A person's genetic sex depends on the presence or absence of a Y chromosome. The cells of a female body have two sex X chromosomes, while the cells of a male body have one X and one Y chromosome. Genetic sex determines the true sex, which is associated with the structure of the gonads. Primary sexual characteristics, i.e. the genital organs, which include the gonads, begin to form in accordance with the hereditary information in the embryo at the 4th week of development. At earlier stages, the rudiments of the genital organs are the same in both the male and female organisms.
Sex differences
The male reproductive gland is the testicle, and the female reproductive gland is the ovary. The presence of a male or female reproductive gland determines the so-called gametic sex (from the Greek gametes - spouse, gamete - spouse), namely the ability of the gland to produce sperm (male reproductive cells) or eggs (female reproductive cells) and produce male or female sex hormones. Sex hormones, in turn, influence the maturation of the genital organs and the appearance of secondary sexual characteristics, which include body features, hair location, structure of the larynx, development of muscles and fat deposits. The activity of the gonads is under the control of the pituitary gland, an endocrine gland located at the base of the brain.
There are significant differences between the sexes not only in the structure of the body, but also in the psyche. For example, women have better developed verbal (speech-related) abilities, while men have better developed mathematical and spatial orientation abilities. Gender (sex hormones) determines a person’s biological, psychological and social life, his sexual identity and behavior. In addition to hereditary factors, the culture to which a person belongs, family upbringing, and other environmental influences also have a significant impact on a person’s sexual behavior.
Let's look at the structure of the gonads.
Male gonad: testicle
The male reproductive gland - the testicle - is a paired organ that produces male reproductive cells - sperm - and male sex hormones - androgens. During the prenatal period, the testicle develops in the abdominal cavity, and at birth it moves into the scrotum, passing through the inguinal canal - a gap in the lower part of the anterior wall of the abdomen. The scrotum is a kind of skin pocket, the temperature inside of which is slightly lower than body temperature (this is necessary for the formation of sperm).
During the descent of the testicle, deviations may occur, as a result of which one or both testicles may stop in the abdominal cavity or inguinal canal. This delay in the descent of the testicles is called cryptorchidism (from the Greek kryptos - hidden - and orchis - testicle). The descent of the testicles should be completed before the age of 7 years, since it is at this age that the seminiferous tubules form in them. Until the testicle is in favorable conditions - in the scrotum, sperm are not formed in it, but sex hormones can be produced.
The testicle is oval in shape, flattened laterally; its length is about 4 cm, width 3 cm, weight 25-30 g. The outside of the testicle is covered by a dense membrane, which is thickened at the posterior edge. From it, septa extend into the testicle, dividing the testicle into lobules, the number of which reaches 300. Each lobule consists of convoluted seminiferous tubules. It is in them that sperm are formed. Then, through a network of other tubules, the sperm are sent to the epididymal duct, where they finally mature. The total length of all testicular tubules reaches 300-400 m.
Spermatogenesis
The process of sperm formation - spermatogenesis - lasts about 64 days in humans. The formation of sperm begins when the body reaches puberty. During puberty, a lumen appears in the convoluted seminiferous tubules and the spermatogenic epithelium begins to function. Sperm are produced continuously throughout the period of sexual activity. As a man ages, the production of germ cells in the convoluted seminiferous tubules decreases, and the tubules themselves become empty. However, high sexual activity slows down this process.
In a healthy adult man, 1 ml of sperm contains about 100 million sperm, and during one ejaculation, 300-400 million are released. If the number of sperm in 1 ml of sperm decreases to 20 million, infertility is usually observed. Although the testicles produce such a huge number of sperm, only one of them fertilizes the egg.
A human sperm has a head, neck and tail. The head of the sperm is ovoid; it contains a nucleus with half the set of chromosomes (23 chromosomes), like the egg. At the top of the head, a special formation contains enzymes that, during fertilization, dissolve the membrane of the egg and facilitate the penetration of sperm into it. Mitochondria are concentrated in the neck, providing the sperm with energy for movement. The movements of the tail allow the sperm to move at a speed of 2-3 mm per minute (however, when moving sperm in the female genital tract, their active motility is not critical).
Testosterone synthesis
In addition to the seminiferous tubules, the testis contains interstitial cells (Leydig cells). It is believed that they synthesize the male sex hormone (androgen) testosterone, which is carried throughout the body in the blood and acts on various cells sensitive to it, stimulating their growth and functional activity. The target cells for testosterone are the cells of the prostate gland (prostate), seminal vesicles, glands of the foreskin, kidneys, skin, etc. Under the influence of androgens, as already mentioned, puberty occurs, secondary sexual characteristics arise, and sexual behavior is formed. A low concentration of androgens activates spermatogenesis, while a high concentration inhibits it. A small amount of female sex hormones - estrogens - is also synthesized in the testicles. Androgens and estrogens are involved in the regulation of growth and development of the musculoskeletal system.
