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Repro > Sexual Differentiation and Disorders > Flashcards

Sexual Differentiation and Disorders Flashcards

1
Q

What is sexual determination?

A

Genetically controlled process 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

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

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3
Q

Which gene creates the testis?

A

The SRY gene

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4
Q

What is SRY?

A

It is a sex determining region Y that switches on briefly during embryo development to make the gonad into a testis. In its absence, an ovary is formed.

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5
Q

What cells does the testis develop?

A

Sertoli cells and Leydig cells

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6
Q

What hormone does Sertoli cells produce?

A

anti-Mullerian hormone (AMH)

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7
Q

What hormone does Leydig cells produce?

A

Testosterone

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8
Q

Where is the SRY gene located?

A

On the Y chromosome

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9
Q

What do the products of the cells the testis influence lead to the development of?

A

The products of the testis influence further gonadal and phenotypic sexual development.

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10
Q

Describe the start of gonadal development

A

A pair of gonads develop that are bipotential. These derive from common somatic mesenchymal tissue precursors called the genital ridge primordia at 3-4 and a half weeks on the posterior wall of lower thoracic lumber region.

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11
Q

What are the three waves of cells that invade the genital ridge?

A
  • Primordial Germ Cells: become either the sperm or oocytes
  • Primitive Sex cords: become either sertoli or granulosa cells
  • Mesonephric cells: become either leydig or theca cells
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12
Q

What is the primordial germ cell migration stage?

A
  • small cluster of cells in the epitelium of the yolk sac
  • expands by mitosis at around 3 weeks
  • migrate to the connective tissue of the hind gut to the region of the developing kidney
  • to the genital ridge - completed by 6 weeks
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13
Q

What is the primitive sex cords stage?

SRY or no-SRY expression?

A
  • Germinal epithelium cells that overly the genital ridge mesenchyme migrate inwards as columns called the primitive sex cords.
  • If there is SRY expression, penetrate the medullar mesenchyme and surround the PGCs to form testis cords and become sertoli cells expressing AMH.
  • If no SRY expression, sex cords are ill-defined and do not penetrate but instead condense in the cortex as small clusters around PGCs. These become granulosa cells.
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14
Q

What is the mesonephric cells stage?
What happens in males?
What happens in females?

A
  • Originate in the mesonephric primodrium that is lateral to the genital ridges
  • MALES: Act under the influence of pre-sertoli cells that express SRY to form; vascular tissue, leydig cells, basement membrane
  • FEMALES: form vascular tissue and theca cells
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15
Q

What does the basement membrane in males form?

A

The seminiferous tubules and rete-testis.

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16
Q

What do theca cells do?

A

They synthesise androstenedione that is a substrate for estradiol production by granulosa.

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17
Q

Summarise the formation of the male gonads

A

Primordial Germ Cells - form spermatozoa
Primitive sex cords - form the sertoli cells that express SRY and release AMH.
Mesonephric cells form leydig cells that release testosterone

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18
Q

Summarise the formation of the female gonads

A

Primordial Germ Cells -> Oocytes
Primitive sex cords -> form the granulosa cells that release estradiol
Mesonephric cells form the theca cells that release androstenedione

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19
Q

What are the two main structures involved in forming the reproductive organs?

A
  • Mullerian ducts

- Wollfian ducts

20
Q

What do the Mullerian ducts do?

A
  • important in females

- inhibited in the male by AMH

21
Q

What do the Wolffian ducts do?

A
  • Important in the male stimualted by testosterone

- Lack of stimulation by testosterone means regression in female

22
Q

Describe internal sexual differentiation

A
  • Testosterone is converted in the genital skin to the more potent androgen dihydrotestosterone. It binds to the testosterone receptor. This causes the differentiation of the male external genitalia:
  • Clitoral area enlarges into penis
  • Labia fuse and become ruggated to form scrotum
  • Prostate forms
23
Q

Summarise the role of AMH

A

Regression of mullarian ducts

24
Q

Summarise the role of testosterone

A

Differentiation and growth of wolffian duct structures, seminal vesicles and vas deferens.

25
Q

Summarise the role of DHT

A

Fusion of labial scrotal folds and growth of phallus and prostate

26
Q

Summarise the role of mullarian ducts

A

Differentiation and growth into uterine tubes, uterus and upper 1/3 of vagina

27
Q

Summarise the lack of androgen

A

Leads to vagina, labia and clitoris

28
Q

What happens to the wolffian ducts in the ovary?

A

Regression

29
Q

What are patients with sexual differentiation disorders called?

A

Disorder of sexual differentiation or DSD

30
Q

What terms are NOT used for patients with DSD?

A

Pseudohermaphrodite or testicular feminisation

31
Q

What is gonadal dysgenesis?

A

Sexual differentiation is incomplete.

  • Missing SRY in male
  • Partial or complete deletion of the second X in females
  • Used as a general term for the abnormal development of gonads
32
Q

What is sex reversal?

A

Phenotype does not match genotype

33
Q

What is intersex?

A

Have some components of both tracts or have ambiguous genitalia. Sex of infant is difficult to determine.

34
Q

What is complete androgen insensitivity syndrome?

A

Patient appears completely at birth
Assigned female gender despite being XY.
Have undescended testes
Usually present with primary amenorrhoea
Lack of body hair can be a sign
Ultrasound scan and karyotype with male levels of androgens
Never respond to androgen so appear and often feel female

35
Q

What is primary amenorrhoea?

A

Lack of menstrual cycle

36
Q

What is partial androgen insensitivity syndrome?

A
  • Incidence is unknown as probably a spectrum
  • Present with varying degrees of penile and scrotal development from ambiguous genitalia to large clitoris.
  • Surgery was universal but now fortunaly considered optional - decisions made by patients and difficult
37
Q

What happens if there is a 5-alpha-reductase deficiency?

A

Testes form, AMH acts, testosterone acts but it isn’t converted into DHT so internal structures form but external structures do not form.
May appear female or may have ambiguous genitalia.

38
Q

What happens at puberty with 5-alpha-reductase deficiency?

A

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

39
Q

What is turner syndrome?

A
  • 1:3000
  • XO have failure of ovarian function
  • ‘Streak’ ovaries = ovarian dysgenesis - illustrates that we need 2 X’s for ovarian development.
  • Uterus and tubes are present but small, other defects in growth and development.
  • May be fertile - many have mosaicism
  • Hormone support of bones and uterus
40
Q

What does corticotrophin releasing hormone (CRH) do?

A

Stimulates pituitary to secrete ACTH

41
Q

What does adrenocorticotrophic hormone (ACTH) do?

A

Rapid uptake of cholesterol into the adrenal cortex. Upregulates cholesterol side-chain cleavage enzyme (P450scc). Increases glucocorticoid secretion.

42
Q

What is congenital adrenal hyperplasia?

A

Congenital adrenal hyperplasia are any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of mineralocorticoids, glucocorticoids or sex steroids from cholesterol by the adrenal glands (steroidogenesis).

43
Q

What happens if the enzyme is blocked in CAH?

A

Children may be wrongly gender assigned at birth, or may have ambiguous genitalia.

44
Q

What happens when there is a lack of aldosterone in CAH?

A

There is a possibilty of ‘self-wasting’ due to lack of aldosterone, this can be lethal.

45
Q

How is CAH treated?

A

Glucocorticoids to correct feedback.

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