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Year 2 Medicine > Sexual Differentiation: How to Make a Boy or a Girl > Flashcards

Sexual Differentiation: How to Make a Boy or a Girl Flashcards

1
Q

Prevalence of genital abnormalities is 1 in ….

A

Prevalence of genital abnormalities is 1 in 4500

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2
Q

Example of genital abnormalities

  • 2 newborns - baby A and B
  • Both genitically male
  • doctors advise parents and perform surgery => female
    • Baby A : happy, twenties (2004); married woman
    • Baby B : never happy, years of depression, began testosterone treatment; lives as a man.
      • At fault - doctor presuming that … + … provided a solution
A

Example of genital abnormalities

  • 2 newborns - baby A and B
  • Both genitically male
  • doctors advise parents and perform surgery => female
    • Baby A : happy, twenties (2004); married woman
    • Baby B : never happy, years of depression, began testosterone treatment; lives as a man.
      • At fault - doctor presuming that surgery + hormones provided a solution
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3
Q

What makes a boy/girl involves 3 main events:

  1. Sex determination, during …
  2. Differentiation of …, week …
  3. Differentiation of … and … genital organs, after week …
A
  1. Sex determination, during fertilization
  2. Differentiation of gonads, week 5
  3. Differentiation of internal and external genital organs, after week 5
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4
Q

Sex Determination

  • Sex is determined at …
  • Inheritance of X/Y from …
A
  • Sex is determined at fertilization
  • Inheritance of X/Y from father
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5
Q

Gonad Origin and Diff

  • At week … primordial germ cells (PGCs) arise from the …
  • PGCs are …potent
  • PGC’ migrate to … … stalk to avoid becoming imprinted
  • Later return, travelling to the genital … (next to kidney) and become the … gonad
A
  • At week 2 primordial germ cells (PGCs) arise from the epiblast
  • PGCs are pluripotent
  • PGC’ migrate to yolk sac stalk to avoid becoming imprinted
  • Later return, travelling to the genital ridge (next to kidney) and become the indifferent gonad
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6
Q

Gonad Origin and Diff (2)

  • At genital …: XX PGCs replicate at …; XY PGCs replicate at the …
A

At genital ridge: XX PGCs replicate at cortex; XY PGCs replicate at the medulla

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7
Q

Gonad gender decision relies on:

  • Genetic …
  • H…

Genetic …:

  • general … factors,
    e. g. Wt1, Sf1
  • specific promoters of … development
    e. g. Sry, Sox9
  • specific promoters of … development
    e. g. Wnt-4, FoxL2
A
  • Genetic switches
  • Hormones

Genetic switches:

  • general transcription factors,
    e. g. Wt1, Sf1
  • specific promoters of testis development
    e. g. Sry, Sox9
  • specific promoters of ovarian development
    e. g. Wnt-4, FoxL2
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8
Q

Genetic switches:

  • general transcription factors,
    • e.g. W.., S..
  • specific promoters of testis development
    • e.g. S…, S…
  • specific promoters of ovarian development
    • e.g. …-4, …L2
A
  • general transcription factors,
    • e.g. Wt1, Sf1
  • specific promoters of testis development
    • e.g. Sry, Sox9
  • specific promoters of ovarian development
    • e.g. Wnt-4, FoxL2
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9
Q

Fate of Gonad Cell lines

  • Fill in blanks where arrows are (what gender, what each makes)
A
  • Left (Female) - follicular cells, oocytes, internal theca cells - future ovary
  • Right (male)- ley dig cells, Pre-spematognia, sertoli cells - future testis
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10
Q

Fate of Gonad Cell Lines

  • Female PGCs => … (primary oocytes)
  • Sex cord cells => … (support and nutrifying the …)
  • Cortex => layer of … cells => secrete … before those generated by the follicles
A
  • Female PGCs => oogonia (primary oocytes)
  • Sex cord cells => granulosa (support and nutrifying the ovum)
  • Cortex => layer of thecal cells => secrete androgens before those generated by the follicles
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11
Q

Fate of Gonad Cell Lines

  • Male PGCs => …
  • … influences definition + identity of … cells => secretion of AMH (Anti-Müllerian Hormone)
  • AMH supresses … development pathway
  • AMH induce cells in intermediate mesoderm to become … => secrete …
A
  • Male PGCs => spermatogonia
  • Sry influences definition + identity of Sertoli cells => secretion of AMH (Anti-Müllerian Hormone)
  • AMH supresses female development pathway
  • AMH induce cells in intermediate mesoderm to become leydig => secrete testosterone
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12
Q

