Human sexual dimorphism: genetic, morphological and physiological aspects

Human sexual dimorphism: genetic, morphological and physiological aspectsUnder the sexual dimorphism understand the division of people into the females and males (men and women). The presence of sexual dimorphism in nature generally reflects the differences in the tasks solved in the process of sexual reproduction by the male and female individuals.  In humans, with the emergence of a culture, sexual dimorphism began to manifest itself in the division of labor, or rather, environmental functions in the population (getting food, giving birth to and raising children, preparing food, building housing, and so on). Due to biological peculiarities, the man was more involved in maintaining the ecological and economic well-being of the family and the community. The woman got the primacy of reproduction of the population, hence her leading role in the biological existence of man. Only recently have there been a tendency to erase the social (but not biological) differences between a man and a woman.

At the organismic level, sexual dimorphism is manifested in sexual characteristics. Allocate primary sexual characteristics and secondary. The primary sexual characteristics include internal genital organs (sex glands (testicles and ovaries) along with the pathways (spermaducts and oviducts), uterus) and external genitalia. The formation of sexual morphological and functional sex characteristics is determined by the presence of this individual in the karyotype of this individual on the 23rd pair of chromosomes of the X or Y chromosome. Individuals that have a XY karyotype develop on the male type and develop male sex characteristics. Individuals with a XX karyotype develop in a female type.

It is believed that sexual characteristics begin to form at 7 weeks after fertilization, when, under the influence of the Y-chromosome genes, a previously undifferentiated gonad begins to turn into a testicle. The role of hormones in this process is not yet known. At week 9, Leydig cells appear in the testicle, which from 10 weeks begin to produce the male sex hormone testosterone. Under the influence of this hormone, previously undifferentiated external genital organs are transformed into a penis and scrotum.

In women, the differentiation of the ovary and external genital organs is apparently not so violent. In the absence of the Y chromosome, nothing happens at week 7, and at week 8 the gonad turns into an ovary. The formation of the external genital organs of the female type occurs at about week 12, obviously, without the participation of hormones.