Removal of both testicles (castration) entails not only the loss of the ability to bear children, but also significant changes in the body: metabolic disorders, changes in the timbre of the voice, cessation of beard and mustache growth, and a delay in overall growth (if it has not been completed).
Prostate
Let's trace the path of sperm after they leave the testicle.
Along the posterior edge of the testicle there is an epididymis, inside which sperm pass through a highly convoluted duct (up to 4-6 m in length) and enter the vas deferens.
The latter leaves the scrotum, rises through the inguinal canal into the abdominal cavity and goes to the bottom of the bladder and the prostate gland located here. Having pierced its wall, it opens into the urethra. The prostate gland covers the initial section of the urethra, into which the ducts of the gland itself and the ejaculatory ducts open.
As it moves forward, secretions from various glands are mixed with the sperm, which together form the liquid part of the sperm. About 70% of seminal fluid is the secretion of the seminal vesicles, 30% is the secretion of the prostate gland. Substances produced by them and the bulbourethral (Cooper) glands liquefy sperm, increase sperm viability and activate them.
Contraction of the muscle fibers of the prostate gland prevents urine from entering the urethra during ejaculation. Enlargement of the middle part of the prostate gland can make it difficult to urinate and lead to sexual dysfunction.
There is a constant interaction between the prostate gland and the testicles: an increase in the secretory activity of the testicles stimulates its development and function. During periods of sexual abstinence, the secretion of the prostate gland enters the blood in large quantities and this inhibits the function of the testicles. On the contrary, with great sexual activity, there is little prostate secretion in the blood and this stimulates the activity of the testicles.
Male urethra
The male urethra begins with an internal opening in the wall of the bottom of the bladder and ends with an external opening on the head of the penis. The urethra serves to remove both urine and semen from the body. Its longest part is located in the corpus spongiosum of the penis. During sexual intercourse, sperm enter the woman's vagina through the urethra.
Female reproductive gland: ovary
The female reproductive gland - the ovary - is a paired organ that produces female reproductive cells - eggs - and female sex hormones - estrogens and progesterone.
Estrogens determine the development of secondary sexual characteristics, progesterone controls the menstrual cycle. During pregnancy, progesterone affects the formation of the placenta, growth and development of the fetus. The ovaries also produce small amounts of male sex hormones.
The ovaries are located in the pelvic cavity on both sides of the uterus. Each ovary is oval in shape, about 3 cm long and weighs about 5-6 g. The surface of the ovary is bumpy due to scars formed at the sites where the eggs are released. Follicles are located and mature in the ovary. Each follicle contains an egg surrounded by fluid.
Ovulation
In a sexually mature, non-pregnant woman, approximately once a month another follicle matures in one of the ovaries, which bursts, releasing an egg (ovulation). A mature follicle (Graafian vesicle) has up to 1 cm in diameter, so after each ovulation a deep scar forms on the surface of the ovary.
At the site of the burst follicle, a corpus luteum develops in the ovary. In the absence of fertilization of the egg, it exists for 12-14 days. If the egg is fertilized and pregnancy occurs, the corpus luteum of pregnancy is formed at the site of the burst follicle. It lasts for 6 months. Cells of the corpus luteum produce the hormone progesterone, which affects the condition of the uterine mucosa (preparation for the implantation of a fertilized egg) and the restructuring of the mother’s body during pregnancy.
During ovulation, the egg is released onto the surface of the ovary. To carry it into the uterus, the fallopian tube is used, the funnel of which, equipped with fimbriae, is located near the ovary. The egg is not capable of independent movement and moves into the uterine cavity due to peristaltic contraction of the wall of the fallopian tube. It is in the fallopian tube that the egg meets the sperm and the egg is fertilized.
Menstruation
If fertilization of the egg does not occur, it is removed from the uterus through the vagina during the next menstruation. After this, a new egg matures in the ovary, which follows the same path. In a sexually mature woman (from approximately 13-14 to 45-50 years), this process is repeated regularly with an interval of 26-30 days and is disrupted only during pregnancy. The laying of female germ cells occurs in the prenatal period. A newborn girl’s ovaries contain up to 800 thousand immature follicles, only a small part of which (400-500) will mature in a woman during her life.
The uterus is a hollow muscular organ in which the fetus develops in the event of fertilization of the egg. The uterus is pear-shaped, about 8 cm long and occupies a central position in the pelvic cavity. Depending on the functional state of the woman, significant changes occur in the uterine mucosa (endometrium). In the case of fertilization of the egg, the embryo is implanted into the endometrium, where its initial development occurs until the formation of the placenta - a special formation through which the fetus is nourished from the mother's body. In the absence of fertilization, menstruation occurs - the rejection of part of the uterine mucosa. After menstruation, the endometrium is restored.
