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Year 1 > Pathways to men and women: sex differentiation > Flashcards

Pathways to men and women: sex differentiation Flashcards

1
Q

What are the steps to sex determination?

A

1) Determination of sex at fertilisation
2) Phenotypic determination with gonad formation
3) secondary sex characteristic development at puberty

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2
Q

What is the genetic makeup of an individual?

A

Composed of 22 autosomes which are genetically and morphologically identical and 1 pair of sex chromosomes which are different.

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3
Q

Where are autosomes carried?

A

In the gametes

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4
Q

What is the gamete in females?

A

Homogametic Oocytes which contain only X chromosomes

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5
Q

What is the gamete in males?

A

Heterogametic oocytes which contain X and Y chromosomes

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6
Q

What is the role of the Y chromosome in genetic determination of sex?

A

It guides the formation of male sex characteristics

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7
Q

What is the structure of the Y chromosome?

A

Contains a pseudoautosomal region, SRY gene, MSR region that contains euchromatin, heterochromatin and the centromere.

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8
Q

When does the primary determination of sex occur?

A

At fertilisation

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9
Q

What is the pseudoautosomal region?

A

Homologous sequence at the end of the Y chromosome identical to the end of the X chromosome that allows them to pair up in meiosis and mitosis.

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10
Q

What is the majority of the Y chromosome composed of?

A

MSR segment formed of euchromatin and heterochromatin

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11
Q

What is the SRY gene?

A

Codes for the Y protein which guides male sex characteristic formation of the gonads via antimullerian hormone production

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12
Q

How do males with XX exist?

A

Translocation of the SRY gene to the X chromosome which means there is still development of the male phenotype via gonads and therefore secondary sex characterisitics.

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13
Q

How do females with XY exist?

A

Silence/mutation to the SRY gene which means Y protein is not expressed and leads to physiological and phenotypic female who is genetically male

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14
Q

Where do the gonads form?

A

In the bipotential gonads/genital ridge, located near to the mesonephros.

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15
Q

What is the mesonephros?

A

Embryological excretory duct which is the temporary kidney

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16
Q

What is the genital ridge?

A

The somatic precursor of the gonads from the mesoderm which sends signals to primordial germ cells to migrate from the hindgut to the allantosis on either side of the dorsal aorta in the mesonephros and form two mesenchymal knots.

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17
Q

What is the stem cell for the gonads?

A

Primordial germ cells, coelomic epithelia and mesenchyme

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18
Q

What are the primordial germ cells?

A

Undifferentiated stem cells from the endoderm which will form the gonads. Prior to migration, they are located in the hindgut in the wall of the embryonic yolk sac.

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19
Q

What is the coelomic epithelia?

A

Epithelia lining the viscera and the body walls of the embryo.

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20
Q

How do the gonads form?

A

Bipotential gonads release migratory signals to the primordial germ cells. They move from the hindgut and deposit on either side of the dorsal aorta in the mesonephros. Coelomic epithelia on the germ ridge proliferate and migrate. If SRY gene is present, they migrate to the medulla and differentiate into Sertolli cells and form spermatic cord. In absence, they migrate to the cortex and differentiates into oocytes and form the cortical cords -> follicle and ovaries.

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21
Q

What is the primitive sex cord?

A

Formed from the differentiation of the coeleomic epithelia of the mesonephral duct surrounding the genital ridge. Creates either the spermatic cord or the cortical cord

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22
Q

How does the male gonad form?

A

SRY gene causes the coeleomic epithelia to migrate into the medulla and differentiate into the spermatic cord with myoid cells lateral where spermatogenesis will occur in the adult. Coelomic epithelia -> testis cordis -> pre-sertoli cells -> sertoli cells. These cause primordial germ cells to become spermatozoa in the medulla of the mesonephros. Formation of androgen producing Leydwig cells finishes production of the testes.

23
Q

What are sertoli cells and which embryonic cell does it form from?

A

Precursor is the coelomic epithelia which differentiate into sertolli cells due to SRY gene. Sertolli cells surround primitive germ cells to -> spermatozoa which occurs in the seminiferous tubules and direct testis formation of the medulla via spermatic cord formation.

24
Q

How does the female gonad form?

