home Audience 5 Sexual dimorphism. Primary and secondary sexual characteristics. Secondary and primary sexual characteristics of men and women

Sexual dimorphism. Primary and secondary sexual characteristics. Secondary and primary sexual characteristics of men and women

Secondary sexual characteristics begin to gradually emerge already in the prepubertal period and reach their greatest development during the puberty period. Essentially, almost all morphological and functional properties of an organism can be classified as secondary sexual characteristics, since they are more or less differently expressed in representatives of one or the other sex. But many sex differences are either not yet sufficiently identified and poorly studied, or do not have significant practical significance.

Already from the age of 7-8, the girl’s appearance noticeably changes: the characteristic development of the subcutaneous fat layer according to the female type begins to be revealed, body shapes begin to be rounded - first in the hips and torso, and then in the shoulder girdle and arms.

Compared to boys, girls develop weaker muscles, and stronger development of the subcutaneous fat layer; the relationship between the circumference of the shoulder and pelvic girdle changes towards a relative increase in the circumference of the latter (in boys, on the contrary). Girls' skin becomes thinner and more delicate than boys' skin.

Shortly before the onset of menstruation, vegetation appears first in the pubic area and then in the armpits; at the same time, hair growth on the head also increases; the remaining areas of the skin, unlike those of males, remain, as a rule, free from hair. It is important to note that hair growth in the area of the external genitalia in girls not only begins earlier than in boys, but is also distinguished by the distribution of hair in the form of a triangle, characteristic of women, with the apex directed downwards and a sharply defined upper border above the pubis.

To secondary sexual characteristics There are also differences in the structure of the larynx, the final development of which during puberty is influenced by the gonads. The difference in the structure of the larynx is completely determined and remains constant from puberty and causes a higher timbre of the voice and weaker development of the “Adam’s apple” in women compared to men.

Very important clinically and biologically are the sexual characteristics of the development of the pelvis and mammary glands, which are closely related to the reproductive function of a woman.

Sex differences in the structure and shape of the pelvis can be detected already in newborns. For example, the width of the cavity and outlet of the small pelvis in girls is greater than in boys. Girls' pelvis is less deep; they have more developed lateral masses of the sacrum. But by the time of birth, differences in the area of the pubic angle become especially clear. So, in particular, the pubic bones of both sides in girls converge at a much greater angle than in boys. In the first decade, the growth of the pelvis occurs almost in parallel with the growth of the entire skeleton; Sexual differences in this asexual period are not sharply revealed or intensified. Only from the age of 8-10 do gender differences in the structure and shape of the pelvis begin to become more and more pronounced, which by the period of puberty are revealed in their entirety.

According to some experts, the pelvis develops unevenly at different periods of a girl’s life. The most intensive growth of the pelvis, according to these data, is observed before the age of 3 (especially during the first year of life), as well as after 10 years. The author further notes that the transverse dimensions of the female pelvis increase faster than the straight one and by the age of 15, on average, they approach the dimensions of the female pelvis. The straight size at this age still lags significantly behind the corresponding pelvic sizes of adult women and continues to increase after 15 years. After 10 years, with increased growth and development of the pelvis, all its sizes, according to the author’s research, still grow more or less evenly, on average within 0.5-1 cm per year, and by the age of 15 the average size of the pelvis reaches: distantia spinarum - 23.3, distantia cristarum - 26.1, distantia trochanterica - 31.2, conjugata externa - 18.4 cm. These figures seem to us somewhat exaggerated, according to at least for most teenagers 15 years old.

The main characteristic features of the female pelvis, as is known, include the following: the female pelvis is much more spacious than the male one; it is wider in the transverse direction, narrower in the vertical; the pubic angle in the female pelvis is obtuse (in the male pelvis acute); The shape of the female pelvic cavity is cylindrical (in men it is funnel-shaped). As for the size of the pelvis, which is so important in obstetrics, they are finally determined only with the completion of the growth of the entire skeleton and largely depend on the general physical development of the body.