Kidney Development

  • Origin: intermediate … (as the reproductive organs)
  • Where: between the … and … plate (each side of the aorta)
  • 3 Stages:
    • … - disappears soon after
    • … - leaves remnants
    • … - becomes kidney
A
  • Origin: intermediate mesoderm (as the reproductive organs)
  • Where: between the somites and lateral plate (each side of the aorta)
  • 3 Stages:
    • Pronephros - disappears soon after
    • Mesonephros - leaves remnants
    • Metanephros - becomes kidney
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13
Q

Pronephros stage of kidney development - what is it?

A

kidney develops and degenerates straight after (the pronephros is a rudimentary, nonfunctional kidney that appears during the third week of development (eight- to nine-somite stage) and regresses by the fifth week.)

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14
Q
  • Gonads are … at start
  • They are linked to … development
  • The middle stage of … development (…) leaves behind ducts that become integral part of the reproductive system
A
  • Gonads are indiferent at start
  • They are linked to kidney development
  • The middle stage of kidney development (mesonephros) leaves behind ducts that become integral part of the reproductive system
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15
Q

Internal Genital Organs

  • Begin differentiation at about week …, formed from a priori identical primordium structures, i.e
    • embryos of … … possess two sets of paired ducts at the start:
      • … a.k.a. Müllerian
      • … a.k.a. Wolffian

​

A
  • Begin differentiation at about week 8, formed from a priori identical primordium structures, i.e
    • embryos of both sexes possess two sets of paired ducts at the start:
      • paramesonephric a.k.a. Müllerian
      • mesonephric a.k.a. Wolffian
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16
Q

Internal Genital Organs - in female embryo​

  • In female embryo: … duct is kept due to the absence of …
  • … duct => becomes … (4)
    • …
    • …
    • …
    • upper part of the …
A
  • In female embryo: Müllerian duct is kept due to the absence of AMH
  • Müllerian duct =>
    • oviduct
    • uterus
    • cervix
    • upper part of the vagina
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17
Q

Internal Genital Organs - in male embryo

  • In male embryo:
    • … causes Müllerian duct regression
    • testosterone promotes … duct differentiation
  • … duct => becomes (3)
    • …
    • vas …
    • … vesicle
A
  • In male embryo:
    • AMH causes Müllerian duct regression
    • testosterone promotes Wolffian duct differentiation
  • Wolffian duct =>
    • epididymis
    • vas deferens
    • seminal vesicle
18
Q

External Genital Organs

  • At first embryos of both sexes show an elevated midline swelling – genital …
  • This consists of:
    • … groove (opening into the urogenital sinus)
    • paired urethral …
    • paired … swellings
A
  • At first embryos of both sexes show an elevated midline swelling – genital tubercle
  • Tubercle consists of :
    • urethral groove (opening into the urogenital sinus)
    • paired urethral folds
    • paired labioscrotal swellings
19
Q

External Genital Organs - Male

  • Some testosterone is converted into … (…)
  • This stimulates development of the …, … and external genitals (… and …)
  • Genital tubercle => …
  • Fusion of the urethral folds => spongy …
  • Labioscrotal swellings => …
A
  • Some testosterone is converted into dihydrotestosterone (DHT)
  • This stimulates development of the urethra, prostate and external genitals (scrotum and penis)
  • Genital tubercle => penis
  • Fusion of the urethral folds => spongy urethra
  • Labioscrotal swellings => scrotum
20
Q

External Genital Organs - Female

  • Absence of …
  • Genital tubercle => …
  • Urethral folds remain open => labia …
  • Labioscrotal swellings => labia …
  • Urethral groove => …
A
  • Absence of DHT
  • Genital tubercle => clitoris
  • Urethral folds remain open => labia minora
  • Labioscrotal swellings => labia majora
  • Urethral groove => vestibule
21
Q

Sexual Differentiation - Abnormalities - 6 types are:

