The wonderful human body!

Secondary sex characteristics, also called secondary sex characteristics, refer to the differences in appearance (shape, posture, appearance, voice, etc.) between men and women other than the genitals, and are the external manifestations of sexual development. Is the newborn baby a boy or a girl? The basis for identification is the reproductive organs: those with penises are boys, and those with vaginas are girls. In this way, the penis and vagina become sexual characteristics - characteristics that are different between the two sexes. The reproductive organs that are already formed at birth are called primary sex characteristics, or primary sex characteristics.

Secondary sexual characteristics are changed due to the action of sex hormones. Gonads are innate. The gonads remain dormant until puberty. Entering puberty, the gonads begin to recover, and the hormones they secrete, sex hormones, determine the development of primary sexual characteristics and the appearance of secondary sexual characteristics in adolescent boys and girls. Therefore, it is generally not until puberty that the differences in secondary sexual characteristics between men and women become obvious. By adulthood, the gender differences in physical appearance between men and women are significant.

If the function of the gonads is impaired, the secondary sexual characteristics will change and produce some abnormal manifestations.

The familiar “hermaphrodites” are also examples of abnormal secondary sexual characteristics, and can be divided into two categories: “true intersex people” and “false intersex people”. True intersex people have gonads of both sexes, that is, testicles and ovaries; while false intersex people have single-sex gonads, that is, they have only male testicles or only female ovaries, but the external genitalia and secondary sexual characteristics are not the same as There are varying degrees of gonadal contradictions, which are more common in intersex people than in true intersex people. For example, in a female pseudo-hermaphrodite, the gonads in the body are ovaries and have female secondary sexual characteristics (auxiliary sexual characteristics), but the external genitalia looks like a male. On the contrary, male pseudo-hermaphrodites have male gonads, testicles and secondary sexual characteristics, but their external genitalia resemble those of women. Intersex can be corrected through surgery and hormone treatment. Those who suspect intersex should seek medical advice as soon as possible, make a clear diagnosis, and receive timely treatment. Otherwise, jokes like "a real man marrying a fake woman" and "a real woman marrying a fake man" are often made. .

The following table is summarized in the rough order of puberty development:

Timetable of puberty development

Age (years) Female Male

8-9 The uterus develops, the pelvis begins to widen, the arms begin to become round, and the secretion of sebaceous glands increases. No change

10-11 Breasts and nipples begin to develop, pubic hair appears, testicles begin to enlarge

12 Vaginal mucosa changes, nipples and areola protrude, internal and external genitalia change, Adam's apple begins to enlarge, The prostate begins to move

13 Nipple pigmentation, breasts are significantly enlarged, pubic hair appears, testicles and penis are enlarged

14 Menarche, axillary hair grows, the sound becomes thicker, and the breasts are swollen

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15 Menstruation gradually changes to the cycle of ovulation, there are obvious pelvic changes, scrotal pigmentation increases, armpit hair grows, beard begins to grow, testicular growth completes, and spermatorrhea appears

16-18 Face Acne, bones close, stop growing taller. Acne on face, hair growing on face and body

19-22

Bone closed, stop growing taller

General Generally speaking, you can judge whether puberty development is normal based on this table. However, the process of puberty development is affected by many factors, and it is common for certain sexual characteristics to develop earlier or later. This is a normal phenomenon.

After a man enters puberty, a "mutation" occurs. In addition to the development and maturity of his reproductive organs, other parts of the body also undergo tremendous changes. From a naughty and cute little naughty, he turned into a tall man with a deep and loud voice. Not only did he have a beard on his face, his Adam's apple protruded in the middle of his neck, but he also had broad shoulders, broad chest, and thick limbs. These phenomena gradually form from adolescence and are not born. These are male secondary sexual characteristics, also called physiological signs of manhood.

Men’s secondary sexual characteristics are produced under the action of male hormones. When a baby is born, the testicles, the main sex organ, are only as big as a peanut. In childhood, they enlarge to the size of a sparrow egg. At this time, the testicles do not produce sperm and only produce a small amount of androgen. During puberty, the testicles enlarge to the size of a pigeon egg and begin to produce sperm and secrete large amounts of androgens. Under the action of androgens, male secondary sexual characteristics also appear.

Men’s secondary sexual characteristics have three distinctive characteristics:

(1) The production of body hair (beard, armpit hair, pubic hair), especially the growth of pubic hair on the reproductive organs, can Seen as the beginning of male sexual maturity.

