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RePro > Embryology of Genital System > Flashcards

Embryology of Genital System Flashcards

1
Q

By when is the genotype of the embryo established by?

A

Fertilization

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2
Q

between weeks _ and _, the embryo remains in an undifferentiated state.

A

1 to 6

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3
Q

When does phenotypic sexual differentiation begin?

A

Week 7

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4
Q

By what week can male and female external genitalia can be recognized?

A

Week 12

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5
Q

By what week is phenotypic differentiation of male and female complete?

A

Week 20

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6
Q

Where do primordial germs originate and where do they migrate to?

A

Originates from the endoderm of yolk sac and invade the dorsal mesnetery and migrate to urogenital ridges (the primitive sex cords)

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7
Q

What guides the migration of the primordial germ cells?

A

C-kit receptor and stem-cell factor expressed on PGCs

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8
Q

What is the outcome if the primitive germ cells do not reach the genital ridges?

A

Gonadal dysgenesis

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9
Q

What is pure gonadal dysgenesis (PGD) ?

A

It’s a form of gonadal dysgenesis where there is a normal set of sex chromosomes (e.g. 46, XX or 46, XY) as opposed to those whose gonadal dysgenesis results from missing all or part of the second sex chromosome. Patients with PGD may have defects of a specific gene on the chromosome.

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10
Q

What are some examples of pure gonadal dysgenesis?

A

Swyer syndrome and XX gonadal dysgenesis

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11
Q

What part of the primitive sex cords do the male reprouctive organs develop from?

A

Medulla of the primitive sex cords. The cortex is for the female.

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12
Q

In the male which primitive duct system develops into the wolfian duct?

A

Mesonephric duct

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13
Q

In the female which primitive duct system develops into the Mullerian duct?

A

Paramesonephric duct

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14
Q

What gene determines fetal sex?

A

Sex-determining region of the Y chromosome (SRY gene)

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15
Q

Synthesis of which SRY protein triggers male development?

A

testis-determining factor (TDF)

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16
Q

Describe the series of events that ensues after the inheritance of XY genotype

A
  1. Activation of sry gene –>TDF
  2. Differentiation of bipotential gonad into testis.
    3a. Sertoli cell differentiation
    3b. Interstitial cell differentiation
  3. Sertoli cell produces mullerian inhibitory substance aka anti-mullerian hormone ( AMH) which gets rid of the paramesonephric duct.
  4. Interstitial cell differentiation produces Leydig cells which promotes steroid synthesis like testosterone which then signals the development of wolfian duct and also stimulates 5a-reductase to convert testosterone into DHT which then goes to produces the secondary male sex characteristics
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17
Q

What does the Mesophric duct develop into in the male?

A

Epididymis, seminal vesicles, and ductus derens

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18
Q

What is the transcriptional reguator for testes differentiation?

A

SOX9

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19
Q

What factor causes the differentiation of bipotential gonad into testis?

A

TDF (testis determining factor) = SRY protein

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20
Q

Which transciptional regulator causes sertoli cell differentiation?

A

SOX9 via SF1

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21
Q

What is Campomelic dysplasia?

A

It is a rare autosomal dominant congenital short limbed dwarfism characterized by congenital bowing of long bones associated with skeletal and extra skeletal features like hypoplastic lungs, malformations of cervical spine, heart, and kidneys

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22
Q

Mutation to what gene is the cause of Campomelic dysplasia?

A

SOX9

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23
Q

What is a characteristic feature of campomelic dysplasia?

A

Male to female sex reversal

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24
Q

What causes interstitial (Leydig) cell differentiation?

A

SOX9 via SF1

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25
Q

The urogenital sinus is formed from the division of _.

A

Cloaca

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26
Q

Name some effects DHT has on sex differentiation.

A
  1. Masculinization of external genitalia and prostate development
  2. Masculinization of the brain
  3. Masculinization of body tissue and systems
  4. Gubernaculum development and testis descent into the scrotum.
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27
Q

What converts testosterone to dihydrotestosterone?

