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203: Reproductive system, fetal development, pregnancy and birth > Sexual differentiation > Flashcards

Sexual differentiation Flashcards

1
Q

Prevalence of genital abnormalities

A

1 in 4500

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2
Q

Sex determination

A

Occurs during fertilisation

X or Y chromosome is inherited from father.

X chromosome inherited from mother.

XY- male
XX- female

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3
Q

Origin of primordial germ cells

A

Arise from the epiblast are week 2

- Pluripotent cells

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4
Q

Differentiation of primordial germ cells

A

Firstly migrates to yolk sac
- Prevents imprinting

Later returns next to genital ridge (next to kidneys)
- Indifferent gonad

XX- replicate at cortex
XY- replicate at medulla

Gender decision is dependant on genetic switches and hormones

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5
Q

Genetic switches

A

Transcription factors
- Wt1, Sf1

Specific promoters of testis development

Specific promoters of ovarian development

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6
Q

Specific promoters of testis development

A

A type of genetic switch that determines the male sex.

Examples

  • Sry
  • Sox9
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7
Q

Supporting cell precursors

A

Bipotential gonad cells that originate from the urogenital ridge

Differentiates into

  • Follicular cells in ovaries
  • Sertoli cells in testis
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8
Q

Primordial germ cells

A

Bipotential gonad cells that originate from the epiblast

Differentiates into

  • Oocytes in ovaries
  • Pro-spermatogonia cells in testis
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9
Q

Steroidogenic precursor cells

A

Bipotential gonad cells from the urogential ridge

Differentiates into

  • Internal theca cells in ovaries
  • Leydig cells in testis
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10
Q

Differentiation of sex cord cells in females

A

Differentiates into granulosa in ovaries

- Supports and nutrifyes the ovum

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11
Q

Differentiation of the cortex in females

A

Forms layer of theca cells

- Secretes androgens

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12
Q

Sry

A

Specific genetic promoter of testis development.

Influences definition and identity of Sertoli cells
- Stimulates AMH secretion.

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13
Q

AMH

A

Anti-mullerian hormone

Produced from sertoli cells under the influence of Sry gene

  • Suppresses female development pathway
  • Induces Leydig differentiation (from intermediate mesoderm)
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14
Q

Origin of kidney

A

Intermediate mesoderm

- Between somites and lateral plate

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15
Q

Pronephros

A

First stage of kidney development

- Disappears right after formation

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16
Q

Mesonephros

A

Structure formed in the second stage of kidney development

Leaves ducts before degeneration
- Ducts become integral part of the reproductive system

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17
Q

Metanephros

A

Final stage of kidney development that fully develops into the kidney

18
Q

Time of internal genital organs differentiation

A

Week 8

19
Q

Origin of internal genitial organs

A

All embryos contain two sets of paired ducts at the start

  • Paramesonephric–> Mullerian
  • Mesonephric—> Wolffian
20
Q

Mullerian duct

A

Kept in the female embryo
- Due to the absence of anti-Mullerian hormone

The duct is composed of:

  • Oviduct
  • Uterus
  • Cervix
  • Upper vagina
21
Q

Differentiation of the male genital organs

A

In the male embryo, AMH and male hormones are secreted
- AMH regresses the mullerian/ paramesonephric duct

  • Testosterone promotes Wolffian duct differentiation
22
Q

Wolffian duct

A

Composed of

  • Epididymis
  • Vas deferens
  • Seminal vesicle
23
Q

Genital tubercle

A

Initial development of external genital organs in both sexes

Both show an elevated midline swelling.