  • C…
  • H…
  • Gonadal …
  • … abnormalities
  • Gonadal …
  • … genitalia
A
  • Chromosomal
  • Hermaphroditism
  • Gonadal dysfunction
  • Tract abnormalities
  • Gonadal descent
  • External genitalia
22
Q

Examples of Chromosomal abnormalities (sexual differentiation)

  • 2 examples are…
A
  • Turner’s syndrome
  • Klinefelter’s syndrome
23
Q

Turner’s Syndrome:

  • Monosomy, …
  • Affects how many people?
    • What gender?
  • …% non-viable embryos
  • Survivors fail to sexually mature at …
  • Exhibit several … abnormalities (next slide)
  • Diagnosis confirmed through …
A
  • Monosomy, XO
  • 1:2500 females (does not affect males)
  • 99% non-viable embryos
  • Survivors fail to sexually mature at puberty
  • Exhibit several physical abnormalities (next slide)
  • Diagnosis confirmed through amniocentesis
24
Q

3 common sign of Turner’s syndrome are:

A
  • rudimentary gonads
  • lack of menstruation
  • lack of breast development
25
Q

Klinefelter’s Syndrome:

  • Karyotype is …, Sex genes are …
  • How many people?
    • What gender?
  • Birth appear …
  • Become …
  • Exhibit some features associated with … development (e.g. …)
  • Diagnosis confirmed through …
A
  • 47, XXY
  • 1:600-1000 male births (does not affect females)
  • Birth appear normal (undetected)
  • Become infertile
  • Exhibit some features associated with female development (e.g. gynecomastia)
  • Diagnosis confirmed through amniocentesis
26
Q

Klinefelter’s Syndrome - common signs include:

A
  • presence of breasts
  • shrunken testes
  • deposition of fat (hips etc)
27
Q

Hermaphroditism

  • Named after the offspring of the Greek gods Hermes and Aphrodite
    • True hermaphrodite
    • Female pseudohermaphrodite
    • Male pseudohermaphrodite
  • (note: these colloquial terms are used for your understanding only and not actually used in the medical profession)
A
  • Named after the offspring of the Greek gods Hermes and Aphrodite
    • True hermaphrodite
    • Female pseudohermaphrodite
    • Male pseudohermaphrodite
  • (note: these colloquial terms are used for your understanding only and not actually used in the medical profession)
28
Q

‘True hermaphrodites’

  • Extremely …
  • Born with both ovarian and testicular tissue (…)
  • 46XX (…+), 45X (…+) and 45X
  • Possible cause e.g. two ova fertilized by two sperm that fuse to form a tetragametic chimera
  • External genitals may be …, or appear to be female or male
A
  • Extremely rare
  • Born with both ovarian and testicular tissue (ovotestis)
  • 46XX (SRY+), 45X (SRY+) and 45X
  • Possible cause e.g. two ova fertilized by two sperm that fuse to form a tetragametic chimera
  • External genitals may be ambiguous, or appear to be female or male
29
Q

‘Female Pseudohermaphrodite’

  • 46, .. with virilization (due to …)
  • Internal sex organs are normal, inc. …
  • External appearance and genitals: appear …
  • Features: … of labia; enlarged …
  • Possible cause: exposure to male hormones … (e.g. from congenital virilizing adrenal hyperplasia
A
  • 46, XX with virilization (due to androgens)
  • Internal sex organs are normal, inc. ovaries
  • External appearance and genitals: male
  • Features: fusion of labia; enlarged clitoris
  • Possible cause: exposure to male hormones prior to birth (e.g. from congenital virilizing adrenal hyperplasia
30
Q

‘Male Pseudohermaphrodite’

  • 46, .. with under…
  • External genitals: incompletely formed, ambiguous or clearly …
  • Some features: blind-ending …, absence of … development, primary …
  • …: normal, malformed or absent
  • Main causes:
    • defective … synthesis
    • defective … action (e.g. receptor disorder)
A
  • 46, XY with undervirilization
  • External genitals: incompletely formed, ambiguous or clearly female
  • Some features: blind-ending vagina, absence of breast development, primary amenorrhea
  • Testis: normal, malformed or absent
  • Main causes:
    • defective androgen synthesis
    • defective androgen action (e.g. receptor disorder)
31
Q