A

Coelomic epithelia in absecence of Y protein migrates to cortex and form cortical cords. It forms granulosa cells which cause primordial germ cells to cluster and form an ovary and later, an egg/oocyte

25
Q

How does spermatogenia occur and what is the site?

A

Primordial germ cells form spermatozoa via action of the sertolli cells in the seminiferous tubules.

26
Q

How doess oogonia occur?

A

From a primordial germ cell, the coelomic epithelia differentiates into granulosa cells and stimulates the chaange via meiosis into a an oocyte.

27
Q

How does SRY gene work?

A

It increases the expression of transcription factor SOX9. SOX9 increases expression of PGD2 and FGF9 and vice versa. SOX9 inhibits Foxl2 for ovary formation and increases antimalarial hormone for male reproductive formation.

28
Q

What prevents the formation of female reproductive hormones?

A

Antimullerian hormone via action of SRY gene.

29
Q

What is the role of FoxL2?

A

Ovary formation. It increases expression of Wrnt4 which then -> granulosa cells which produce oestrogen and progesterone. In development, granulosa cells case primordial germ cells to form the oocytes

30
Q

What is the indication of PDG2?

A

Pre-sartolli cell formation from coeleomic epithelia.

31
Q

How do ovo testis occur?

A

Female embryo is exposed excess androgens. The SOX9 transcription factor is silenced or mutated- there is expression of both antimalarial hormone and FoxL2

32
Q

What is the source of testosterone and androgens in males?

A

Leydwig cells

33
Q

What is a blastema?

A

Collection of undifferentiated cells

34
Q

Where does sperm mature and store?

A

In the epidymis

35
Q

How does sperm move from the testicle to the epididymis?

A

Via the ras testis.

36
Q

What is a myoid cell?

A

Forms the smooth muscle of the seminiferous tubules, ras testis and ras blastema.

37
Q

What is a leywig cell?
.

A

Source of androgen production in males

38
Q

What are theca cells?

A

Source of androgen production in females and supports follicle development. Androgens are precursors to oestrogen biosynthesis.

39
Q

What are the granulosa cell?

A

Endocrine cells which produce oestrogen and progesterone.

40
Q

What is the role of Wolffian duct?

A

It forms the internal male genitalia in the mesonpehric region of the vas deferens and epidymis via action of the androgens and anti-Mullerian hormone to cause regression of the Mullerian duct.

41
Q

What is the role of the Mullerian duct?

A

It forms the internal female genitalia of the cervix, uterus and vaginal canal via action of the Foxl2 transcription factor. It causes regression of the Wolfian duct.

42
Q

What is third wave migration?

A

Migration of cells for the regression of the Wolffian or the Mullerian duct.

43
Q

Which cells migrate in men?

A

Leydwig cells, myoid cells and vascular tissue.

44
Q

Which cells migrate in women?

A

Theca cells and vascular tissue.

45
Q

What determines the sex of the genital tract?

A

Presence of testes. This is formed by androgens and the anti-mullerian hormone to maintain the Wolffian tract and cause regression of the Mullerian.

46
Q

What is gonadarche?

A

Beginning of puberty

47
Q

What is neuronal sex?

A

Sex of the hypothalamus

48
Q

What are secondary sexual characteristics?

A

Breasts, voice, genitalia growth and musculature.

49
Q

Which part of the brain is involved in sex?

A

Hypothalamus.

50
Q

What determines the sex of the hypothalamus?

A

Production of androgen and receptivity of the body’s androgen receptors.

51
Q

What is Turner’s syndrome?

A

Disorder of sexual differentiation. Singular X chromosome. Presence of ovaries but infertile and has short stature, low hairline, brown nevis spots.

52
Q

What is Klinefelter syndrome?

A

Disorder of sexual differentiation with XXY and has breast development, osteoporosis, smaller male genitalia, female pattern pubic hair and tall stature.

53
Q

What is androgen insesnitivity syndrome?

A

Androgen production normal however receptors fail to respond to androgen. Results in the development of phenotypic female with no ovaries or uterus and internal male genitalia despite external vagina.

54
Q

What is congenital adrenal hyperplasia?

A

During development, low corticosteroid production means there is high foetal adrenale production that causes maintenance of both the Wolffian and Mullerian duct and leads to both male and female internal adn external genitalia.

Year 1 (191 decks)

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