What does secondary sex characteristics mean. Primary and secondary sexual characteristics
Secondary sexual characteristics, signs that characterize changes in the structure and function of various organs that determine both puberty and gender. It should be distinguished from the primary sexual characteristics that identify the genitals. Secondary sexual characteristics depend on the primary ones, develop under the influence of sex hormones and appear during puberty. These include features of the development of the musculoskeletal system, body proportions, subcutaneous fat and hairline, the degree of development of the mammary glands, voice timbre, behavioral features, and many others.
Under the influence of female sex hormones, girls rapidly increase in height and body weight, and the limbs grow faster than the torso; the shape of the skeleton changes, especially the pelvis, as well as the figure due to the deposition of fat, mainly in the buttocks, abdomen and hips; body shapes are rounded, the skin becomes thinner and softer. The growth of the mammary glands begins, the areola protrudes. Subsequently, the mammary glands increase, adipose tissue is deposited in them, they take the form of a mature mammary gland. Pubic hair appears, then in the armpits, their growth on the head intensifies. The growth of pubic hair in girls begins earlier than in boys, and is characterized by a distribution characteristic of women in the form of a triangle with a top directed downwards and a sharply defined upper border above the pubis. The sweat glands, especially the glands of the armpits, begin to secrete sweat with an odor inherent in the female sex. The secretion of the sebaceous glands increases, as a result of which, in the second half of puberty, the formation of juvenile acne sometimes occurs. In most girls, after 2-3 years from the onset of the appearance of secondary sexual characteristics, at the age of 12-13 years, menstruation begins (see Menarche) - the main sign of puberty, indicating the body's ability to become pregnant. However, the general maturity of the organism occurs after a few years, during which there is a further development of secondary sexual characteristics and the formation of the reproductive function, preparing the girl's body to perform the function of motherhood.
In boys, the appearance of secondary sexual characteristics is characterized by more intense body growth, an increase in muscle mass, increased growth of the penis and testicles (which is sometimes accompanied by a slight soreness). The shape of the larynx changes, the voice becomes rougher, lower, pigmentation of the skin of the scrotum, vegetation on the pubis and in the armpits appear, mustaches and beards begin to break through, the Adam's apple ("Adam's apple") appears. Many young men during this period have swelling of the mammary glands and increased sensitivity of the nipples. At the age of 14 - 15, young men often have sexual arousal, and at night - a spontaneous eruption of the seed (pollutation). The seminiferous tubules of immature boys are filled with spermatogonia, and only with the beginning of the functioning of the sex glands capable of producing mature spermatozoa, the young man's body enters the time of puberty, further development of secondary sexual characteristics and maturity, which occurs by 23-25 years.
Secondary sexual characteristics are pronounced not only in humans, but also in animals. These characteristics are of great importance either for attracting an individual of the opposite sex, or for fighting for it. The primary sexual characteristics include the gonads and reproductive organs. Secondary - develop during puberty under the influence of sex hormones.
Dependence of secondary sexual characteristics on primary ones
There is a direct relationship between secondary sexual characteristics and primary ones. Their development is greatly influenced by sex hormones, and they begin to be produced during puberty. During this period, changes occur:
- musculoskeletal system;
- subcutaneous fat;
- body proportions;
- hairline;
- features of behavior;
- mammary glands;
- voice timbre.
Dependent secondary sex characteristics are also called eusexual and develop along with the gonads. And independent signs (pseudosexual) develop regardless of the function of the gonads.
Female secondary sexual characteristics
Female sex hormones have an impact on a fairly rapid increase in height and body weight. It is worth noting that in this case the growth of the limbs occurs much faster than the torso. The shape of the skeleton and especially the pelvis is changing. The figure also changes mainly in the buttocks, hips and abdomen, the body shapes are rounded, and the skin becomes softer and thinner. The mass of adipose tissue increases. Increased female hair growth. Menstruation begins. All this refers to secondary sexual characteristics.
In girls, the active growth of the mammary glands begins, as a result of which the areola darkens quite strongly, and the nipples also increase. As the breast enlarges, adipose tissue accumulates in it, which leads to the final formation of a mature mammary gland.
Male secondary sexual characteristics
The secondary sexual characteristics of boys are manifested in a more active growth of the body, in 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. The beard and mustache begin to grow, men are characterized by greater 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 the gender of a person. Do not confuse them with primary sexual characteristics that identify the genitals.