Differences in the size and shape of the female pelvis also determine some characteristic features of the female body that are not related to its reproductive function. So, for example, the significantly greater width of the female pelvis in the transverse direction compared to the male one determines to a large extent the characteristic features of the external appearance of a woman, and the peculiarity of the location of the lower extremities in relation to the female pelvis, also determined by the length of its diameter, is reflected in the female gait, which is noticeably different from men's. All of these features begin to clearly emerge by the end of the first decade of life.

As already mentioned, The most important secondary sexual characteristics include the structure and activity of the mammary glands. The development of mammary (mammary) glands, as well as other sexual characteristics, occurs unevenly. By the time a girl is born, her mammary glands do not present any special differences from those of boys. The mammary glands of a newborn baby, located under the fourth rib, are only a few millimeters in diameter and can be felt in the form of a small grain. Microscopically, the gland has a tubular structure and consists of 12-15 underdeveloped lobules. During the first days of life in newborns of both sexes, apparently under the influence of maternal (placental) hormones, the mammary glands begin to increase to a greater or lesser extent, reaching their maximum size (up to the size of a large hazelnut or pea) by the end of the 1st year. or by the middle of the 2nd week. From the swollen gland, as a rule, a secret is released when pressed, similar in appearance and content to a woman’s colostrum. Since the secretion is usually not released spontaneously, accumulating in the gland itself, then later the lumens of the latter expand and the gland appears to the touch as if “cystic” changed.

After 2-3 weeks, the mammary glands of infants undergo reverse development: the enlarged lumens begin to collapse again, dense connective tissue develops; the swollen glands gradually become denser and smaller. Enlargement of the mammary glands and release of colostrum can be observed within 2-6 weeks. In premature infants, the described phenomena are observed less frequently; they usually begin later and are less pronounced. J. Zilberberg notes that complete reverse development of the gland to the state of the so-called “quiet gland of the child” is achieved only by the 5-7th month of his life. N.P. Gundobin points out that in sections of the mammary glands of 3-4-month-old children, cellular decay, milk globules and other phenomena of incomplete involution of the glands could be detected. The described changes can contribute, especially under mechanical influences, to the occurrence of an inflammatory process in the girl’s mammary gland, followed by possible death of the gland or its functional failure. This should be taken into account when providing hygienic care for newborns and infants.

After involution of the mammary glands, their further development until puberty occurs extremely slowly. With the onset of this period, girls and most boys experience a noticeable enlargement of the mammary glands, in which hyperplasia processes occur. But if in boys this is of a transient nature and the swollen glands undergo reverse development quite quickly, then in girls from this time on the development of the mammary glands continues more and more intensively. According to Dutch authors Vant Land and de Haas, breast development begins approximately two years before the onset of menstruation.

Particularly rapid growth of the mammary glands is usually observed after the onset of menstruation, when these glands begin to acquire an alveolar structure. Underdeveloped lobules grow, their number increases. The milk ducts begin to branch and give rise to lateral hollow protrusions. A connective tissue stroma develops, and fat is deposited around the glands. The mammary glands increase in size and by the time of puberty they already occupy the space between the III-VI ribs. However, the final development of the mammary gland as a lactation organ occurs only after pregnancy and ends with the beginning of feeding.

A girl’s sexual development also affects her psyche. Long before puberty, during the years of childhood, girls’ inclinations, activities, and games acquire their own special direction, which differs in many respects from that characteristic of a boy of the corresponding age. During puberty, interest in sexual issues begins to awaken and grow. An attraction to males appears, which, with proper upbringing and the absence of bad influences or pathological deviations, does not usually have the character of a definite attraction to sexual intimacy, as is observed in boys during puberty. In females, this feeling usually appears much later, often only after the onset of sexual activity.

By and large, secondary sexual characteristics include all characteristics of the body that depend on gender. Secondary sexual characteristics begin to appear in the prepubertal period. If until the age of 6-7 years girls and boys can be confused, especially if they are dressed in clothes that do not indicate their gender, then by the age of 7-8 years the appearance of girls and boys is noticeably different.

First changes

The first changes concern the skin. In girls it remains tender, thin and soft, but in boys it begins to thicken and become denser. The subcutaneous fat layer also has its own characteristics at this age. Girls begin to smooth out their body shapes, while boys become more angular. It is becoming more and more noticeable in physical strength: boys from the age of 7-8 are stronger and more resilient, while the muscular system of girls is weaker and is not ready for overload.

