Video Transcript
In this video, we will learn about
puberty, an important process that occurs in the body during our adolescence. We will define what puberty is,
describe some of the typical changes that occur in biological males and biological
females during puberty, and how they can be influenced by sex hormones.
You may already be aware that as we
grow from a baby into a fully grown adult, many changes take place inside and
outside our bodies. In this video, we’ll be learning
about the stage in life where a child becomes an adult, a period of change called
adolescence.
During adolescence, a number of
physical changes occur as an individual reaches sexual maturity. This is called puberty. Puberty is the stage in life at
which many of us develop the physical ability to reproduce. So many of the changes that occur
affect the reproductive organs. In spite of a person being
physically capable of reproduction at the onset of puberty, they are unlikely to be
mentally or emotionally prepared for such a responsibility, however.
Different people start puberty at
different times. The average age at which biological
females begin puberty is around 11 years old. Puberty tends to start a little
later for biological males, around 12 years old. It is perfectly normal for an
individual to start puberty at any age between eight and 14.
As we mentioned, there are many
physical and emotional changes that occur during this progression from childhood
into adulthood. It is important to note that it is
entirely normal for every individual to have a unique experience during puberty. The changes that occur during
puberty are caused by hormones, particularly sex hormones. Hormones are chemical messengers,
which are usually transported in the bloodstream throughout an organism’s body to
regulate certain target cells’ activity. Sex hormones specifically are
primarily produced in a person’s sex organs, which are sometimes called gonads.
Let’s start by learning some
examples of changes that are usually common to both biological males and females
experiencing puberty, before we explore how they differ between the biological sexes
in more detail. Both males and females are likely
to experience a growth spurt during puberty, which means they will suddenly increase
in height over a relatively short period of time. Let’s see an example of the pattern
of growth experienced by males and females during adolescence by looking at this
graph.
The vertical 𝑦-axis shows height
in centimeters, and the horizontal 𝑥-axis shows age in years. The pink line on this graph
represents the growth of a typical female. As we can see, it becomes steeper
just before the age of 12 as her growth spurt begins. In males, the growth spurt caused
by puberty tends to occur about two years later than in females. On this graph, we can see the
growth of a typical male represented by an orange line, which becomes far steeper
just before the age of 14, as his growth spurt begins. That’s why girls are usually taller
than boys around this age.
Let’s see some other changes that
occur during puberty which are common to both biological sexes. Both males and females start to
develop extra body hair. This includes pubic hair, which is
hair that grows around the genitals, and underarm, or armpit, hair. Many individuals start to develop
spots, or acne, particularly on their faces. Often, puberty can also result in
an individual sweating more. Emotional changes are very common
in both sexes. These can include mood swings,
feeling stressed and short-tempered, and an increase in the intensity of
emotions. This is because hormones also
change the way our brain is organized and how it functions.
The main sex hormones produced by
biological females are estrogen and progesterone. And in males, the main sex hormone
is testosterone. It’s worthwhile noting that both
biological sexes actually produce small quantities of the other sex’s sex hormones
too. Let’s explore how hormones can
affect individuals experiencing puberty in some more detail, starting with
biological males.
The testes are a biological male’s
primary sex organs. Males typically have two testes,
each of which is called a testis. They hang outside the body core,
beneath an organ called the penis. Under the effect of hormones
released by a gland at the base of the brain, called the pituitary gland, the testes
develop and become larger. It’s common that one testis is
larger and lower than the other one. During puberty, the testes start to
produce sperm.
The testes also start to produce
higher levels of testosterone. This hormone is the primary cause
of the body changes in biological males during puberty. For example, testosterone can
encourage the growth of body hair, the testes, and the penis. Males typically develop thicker,
coarser facial hair during puberty under the influence of high testosterone
levels. As their bodies also release small
quantities of testosterone, it is common for biological females to develop some
facial hair too, especially above the upper lip, though this is typically thinner
and finer hair than in males.
Testosterone can also cause a
deepening of voice in both sexes, which is particularly pronounced in biological
males. We often say that a male’s voice
breaks when it develops a significantly lower tone during puberty. Other changes that can occur
include increased bone and muscle growth. During puberty, males commonly
experience involuntary erections that may be caused by random changes in
testosterone levels. An erection is a hardening of the
penis that causes it to enlarge and stand upward or outward. Males can also experience
involuntary ejaculation, which is when sperm exits the body via the penis. These events can happen
unexpectedly during puberty. But they are both common and
normal.
Now, let’s take a look at the
changes that are typically unique to biological females during puberty. The ovaries are sex organs of a
biological female, and most females have two of them. The uterus is the part of the
female body where a baby grows during pregnancy. The uterus is connected to a
female’s external genitals by a muscular tract called the vagina. Under the effect of hormones
released by the pituitary gland, the ovaries start to produce higher quantities of
sex hormones.
You may recall that estrogen and
progesterone are the hormones that are primarily responsible for the changes that
occur in females during puberty. Estrogen controls ovulation. Ovulation occurs when an egg cell,
the female sex cell, is released from an ovary. If this egg cell is fertilized by a
male sex cell, a sperm cell, it might eventually develop into an embryo. This embryo may then attach to the
lining of the uterus through a process called implantation, which is crucial for the
further development of the embryo, allowing it to grow into a new human life within
the female’s uterus.
Estrogen is responsible for many of
the physical changes that occur in the female body during puberty. For example, it can influence the
development of breasts and widening of the hips. Progesterone is particularly
important in regulating the thickness of the lining of the uterus. The uterine lining must be thick
for the successful implantation of an embryo.