Secondary sexual characteristics directly depend on the primary ones. They begin to appear during maturation, when the level of sex hormones rises. These features 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 at about 10-11 years of age. 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 is changing. Fat is deposited in the thighs, buttocks and abdomen, due to which the shape of the body is rounded. The skin becomes soft and thin. There is a growth and development of the mammary glands and protrusion of the areola. In the future, the mammary glands will increase. It accumulates in them, which contributes to the formation of a mature mammary gland. Increased hair growth on the head. They appear in the armpits and on the pubis. The latter occurs much earlier in girls than in boys. Women are characterized by the distribution of hair in the form of a triangle with a clear border above the pubis.
At this time, they begin to work actively and emit a characteristic female smell. They begin to work as a result of which most teenagers have some skin problems in the form of youthful acne and blackheads.
Two to three years after the onset of the symptoms described above, girls begin menstruation. It is she who is considered the main sign of puberty. Menstruation indicates that the girl is able to become pregnant. At this age, it is necessary to talk with the child as often as possible and explain all the changes that are happening to the body. It is very important to correctly tell about sexual life and all the dangers associated with it.
Sexual characteristics that are actively developing at this age do not indicate the maturity of the body. The onset of 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 a few years. Usually it is 17-18 years old. By this time, the secondary sexual characteristics are already well developed, and the reproductive system is functioning in full force. Only now can we say that the girl's body is ready for motherhood.
The development of boys occurs 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 coarser and becomes lower. Hair appears in the armpits and face. Some young men have glands and high sensitivity of the nipples. By the age of 15, they have sexual arousal and wet dreams are possible.
In boys, the seminiferous tubules are filled with spermatogonia. Starting from the moment when the sex glands are able to produce mature spermatozoa, we can talk about the entry of a young man into puberty. The development of secondary sexual characteristics in men occurs up to 23-25 years. As a rule, by this age, the appearance of a man is already fully formed. He is able to lead a normal sexual life and raise offspring.
Sex education plays an important role in the lives of boys and girls. Parents should explain the rules of conduct in an easy and accessible way. Children should not be allowed to learn about the relationship of men and women from TV screens or from friends. Such knowledge can bring considerable harm to even very young people.
Primary and secondary sexual characteristics - Test, section Biology, Test work on genetics Sexual Characteristics, Morphological And Functional Characteristics, Determine Sex ...
Sexual characteristics, morphological and functional characteristics, determine the sex of the organism. They are divided into primary and secondary. Primary and secondary signs are genetically determined, their structure is already laid down in a fertilized egg long before the birth of a child. Primary sexual characteristics are signs related to the structure of the genital organs. They are laid in embryogenesis and are formed by the time the organism is born. Primary sexual characteristics are understood as gonads or gonads (testes in males, ovaries in females) and other genital organs: vas deferens, oviducts, uterus, etc. Secondary sexual characteristics are not directly involved in reproduction, but contribute to the meeting of representatives of the two sexes. They depend on primary sexual characteristics, develop under the influence of sex hormones and appear in humans during puberty. Secondary sexual characteristics, a set of features or characteristics that distinguish one sex from another (with the exception of the gonads, which are primary sexual characteristics). Examples of secondary sexual characteristics of a person: in men - mustache, beard, voice timbre, protruding cartilage on the larynx ("Adam's apple"); in women - a typical development of the mammary glands, the shape of the pelvis, a greater development of fatty tissue. Secondary sexual characteristics of animals: the characteristic bright plumage of male birds, odorous glands, well-developed horns, fangs in male mammals. Secondary sexual characteristics persist constantly (for example, differences in body size and proportions, coloration; manes in male lions and baboons, horns in male ungulates) or appear only during the mating seasons (for example, coloration and nuptial attire of some fish and birds). Seasonal secondary sexual characteristics also include mating behavior (“courtship”, tournaments, nest building, etc.). Secondary sexual characteristics help individuals of different sexes find and recognize each other, stimulate the maturation of the gonads and the sexual behavior of females, and play an important role in sexual selection. Studies on castration and