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Human Physiology - Hormones and Health > Sex Determination and Sexual Differentiation > Flashcards

Sex Determination and Sexual Differentiation Flashcards

1
Q

what three levels do differences between males and females exist

A

genetic sex
gonadal sex
phenotypic sex

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2
Q

when is genetic sex determined
what determines it

A

at time of fertilization
depends on if the sex chromosome contained in the fertilising sperm

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3
Q

what determines gonadal sex

A

genetic sex
presence of absence of Y c’some

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4
Q

what are the features of a sexually undifferentiated foetus reproductive organs

A

both male and female internal ducts present (Wolffian and Mullerian ducts)
cloaca (forms external genitalia)
bipotential gonadal ridge (forms gonads)

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5
Q

what is the SRY gene
what does it encode

A

Sex-determining Region of Y c’some t
encodes testes determining factor

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6
Q

what is the role of TDF

A

acts as a transcription factor for testicular differentiation genes e.g.
MIF and androgen receptors

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7
Q

what determines phenotypic/anatomic sex

A

gonadal sex

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8
Q

why does the removal of gonads from either sex foetuses result in a female adult

A

sexual characteristics of other tissues are determined by the gonads not the chromosomes in the tissues

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9
Q

what is the Mullerian duct

A

foetal internal duct that differentiates to become internal female genitalia

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10
Q

what is the Wolffian duct

A

foetal internal duct that differentiates to become internal male genitalia

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11
Q

pathway leading to Mullerian duct regression

A

male SRY gene -> TDF -> testis containing Sertoli cells -> MIF -> Mullerian duct regression

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12
Q

pathway leading to Wolffian duct development

A

male SRY gene -> TDF -> testis containing Leydig cells -> Testosterone -> Wolffian duct development

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13
Q

pathway leading to Mullerian duct development

A

no male SRY gene -> no TDF -> ovary -> no MIF inhibition -> Mullerian duct development

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14
Q

pathway leading to Wolffian duct regression

A

no male SRY gene -> no TDF -> ovary -> no Testosterone stimulation -> Wolffian duct regression

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15
Q

XY early castrate

A

no T
no MIF
Mullerian ducts develop

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16
Q

XX early castrate

A

no T
no MIF
Mullerian ducts develop

17
Q

XY unilateral early castrate

A

Untreated side has normal development
treated side no T and no MIF so Mullerian ducts develops

18
Q

XY early castrate treated with T

A

T
no MIF
Wolffian duct develops
Mullerian duct not inhibited and also develops

19
Q

XX treated with T

A

T
no MIF
Wolffian duct develops
Mullerian duct not inhibited and also develops

20
Q

what hormone controls development of external genitalia
how is it synthesised

A

DHT
Testosterone - 5α-reductase -> dihydrotestosterone

21
Q

what causes male phenotypic sex

A

DHT causes cloaca to develop male

22
Q

what causes female phenotypic sex

A

no T so no DHT so cloaca reverts to female

23
Q

what happens in OY and OX aneuploidies

A

OY - lethal cannot be born
OX - female with Turner’s syndrome

24
Q

Turner’s syndrome symptoms

A

non-functional ovaries - absence of menstrual cycle
sterility
short stature
webbed neck ?!
webbed feet

25
Q

what is a true hermaphrodite

A

gonadal tissue and germ cells must be present (how is that possible if they come from the same thing? one of each?)

26
Q

what is a male pseudohermaphrodite
what causes it

A

only testicular tissue but with some female morphological features
failure of synthesis or action of hormones

27
Q

what is a female pseudohermaphrodite
what causes to

A

only ovarian tissue but with some male morphological features
inappropriate synthesis/exposure to androgens

28
Q

what is 21-hydroxylase
what happens in deficiency

A

enzyme involved in aldosterone and cholesterol synthesis
deficiency results in genetic females with male features, disrupted or lack of menstruation and ambiguous genitalia (?!)

Human Physiology - Hormones and Health (8 decks)

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