A

5a-reductase

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28
Q

Which subset of 5a-reductase is responsible for development of the reproductive tract (epididymis, seminal vesicle, prosterate..etc)

A

5-a-reductase II

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29
Q

Which subset of 5-a- reductase is made in the liver and skin only?

A

5a-reductase I

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30
Q

By what week is the medullary cords of the sex cord degenerated in female?

A

Week 10

31
Q

Where does the primordial follicle (oogonium + follicular cells) start it’s formation?

A

In the cortical cords of the primitive sex cords.

32
Q

Does all of the mesonephric ducts degenerate in the female?

A

No. Most of it do, except for the epoophoron and paroophoron found int he mesentery of the ovary.

33
Q

What is Gartner’s duct?

A

portions of the mesospheric duct that remain in the female.

34
Q

On which chromosome and sex is the gene DAX found

A

On the X chromosome of both male and female.

35
Q

What gene upregulates DAX1?

A

WTN4

36
Q

in the male, DAX expression is suppressed by what?

A

Expression of SRY via SR1

37
Q

What is the outcome of DAX1 duplication in the male?

A

Prevention of testis formation resulting in a 46 XY female

38
Q

In the female, SOX) and AMH expression is inhibited by _.

A

DAX1

39
Q

What role does WTN4 play in the development of female reproductive organs?

A

WNT4 upregulates DAX1 and it also regulates other genes that control ovarian development

40
Q

How does the paramesonephric ducts develop?

A

Develops during 6th week as invaginations of epithelium lateral to mesonephros. Cranial end opens into periotneal cavity and distal ends join to form uterovaginal primordium which connects to the urogenital sinus.

41
Q

What parts of the paramesonephric duct becomes the uterine tubes and what part becomes the epithelium and glands of the uterus, epithelium of the upper 1/3 of the vagina and the muscular wall of the vagina?

A

The paired portions of the paramesonephric ducts become the uterine tube.
The Uterovaginal primordium becomes the other parts.

42
Q

Explain the embryonic origin of formation of the vagina.

A

Upper portion develops from the uterovaginal primordium and the inferior portion develops from the urogenital sinus.

43
Q

By what week/month does the sinovaginal bulbs present?

A

By the end of the 3rd month.

44
Q

Explain how the fornices and the upper portion of the vagina are formed and how the lower portion of the vagina is formed.

A

The fornices and the upper protion of the vagina are fromed by vauolization of the paramesonephric tissue. The lower portion of the vagina is formed by vaculization of the sinovaginal bulbs.

45
Q

partial or total atresia of the distal portion of both paramesonephric ducts will result in atresia of what structures?

A

Cervix and vagina

46
Q

In 46, XY male, a persistence of paramesonephric ducts is due to _

A

Low levels of AMH or abnormal response to normal AMH

47
Q

What is Mayer-Rokitansky-Kuster-Hauser Syndrome (MRKH)?

A

Mullerian (paramesonephric) agenesis resulting in missing uterine tubes, uterus and variable malformations of the upper portion of the vagina. The lower vagina ends in a blind pouch.

48
Q

An adolescent presents with cyclic and persistent pelvic pain and primary amenorrhea. Upon PE, an abnormal abdominal mass was palpated. Upon further workup and imaging, it was shown passage of blood into the uterine tubes causing hematosalpinx leading to endometriosis and adhesion formations. What is the likely diagnosis?

A

Imperforate hymen

49
Q

In both sexes, the external genitalia develops from _

A

genital tubercle which develops near the cloacal membrane

50
Q

The urorectal septum divides the cloacal membrane into _

A

urogenital and anal membranes.

51
Q

The Cloaca divides into _

A

urogenital sinus and rectum

52
Q

What does the genital tubercle become in the male and female?