transplantation of the gonads (from an individual of one sex to an individual of the other sex) have shown the relationship between the function of the gonads and the development of secondary sexual characteristics in mammals, birds, amphibians and fish. These experiments allowed the Soviet researcher M. M. Zavadovsky to conditionally divide secondary sexual characteristics into dependent (eusexual), which develop in connection with the activity of the sex glands, and independent (pseudosexual), the development of which occurs regardless of the function of the sex glands. Dependent secondary sexual characteristics in the case of castration of the animal do not develop. If by this moment they have already managed to develop, then gradually they lose their functional significance and sometimes completely disappear. As a result of castration of males and females, basically similar forms are obtained; if such an "asexual" individual is transplanted with a gonad or a sex hormone is injected, then characteristic dependent secondary sexual characteristics of the corresponding sex develop. An example of such experiments is the development in a castrated hen, under the influence of the male gonad, of a rooster's headgear (comb, beard, catkins), a rooster's voice, and male behavior. Independent secondary sexual characteristics, such as spurs or cock plumage, develop without the participation of sex hormones, which was established by experiments with the removal of the genital glands: these signs are also found in castrated cocks. In addition to dependent and independent second sexual characteristics, there is also a group of somosexual, or tissue-sexual, secondary sexual characteristics that are inherent in only one sex, but do not depend on the function of the sex glands; in the case of castration, sex differences in these characteristics are completely preserved. This group of secondary sexual characteristics is characteristic of insects.
4. Mutational variability
Mutational variability- variability caused by the action of mutagens on the body, resulting in mutations (reorganization of the reproductive structures of the cell). Mutagens are physical (radiation radiation), chemical (herbicides) and biological (viruses). The term "mutation" (from lat. mutatio- change) has long been used in biology to refer to any abrupt changes. For example, the German paleontologist W. Waagen called the transition from one fossil form to another a mutation. The appearance of rare traits, in particular, melanistic forms among butterflies, was also called a mutation. Modern ideas about mutations were formed by the beginning of the 20th century. For example, the Russian botanist Sergei Ivanovich Korzhinsky in 1899 developed an evolutionary theory of heterogenesis based on the concept of the leading evolutionary role of discrete (discontinuous) changes. However, the most famous was the mutational theory of the Dutch botanist De Vries (1901), who introduced the modern, genetic concept of mutation to denote rare variants of traits in the offspring of parents who did not have this trait. De Vries developed a mutation theory based on observations of a widespread weed plant, biennial aspen, or evening primrose ( Oenothera biennis). This plant has several forms: large-flowered and small-flowered, dwarf and giant. De Vries collected seeds from a plant of a certain form, sowed them and received 1 ... 2% of plants of a different form in the offspring. Later it was found that the appearance of rare variants of the trait in evening primrose is not a mutation; this effect is due to the peculiarities of the organization of the chromosome apparatus of this plant. In addition, rare variants of traits may be due to rare combinations of alleles (for example, the white color of plumage in budgerigars is determined by a rare combination aabb).
The main provisions of the mutation theory of G. De Vries remain valid to this day and boil down to the following:
1. Mutations occur suddenly, abruptly, as discrete changes in traits.
2. Unlike non-hereditary changes, mutations are qualitative changes that are passed down from generation to generation.
3. Mutations manifest themselves in different ways and can be both beneficial and harmful, both dominant and recessive.
4. The probability of detecting mutations depends on the number of individuals studied.
5. Similar mutations can occur repeatedly.
6. Mutations are not directed (spontaneous), that is, any part of the chromosome can mutate, causing changes in both minor and vital signs.
Mutational variability is manifested in the phenotype, and in fact, only by the presence of qualitatively new features and properties of the organism can one assume its occurrence. Changes in the phenotype are caused by a violation of hereditary structures, which is determined by the influence of various environmental factors. In other words, the external environment, acting on the genotype, causes its structural changes, leading to the formation of new features and properties of the organism. In this regard, the study of mutations should be carried out from different positions: from the point of view of the nature of changes in the genotype, their localization in various cells and tissues, the phenotypic expression and evolutionary role of mutations, and also from the point of view of the nature of the causative factor.