Menstruation, like ovulation, occurs once a month, but ovulation does not coincide with menstruation, but precedes it, occurring approximately in the middle of the period between two menstruation. Both of these processes are carried out as a result of the cyclic release of pituitary hormones. There are no periods during pregnancy.
Menopause
After functioning for more than 30 years, the ovaries become depleted and eventually cease to be a source of eggs and hormones. The most obvious sign of ovarian failure is the cessation of menstruation. Therefore, this period is called menopause. Menopause occurs at the age of 45-50 and marks the end of a woman's reproductive life. During this period, some unpleasant symptoms are possible due to a decrease in the production of hormones in the ovaries.
Instead of a conclusion
This article examines only some of the features of the structure and functioning of the internal genital organs, the most important role among which is played by the gonads. For a good quality of life, this sphere of vital activity of the human body must manifest itself in full.
Sex glands(seminal glands in men and ovaries in women) are glands that have a mixed function. Due to the exocrine function of these glands, male and female reproductive cells are formed - spermatozoons and eggs. The endocrine function is manifested by the formation and release of male and female sex hormones, which directly enter the blood.
Ovaries
The ovaries are localized in the pelvic cavity, not covered by peritoneum and surrounded on the outside by a single layer of superficial (or germinal) epithelial cells. The main hormone-producing part of the ovaries is the cortex. It contains follicles among the connective tissue stroma. The bulk of them are primordial follicles, which represent an egg. During the period of postnatal life, a large number of primordial follicles die, and before puberty their number in the cortical layer decreases by 5-10 times. Along with primordial follicles, the ovaries also contain follicles that are at various stages of development or atresia, as well as yellow and white bodies. The central part of the ovary is occupied by the medulla, in which there are no follicles. In it, among the connective tissue, the main ovarian blood vessels and nerves pass. The reproductive period of life is characterized by cyclical changes in the ovaries, which determine the maturation of the follicles, their rupture with the release of a mature egg (ovulation), the formation of the corpus luteum with its subsequent involution in the event of no pregnancy.Testicles or seminal glands
Seminal glands, or testes, the outside is covered with a dense connective tissue membrane - a protein capsule. On the posterior surface it thickens and enters the spermatic gland, forming the maxillary body. Connective tissue septa diverge from it, dividing the gland into lobules. They contain seminiferous tubules, as well as blood vessels and interstitial tissue. The convoluted seminiferous tubules are the organ where spermatogenesis occurs; their formation ends only during puberty. From the age of 10, epithelial cells - supporting cells (Sertoli cells) - are formed in the seminiferous tubules. The cytoplasm of these cells contains numerous inclusions of fatty, protein and carbohydrate nature; they also contain a lot of RNA and enzymes, which indicates their high synthetic activity. In the capillaries of the seminal glands, interstitial cells (Leydig cells) are located in compact groups, which have a well-developed capillary network, as well as numerous mitochondria. In the cytoplasm of these cells there are inclusions - fat, protein, crystalloids, which indicates the participation of cells in hormone production (steroidogenesis). The close proximity of interstitial cells to capillaries promotes the release of sex (androgenic) hormones into the bloodstream.Gonadal hormones.
Sex hormones are divided into male and female. Male hormones include androgens, the main representative of which is testosterone, and a small amount of estrogens, formed as a result of androgen metabolism. Female hormones include estrogens, progestins (estradiol, estrone, progesterone), as well as low concentrations of androgens. That is, the bodies of men and women produce the same hormones, but in different quantities.Estrogens and progestins
Estrogens and progestins are synthesized in the ovaries by the cells of the corpus luteum and in the placenta, androgens - in the testicle by interstitial cells.The development of the gonads and the entry into the blood of the sex hormones they produce determine sexual development and maturation. Puberty in humans occurs at the age of 12-16 years. It is characterized by the full development of primary and the appearance of secondary sexual characteristics. Primary sexual characteristics include the sex glands (testes, ovaries) and genital organs (penis, prostate, clitoris, vagina, labia majora and minora, uterus, oviducts). They determine the possibility of sexual intercourse and childbearing.
Secondary sexual characteristics- these are those features of a sexually mature organism that distinguish a man from a woman.
In men, secondary sexual characteristics are: the appearance of hair on the face, on the body, “changes in the timbre of the voice, body shape, as well as the psyche and behavior.
In women, secondary sexual characteristics include: special arrangement of hair on the body, changes in the shape of the pelvis, development of the mammary glands.
