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Reproduction > Sexual Differentiation And Disorders > Flashcards

Sexual Differentiation And Disorders Flashcards

1
Q

What is the definition of sexual determination?

A

→ Genetically controlled process dependent on the switch on the Y chromosome

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2
Q

What is sexual differentiation?

A

→ The process by which internal and external genitalia develop as male or female

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3
Q

What does gender depend on?

A

→ A switch gene in the Y chromosome

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4
Q

What is genotypic sex?

A

→ XY

→ XX

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5
Q

What is gonadal sex?

A

→ Testes

→ Ovaries

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6
Q

What is phenotypic sex?

A

→ outward appearance

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7
Q

What is Legal sex?

A

Passport/birth certificate

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8
Q

What is gender identity?

A

→ How you feel / not always the same as phenotypic

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9
Q

What is the first event that occurs that determines sex?

A

→ Genetic signal which then form testes or ovaries

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10
Q

What gene creates the testes?

A

→ The SRY gene

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11
Q

In the absence of the Y chromosome what develops?

A

→ Ovaries

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12
Q

What does SRY mean?

A

→ Sex determining region

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13
Q

When does the SRY region switch on and what happens when it is switched on?

A

→ During embryo development in > week 7

→ makes gonad into testis

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14
Q

What two types of cells are in the testis?

A

→ Sertoli cells

→ Leydig cells

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15
Q

What do Sertoli cells make?

A

→ Produce anti mullerian hormone

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16
Q

What do Leydig cells make?

A

→ Testosterone

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17
Q

What is SRY?

A

→ A transcription factor that causes self transcription

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18
Q

What happens after fertilization (gonads)?

A

→ A pair of gonads develop which are bipotential

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19
Q

What is the precursor of gonads derived from?

A

→ Somatic common mesenchymal tissue precursors called genital ridge primordia

on posterior wall of lower thoracic lumbar region

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20
Q

What do the genital ridges become?

A

→ Ovaries or testes

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21
Q

What does the Mullerian duct become?

A

→ Uterus
→ Uterine tubes
→ Upper third of vagina

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22
Q

What does the Wolffian duct become?

A

→ Vas deferens

→ Prostate

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23
Q

What are the 3 types of cells that invade the genital ridge?

A

→ Primordial germ cells
→ Primitive sex cords
→ Mesonephric cells

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24
Q

What do primordial germ cells become?

A

→ Sperm or oocytes

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25
Q

What do primitive sex cords become?

A

→ Sertoli cells

→ or Granulosa cells

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26
Q

What do mesonephric cells become?

A

→ Leydig cells

→ Theca cells

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27
Q

Describe primordial germ cell migration

A

→ Small clusters of PGC cells in the epithelium of the yolk sac expand at 3 weeks
→ Migrate to the connective tissue of the hindgut to the region of the developing kidney and onto the genital ridge

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28
Q

Describe what happens to primitive sex cords in the male

A

→SRY expression
→Penetrate the medullary mesenchyme and surround the primordial germ cells to form testis cords
→Eventually become sertoli cells which express anti Mullerian hormone

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29
Q

Describe what happens to primitive sex cords in the female

A

→No SRY expression
→Sex cords are ill defined and do not penetrate deeply but instead condense in the cortex as small clusters around PGCs
→become granulosa cells

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30
Q

What type of structures do the sex cords form?

A

→ Tubular structures with germ cells inside of them

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31
Q

Where do mesonephric cells originate from?

A

→ Mesonephric primordium which are lateral to the genital ridges

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32
Q

What do mesonephric cells in males act under the influence of?

A

→ Pre sertoli cells that are already there and express SRY

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33
Q

What do mesonephric cells form in males?

A

→ Leydig cells - synthesize testosterone- do not express SRY themselves
→ Basement membrane
→ Vascular tissue

34
Q

What does the basement membrane form in males?

A

→ Seminiferous tubules and rete-testis

35
Q

What do mesonephric cells form in females?

A

→ Theca cells

→ Vascular tissue

36
Q

What do Leydig cells synthesize?

A

→ Testosterone

37
Q

What do Theca cells synthesize?

A

→ Androstenedione which is a substrate for estradiol production

38
Q

What hormone does the male gonad produce that the female gonad does not?

A

→ Anti mullerian hormone

39
Q

What do Sertoli cells make and what does this do to the Leydig cells?

A

→ Anti mullerian hormone

→ causes Leydig cells to synthesize testosterone

40
Q

Give a summary of the 3 types of cells in males and what they produce?

A

Primary germ → Sperm cells
Primitive sex cords → Sertoli cells (AMH, SRY)
Mesonephric cells → Leydig cells (testosterone)

41
Q

Give a summary of the 3 types of cells in females and what they produce?

A

Primitive germ → oocytes
Primitive sex cords → Granulosa cells (Estradiol)
Mesonephric cells → Theca cells (androstenedione)

42
Q

What are Mullerian ducts inhibited by?

A

→ AMH

43
Q

What are wolffian ducts stimulated by and why do they regress?

A

→ Regress if there is lack of stimulation by testosterone

→ Stimulated by testosterone

44
Q

Where is testosterone converted?

A

→ Genital skin

45
Q

What is testosterone converted into?

A

→ dihydrotestosterone

46
Q

What enzyme is used to convert testosterone?

A

→ 5areductase

47
Q

What form of testosterone is more potent?