Closer to 11-13 years of age, pubic hair begins to grow in both sexes. If in girls it is a characteristic triangle with the apex directed downward, then in boys the hair grows more intensively, there is no clear boundary, and there is often a “path” of hair from the pubis to the navel. In addition, boys begin to experience intensive hair growth on their legs and armpits; at the age of 16-18, some boys also begin to have hair on their chests.

Readiness for having children

The next stage, at which secondary sexual characteristics appear even more intensely, is 13-15 years of age. In girls, their first menstruation begins and their breasts begin to enlarge, and in boys, the penis noticeably increases in size. In fact, representatives of both sexes are already ready for procreation, but the overall maturity of the body occurs much later than puberty.

Around the same period, young men begin to develop their first vellus facial hair – and a mustache, although some facial hair begins to grow only at the age of 17-18. One of the characteristic sexual characteristics inherent in the male sex is a change in the larynx, the “Adam's apple” increases in size, the timbre of the voice changes, the voice becomes rougher. They usually say that the voice “breaks.”

The skeletal structure of men and women is also significantly different, this is especially noticeable in the pelvis. These differences are clearly visible even in infants, but they become most pronounced by the age of 13-15 years. Girls have less deep, but wider. This is related to the function of childbirth. And young men have a narrower and deeper pelvis.

The absence of secondary sexual characteristics indicates diseases of the endocrine system or other disorders.

Secondary sexual characteristics are clearly expressed not only in humans, but also in animals. These characteristics are of great importance either in attracting an individual of the opposite sex or in fighting for it. Primary sexual characteristics include the gonads and genitals. Secondary - develops during puberty under the influence of sex hormones.

Dependence of secondary sexual characteristics on primary ones

There is a direct dependence of secondary sexual characteristics on primary ones. Their development is greatly influenced by sex hormones, and they begin to be produced during puberty. During this period changes occur:

Dependent secondary sex characteristics are also called eusexual and develop together with the gonads. And independent characteristics (pseudosexual) develop independently of the function of the gonads.

Female secondary sexual characteristics

Female sex hormones influence a fairly rapid increase in height and body weight. It is worth noting that the growth of the limbs occurs much faster than the body. The shape of the skeleton and especially the pelvis changes. The figure also changes mainly in the area of the buttocks, thighs and abdomen, body shapes are rounded, and the skin becomes softer and thinner. The mass of adipose tissue increases. Increases female-type hair growth. Menstruation begins. All this refers to secondary sexual characteristics.

In girls, active growth of the mammary glands begins, as a result of which the nipple circles darken quite strongly, and the nipples also enlarge. As the breasts enlarge, adipose tissue accumulates in them, which leads to the final formation of a mature mammary gland.

Male secondary sexual characteristics

Secondary sexual characteristics of boys are manifested in more active body growth and an increase in muscle mass. Formation of a narrower pelvis with broad shoulders.

In men, the shape of the larynx changes, the voice becomes rough and low, and an Adam's apple appears. A beard and mustache begin to grow, men are characterized by more body hair, and the hair is distributed according to the male type: on the face, on the chest, on the stomach, etc.

Secondary sexual characteristics determine the changes that occur in the structure and functions of various organs. They characterize a person's gender. They should not be confused with primary sexual characteristics that identify the genitals.

Secondary sexual characteristics directly depend on the primary ones. They begin to appear during puberty, when the level of sex hormones increases. These signs include: the development of the mammary glands, features of the hairline, body proportions, the musculoskeletal system, subcutaneous fat, differences in behavior and much more.

Signs in girls appear around 10-11 years old. Under the influence of hormones, body weight and height rapidly increase. The limbs grow faster than the body itself. The shape of the pelvis and the entire skeleton as a whole changes. Fat is deposited in the thighs, buttocks and abdomen, resulting in a rounded body shape. The skin becomes soft and thin. There is growth and development of the mammary glands and protrusion of the isola. In the future, the mammary glands will increase in size. They accumulate, which contributes to the formation of a mature mammary gland. Hair growth on the head increases. They appear in the armpits and pubic area. The latter occurs much earlier in girls than in boys. For women, hair distribution is typical in the form of a triangle with a clear border above the pubis.