There are several classifications of mutations according to various criteria. Möller proposed to divide mutations according to the nature of the change in the functioning of the gene into hypomorphic(altered alleles act in the same direction as wild-type alleles; only less protein product is synthesized), amorphous(a mutation looks like a complete loss of gene function, for example, a mutation white in Drosophila) antimorphic(the mutant trait changes, for example, the color of a corn kernel changes from purple to brown) and neomorphic. In modern educational literature, a more formal classification is also used, based on the nature of changes in the structure of individual genes, chromosomes, and the genome as a whole. Within this classification, the following types of mutations are distinguished:
- genomic;
- chromosomal;
- genetic.
Genomic- polyploidization (the formation of organisms or cells whose genome is represented by more than two (3n, 4n, 6n, etc.) sets of chromosomes) and aneuploidy (heteroploidy) - a change in the number of chromosomes that is not a multiple of the haploid set (Inge-Vechtomov, 1989) . Depending on the origin of chromosome sets, among polyploids, allopolyploids are distinguished, which have sets of chromosomes obtained by hybridization from different species, and autopolyploids, in which there is an increase in the number of sets of chromosomes of their own genome, a multiple of n.
At chromosomal mutations large rearrangements of the structure of individual chromosomes occur. In this case, there is a loss (deletion) or doubling of a part (duplication) of the genetic material of one or more chromosomes, a change in the orientation of chromosome segments in individual chromosomes (inversion), as well as the transfer of part of the genetic material from one chromosome to another (translocation) (extreme case - combination of whole chromosomes, Robertsonian translocation, which is a transitional variant from chromosomal mutation to genomic mutation).
On genome the level of changes in the primary DNA structure of genes under the influence of mutations is less significant than with chromosomal mutations, however, gene mutations are more common. As a result of gene mutations, substitutions occur, deletions and insertion of one or more nucleotides, translocations, duplications and inversions different parts of the gene. In the case when only one nucleotide changes under the influence of a mutation, they speak of point mutations. Since DNA contains only two types of nitrogenous bases - purines and pyrimidines, all point mutations with base substitution are divided into two classes: transitions (replacement of purine for purine or pyrimidine for pyrimidine) and transversions ( replacing a purine with a pyrimidine or vice versa). Four genetic consequences of point mutations are possible: 1) the preservation of the meaning of the codon due to the degeneracy of the genetic code (synonymous nucleotide substitution), 2) a change in the meaning of the codon, leading to the replacement of the amino acid in the corresponding place of the polypeptide chain (missense mutation), 3) the formation of a meaningless codon with premature termination (nonsense mutation). There are three meaningless codons in the genetic code: amber - UAG, ocher - UAA and opal - UGA (in accordance with this, mutations leading to the formation of meaningless triplets are named - for example, an amber mutation), 4) reverse substitution (stop codon to sense codon).
By influence on gene expression mutations fall into two categories: base pair mutations And frameshift type. The latter are deletions or insertions of nucleotides, the number of which is not a multiple of three, which is associated with the triplet nature of the genetic code. Primary mutation is sometimes called direct mutation, and a mutation that restores the original structure of the gene, - back mutation, or reversion. A return to the original phenotype in a mutant organism due to the restoration of the function of the mutant gene often occurs not due to true reversion, but due to a mutation in another part of the same gene or even another non-allelic gene. In this case, the back mutation is called a suppressor mutation. The genetic mechanisms by which the mutant phenotype is suppressed are very diverse.
Kidney mutations- persistent sudden genetic changes in individual plant buds. During vegetative propagation, they are preserved. Many varieties of cultivated plants are bud mutations.
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Insufficient development of secondary sexual characteristics often indicates serious disorders in the endocrine system women and related diseases.
Characteristics of secondary sexual characteristics
Primary sexual characteristics are structural features of the reproductive system, genitals. Secondary sexual characteristics are bodily or somatic traits that form differences in both sexes. There are also tertiary features. They are unique to humans. This is the awareness of gender or gender identity, and the associated rules of behavior in society.Female secondary sexual characteristics include:
- Developed mammary glands.
- High tone of voice.
- Pubic hair on the female type: the upper border is a clear horizontal line. The hairline itself in the intimate area has the form of a triangle, turned base up.
- Features of the hairline in other places. Hairiness of the armpits. Lush soft silky hair on the head. Vegetation on the face is absent or weakly expressed. The same goes for the limbs.
- Body features. The bone skeleton is not as massive as in men. Musculature is also weakly expressed. Relatively high fat content. Fat is concentrated on the thighs and buttocks. The pelvis is expanded, the shoulders are narrowed.