A

→ dihydrotestosterone

48
Q

Describe how DHT cause differentiation of male external genitalia

A

→ Clitoral area enlarges into penis
→ Labia fuse and become rugated to form scrotum
→ Prostate forms

49
Q

Why is there no differentiation of female genitalia into male genitalia if 5a reductase is present?

A

→ there is no substrate (testosterone)

50
Q

Flowchart of sequence leading to differentiation of external male genitalia

A 
SRY is expressed with a Y chromosome
↓
Sertoli cells form
↓
Testis formation occur
↓
Sertoli cells secrete AMH
↓
Regression of Mullerian duct
↓
Leydig cells secrete testosterone
↓
Growth of Wolffian duct
↓
Testosterone is acted on by 5 a reductase to DHT
↓
development of male external genitalia
51
Q

Flowchart of sequence leading to differentiation of external female genitalia

A 
no Y chromosome
↓
no AMH
↓
Mullerian ducts grow
↓
Ovary doesn't produce testosterone
↓
Wolffian ducts regress
↓
External female genitalia develop
52
Q

What is gonadal dygenesis?

A

→ Sexual differentiation is incomplete

→ Missing SRY in male or partial or complete deletion of X in female

53
Q

What is sex reversal?

A

→ Phenotype does not match genotype

→ may be male genotypically but externally female

54
Q

What is intersex?

A

→ have some components of both tracts or ambiguous genitalia

→ Sex of infant is difficult to determine

55
Q

What is androgen insensitivity syndrome?

A

→ XY individual making testosterone but it has no effect

56
Q

What is a clue to androgen insensitivity?

A

→ lack of body hair

→ Amenorrhoea

57
Q

What occurs in a 5 alpha reductase deficiency?

A

→ Testes form and AMH acts so Mullerian ducts regress, Wolfian ducts develop
→ Internal structures form
→ External structures do not develop
→ Appear mainly female

58
Q

What is turner syndrome?

A

→ When there is the absence of an X chromosome

59
Q

What are the characteristics of turner syndrome?

A

→ Streak ovaries
→ ovarian dysgenesis
→Uterus and tubes are present but small, other defects in growth and development.
→

60
Q

How does congenital adrenal hyperplasia work?

A

→ when an XX female is exposed to high levels of androgens in utero

61
Q

What does the adrenal gland make?

A

→ Steroids

62
Q

What are the main steroids that the adrenal gland makes?

A

→ Aldosterone and cortisol

63
Q

Where are the rest of the steroids made and what are they called?

A

→ In the gonads
→ Testosterone
→ progesterone
→ Estrogen

64
Q

What is the structure of cholesterol?

A

→ 3 six sided rings

→ one 5 sided ring

65
Q

What is the difference between the estrogens?

A

→ THe number of OH groups on them

66
Q

What happens if 21 hydroxylase doesn’t work?

A

→ Cortisol not produced
→ More ACTH produced (negative feedback)
→ ACTH causes cholesterol to be taken up
→ Cholesterol is converted into androgens instead

67
Q

What happens to girls when 21 hydroxylase doesn’t work in utero?

A

→ Increase in testosterone
→ Growth of wolffian duct
→ External genitalia are male

68
Q

What is the treatment for 21 hydroxylase deficiency?

A

→ Glucocorticoid

69
Q

Describe how estrogens are made

A

→Cholesterol is imported into the cell and has the carbons from carbon 21-27 cleaved
→ it becomes prenenolone (progestagens) which has 21 carbons and two carbons are removed
→ this makes androgens which have 19 carbons and another carbon is removed
→this forms estrogens which have 18 carbons

70
Q

What does 21 hydroxylase do?

A

→ Convert cholesterol into cortisol and aldosterone

71
Q

Where is the SRY gene found on the chromosome?

A

close

to the end of the short arm of the human Y chromosome

72
Q

What is the pseudoautosomal region on a chromosome?

A

Homologous sequences of nucleotides on the X and Y chromosomes. Genes inherited just like any autosomal genes

73
Q

Compare what Sertoli and granulosa cells form

A

→Sertoli cells form long tubes with primordial germ cells inside them
→Granulosa cells form clumps around primordial cells

74
Q

What are the features of androgen insensitivity syndrome?

A

→Testes form and make AMH so Mullerian ducts regress.
→No differentiation of Wolffian ducts
→No external male genitalia
→Dihydrotesterone is made and because it binds to same receptors as testosterone, its not detected

75
Q

How is AIS diagnosed?

A

→Ultrasound scan and karyotype with male levels of androgens.
→Never responded to androgen so appear and often feel female.

76
Q

What happens in puberty of those with 5-a-reductase deficiency?

A

→Need to assess potential as high testosterone level which will occur at adrenarche
→puberty may induce virilisation.

77
Q

What does Turner syndrome show about X-inactivation?

A

It isn’t the entire X-chromosome that is switched off.

→There are pseudo autosomal regions still on required for ovarian development

78
Q

What does the severity of Turner’s syndrome depend on?

A

→when the X-chromosome is switched off. If switched off at one cell stage then it would be most severe. But if lost later on then there a mixture of two Xs and one Xs

79
Q

What can be lethal in CAH?

A

→salt wasting due to lack of aldosterone

80
Q

What are the features of CAH?

A

→No SRY so no testes and no AMH.
→Mullerian ducts remain.
→Masculinised external genitalia,
→androgen levels not usually high enough to fully rescue Wolffian ducts.

Reproduction (12 decks)

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