The sexual life cycle of a male begins a little more than seven months before he is born, when, in response to genetic instructions from a chromosome in his father’s sperm, the previously neutral embryo starts to develop male sexual characteristics. When he is a teen, sexuality becomes more pronounced and boys during puberty begin what can seem their rapid transition to sexual maturity.
Although the sex of an unborn child is determined from the moment the egg is fertilized, the internal and external reproductive organs of both sexes are identical for the first few weeks of life in the womb. About seven weeks after conception, however, the male embryo begins to develop testes which produce the male sex hormone, testosterone. This enables the penis, scrotum and seminal vesicles to form.
The developing testes also secrete another hormone – female duct-inhibiting substance. This causes the structures, which in a female would develop into the vagina, uterus and Fallopian tubes, to wither away.
At birth, although boys tend to weigh a little more than girls, their bone structure and certain organs are usually less well developed. This may be the reason why a higher proportion of boys tend to be stillborn or to die soon after birth. Because of their genetic make-up, boys are more prone to many infectious diseases than girls. Some are also vulnerable to certain inherited disorders, such as colour blindness and haemophilia.
But apart from this, there are relatively few physical differences between the sexes until they reach puberty – their body shape, average height, weight and growth patterns are very similar. Boys usually reach puberty between 13 and 15 years, and the acceleration in the rate of growth which precedes it usually begins at 12.
Boys during puberty
During puberty, the sex and other hormones, which are produced by the body in considerable quantities at this time, change a boy or girl into a physically mature adult capable of reproduction. In a boy, this means the ability to ejaculate healthy sperm.
The onset of puberty can vary a good deal from one country and culture to another, although there seems to be no obvious reason for this.
The age at which puberty begins can also vary considerably from one individual to another – in boys any time between 9 ½ and 13 ½ is considered to be normal.
When a boy reaches puberty, his testes, scrotum and penis rapidly increase in size, and so do his internal reproductive organs – the seminal vesicles (which produce seminal fluid) and the prostate gland – and he is able to ejaculate. He also develops secondary sexual characteristics, such as pubic hair, underarm and facial hair and a much deeper voice.
His growth rate speeds up and his body changes its proportions. His shoulders become wider and heavier, his trunk lengthens and his chest deepens so that the body takes on an inverted triangular shape. His legs and arms lengthen and become much more muscular, and he becomes stronger and heavier.
These changes are brought about by an increase in the body’s production of human growth hormone together with testosterone, the male sex hormone.
At a time which varies according to each individual’s genetic clock, the pituitary gland on the underside of the brain begins to increase its manufacture of growth hormone, which is responsible for a boy’s height and weight gain.
Together with the gonadotrophins, testosterone leads to the manufacture of sperm in the testes. It also stimulates a boy’s sexual interest, is responsible for the development of his male characteristics and, probably in association with growth hormone, increases his strength and muscle mass.
Underarm hair usually begins to grow about two years after pubic hair first appears, and is accompanied by the development of facial hair on the upper lip.
Body hair begins to spread over legs, arms and chest, and will continue to do so for several years after the other changes are complete.
Owing to the effect of testosterone, the skin becomes coarser and the pores enlarge during puberty. The sweat and sebaceous glands grow and become more active.
Stages of puberty in boys. Boys during puberty experience progressive genital development – the maturing of the testes and growth in penis size – and pubic hair growth. The gradual change in body shape can also be seen.
Change in voice
Towards the end of puberty, usually-when he is between 12 and 14 years old, a boy’s voice starts to break. This is the result of an increase in the size of the larynx, or voice box, and the lengthening of the vocal chords which deepen an octave. These developments are also due to the increased testosterone.
Although the beginning of adolescence coincides with the onset of puberty, adolescence usually goes on for much longer, spanning the decade or so between childhood and adulthood. How long it lasts depends more on social and economic factors than on age.
Learning ability and reasoning power are at their peak in adolescence, and a young person will, for the first time, be able to make rational decisions and choices.
He will also be trying to adjust to the physical changes taking place within him and to the expectations of the society in which he lives.
Boys’ sexual awakening
At puberty, boys become intensely aware of their own sexuality. Erotic dreams and fantasies become increasingly frequent. By the age of 13, many boys are sexually mature – though boys’ erections may be there pre-puberty – and able to reach a climax, experience orgasm and ejaculate semen.
It is vital not to criticise or express disapproval, even if unspoken, of boys’ erections, even if they are young teens or even very young and pre-pubescent. Young boys may not even know they have an erection if they are not sexually aware. Either way, an influential adult’s disapproval of a boy’s erection can lead to long term psychological damage.
By 15, most boys will be having orgasms two or three times a week on average. In the majority of cases these will be due to masturbation, but they may also be the result of sexual dreams, petting or intercourse.
Nearly all boys have masturbated by the age of 15, and there is nothing damaging or abnormal about it. Indeed, it could be said that boys should masturbate in order to become more sexually confident.
A boy’s early sexual experience with girls is usually limited to petting – touching the genitals and stimulating other areas of the body, but stopping short of intercourse.
Nowadays, especially in western countries where effective contraceptive methods are readily available, more young people regard sexual intercourse as a normal form of social behaviour, although boys are less likely than girls to have intercourse for the first time as part of a caring relationship. In the United Kingdom most men have had intercourse before marriage, starting mostly between 17 and 21, and about 50 per cent of men have had intercourse by the age of 19.
Changes in a boy’s body at puberty. The testes begin to produce testosterone which stimulates genital growth.
A man is sexually mature almost as soon as the changes of puberty are complete and he is able to ejaculate healthy sperm, but it may take much longer for him to become emotionally and psychologically mature.
Maturity does not have a fixed beginning or end, and a man may remain sexually active until he is well into old age.
From about 40 onwards, the testes become less efficient at producing both sperm and testosterone, but this decline is very gradual and extends over a period of 20 to 30 years. The results are a decrease in the size and firmness of the testes, and a lower level of fertility, greater difficulty in obtaining an erection, fewer ejaculations, and an increase in the time between ejaculation and the next erection.
Two important factors in maintaining sexual activity into old age for men are good health, a certain degree of fitness and the continuing interest in sex of their partners.