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MD3002 post MSA > development of the reproductive system and sex determination > Flashcards

development of the reproductive system and sex determination Flashcards

1
Q

What is the name given to describe female gametes

A

homogametic

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2
Q

what determines sex

A

the presence or absence of the Y chromosome

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3
Q

describe the functions of the genes contained on the Y chromosome

A

contains a regulatory gene that control genes for testes development. Also contains genes unrelated to sex development.

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4
Q

describe the genotype in XY females

A

part of the small arm of the Y chromosome is missing or mutated

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5
Q

describe the genotype in XX males

A

they have a section of the Y chromosome translocated to an autosome or X chromosome

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6
Q

what is the gene on the Y chromosome that determines sex

A

SRY

sex determining region of the Y chromosome

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7
Q

what does SRY encode

A

a transcription factor that regulates expression of genes on other chromosomes responsible for testes

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8
Q

What happens after gonadal differentiation

A

gonadal hormones are responsible for sexual dimorphism

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9
Q

what two cell types form gonads

A

somatic mesenchyme and primordial germ cells

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10
Q

what forms the genital ridge

A

proliferation of the surface epithelium and condensation of mesenchyme forming sex cords

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11
Q

when do gonads differentiate

A

7th week

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12
Q

what do primordial germ cells originate from

A

epiblast in the wall of the yolk sac

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13
Q

where do primordial germ cells migrate to

A

genital ridge by chemotaxis and ameboid movement

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14
Q

how many primordial germ cells are there

A

initially ten but they divide mitoticaly en route until there are about 2000

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15
Q

when do the PGCs invade the genital ridges

A

6 weeks and then become surrounded by the primitive medullary sex cords

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16
Q

what happens if PGCs fail to enter the genital ridge

A

gonads do not develop

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17
Q

what do medullary sex cords go on to develop in the male

A

testes cords (medulla) and then rete testes (mesonephric cords)

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18
Q

what do medullary sex cords go on to develop in the female

A

degenerate

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19
Q

where do primordial germ cells come to reside in the male

A

testis cords

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20
Q

what are sertoli cells derived from

A

mesoderm in the cords

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21
Q

what do Leydig cells develop from

A

mesenchyme in interstitial spaces

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22
Q

when do Leydig cells start producing testosterone

A

8 week

23
Q

what does testosterone do in the male foetus

A

influences the development of the genital ducts and external genitalia

24
Q

what does absence of a Y chromosome lead to

A

degeneration of primitive sex cords

25
Q

when do the second set of cords form in the female

A

12 weeks

from mesenchyme to form cortical cords

26
Q

what do the cortical cords do

A

surround each oogonium with epithelial follicular cells forming follicles

27
Q

when do the dual ductal systems form (forms internal genitalia)

A

7 weeks

28
Q

what ducts give rise to the male ductal system

A

mesonephric duct aka Wolffian

29
Q

what ducts give rise to the female ductal system

A

paramesonephric ducts aka Mullerian

30
Q

what other transcription factors are involved in differentiation of Sertoli and Leydig cells

A

SOX9 and SF1

31
Q

what hormone do sertoli cells express leading to regression of the Mullerian ducts and preventing development of female structures

A

AMH - anti mullerian hormone

32
Q

what do Leydig cells secrete in order to support development of the wolffian ducts and virilisation

A

testosterone

33
Q

what do mullerian ducts form in the absence of hormones

A

fallopian tubes

34
Q

what genes are involved in preventing maleness

A

WNT4 (ovary determing gene) up regulates DAX1 which inhibits the function of SOX9

35
Q

how does WNT4 promote female development

A

regulates genes responsible for ovarian differentiation

36
Q

what hormone simulates mullerian ducts to develop into femal internal genitalia

A

oestrogens

37
Q

what forms the lower vagina

A

paramesonephric tubercle aka sinovaginal bulb

38
Q

what forms the vagina plate

A

two evaginations growing out from the pelvic side

39
Q

when is vaginal outgrowth complete

A

20 weeks

40
Q

what is the genotype of turner’s syndrome

A

45 X0

41
Q

describe the ovary in turner’s syndrome

A

streak ovary as two X chromosomes are needed for full ovarian development

42
Q

what are the features of turner’s syndrome

A 
deficiency in ovarian steroids 
lack of secondary sex characteristics and infertility 
short stature 
webbed neck 
skeletal deformities 
and others
43
Q

what is genotype of Klinefelter’s

A

47 XXY (44 autosomes)

44
Q

what are the features of Klinfelter’s

A

male phenotype
incomplete virilisation and breast enlargement
small testes and fewer spermatogonia

45
Q

what is pseudohermaphroditism

A

gonads appropriate to their genotype but external genitalia of the opposite sex

46
Q

give an example of a pseudohermaphroditism

A

androgen insensitivity syndrome, 46 XY

47
Q

what are the features of androgen insensitivity syndrome

A

dysfunctional androgen receptor
wolffian ducts degenerate
female duct degenerate
undescended testes

48
Q

what are the symptoms and signs of androgen insensitivity syndrome

A 
appear female
vagina may be short or blind ended
sparse body hair
infertile 
no menarche
49
Q

what is adrenogenital syndrome

A

congenital adrenal hyperplasia
XX
over active adrenal glands
large amounts of steroid hormones which are androgenic
development of wolffian ducts and male external genitalia
female ducts also persist

50
Q

what structure is the precursor to the gonads

A

genital ridge

51
Q

what do cortical cords become

A 
ovarian follicles
(from mesenchyme)
52
Q

what do the medullary cords become

A

testis cords which then become the rete testis

they secrete protein to nourish the sertoli cells

53
Q

what cell secretes AMH

A

sertoli cells

MD3002 post MSA (66 decks)

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