Puberty (male)
Puberty generally marks the beginning of adolescence, but the two things are not identical. Adolescence itself can be defined as the period between the onset of sex steroid secretion until full adult height is reached. Puberty is considered to be the beginning years of adolescence, and is complete when girls experience their first menstrual period or viable sperm is present in the ejaculate for the first time in boys. In Western nations such as Australia, girls attain puberty at around age 12, and boys at around 13.
Hormones and puberty
When the hypothalamus (a part of the brain) matures, it begins to produce and secrete a chemical called gonadotrophin releasing hormone (GnrH). GnRH then affects a different part of the brain, the pituitary, causing it to secrete two hormones crucial to normal reproductive function – lutenising hormone (LH) and follicle-stimulating hormone (FSH). These then stimulate cells in the testes, causing them to enlarge – the first sign of male puberty.LH and FSH act on cells of the testes, causing them to produce testosterone and androgen-binding protein (ABP). ABP helps to raise testosterone levels in the testes. Testosterone plays an important role in the physical changes associated with puberty, and in testicular maturation. However, FSH needs to be present in sufficient amounts for testosterone to have its effects.
In addition to the enlargement of the testes, testosterone produces several other changes in the male body that are associated with puberty.
Changes to the body during puberty
Testosterone
produces the general distinguishing characteristics of the masculine
body, causing changes to the sexual organs themselves as well as being
responsible for secondary sexual characteristics:Changes to the penis, scrotum and testes
These three organs enlarge by about 8 times by the age of 20 years. The internal ducts and glands of the reproductive system also increase in size during puberty. Males experience erections more frequently, and “wet dreams“, involuntary emissions of semen during sleep often accompanied by erotic dreams, often occur.
Changes in hair distribution
Hair grows around the pubic, underarm and facial areas. Hair around the pubic area generally extends upwards to the abdomen, sometimes reaching the belly button. Hair on the chest also develops, and less often on other regions of the body such as the back. Hair already present on most other portions of the body, such as the legs, becomes more prolific.
Changes to the voice
The larynx enlarges during puberty, initially resulting in a cracking voice, but gradually resolving into a deeper typically adult masculine voice.
Changes to the skin
The skin becomes thicker over the entire body. Sebaceous glands in the skin secrete increased amounts of sebum, especially on the face, which can lead to the development of acne. Acne is one of the most common features of male adolescence as the body is first exposed to increased testosterone. The skin normally adapts to these high testosterone levels over the years, gradually overcoming the acne.
Changes to muscle development and growth
Muscle mass increases. Males increase their muscle mass about 50% more than females. Increased protein is also found in non-muscular parts of the body.
Changes to the bone
The bones grow significantly thicker when circulating testosterone increases. The overall quantity of bone is increased, causing more calcium to be retained. Testosterone also acts on the pelvis, making it narrower and longer, causing a funnel-like shape, as opposed to the broad oval-like shape of the female pelvis, which is better suited to childbearing.
Changes to the blood
Testosterone stimulates the production of red blood cells, so that the quantity and proportion of red blood cells in males is higher than females.
Changes to the brain
Testosterone awakens the libido, or sex drive. In addition, many psychological changes during puberty occur that change the way a person’s mind works.
Psychological changes during puberty
During the course of puberty and
adolescence, young people begin to shift away from concrete thinking to
the more adult abstract thinking. Concrete thinking occurs when objects
have to represent “things” or “ideas” for problem-solving. In contrast,
abstract thinking is the ability to use internal symbols or images to
represent reality. Young people are therefore able to move from thinking
literally to thinking hypothetically about the future, and to assess
multiple outcomes when faced with a problem.Early puberty
During the early stages of puberty, concrete thinking still dominates but during this time early moral concepts begin to appear. Sexual orientation may also develop at this stage.
Mid-puberty
Mid-puberty, abstract thinking begins to feature more prominently. Many young people at this stage still have a sense of “invincibility” akin to that during childhood. The law is still generally identified as a guide to what is right, and its morality is not questioned. Fervent ideology may also start to develop, for example in the form of religious or political views.
Late puberty
Late in puberty, there is the development of complex abstract thinking and the identification of differences between law and morality, leading to questioning of the law and authoritative figures. Personal identity is also further developed.