The nature of the influence of the gonads and their hormones on various functions of the body is clearly manifested when the gonads are removed, or castration. The changes that occur depend on when castration is performed - before or after puberty. If castration was carried out before puberty, the development of the genital organs stops and sexual desire (libido) does not manifest itself in the future. The shape of the skeleton changes due to lengthening of the limbs due to the fact that the ossification of cartilage is delayed. Castrated people, as a rule, have high growth with disproportionate development of the limbs (eunuchoid type, or hypogonadal gigantism). In women, there is an undeveloped pelvis, which retains a child’s shape, and the mammary glands are underdeveloped. Men do not grow mustaches, beards, or armpit hair; their voice remains childish. If castration is carried out in adulthood, then the reverse development of primary sexual characteristics occurs, although sexual attraction to the opposite sex remains. In men, after removal of the gonads, facial hair stops growing, the border of pubic hair becomes horizontal, and the tempo of the voice approaches that of a child. Metabolic disorders, especially fat metabolism, are observed, and therefore a tendency to obesity develops.
In the early stages of embryogenesis (approximately at the end of the 3rd month), the male gonads become hormonally active, i.e. synthesize androgens (in particular, testosterone), under the influence of which the genital organs acquire a structure characteristic of the male sex. The formation of androgens ceases after the completion of embryonic development of the male fetus. During puberty, the activity of the gonads in boys is restored, and in girls their internal secretion occurs for the first time. Under the influence of androgens in boys and estrogens and gestagens in girls, the genital organs grow and mature.
Androgens
Androgens are also needed for the normal maturation of spermatozoons, maintaining their motor activity, identifying and implementing sexual behavioral reactions. They significantly affect metabolism, have an anabolic effect - they enhance protein synthesis in various tissues, especially in muscles; reduce fat content in organs, increase basal metabolism. Androgens affect the functional state of the central nervous system and higher nervous activity. After castration, various changes occur in the mental and emotional spheres.Estrogens
Estrogens stimulate the growth of the oviduct, uterus, vagina, proliferation of the inner layer of the uterus - the endometrium, promote the development of secondary female sexual characteristics and the manifestation of sexual reflexes. In addition, estrogens accelerate and enhance contraction of the uterine muscles and increase the sensitivity of the uterus to the neurohypophysis hormone oxytocin. They stimulate the development and growth of the mammary glands.The physiological significance of progesterone is that it ensures the normal course of pregnancy. Under its influence, the mucous membrane (endometrium) of the uterus grows, which promotes the implantation of a fertilized egg in the uterus. Progesterone creates favorable conditions for the development of decidual tissue around the implanted egg, maintains the normal course of pregnancy by inhibiting contractions of the muscles of the pregnant uterus and reduces the sensitivity of the uterus to oxytocin. In addition, progesterone inhibits the maturation and ovulation of follicles due to inhibition of the creation of the hormone lutropin by the adenohypophysis.
The extragenital effects of sex hormones include, for example, the anabolic effect of androgens, i.e. increased protein synthesis, catabolic effect of progesterone, the effect of androgens and gestagens on bone growth, increased basal body temperature, etc.
Cells of the corpus luteum of the ovaries, in addition to producing steroid hormones, synthesize the protein hormone relaxin. Increased secretion of relaxin begins in the later stages of pregnancy. The significance of this peptide hormone is the weakening (relaxation) of the ligament of the pubic symphysis with other pelvic bones, the mechanism of which is associated with an increase in the level of cAMP in chondrocytes. This causes the molecular components of their bond to disintegrate. In addition, under the influence of relaxin, the tone of the uterus and its contractility, especially the cervix, decrease. Thus, this hormone prepares the mother’s body for the upcoming birth.
Regulation of the formation of sex hormones
Regulation of the secretion of female sex hormones(progesterone and estradiol) is achieved with the help of two gonadotropic hormones - follicle-stimulating(FSH) and luteinizing(LG). Under the influence of FSH, ovarian follicles develop and the concentration of estradiol increases, and when the ruptured follicle is converted (under the influence of PG) into the corpus luteum - progesterone. Sex hormones accumulated in the blood act on the hypothalamus or directly on the pituitary gland according to the principle of positive or negative feedback. An increased concentration of estradiol leads to an increase in LH levels (positive feedback), and progesterone in large quantities inhibits the release of FSH and LH (negative feedback, prevents the maturation of the next follicle).Regulation of the secretion of male sex hormones(testosterone) also triggers a cascade: the hypothalamus - gonadotropic hormones - FSH and LH, which are carried into the seminal glands and act respectively on supporting and interstitial cells. Under the influence of LH, testosterone is released, and under the influence of FSH, spermatogenesis is activated. Testosterone accumulated in the blood inhibits the secretion of LH. In parallel, supporting cells secrete the polypeptide inhibin, which suppresses the secretion of FSH. Prolactin is definitely involved in the regulation of sex hormone secretion.
