Neuro quiz 1 Flashcards
Sex determination
early developmental process (процесс раннего развития) that determines if a person will be M or F.
If sperm has Y chromosome – Male. 2 X chromosomes – Female.
sexual differentiation
In the first few weeks after conception (зачатия), the embryo’s gonads - the organs that will become either the ovaries (яичниками) or the testes (семенниками) - are indifferent (безразличны), meaning they could develop into either type of reproductive organ (могут развиться в любой тип репродуктивного органа). This state is maintained by the balance between several different genes and signaling pathways (различными генами и сигнальными путями), none of which are strongly pushing the gonads (гонады) toward becoming either testes or ovaries.
Six weeks after conception, the situation changes if the Y chromosome is present in the cells of the embryo. The Y chromosome carries a gene called SRY (Sex-determining Region Y) that plays a pivotal role in testis differentiation. The protein product of the SRY gene is a transcription factor that upregulates genes involved in testis (формировании яичек) formation and downregulates genes (подавляет регуляцию генов) involved in ovarian (яичников) formation.
In the absence of a Y chromosome (and hence the absence of the SRY gene), the default (по умолчанию) pathway leads to the development of ovaries.
Gonads
Gonads are organs that produce germ cells or gametes (половые клетки или гаметы). In men, the gonads are the testicles (яички) that produce sperm, and in women, the gonads are the ovaries (яичники) that produce eggs. Gonads also produce hormones that regulate the development of secondary sexual characteristics and other aspects of sexual development and functioning.
Secondary sexual characteristics (вторичные половые признаки)
Secondary sexual characteristics are these features that differentiate males and females. Unlike primary sexual characteristics (первичных половых признаков), which include the direct organs of reproduction (such as ovaries and testes - яички), secondary sexual characteristics begin to manifest (проявляться) only during and after puberty.
Secondary sexual characteristics in males include, for example, the development of chest muscles, voice deepening (углубление), facial and body hair growth, as well as increased muscle mass and shoulder width (ширины). In females, secondary sexual characteristics include breast enlargement, hair growth in the armpit (в подмышечной впадине) and bikini area, and an increase in hip (бедер) width.
These changes are stimulated by hormones produced by the gonads (ovaries in females and tested in males). The main hormones responsible for these changes are estrogens in females and androgens (such as testosterone) in males.
sexual differentiation of an embryo into a male or female
The sexual differentiation of an embryo into a male or female depends on hormones secreted by the gonads. If an embryo carries a Y chromosome, the SRY gene it contains (содержащийся в нем ген SRY) will trigger (запустит) the development of testes in the early indifferent gonads (в ранних индифферентных гонадах). The testes then secrete (выделяют) testosterone and other masculinizing hormones that promote the development of male structures (способствуют развитию мужских структур) and inhibit the development of female structures.
Early in development, all embryos have two pairs of ducts (протоков): the Wolffian and the Müllerian. The Wolffian ducts can develop into the epididymis (придаток яичка), vas deferens (семявыводящий проток), and seminal vesicles (семенные пузырьки) in males. These are the tubes that sperm travel through from the testes to the outside of the body (наружу). Testosterone secreted by the testes triggers the development of the Wolffian ducts (запускает развитие вольфовых протоков) into these male reproductive structures.
The Müllerian ducts can develop into the uterus (матку), fallopian tubes, and the upper part of the vagina in females. In the absence of testes and the hormones they produce, the Müllerian ducts develop into these female reproductive structures.
If the embryo develops testes, these glands (железы) also produce a hormone called Müllerian-inhibiting substance (MIS, also known as anti-Müllerian hormone or AMH). MIS prevents the Müllerian ducts from developing into female reproductive structures. the presence of testes causes the embryo to develop male structures (from the Wolffian ducts) and prevents it from developing female structures (from the Müllerian ducts).
in an embryo that develops ovaries, the absence of testosterone allows the Müllerian ducts to develop into female reproductive structures, and the absence of MIS means that these structures are not inhibited. The Wolffian ducts, without testosterone to stimulate their development, wither away.
the Wolffian ducts and the Müllerian ducts
Females: Müllerian ducts develop into fallopian tubes, uterus, & vagina – only part of Wolffian ducts remains (остается только часть вольфовых протоков).
Males: Wolffian ducts develop into epididymis (придаток яичка), vas deferens (емявыводящий проток), and seminal vesicles (семенной пузырек); Müllerian ducts shrink (сокращаются).
In females (who have two X chromosomes), there is no secretion of the hormones that stimulate the development of the Wolffian ducts. Therefore, these ducts degenerate (вырождаются).
without the hormone that suppresses the development of the Müllerian ducts (Müllerian-inhibiting factor or MIF), these ducts continue to develop. The Müllerian ducts form the fallopian tubes, the uterus, and the upper part of the vagina.