At this time, they begin to actively work and emit a characteristic feminine smell. They begin to work as a result of which most teenagers have some skin problems in the form of juvenile acne and acne.

Two to three years after the symptoms described above appear, girls begin menstruation. It is considered the main sign of puberty. Menstruation indicates that a girl is capable of becoming pregnant. At this age, it is necessary to talk with the child as often as possible and explain all the changes occurring in the body. It is very important to correctly talk about sex life and all the dangers associated with it.

Sexual characteristics that actively develop at this age do not indicate the maturity of the body. Pregnancy is very harmful to health and affects the ability to have children in the future.

The general maturity of the female body occurs after several years. Usually this is 17-18 years old. By this time, secondary sexual characteristics are already well developed, and the reproductive system is functioning at full strength. Only now can we say that the girl’s body is ready for motherhood.

Boys develop a little later. Secondary sexual characteristics are characterized by intensive growth of the body, penis and testicles, as well as an increase in body weight. Due to the fact that the shape of the larynx changes, the voice becomes rougher and lower. Hair appears in the armpits and face. Some young men experience glands and high sensitivity of the nipples. By the age of 15, they become sexually aroused and have possible wet dreams.

In young men, the seminiferous tubules are filled with spermatogonia. Starting from the moment when the gonads are capable of producing mature sperm, we can talk about the young man entering puberty. The development of secondary sexual characteristics in men occurs before the age of 23-25. As a rule, by this age a man’s appearance is already fully formed. He is able to lead a normal sex life and raise offspring.

Sex education plays an important role in the lives of boys and girls. Parents should explain the rules of behavior in an easy and accessible form. Children should not be allowed to learn about relationships between men and women from TV screens or from friends. Such knowledge can cause considerable harm to very young people.

There are a number of differences in the structure and functions of body organs that determine the belonging of all organisms to one sex or another. Primary and help to distinguish a man from a woman and a female from a male, despite the fact that they are determined by the same genes, which under the influence of special hormones can manifest themselves to a greater or lesser extent. Underdevelopment or pathological changes in the ovaries, as a rule, significantly weaken the effect, which leads to the manifestation of secondary symptoms in men. The organism of the latter

in turn, it can also show changes that are not inherent to it, and the reason for this is often the suppression of the normal functioning of the testes. From this we can conclude that the primary sexual characteristic includes the organ that is responsible for fertilization and fetal development. is one of the most important in the body, so its health should be maintained for as long as possible.

Penis, prostate and testicles in men.

Vagina, uterus and ovaries in women.

Secondary signs of sexual development are observed in both women and men, but they manifest themselves to varying degrees.

Signs of secondary puberty

Hair growth in men appears on the face, abdomen, chest, back, lower and upper extremities, as well as in the pubic area. In women, this phenomenon is observed in moderate quantities under the arms, in the bikini area and on the legs. In addition, there are differences in the skeleton and muscles: men have a wider chest and shoulders, longer limbs, a narrower pelvis, and greater muscle and bone mass. Subcutaneous tissue is more developed in the abdomen, while in women it is localized on the thighs and buttocks. men are thicker, their voices are rougher, and their Adam’s apple is pointed. The mammary glands, as a rule, are not developed and are not able to secrete breast milk to feed the offspring. If primary sexual characteristics are characterized by a certain structure, then secondary ones may have some differences among representatives of the same sex.

Features of the development of sexual characteristics

Sexual development in women and men occurs at different times: eggs, for example, are formed during development, but they begin to grow only at the age of 8-12 years. Male sperm are produced

testicles much later, after about 13 years. Primary sexual characteristics, along with secondary ones, are formed as a result of the influence of certain hormones: in women, these are those that prepare the body for pregnancy, and in men, testosterone.

There are cases when one individual may have both female and male glands at the same time. This phenomenon is called hermaphroditism and occurs due to abnormal development of the reproductive system. If primary sexual characteristics appear early, then secondary ones are formed during the growth of the body. Ultimately, the individual reaches biological maturity, including sexual maturity, which occurs after the completion of physiological and morphological development. From this moment on, the body is capable of reproducing healthy, full-fledged offspring.