Composed of

  • Urethral groove
  • Paired urethral folds
  • Paired labioscrotal swellings
24
Q

Development of male external genital organs

A

Some testosterone—> DHT

DHT stimulates the development of:

  • Urethra (spongy urethra from urethral fold fusion)
  • Prostate
  • Scrotum (from labioscrotal swellings)
  • Penis (from genital tubercle)
25
Q

Development of female external genital organs

A

No DHT stimulates:

  • Clitoris (from genital tubercle)
  • Labia minora (from open urethral fold)
  • Labia majora (labioscrotal swelling)
  • Vestibule (from urethral groove)
26
Q

Turner’s syndrome

  • Genetics
  • Prevalence
  • Prognosis of embryos
  • Diagnosis
A

Monosomy
- XO

1:2500 females

99% of embryos are not viable

Diagnosed by assessing karyotype from amniocentesis

27
Q

Turner’s syndrome

- Clinical presentation [6]

A

Short stature
- Low oestrogen

Underdeveloped gonads

Webbed neck

Failure to undergo puberty/ menstruation

Constricted aorta

Shorter metacarpal IV/ small finger nails

28
Q

Klinefelter’s syndrome

  • Genetics
  • Prevalence
  • Diagnosis
A

47 XXY

1:600-1000 male births

Appear normal at birth
- Diagnosed via karyotyping (amniocentesis)

29
Q

Klinefelter’s syndrome

- Presentation

A

Tall height
- Excess oestrogen

Reduced facial/body hair

Gynaecomastia

Osteoporosis

Feminine fat distribution

Testicular atrophy

30
Q

True hermaphrodite

  • Description’
  • Genetics
  • Possible cause
A 
Rare condition where an individual is born with ovarian and testicular tissue.
Genital may be
- Ambigous
- Male/ female
Genetics
- 46 XX (SRY+)
- 45 X (SRY +)
- 45 X

Cause
- Two ova fertilised by two sperm and fused

31
Q

Female pseduohermaphrodite

A

46 XX with virilization
- Excess androgens

Normal internal genital organs

Male external appearance and genitals

Fusion of labia, large clitoris

Possible cause
- XS androgen exposure during pregnancy (i.e in CAH)

32
Q

Male pseduohermaphrodite

  • Genetics
  • External genitalia
  • Testis
  • Other features
A

46, XY with undervirilization

External genital
- Incomplete/ ambiguous/ female

Other features

  • Blind-ending vagina
  • No breast
  • Primary amenorrhea

Testis
- Normal/ malformed/ absenct

33
Q

Male pseduohermaphrodite

- Main causes

A

Defective androgen synthesis in utero

Defective androgen action (receptor disorder)

34
Q

Androgen insensitivity syndrome

  • Other name
  • Prevalence
  • Description
A

Known as testicular feminization

1:20000-64000 male births

Dysfunction receptor to male hormones

35
Q

Leydig cell hypoplasia

A

Possibly caused by insensitivity to LH

Leydig cells do not produce LH

Features

  • External genitalia female/ slightly ambigous
  • No female internal genitalia
36
Q

XY gonadal dysgenesis

A

Also known as Swyer’s syndrome
- Sry gene alteration

External- female

No functional gonads

  • No testicular differentiation
  • No menstruation
  • May develop into malignancy
37
Q

Unicornuate uterus

A

Congenital mullerian anomaly

Only connected to one fallopian tube+ ovary
- Endometrial space is halved.

38
Q

Cryptotchidism

  • Description
  • Prevalence
A

Undescended testis
- Can be unilateral/ bilateral

-30% premature males, 3-4% term males

39
Q

Undescended ovaries

A

Much less common than cryptochidism

Detected with clinical fertility assessment

40
Q

Male hypospadia

  • Description
  • Prevalence
A

Failure of male urogenital folds to fuse
- Proximal displaced urethral meatus

1:125 male births

41
Q

Sexual behaviour

A

Gene expression is important in acquiring gender identity
- Inactivation of genes from x chromosome showed predisposition to transexualism in animal studies.

Gene expression in brain takes place way before gonadal development (Week 2)

42
Q

Differing gene expression in male and female brain

A

Mouse embryos showed 51 genes different between male and female
- Active genes before gonads develop (week 2)

203: Reproductive system, fetal development, pregnancy and birth (23 decks)

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