Placental hormones
The placenta communicates between the mother’s body and the fetus and is at the same time the lungs, intestines, liver, kidneys and endocrine gland for the fetus. It has three main structures: chorionic, basement membrane and the parenchymal part located between them consists of chorionic villi, stem part and microvillous space.The placenta performs many different functions, including metabolic (formation of enzymes, participation in the breakdown of proteins, fats and carbohydrates) and hormonal (forms two groups of hormones - protein and steroid). Protein hormones are human chorionic gonadotropin, placental lactogenic hormone (somatomotropin) and relaxin. Steroid hormones of the placenta include progesterone and estrogens (estriol). Hypothalamic releasing hormones were also detected in the placenta.
Human chorionic gonadotropin- glucoprotein formed by syncytial trophoblast cells of the placenta. Maximum secretion is observed in the 7-12th week of pregnancy. Later, hormone production decreases several times. Human chorionic gonadotropin passes into the mother's blood. Its transport into the fetal body is limited. Therefore, the concentration of the hormone in the mother’s blood is 10-20 times higher than its content in the fetal blood.
The physiological role of human chorionic gonadotropin lies in its luteinizing effect, that is, it acts similarly to the luteinizing hormone (lutropin) of the adenohypophysis. Chorionic gonadotropin stimulates the growth of ovarian follicles, causes ovulation of mature follicles, and promotes the formation of the corpus luteum in the ovaries. In addition, the hormone has a steroid effect - it stimulates the formation of progesterone in the corpus luteum of the ovaries.
The protective function of the hormone and its ability to prevent detachment of the embryo are noted. Human chorionic gonadotropin also has an antiallergic effect.
Placental lactogenic hormone (somatomotropin)- protein hormone of the placenta. Its secretion begins from the 6th week of pregnancy. Then its production progressively increases and at the end of pregnancy reaches its maximum level (up to 1 g per day). In small quantities, the hormone penetrates the placental barrier into the fetal blood. The physiological role of the hormone lies primarily in its ability to influence the mammary glands of a pregnant woman (prolactin of the adenohypophysis has a similar effect). In addition, placental lactogenic hormone affects metabolic processes in both the maternal body and the fetus. The metabolic effect of the hormone is associated with its ability to influence protein metabolism, which is manifested by an increase in protein synthesis and increased nitrogen retention in the mother’s body. At the same time, the content of free fatty acids in the blood increases, and the body's resistance to the hypoglycemic effect of insulin increases.
Relaxin is secreted intensely in the later stages of pregnancy. The significance of this peptide hormone is to weaken the connection of the pubic symphysis with other pelvic bones. In addition, under the influence of relaxin, the tone of the uterus (especially the cervix) and its contractility decrease. Thus, this hormone prepares the mother's body before childbirth.
Steroid hormones of the placenta. Progesterone is actively formed in the placenta in the 5-7th week of pregnancy. Over time, its production progressively increases (10 times). The hormone enters in large quantities into the blood of the mother and fetus. It causes weakening of the muscles of the uterus, reduces its contractility, sensitivity to estrogen and oxytocin, and promotes the accumulation of water and electrolytes (especially sodium) in the tissues of the uterus and throughout the pregnant woman’s body.
Together with estrogens, progesterone promotes the growth and stretching of the uterus, as well as the development of the mammary glands, preparing them for subsequent lactation.
The role of hormones of the opposite sex in the regulation of body functions.
The male sex hormone testosterone is constantly secreted in the adrenal glands and much less in the ovaries of a healthy woman (250 mcg is produced per day in women, and 7000 mcg in men). Its action is aimed at stimulating hair growth on the pubis and armpits. With overproduction of androgens, signs of virilism appear - body hair growth, temple baldness, menstrual irregularities.
In a man’s body, prolactin plays a particularly noticeable role, the concentration of which in the blood is not much lower than in a woman’s body. Although prolactin itself significantly affects the male reproductive system, it significantly enhances the effect of LH on steroidogenesis in interstitial cells, increases the number of androgen-sensitive receptors in
Before the onset of puberty, the amounts of male and female hormones in boys and girls are approximately the same. With the onset of puberty, the ovaries produce several times more female sex hormones, and the testes produce several times more male sex hormones.
Male sex hormones - androgens (androsterone, testosterone, etc.) are produced in the tissues of the testes. Testosterone regulates the process of spermatogenesis, the development of secondary sexual characteristics, and affects the level of protein and carbohydrate metabolism.