Androgen Insensitivity Syndrome (AIS) - Male Pseudohermaphrodite

  • A.k.a. testicular …
  • Affects 1:…-… male births
  • (…) hormones are normal
  • Dysfunctional … to these hormones
A
  • A.k.a. testicular feminization
  • Affects 1:20000-64000 male births
  • (Male) hormones are normal
  • Disfunctional receptor to these hormones
32
Q

Leydig Cell Hypoplasia - Male Pseudohermaphrodite

  • Leydig cells do not secrete …
  • Possible reason: body insensitive to …
  • … genitalia normally female/slightly ambiguous
  • No female … genitalia (…) develops
A
  • Leydig cells do not secrete testosterone
  • Possible reason: body insensitive to LH
  • External genitalia normally female/slightly ambiguous
  • No female internal genitalia (uterus) develops
33
Q

Gonadal dysfunction

  • e.g. XY gonadal dysgenesis, a.k.a. … Syndrome
  • Associated with … karyotype
  • Cause: alteration to … gene
  • External appearance: … (no …)
  • No functional gonads (no … differentiation)
  • Gonad may develop into …
A
  • e.g. XY gonadal dysgenesis, a.k.a. Swyer’s Syndrome
  • Associated with XY karyotype
  • Cause: alteration to Sry gene
  • External appearance: female (no menstruation)
  • No functional gonads (no testicular differentiation)
  • Gonad may develop into malignancy
34
Q

Tract Abnormalities

  • Some examples:
    • Uterine: e.g. … uterus
    • Vagina: e.g. …
    • Ductus Deferens: … or … absence, failure of … duct to differentiate
A
  • Some examples:
    • Uterine: e.g. unicornuate uterus
    • Vagina: e.g. agenesis
    • Ductus Deferens: unilateral or bilateral absence, failure of mesonephric duct to differentiate
35
Q

Gonadal Descent

  • More apparent and common in … (…) than on … (undescended …)
  • …:
    • may be unilateral/bilateral
    • occurs 30% …; 3-4% term …
    • descent may take place during year …
  • Undescended …:
    • quite …
    • detected in clinical … assessment
A
  • More apparent and common in males (cryptorchidism) than on females (undescended ovaries)
  • Cryptorchidism:
    • may be unilateral/bilateral
    • occurs 30% premature; 3-4% term males
    • descent may take place during year 1
  • Undescended ovaries:
    • quite rare
    • detected in clinical fertility assessment
36
Q

External genitalia - abnormalities

  • The most common: male …
    • 1:… live male births
    • Failure of male … folds to fuse
    • Outcome: proximally displaced urethral …
A
  • The most common: male hypospadia
    • 1:125 live male births
    • Failure of male urogenital folds to fuse
    • Outcome: proximally displaced urethral meatus
37
Q

Crucial stage of sexual development is week

38
Q

The Brain and Behaviour: Sexual Differentiation

  • What also makes us a boy or girl: … behaviour
  • Research from mutants revealed that the brain acquires its ‘gender …’ not from the influence of … hormones…
  • … but instead from gene …, given the correlation between inactivation of genes from the … chromosome and predisposition to …
A
  • What also makes us a boy or girl: sexual behaviour
  • Research from mutants revealed that the brain acquires its ‘gender identity’ not from the influence of sex hormones…
  • … but instead from gene expression, given the correlation between inactivation of genes from the X chromosome and predisposition to transexualism
39
Q

The Brain and Behaviour: Sexual Differentiation - Example

  • In mouse embryos, … genes are expressed differently between male and female brain prior to advent of sex hormones (RT-PCR)
  • These genes are active before … even develop, let along …, about week … of development
A
  • In mouse embryos, 51 genes are expressed differently between male and female brain prior to advent of sex hormones (RT-PCR)
  • These genes are active before gonads even develop, let along differentiate, about week 2 of development
40
Q

The Brain and Behaviour: Sexual Differentiation

  • Money, J: ‘Gender identity is one’s own categorization of one’s individuality… as experienced in self awareness of one’s own mental processes and own’s actual behaviour’
  • This breakthrough can potentially help surgeons to decide which gender to opt in cases of genital … or of …
A
  • Money, J: ‘Gender identity is one’s own categorization of one’s individuality… as experienced in self awareness of one’s own mental processes and own’s actual behaviour’
  • This breakthrough can potentially help surgeons to decide which gender to opt in cases of genital malformation or of transexualism

Year 2 Medicine (162 decks)

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