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Reprooooooooo > Sexual differentiation and disorders > Flashcards

Sexual differentiation and disorders Flashcards

1
Q

What is sexual determination?

A

It is the genetic process that is dependent on the switch on the Y chromosome
Chromosomal determination of male or female

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2
Q

What is sexual differentiation?

A

Is the process by which internal or external genitalia develop as male or female

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3
Q

What are both sexual determination and differentiation and what do they consist of?

A

Sexual determination and differentiation are contiguous and consist of several stages

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4
Q

What are the levels involved in sex differentiation?

A
  • An early embryo can be said to have a genotypic sex like xx or xy
  • In the next level of complexity as the embryo develops, we can say it has a gondal sex, so either testes or ovaries
  • Beyond this, we can say a person can have phenotypic sex
  • Above this we have the legal sex
  • Above all we have gender identity
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5
Q

What does the SRY gene create?

A

The SRY gene creates the testis

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6
Q

When do ovaries develop?

A

In the absence of Y chromosome

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7
Q

What cells do the testis form which make important hormones?

A
  • Sertoli cells

- Leydig cells

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8
Q

What hormone do sertoli cells produce?

A

Sertoli cells produce anti-Mullerian hormone (AMH)

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9
Q

What hormone do leydig cells produce?

A

Leydig cells make testosterone

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10
Q

Steps involved in gonadal development

A
  • After fertilisation a pair of gonads develop which are bipotential
  • Their precursor is derived from common somatic mesenchymal tissue precursors called the genital ridge primordia on the posterior walls of the low thoracic lumbar region
  • Genital ridges become the testes or ovaries
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11
Q

What would the mullerian ducts develop into?

A

Mullerian duct would develop into the uterus and uterine tubes

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12
Q

What would the wolfian ducts develop into?

A

Wolfian ducts will develop into the vas deferens and prostate

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13
Q

What are the 3 waves of cells that invade the genital ridge and what do they become in both male and female?

A
  1. Primordial germ cells- become sperm (males) or oocytes(female)
  2. Primitive sex cords- become sertoli cells (male) or granulosa cells (female)
  3. Mesonephric cells-become blood vessels and leydig cells (male) or theca cells (female)
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14
Q

What are primordial germ cells?

A

Initially a small cluster of cells in the epithelium of the yolk sac and expands by mitosis at around 3 weeks

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15
Q

Where do primordial germ cells migrate to?

A

They migrate to the connective tissue of the hind gut, to the region of the developing kidney and on to the genital ridge- completed by 6 weeks

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16
Q

What are primitive sex cords?

A

They’re cells from the germinal epithelium that overlies the genital ridge mesenchyme and migrate inwards as columns called the primitive sex cords

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17
Q

What do primitive sex cord do when their is SRY expression?

A
  • Primitive sex cords penetrate the medullary mesenchyme and surround the PGCs to form testis cords
  • Eventually they become sertoli cells which express AMH
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18
Q

What do primitive sex cords do when there isn’t SRY expression?

A
  • Sex cords are ill defined and do not penetrate deeply but instead condense in the cortex as small clusters around PGCs
  • Eventually become granulosa cells
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19
Q

Where do mesonephric cells originate?

A

These originate in the mesonephric primordium which are just lateral to the genital ridges

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20
Q

What do mesonephric cells in male act under the influence of and form what?

A

In males they act under the influence of pre sertoli cells to form:

  • Vascular tissue
  • Leydig cells
  • Basement membrane which contribute to the formation of seminiferous tubules and rete-testis
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21
Q

What do mesonephric cells in females without the influence of SRY form?

A

They form:

  • Vascular tissue
  • Theca cells
22
Q

What are mullerian ducts inhibited in the male by?

A

Inhibited in the male by AMH

23
Q

What are wolffian ducts stimulated by?

A

Stimulated by testosterone

24
Q

What does lack of stimulation of wolffian ducts mean?

A

Lack of stimulation by testosterone means regression in female

25
Q

How does testosterone convert to DHT and where?

A

Testosterone converted by 5 alpha reductase in the genital skin to DHT

26
Q

What else binds to testosterone receptor?

A

DHT also binds to testosterone receptor, but is more potent than testosterone

27
Q

What does DHT cause and the changes observed?

A

DHT causes differentiation of the male external genitalia:

  • Clitoral are enlarges into penis
  • Labia fuse and become ruggated to form scrotum
  • Prostate forms
28
Q

Disorders of sexual differentiation(Gonadal dysgenesis)

A
  • Sexual differentiation is incomplete

- Usually missing SRY in male, or partial or complete deletion of second x in female

29
Q

Disorders of sexual differentiation(Sex reversal)

A

-Phenotype doesn’t match genotype

30
Q

Disorders of sexual differentiation(Intersex)

A

-Have some component of both tracts or have ambiguous genitalia

31
Q

What does androgen insensitivity syndrome result in?

A
  • Testes form and make AMH so mullerian ducts regress
  • No differentiation of wolffian ducts
  • No external male genitalia
32
Q

Complete AIS

A
  • Appears completely female at birth

- Usually present with primary amenorrhoea

33
Q

Partial AIS

A

-Present with varying degrees of penile and scrotal development from ambiguous genitalia to large clitoris

34
Q

What does a 5 alpha reductase deficiency result in?

A
  • Testosterone is made but not DHT
  • Testes form and make AMH so mullerian ducts regress
  • Wolffian ducts develop
  • No external male genitalia
35
Q

Why does incidence vary in 5 alpha reductase deficiency?

A

Incidence varies enormously as it can be autosomal recessive and can depend on inter related marriage

36
Q

What do we need to assess at puberty with 5 alpha reductase deficiency?

A

At puberty we need to assess potential high testosterone levels which will occur at adrenarche and puberty may induce virilisation

37
Q

What is 45XO also known as ?

A

Also known as turners syndrome

38
Q

What does XO have a failure of?

A
  • Failure of ovarian function

- Uterus and tubes are present but small

39
Q

Comment on fertility in turners syndrome

A

May be fertile and may have mosaicism

40
Q

What is required in turner’s syndrome?

A

Hormone support of bones and uterus required

41
Q

When does congenital adrenal hyperplasia occur?

A

Happens when a XX female is exposed to high levels of androgens in utero

42
Q

What makes steroids?

A

Adrenal glands

43
Q

What precursor forms progesterone and how?

A

Cholesterol is the precursor and is imported into the cell and from carbon 21 onwards, these are clipped off forming progesterone

44
Q

What happens when you clip off an additional 2 carbons from a progesterone with 19 carbons in total?

A

Forms an androgen

45
Q

What happens when you clip off 1 additional carbon from an androgen with 18 carbons in total?

A

Form estrogen now

46
Q

What happens if 21 hydroxylase enzyme fails?

A

If 21 hydroxylase enzyme fails, we’re unable to make cortisol

47
Q

What happens when you can’t make cortisol in a foetus?

A

You start making more androgens:

  • If you make no cortisol, there’s no negative feedback and ACTH increases
  • ACTH causes more cholesterol to be taken up
  • You then produce more androgens
  • So in a baby girl, there would be an increase in testosterone
48
Q

What does congenital adrenal hyperplasia result in?

A
  • No SRY so no testes and no AMH
  • Mullerian ducts remain
  • Masculinised external genitalia, but androgen levels are not usually high enough to rescue the wolffian ducts
49
Q

What is there a possibility of in congenital adrenal hyperplasia?

A

There may be the possibility of salt wasting due to a lack of aldosterone and this can be lethal

50
Q

How do we correct the feedback in congenital adrenal hyperplasia?

A

Need treatment with glucocorticoids to correct feedback

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