Female sex hormones - estrogens (estrol, estriol, estradiol) are produced in the ovaries. They participate in the regulation of puberty and the development of secondary sexual characteristics in girls, regulate the menstrual cycle, and when pregnancy occurs, regulate its normal course. In the ovaries, at the site of the burst follicle (Graafian vesicle), a corpus luteum is formed. The corpus luteum produces the hormone progesterone, which prepares the uterine mucosa for implantation of a fertilized egg, stimulates the development of the mammary glands and the muscular layer of the uterus, and regulates the normal course of pregnancy in its initial stages. During pregnancy, the placenta also produces female sex hormones that regulate the course of pregnancy and childbirth.
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See what “sex glands” are in other dictionaries:
Modern encyclopedia
- (gonads) organs that form sex cells (eggs and sperm) in animals and humans, as well as producing sex hormones. Male gonads testes, female ovaries; mixed sex glands are hermaphroditic (in some worms, ... ... Big Encyclopedic Dictionary
Sex glands- (gonads), organs that form reproductive cells (eggs and sperm) in animals and humans, as well as producing sex hormones. Male gonads testes, female ovaries; mixed sex glands are hermaphroditic (in some worms, ... ... Illustrated Encyclopedic Dictionary
GENITAL GLANDS- GENITAL GLANDS, or gonads, glands that produce germ cells (generative function of the pancreas) and sex hormones (endocrine function of the pancreas). (Comparative anatomy and embryology of the pancreas, see Genitourinary organs.) The male reproductive glands are called... ... Great Medical Encyclopedia
- (synonym - gonads), organs that form sex cells (see Gametes) and sex hormones. They are an integral part of the genital organs. They perform mixed functions, since they produce products not only external (potential... ... Sexological encyclopedia
- (gonads), organs that form reproductive cells (eggs and sperm) in animals and humans, as well as producing sex hormones. Male gonads testes, female ovaries; mixed sex glands are hermaphroditic (in some worms, ... ... Encyclopedic Dictionary
Human organs that form sex cells (gametes) and produce sex hormones. They form the sex of the individual, sexual instincts and behavior, etc. The male gonads (testes) produce sperm and hormones that stimulate development and function... ... Biological encyclopedic dictionary
Gonads, organs that form reproductive cells (eggs and sperm) in animals and humans. P.J. Higher animals secrete sex hormones into the blood. Intrasecretory function of pancreas. regulated by gonadotropic hormones (See Gonadotropic... ... Great Soviet Encyclopedia
- (gonads), organs that form reproductive cells (eggs and sperm) in animals and humans, as well as producing sex hormones. Husband. P.J. testes, female ovaries; mixed P. f. hermaphroditic (in some worms, mollusks, etc.) ... Natural science. Encyclopedic Dictionary
GENITAL GLANDS- organs in which sex cells are formed (in women these are the ovaries, which produce eggs, and in men, these are the testes, which produce sperm), as well as sex hormones... Encyclopedic Dictionary of Psychology and Pedagogy
Books
- Textbook of physiology, Bykov K. M., Vladimirov G. E., Delov V. E., The publication is a textbook for students of medical institutes, which determines its composition and selection of material. As the authors write in the Preface, this edition of the textbook is more... Category: Human Anatomy and Physiology Publisher: State Publishing House of Medical Literature,
- A Work in Black (audiobook MP3 on 2 CDs), Gustav Meyrink, “Even though from the point of view of intelligence and high spirituality, the later novels of Gustav Meyrink are more significant, opening up such abysses that are breathtaking, but these stories, ... Category: Classic and modern prose Publisher: Bibliophonika, audiobook
The result of these processes is the development of mature sperm and eggs by the time of puberty.
Secondly, the gonads contain special complexes associated with endocrine function. They produce sex hormones associated not only with the regulation of the function of the reproductive apparatus; they influence all types of body activity related to the reproductive process and somatic development.
The action of sex hormones manifests itself already in the early stages of embryonic development, determining the differentiation of the body in the direction of one sex or another, the reproductive apparatus and the structure of a number of systems. The influence of hormones is especially pronounced during puberty.
The level of sex hormones in the blood and their utilization in tissues also determines the functional activity of the hypothalamic centers. This regulation is carried out according to the principle of feedback. Thus, the body ensures an optimal level of hormones for the age period and living conditions.
In women, the centers control FSH and LH pituitary hormones, which have a regulatory effect on the gonads. The level of sex hormones regulates the secretion of gonadotropin-releasing hormone.