Early onset of puberty – precocious puberty
Precocious puberty can occur as a result of abnormalities of the central nervous system that disrupt GnRH secretion, or it can be independent of GnRH secretion. The onset of puberty before the age of 9 generally defines precocious puberty in
boys, and involves early physical changes of puberty, as well as
accelerated linear growth and bone maturation. This can ultimately lead
to a short adult stature because the bones stop growing early.
Delayed puberty
When
a male shows no signs of entering puberty by the age of 14 (no
enlargement of the testes), puberty is generally said to be delayed.
Puberty can be delayed by a number of different factors, including inadequate nutrition, chronic illness, severe levels of stress and problems with interactions between the brain and the reproductive system.Stages of puberty Female .....
1. Breast development (Thelarche)This is the first noticeable sign of puberty in females. The internal structures of the breast begin to develop under the influence of hormones including oestrogen and progesterone. Growth hormone and glucocorticoids then complete the development of the network of ducts within the breast, while fatty and fibrous tissue enlarge the breast. Breast development is generally completed at around the age of 20. However, minor changes occur with each menstrual cycle and the breasts change dramatically during pregnancy.
2. Growth of pubic and underarm hair (Pubarche)
Hair begins to grow and proliferate around the pubic area and under the arms. Oil and sweat glands also form, especially in the underarm area. Androgens, which are a class of hormones that includes testosterone, are secreted by the ovaries, causing these changes. These androgrens also stimulate the sex drive in both males and females. Women secrete relatively little androgen compared to men.
3. Menstruation (Menarche)
The first menstrual period, also known as menarche, marks the end of puberty. The average age of menarche has declined over the past decade in Western nations and is now about 12 years of age. This is thought to be due to improved nutrition. Attaining menarche does not nesessarily mean that a girl is fertile as the first few menstrual cycles are not likely to result in the release of an egg (ovulation). Ovulation generally begins to occur regularly about a year after menarche.
Progesterone and oestrogen
Progesterone
and oestrogen are important hormones in the development of adult
reproductive function. Levels of both hormones increase significantly
during puberty, resulting in many changes to the body.Progesterone mainly affects the uterus (the womb) to prepare it for pregnancy during the second half of the menstrual cycle. It thickens the uterus lining in preparation for a fertilised egg to implant. If fertilisation does not occur, this lining breaks down and is discharged as a menstrual bleed.
The oestrogens stimulate most of the other changes associated with puberty.
One effect of oestrogen is to change the female sex organs from those of a child into those of an adult. It stimulates the growth of the ovaries, fallopian tubes, uterus and vagina. The external genitalia, including the labia minora and labia majora, also increase in size.
Oestrogens are also responsible for the development of the breasts. An extensive ductile system is developed and additional fat is deposited in the area. The ability to produce milk also comes about as a result of the influence of oestrogen.
The reabsorption of bone is inhibited by oestrogens. This results in bone growth, so that the female growth in height during puberty is rapid for several years. However, oestrogens also cause the bones to stop growing earlier than they do in males, leading to the growth of women ceasing several years earlier than the growth of men. Women are therefore generally shorter in stature.
Oestrogens increases the deposition of fatty tissue, so that women have a higher percentage of body fat than men. Fat is particularly deposited in the hips, thighs, buttocks and breasts. This produces the characteristic female “hourglass” figure. Skin is also thickened in females, although it remains thinner, softer and warmer than in males of the same age.
Psychological changes during puberty
During
the course of puberty and adolescence, young people begin to shift away
from concrete thinking to the more adult abstract thinking. Concrete
thinking occurs when objects have to represent “things” or “ideas” for
problem-solving. In contrast, abstract thinking is the ability to use
internal symbols or images to represent reality. Young people are
therefore able to move from thinking literally to thinking
hypothetically about the future, and to assess multiple outcomes when
faced with a problem.Early puberty
During the early stages of puberty, concrete thinking still dominates, but early moral concepts begin to appear. Sexual orientation may also develop at this stage.
Mid-puberty
Mid-puberty, abstract thinking begins to feature more prominently. Many young people at this stage still have a sense of “invincibility” akin to that during childhood. The law is still generally identified as a guide to what is right, and its morality is not questioned. Fervent ideology may also start to develop, for example in the form of religious or political views.
Late puberty
Late in puberty, there is the development of complex abstract thinking and the identification of differences between law and morality, leading to questioning of the law and authoritative figures. Personal identity is also further developed.