Generally, pubic hair appears earliest, around the age of 12 to 13. A small amount of lighter and finer hairs can be seen on both sides of the root of the penis. Later, it gradually spread to the perineum, the color gradually turned black, and the hair became thick and curly. In late adolescence, pubic hair also appears on the inner thighs, pubic symphysis, and around the anus. Armpit hair appears about a year later than pubic hair, and generally starts from the center of the armpit and spreads to the surrounding areas. The germination of beard begins around the age of 15, starting from both sides of the upper lip and gradually growing toward the middle. Later, it will also appear on the temples and chin. Some people grow into beards at a certain point. Beards on the chin do not grow until the boy's sexual organs are fully developed.

(2) Voice change, the voice changes from high-pitched to deep, and the Adam's apple protrudes in the middle of the neck. Generally speaking, the length of the buried vocal cords of young children is 9-10mm. After entering puberty, the thyroid cartilage of the larynx will change drastically, so the Adam's apple becomes obvious. The vocal cords have also become longer, about 13-14mm. The voice changes later, around the age of 14. The Adam's apple only accelerates after the rapid growth of the stem stops.

(3) The testicles and penis become larger. Under the action of male hormones, the development of the penis becomes more obvious. As the testicles mature, semen will also be secreted and even nocturnal emissions may occur.

These all indicate that boys have entered puberty.

The order of appearance of secondary sex characteristics in boys: 11-12 years old, 13-14 years old, 15-16 years old, 17-18 years old, 19 years old and later

Physical development characteristics: height spurt begins, testicles , the penis begins to grow and Adam's apple appears. Voice changes, pubic and armpit hair appear, and peak height growth occurs. Nocturnal emission for the first time, beard appears, penis and testicles are close to those of adults. Body hair is close to that of an adult. Epiphyseal healing begins, resulting in tall stature, broad shoulders, and rough skin.

The secretion of estrogen in women during puberty promotes the development of secondary sexual characteristics.

Estrogen and progesterone secreted by the female ovaries. This affects secondary sexual characteristics.

The first is the development of the breasts. When a girl reaches puberty rapidly, her ovaries secrete a large amount of estrogen. The estrogen is transported to the breasts through the blood circulation throughout the body, directly Affects breast development. Girls' breast development begins about 3-4 years before menarche; this time is equivalent to the fifth or sixth grade of elementary school or the first grade of junior high school. At this time, the darker areola around the nipple is swollen, and the breast ducts and fatty tissue under the nipple and areola are enlarged, causing the breast to protrude outward. The breast will be rounder and more prominent than before. The areola is wider. At this time, a swollen and painful hard knot appears around the nipple. If you accidentally touch it, the nipple area will hurt. This period is called the areolar stage of breast development. Breast pain often causes anxiety and fear in girls. In fact, this change is the only way for breast development. When the breasts mature, they will no longer hurt. When playing, be sure to protect your breasts to avoid hitting the developing parts. When reading and writing, keep a fist-width distance between your chest and the edge of the table. Do not let your chest press against the edge of the table, which will compress breast development. After entering junior high school, the muscles around the areola of girls begin to develop, the bulge of the chest is vaguely visible, and the breasts gradually form hemispheres. By the time they graduate from junior high school, some girls' breasts are fully developed and their mammary glands are very developed so that they can secrete milk as mothers in the future. Small holes appear on the top of their nipples for the discharge of milk in the future. The breast phase called breast development. It takes about three or four years for breasts to develop until they are close to maturity. The speed of breast growth has nothing to do with the size of the breasts in the future, nor the amount of milk secreted in the future. Breasts are female lactation organs and one of the most distinctive symbols of women. Once girls get over the shyness caused by the beginning of breast development, they will be pleasantly surprised to find that having a pair of mature breasts is something a girl can be proud of!

The buttocks are prominent. The pelvis becomes wider. Fat also begins to be distributed to the buttocks, chest, shoulders and other parts, and the pelvis begins to widen. The body gradually develops towards that of an adult woman. In addition, the skin becomes delicate, smooth and soft, and the plump body shows the feminine beauty and beauty of women.

Pubic hair development in women generally lags behind breast development. Armpit hair develops later than pubic hair, and most women have sparse armpit hair.