In men, the sex gland is the testicle and epididymis. Before birth, the testicles descend from the abdominal cavity through the inguinal canal into the scrotum, which is important for creating temperature conditions 2-3 degrees below the body's core temperature. This difference in temperature is necessary for spermatogenesis. Two mechanisms contribute to this difference. First, there is the venous plexus, which serves as a countercurrent heat exchanger between the warm arterial blood flowing to the testicles and the cooler venous blood flowing away from them. Secondly, depending on the condition of the muscle that lifts the testicle, the optimal distance in the position of the testicle in relation to the body is adjusted. If the testicles are exposed to elevated temperatures or fever for a long time, this can lead to temporary infertility as a result of a temporary disruption of spermatogenesis.
In women, the gonads are the ovaries. They are located in the pelvic cavity at the side walls. The average sizes of the ovaries are as follows: length 3-4 cm, width – 2-2.5 cm, thickness – 1-1.5 cm, weight – 6-8 g. In the ovary, there are uterine and tubal ends. The tubal end is raised upward and faces the funnel of the fallopian tube. The ovary is movably connected by ligaments to the uterus and the pelvic wall.
The ability to fertilize in women, unlike men, changes cyclically, since the formation of mature eggs occurs irregularly in them. In contrast to the male body, in which millions of gametes are formed every day, in the female body one or several eggs mature, and then at a certain time.
Like the male gonads, the ovaries perform a dual function: the formation of germ cells (ovogenesis) and the synthesis of female sex hormones (steroidogenesis). The main female sex hormones are estradiol, which is formed during the development of the follicle, and progesterone, synthesized in the corpus luteum. The ovary also produces inhibin, a hormone that regulates the secretion of FSH.
Mixed glands also include the sex glands. The testis (testicle) has the shape of a somewhat compressed ellipsoid. In an adult, its weight at an average age is 20-30 g. In children, the weight of the testicle (g) at 8-10 years is 0.8; 12-14 years old - 1.5; 15 years - 7.
The testicles grow rapidly up to 1 year and from 10 to 15 years. The period of puberty for boys is from 15-16 to 19-20 years. It fluctuates individually. The outside of the testicle is covered with a fibrous membrane, from the inner surface of which a growth of connective tissue wedges into it along the posterior edge. From this growth thin connective tissue crossbars diverge, which divide the gland into 200-300 lobules. The lobules are divided into: 1) seminiferous tubules and 2) intermediate connective tissue. The wall of the convoluted tubule consists of two types of cells: those that form sperm and those that participate in the nutrition of developing sperm. In addition, the loose connective tissue connecting the tubules contains interstitial cells. Spermatozoa enter the epididymis through the straight and efferent tubules, and from it into the vas deferens. Above the prostate gland, both vas deferens become the ejaculatory ducts, which enter this gland, pierce it and open into the urethra. The prostate gland (prostate) finally develops around age 17. Weight for an adult is 17-28 g.
Rice. 96. Male genital organs:
1 - testicle, 2 - epididymis, 3 - vas deferens, 4 - seminal vesicle, 5 - bladder, 6 - prostate gland, 7 - opening of the ejaculatory duct, 8 - urethra, 9 - Cooper's glands, 10 - cavernous bodies of the penis, 11 - cavernous body of the urethra, 12 - glans penis
Spermatozoa are highly differentiated cells 50-60 µm long, which are formed at the beginning of puberty from the primary germ cells of spermatogonia. The sperm has a head, neck and tail. 1 mm3 of seminal fluid contains about 60 thousand sperm. Sperm ejected at one time has a volume of up to 3 cm3 and contains about 200 million sperm.
Male sex hormones - androgens - are formed in interstitial cells, which are called the puberty gland, or puberty. It is also possible that they form in the epithelium of the seminiferous tubules. Androgens: testosterone, androstanedione, androsterone, etc. Female sex hormones - estrogens - are also formed in the intersitial cells of the testicle. Estrogens and androgens are derivatives of steroids and are similar in chemical composition. Dehydroandrosterone has the properties of male and female sex hormones. Testosterone is 6 times more active than dehydroandrosterone.
Rice. 97. Sex cells. A - sperm; B - egg cell:
1 - head of the sperm, 2 - middle, or connecting section, 3 - tail of the sperm, 4 - follicular cells surrounding the egg, 5 - nucleus of the egg cell, An - animal pole of the egg, Veg - vegetative pole of the egg
The female gonads - the ovaries - have different sizes, shapes and weights depending on age and individuality. In a woman who has reached puberty, the ovary looks like a thickened ellipsoid weighing 5-8 g. The right ovary is slightly larger than the left. A newborn girl has an ovary weight of 0.2 g. At 5 years old, the weight of each ovary is 1 g, at 8-10 years old - 1.5 g, at 16 years old - 2 g. The ovary consists of two layers: the cortex and the medulla. Egg cells are formed in the cortex. The medulla consists of connective tissue containing blood vessels and nerves. Female egg cells are formed from primary egg germ cells - oogonia, which, together with feeding cells - follicular cells - form primary egg follicles. Each ovarian follicle is a small egg cell surrounded by a number of flat follicular cells. In newborn girls they are numerous and almost adjacent to each other, but in old women they disappear. In a 22-year-old healthy girl, 400 thousand primary follicles were found in both ovaries. During life, only about 500 primary follicles mature and produce egg cells capable of fertilization, while the rest atrophy.