- Some features of the functioning of the reproductive system are also considered secondary sexual characteristics, namely: a regular cycle with menstrual flow.
The laying of geniuses occurs even in the prenatal period, for about 12 weeks. pregnancy. At this time, the genital tubercle is transformed into the male or female genitalia. Secondary sexual characteristics appear much later, during puberty, in puberty. Puberty in women ends by the age of 18-19.
At this time, a woman reaches puberty and fertility (ability to bear children). This is indicated by the presence of secondary sexual characteristics. If, by the end of puberty, the secondary sexual characteristics have not reached the proper degree of severity, they speak of their underdevelopment.
Reasons for absence secondary sexual characteristics
The endocrine system is responsible for the development of secondary sexual characteristics. In women, they appear under the influence of female sex hormones, estrogen secreted by the ovaries. The latter are controlled by the pituitary and hypothalamus. These brain structures, in turn, are in close relationship with the thyroid gland, the adrenal glands. Any violations in this well-established, but easily vulnerable system will lead to insufficient development of secondary sexual characteristics and other negative consequences.Among the reasons for these violations:
- Chromosomal abnormalities
- Genetic anomalies
It is noteworthy that estrogens are synthesized from male androgens under the action of the aromatase enzyme. Therefore, a genetic defect in aromatase will lead to a decrease in the amount of estrogens and to the accumulation of androgens. The same thing will happen with a deficiency of another enzyme, C21-hydroxylase, as a result of which the adrenal glands intensively produce androgens.
- Pathology of pregnancy
- Organic lesions of the CNS (central nervous system)
- ovarian dysplasia
- Other reasons
Signs of virilization
Thus, the underdevelopment of secondary sexual characteristics is a consequence estrogen deficiency with a relative or absolute predominance of androgens. Although in some situations, with a high level of androgens (hyperandrogenism), the amount of estrogen increases compensatory. But androgens still predominate. In the form of a woman, masculine traits appear. This phenomenon is called virilization (lat. virilis - man). signs virilization:
- Low tone of voice.
- Underdeveloped, weakly contoured mammary glands.
- hirsutism- the presence of facial hair.
- Excessive hair growth in other parts of the body. Pubic hair on the male type with the presence of a "path" to the navel. Increased hair stiffness.
- Increased oiliness of the skin (oily seborrhea). The appearance of acne on the skin (acne).
- The appearance of the "Adam's apple" - a protruding tub.
- Male body type - narrowed pelvis, broad shoulders, well-developed muscles.
- Changes in the menstrual cycle. Violation of ovulation (anovulation) is accompanied by prolonged amenorrhea, lack of menstruation. In other cases, they may be sparse and irregular.
This is especially true for gene-chromosomal anomalies, when the pathology of the reproductive system is combined with neuropsychiatric disorders (oligophrenia, convulsive syndrome) and somatic changes.
Somatic changes are largely characteristic of PCOS. Patients develop tissue resistance to insulin. The consequence of this is type II diabetes and obesity. Moreover, fat is deposited according to the central or male type - on the anterior abdominal wall.
Due to the increase in the level of lipid (fatty) compounds, atherosclerosis and related diseases develop - hypertension, coronary artery disease (ischemic heart disease). If the level of estrogen increases compensatory, the risk of malignant neoplasms of the uterus and mammary glands increases.
What to do with underdevelopment of secondary sexual characteristics
First of all, it is necessary to establish the reason lack of secondary sexual characteristics. To do this, examine the blood for hormones. Determine the level of all major hormones: estrogens, androgens, pituitary hormones, thyroid gland, adrenal glands. Further diagnostics is aimed at identifying possible structural changes. For this purpose, they carry out: - x-ray of the bones of the skull
- CT and MRI of the skull, brain
- dopplerography of intracranial vessels
- Ultrasound of the thyroid gland, ovaries, adrenal glands.
If the underdevelopment of secondary sexual characteristics has arisen against the background of congenital structural changes in the reproductive system, plastic surgery of the uterus and vagina is performed. An equally important task is to artificially form the menstrual cycle. To do this, estrogens alternate with synthetic progestins (analogues of the hormone progesterone). With successful treatment, the appearance changes in a positive direction, the menstrual cycle becomes regular, a woman can become pregnant and give birth.