The formation of secondary sexual characteristics in adolescent females: the breasts develop more fully and the nipples often become larger.

The characteristics of female sexual maturity: it is marked by regular monthly ovulation. This regular ovulation means that women have reached sexual maturity and have fertility, which means that menstruation has begun regularly.

The order of appearance of secondary sex characteristics in girls: 8-10 years old, 11-12 years old, 13-14 years old, 15-16 years old, 17-18 years old, 19 years old and later

Physical development characteristics: height prominence Increase begins. Breasts begin to develop, pubic hair appears, and height suddenly reaches its peak. Menarche, armpit hair appears, voice becomes thinner. Fat accumulation increases, buttocks become rounder, and menstruation becomes regular. The epiphyses begin to close. Slim body, delicate skin.

With the development of secondary sexual characteristics, the female third sex gradually becomes more feminine due to the influence of cultural and social factors. The differences from men in terms of personality, hobbies, emotions, behaviors, etc. become more obvious. .

No matter male or female, there will be differences in secondary sexual characteristics between the same gender. Sometimes these differences are quite obvious, but we cannot say what is normal and what is abnormal. of. Because there are individual differences in secondary sexual characteristics.

Related references: Tertiary sexual characteristics: the female uterus, vagina and vulva, and the male epididymis, prostate and penis. These accessory reproductive organs and the direct controllers of the development of male and female secondary sexual characteristics are sex hormones . Sex hormones are mainly secreted by the gonads (testicles, ovaries) and partly by the adrenal cortex. Sex hormones include "estrogens", "androgens" and "progestins". These three hormones are actually found in both men and women, but men have more androgens and women have more estrogen. Androgen can promote the development and maintenance of the prostate, seminal vesicles, penis, beard and Adam's apple, etc., and also promote muscle development. Estrogen can promote the development of fallopian tubes, uterus, vagina and vulva and maintain them in a mature state. It can also inhibit the growth of beards and promote subcutaneous fat deposition. The secretion of sex hormones is controlled by the pituitary gland "gonadotropin", and the secretion of gonadotropin is controlled by the hypothalamus "gonadotropin-releasing hormone". The pituitary gland is a pea-sized endocrine gland located in the center of the cranial cavity. It hangs directly below the hypothalamus and communicates with the hypothalamus through a special vascular system. In the first seven or eight years of life, the development of the hypothalamic sexual center is not mature enough and is inhibited by the pineal gland, another endocrine gland in the cranial cavity. By the age of eight or nine, the sexual center of the hypothalamus has matured. At the same time, the pineal gland has degenerated and gradually calcified, eliminating the inhibition on the hypothalamus, so the hypothalamus begins to secrete "gonadotropin-releasing hormone", causing the pituitary gland to It also begins to secrete "gonadotropins", so the gonads develop, the secretion of sex hormones increases, and the development of accessory reproductive organs and secondary sexual characteristics begins.

Secondary sexual characteristics in girls during puberty

What is puberty? Puberty is a series of changes that occur as you grow and mature until you are able to have children.

Puberty usually occurs between the ages of 10 and 16 in girls. Your essence as a wonderful and unique individual does not change during adolescence. However, many other aspects will change.

In short, you will undergo the following changes during puberty:

1. Slight changes in body odor

2. Increased buttocks

4. Armpit hair appears

5. Nipples become darker

6. Breasts become larger

7 , increased pubic hair

8. Menarche

These are secondary sexual characteristics of women. Secondary sexual characteristics of boys during puberty

When boys enter puberty, their bodies grow rapidly under the action of sex hormones. The average growth rate is about 6-8 centimeters per year, the bones and muscles begin to become thicker and thicker, the voice becomes deeper, pubic and armpit hair grows on the pubic area and armpits, and beards gradually grow. These are male secondary sex characteristics.

The development of male external genitalia during adolescence generally begins around the age of 12. During this period, the testicles and scrotum begin to enlarge, the scrotum gradually becomes darker, and thick pubic hair gradually grows. On average, after about 3 years, the penis grows and increases in diameter until it reaches sexual maturity.

In addition to the emergence of the above-mentioned secondary sexual characteristics, the main physiological change during puberty is the maturation of the reproductive system. At this time, the testicles begin to "produce" sperm and secrete male hormones.

From this time on, boys begin to experience nocturnal emissions, develop sexual desire, and have the ability to have children, becoming men in the true sense.