Follicles reach full development during puberty, from about 13-15 years of age, when some mature follicles secrete the hormone estrone.
The period of puberty (puberty) lasts in girls from 13-14 to 18 years.
Rice. 98. Internal genital organs of a woman (incision):
/ - ovary, 2 - Graafian vesicle, 3 - internal opening of the fallopian tube, 4 - fallopian tube, 5 - place where the tube enters the uterus, 6 - uterine body cavity, 7 - cervical canal, 8 - external opening of the uterus, 9 - vagina
Maturation consists of an increase in the size of the egg cell. Follicular cells multiply rapidly and form several layers. The growing follicle begins to sink deep into the cortex, is surrounded by a fibrous connective tissue membrane, fills with fluid and enlarges, turning into a graafian vesicle. In this case, the egg cell with the surrounding follicular cells is pushed to one side of the vesicle. The mature Graafian vesicle is adjacent to the very surface of the ovary. Approximately 12 days before the graafian menstruation, the vesicle bursts and the egg cell, together with the surrounding follicular cells, is thrown into the abdominal cavity, from which it first enters the funnel of the oviduct, and then, thanks to the movements of the ciliated hairs, into the oviduct and into the uterus. This release of an egg is called ovulation. If the egg cell is fertilized, it attaches to the wall of the uterus and an embryo begins to develop from it.
After ovulation, the wall of the Graafian vesicle collapses and in its place, a temporary endocrine gland is formed on the surface of the ovary - the corpus luteum. The corpus luteum hormone, progesterone, prepares the uterine mucosa to receive the embryo. If fertilization has occurred, the corpus luteum persists and develops throughout the entire pregnancy or most of it. The corpus luteum of pregnancy reaches 2 cm or more and leaves behind a scar for a long time. If fertilization does not occur, the corpus luteum atrophies and is absorbed by phagocytes (periodic corpus luteum), after which new ovulation occurs.
In women, the sexual cycle manifests itself in menstruation.
The first menstruation appears after the maturation of the first egg cell, the bursting of the Graafian vesicle and the development of the corpus luteum. On average, the sexual cycle lasts 28 days and is divided into 4 periods: 1) restoration of the uterine mucosa for 7-8 days, or the rest period, 2) proliferation of the uterine mucosa and its enlargement for 7-8 days, or preovulation, caused by increased secretion of folliculotropic hormone of the pituitary gland and estrogens, 3) secretory - release of a secretion rich in mucus and glycogen in the uterine mucosa, corresponding to the maturation and rupture of the Graafian vesicle, or ovulation, 4) rejection, or post-ovulation, lasting an average of 3-5 days, during which the uterus contracts tonically, its mucous membrane is torn off in small pieces and 50-150 cm3 of blood is released. The last period occurs only in the absence of fertilization.
Estrogens: estrone, or follicular hormone, estriol and estradiol. They are formed in the ovaries, where small amounts of androgens are simultaneously secreted. Progesterone is produced in the corpus luteum and placenta. During the period of rejection, progesterone inhibits the secretion of folliculotropic hormone and other gonadotropic hormones of the pituitary gland, which reduces the formation of estrogen in the ovary.
Sex hormones have a significant impact on metabolism. Androgens stimulate protein synthesis in the body and in muscles, which increases their mass, promotes bone formation and therefore increases body weight. They reduce glycogen synthesis in the liver. Estrogens, on the contrary, increase glycogen synthesis in the liver and fat deposition in the body. Sex hormones determine the quantitative and qualitative characteristics of the metabolism of male and female organisms, which determine the development of the external and internal genital organs, or primary sexual characteristics. These include: the penis, testes, genital tract in men; vagina, uterus, ovaries, oviducts in women. Sex hormones also determine the development of secondary sexual characteristics: characteristic body structure, relatively tall stature, relatively narrow pelvis, mustache and beard, hairiness of the chest, arms and legs, low voice in men; characteristic body structure, relatively short stature, relatively wide pelvis, absence of mustache and beard, high voice, fat deposits on the pubis and buttocks, developed mammary glands in women.
In girls, the mammary glands, or mammary glands, develop during puberty due to increased production of estrogen. Before menstruation, they swell and increase slightly.