A

Male: penis
Female: clitoris

53
Q

What does the Labioscrotal swelling become in the male and female?

A

Male = scrotum

Female: labia majora

54
Q

What does the urogenital fold become in the male and female?

A

Male: Spongy urethra
Female: Labia manora

55
Q

In the female, what hormone influence the development of both the internal female duct system as well as the external genitalia?

A

estrogens

56
Q

In a male, if there are errors in the production of or sensitivity to androgenic hormones, which characteristics are predominant and what is that it due to?

A

predominatly female characteristics of the external genitalia due to the influence of maternal/placental estrogens.

57
Q

What is cryptorchidism?

A

Undescended testes.

58
Q

By when should the testes have descended?

A

within the first year of life.

59
Q

What is hypospadias?

A

Incomplete fusion of the urethral folds leading to urethra opening onto the ventral aspect of the penis.

60
Q

What can cause hypospadias?

A

Inadequate androgen production or inadequate receptor sites for DHT

61
Q

A baby with bladder extrophy is also likely to have what type of spadias (epi or hypo)?

A

Epispadias.

62
Q

Explain the characteristics of Klinefelter syndrome.

A

It is a DSD with 47, XXY

  • small testes, low levels of testosterone
  • poorly developed secondary sexual characteristics and gynocomastia
  • elongate limbs
  • testosterone replacement therapy can help.
63
Q

Explain the characteristics of Turner’s syndrome.

A
  • 45, X
  • short stature, no adolescnet growth spurt, broad chest, webbed weck, congenital heart disease.
  • Ovary devleopment is abortive
  • secondary sex characteristics do not develop
  • Estrogen replacment therapy helps.
64
Q

what is the karyotype of Mosaic form of turner syndrome

A

46, XX

65
Q

What is pseduointersexuality?

A

External genitalia of one sex accompanies the gonads of the other sex

66
Q

A 46, XX, DSD can be induced by _

A

prenatal exposure to androgens

67
Q

A baby with 46, XX, DSD presents with clitoral hypertrophy at birth. This type of hypertrophy can be due to exposure of androgens after what week of development?

A

Week 12.

68
Q

What is the significance of the level of androgen exposure relative to embryonic developmental time frame?

A

Exposure at progresively earlier stages of differentiation leads to retention of the urogenital sinus and labioscrotal fusion. If the exposure is early enough, the labia will fuse to form a penile urethra.

69
Q

What is classic virilizing adrenal hyperplasia (46, XX, DSD)

A

It is a form of female intersex (46, xx) where severe forms of adrenal hyperplasia have ambiguous genitalia at birth due to exces adrenal androgen production in utero. The ambiguous genitalia can range from complete fusion of the labioscrotal folds and a phalic urethra to only clitoromegaly, partial fusion of the labioscrotal folds, or both.

70
Q

True or false: in classic virilizing adrenal hyperplasia (46, XX, DSD) ovaries do not form due to the excess androgen exposure.

A

False. No abnormalities of ovaries are seen.

71
Q

What is androgen insensitivity syndrome?

A

It’s a 46, XY DSD.
X-linked disorder in which receptors remain unresponsive to androgens and thus male fetus do not masculinize.
-external genitalia are feminine
-internally they have nonfunctioning undescended testes.
-at puberty secondary female sexual characteristics may appear due to estradiol from testosterone aromatization

72
Q

What is 5-a reductase deficiency (5-ARD)?

A

Autosomeal recessive condition resulting in the inability to convert testosterone to the more physiologically active DHT. Because DHT is needed for normal masculinzation of the external genitalia in utero, genetic males with 5-ard are born with ambiguous genitalia (underdevelopment of penis, scrotum or pseduovaginal perineoscrotal hypospadias)

73
Q

What is the karyotype for 5-ARD?

A

46, XY, DSD

74
Q

What is true intersex or ovotesticular DSD?

A

DSD where both ovarian and testicular tissue are present

-ambiguous external genitalia.

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