In males (who have one X and one Y chromosome), the SRY gene on the Y chromosome leads to the development of testes, which produce testosterone and MIF. Testosterone promotes the development of the Wolffian ducts into the epididymis, vas deferens, and seminal vesicles, which are parts of the male internal reproductive system. At the same time, MIF causes the Müllerian ducts to degenerate, preventing the development of female internal reproductive structures.
sex differentiation at 15 weeks of gestation (беременности)
If the fetus (плод) is male (XY), the testes have been forming from week 7 when the SRY gene on the Y chromosome triggered their development from the indifferent gonads (половые железы). Around week 12, they began to produce testosterone, driving the further masculinization (маскулинизации) of the fetus. By 15 weeks, the testes are continuing to mature (созревать, развиваться), and the penis and scrotum (мошонка) are beginning to take shape.
If the fetus is female (XX), the ovaries began to differentiate from the indifferent gonads around week 7, but in the absence of SRY and testosterone, the process led to the formation of ovaries. By 15 weeks, the ovaries are continuing to develop and the external female genitalia (the clitoris and labia-половые губы) are beginning to form.
Two hormones from the testes make the system masculine
Testosterone – promotes the development of the Wolffian system.
Anti-müllerian hormone (AMH) – induces (вызывает) the regression of the Müllerian system.
Testosterone in development
Testosterone also masculinizes other structures in utero (внутриутробно): prostate gland (предстательную железу), scrotum (мошонку), and penis. Default process is to develop female external genitalia.
5α-reductase is an enzyme (фермент) that converts (преобразует) testosterone into the more powerful 5α-dihydrotestosterone (DHT), necessary to form male genitalia (необходимый для формирования мужских гениталий).
Gonadal sex (гонадальный пол - пол половых желёз — яички или яичники)
Gonadal sex refers to the type of gonads (the sex organs that produce sex cells, or gametes) that an individual has. Gonadal sex is one of several aspects of an individual’s biological sex, which also includes chromosomal sex, hormonal sex, morphological sex, and phenotypic sex.
Gonadal sex is typically binary: individuals either have testes (male gonadal sex) or ovaries (female gonadal sex). The development of gonadal sex is directed by genes on the sex chromosomes, with the SRY gene on the Y chromosome triggers the development of testes.
there can be intersex conditions (conditions where an individual has sexual anatomy, reproductive organs, and/or chromosome patterns that don’t fit typical definitions of male or female) where gonadal sex might not be strictly binary. For instance, some people might have one ovary (яичник) and one testis (яичко) (a condition called ovotestis), or their gonads might have some aspects (могут иметь некоторые особенности) of both testes and ovaries.
Chromosomal, hormonal, morphological, and phenotypic sex
Chromosomal Sex: sex chromosomes an individual inherits (наследует) from their parents. males have one X and one Y chromosome (XY) and females have two X chromosomes (XX). However, variations can occur such as in Turner syndrome (XO) and Klinefelter syndrome (XXY).
Hormonal Sex: the dominant hormones are produced by an individual’s gonads. Testosterone is produced in larger quantities in males, while estrogen and progesterone are produced in larger quantities in females. Hormonal sex influences the development of secondary sexual characteristics like facial hair in males or breast development in females.
Morphological Sex: the structure of an individual’s internal and external reproductive organs (строение внутренних и внешних репродуктивных органов индивидуума). males have testes, a penis, and associated structures. females have ovaries, a uterus (матка), a vagina, and associated structures.
Phenotypic Sex: physical and physiological characteristics of an individual - result from the interaction of its genetic makeup with the environment (результатом взаимодействия его генетического состава с окружающей средой). This includes secondary sexual characteristics.
Phenotypic sex: internal and external characteristics (chatgpt)
Internal: For males, the prostate gland (предстательная железа), seminal vesicles (семенные пузырьки), and vas deferens (семявыводящий проток). For females, the uterus (матка), fallopian tubes, and the inner part of the vagina. The presence or absence of these structures is usually determined by hormones produced by the gonads (testes or ovaries).
External: For males, a penis, scrotum (мошонка), more body hair, broader shoulders, and a deeper voice. For females, a vulva (which includes the external part of the vagina), breasts, less body hair, wider hips (более широкие бедра), and a higher pitched voice (более высокий тембр голоса).
Phenotypic sex: internal and external characteristics (Limor)
phenotypic sex:
internal: 1. AMH causes mullerian ducts to regress. in absence of AMH mullerian ducts form fallopian tubes, uterus, and inner vagina. 2. testosterone induces wolffian ducts to form epididymis, vas deferens, and seminal vesicles and other tissues to form prostate and bulbourethral gland (других тканей для формирования предстательной железы и бульбоуретральной железы). In absence of testosterone, wolffian ducts regress, and no prostate or bulbourethral gland forms.
external: DHT induces skin to form scrotum (стимулирует образование кожи в мошонке), tubercle forms penis (бугорок формирует пенис). In absence of DHT skin forms labia (половые губы) and outer vagina, tubercle forms clitoris (бугорок образует клитор).
