished spending a month alone in her room, she makes a meal and a special drink from cassava and gives it to her family and other people in her village. The young woman is now considered an adult and can wear a necklace of feathers and a waistband with flowers. She also puts pink makeup made from plants on her face.
***Ghana**. When young women of some tribes in Ghana, Africa, have had their first period, they spend two to three weeks away from their family and friends. The queen mother of the town or village where they live and other older women teach the young women about sex and birth control. The young women also learn how to relate to men so that they can have a good marriage. After this, the young women appear at an event attended by the chief and everybody in the town or village. Young men also come to choose women to marry.

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## Other websites
* Growing Up Sexually: A World Atlas 
* NIH guide to puberty and adolescence
* "Puberty in Girls" from AboutKidsHealth, The Hospital for Sick Children, Toronto, Canada 
* "Puberty in Boys" from AboutKidsHealth, The Hospital for Sick Children, Toronto, Canada 
* Teen Forums – Puberty