Along with the physical changes
caused by these hormones, biological females usually start to have an approximately
monthly menstrual cycle during puberty. Let’s take a closer look at the
different parts of the menstrual cycle to work out why it is important.
The menstrual cycle begins with
menstruation, sometimes called a period, with most biological females experiencing
their first period between 12 and 14 years old. A period involves the uterine
lining breaking down, shedding blood and other material out of the female’s body
through the vagina. Each menstrual cycle is marked from
the first day of one period to the beginning of the next period. Periods normally last for between
two and seven days and occur on average every 28 days. But the intervals between periods
can be longer or shorter. The duration of periods will also
vary considerably between females and can change throughout life. After it has been shed during a
period, the uterine lining begins to thicken again.
The next stage of the menstrual
cycle is ovulation, which you may recall is triggered by an increase in estrogen
levels and involves an egg cell being released from an ovary. Ovulation usually occurs around 14
days after the first day of the period. After ovulation, the uterine lining
remains thick until approximately day 28. This is achieved due to high levels
of progesterone, preparing the uterine lining to receive an embryo if an egg cell is
fertilized. If fertilization does occur, the
female will not have a period. And the uterine lining will be
maintained for the duration of pregnancy. This pauses the menstrual cycle
until the female is no longer pregnant.
However, if the egg cell that is
released during ovulation is not fertilized by a sperm cell, another period will
occur. And the uterine lining is shed
through the vagina along with the unfertilized egg cell to prepare for another
potential fertilization. The menstrual cycle ends
irreversibly during menopause, when the ovaries no longer release egg cells and
periods stop. Once this occurs, a female can no
longer have a natural pregnancy. Let’s apply what we’ve learned
about puberty to some practice questions.
Many changes occur in the body
during puberty. In particular, growth rate
increases rapidly. The provided chart shows the growth
of a biological female and a biological male between the ages of four and 20. On the basis of their growth, which
of the following statements is most likely to be wrong about the puberty of these
individuals? (A) The biological female is most
likely to have finished her puberty first. (B) The biological male’s puberty
most likely happened between the ages of 13 and 17. (C) The biological male is most
likely to have started his puberty first. Or (D) the biological female’s
puberty most likely happened between the ages of 11 and 16.
We are given a graph showing how
the height of a biological male and female changes as they increase in age. We are asked to use their rate of
growth to identify which of the statements provided is most likely to be wrong. Let’s first establish what the
graph shows us about the growth of each individual. As the 𝑦-axis indicates height and
the 𝑥-axis age, we can deduce that the steeper the line on the graph, the higher
the rate of growth.
You may recall that during puberty,
a growth spurt usually occurs. This is true for both biological
males and biological females. By looking for the steepest parts
of the line for both the biological male shown in blue and biological female shown
in pink, we can work out between what ages their puberty most likely took place.
The pink line showing the growth of
the female increases at a similar rate until around 11 years of age, after which
there’s a rapid period of growth. This rapid growth continues until
the female is around 13 years of age, at which point the rate starts to decrease and
growth slows down. With this information, statement
(D), the biological female’s puberty most likely happened between the ages of 11 and
16, appears to be correct, as a growth spurt often indicates the start of
puberty. Knowing this, we can eliminate
option (D), as we are looking for the statement that is most likely to be
incorrect.
For the biological male, the most
rapid growth occurs between around 14 and 15 years of age. This suggests that option (B), the
biological male’s puberty most likely happened between the ages of 13 and 17, is
also valid and cannot be the correct answer choice.
Based on the rate of growth, the
biological female is most likely to have started and finished puberty first, as this
will correspond with her earlier growth spurt. This suggests that option (A), the
biological female is most likely to have finished her puberty first, is also not the
correct answer to this question. It is most likely incorrect that
the biological male started his puberty first, as his growth spurt occurs around 14
years of age, compared to between 11 and 12 for the female. Therefore, the statement that is
most likely to be wrong is (C): the biological male is most likely to have started
his puberty first.
Let’s try another question
together.
What molecules in the human body
are responsible for causing the physical and emotional changes that occur during
puberty? (A) Enzymes, (B) white blood cells,
(C) sugars, (D) neurotransmitters, or (E) hormones.
As this question concerns changes
in the body during puberty, let’s start by defining what puberty is. Puberty describes all the physical
changes that occur during adolescence, the period of transition between childhood
and adulthood. Puberty marks the start of the
period when an individual becomes sexually mature and physically capable of
reproduction. The physical changes that occur
during puberty are triggered by molecules called hormones. Hormones are chemical
messengers. They are transported in the blood
to their target cells, where they can trigger a wide range of effects.
Some of the key hormones that
influence puberty are sex hormones. In biological females, the main sex
hormones that influence puberty are estrogen and progesterone. In biological males, testosterone
is the sex hormone primarily responsible for the changes that occur during
puberty. Now we can answer this question
correctly. The molecules in the body that are
responsible for causing the changes that occur during puberty are (E) hormones.
Let’s recap some of the key points
we have covered in this video about puberty. Adolescence is the period of change
from child to adult and is accompanied by physical changes called puberty. The changes that occur during
puberty are mostly due to sex hormones. In particular, testosterone is
secreted by the testes in biological males and estrogen and progesterone from the
ovaries in biological females.
Some changes that commonly occur in
both biological males and females during puberty are the growth of extra body hair,
such as pubic and underarm hair. Some physical changes that take
place in most biological males during puberty include the growth of coarse facial
hair, voice breaking, increased bone and muscle growth, and genitals becoming
larger. Some physical changes that take
place in most biological females during puberty include breasts developing, hips
widening, and the start of the menstrual cycle.
