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Repro > Embryo Of Genital System > Flashcards

Embryo Of Genital System Flashcards

1
Q

What happens during weeks 1-6 for genital system of embryo?

A

Remains in an undifferentiated state

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2
Q

What happens at week 7 for the genital system of embryo?

A

phenotypic sexual differentiation begins

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3
Q

What happens at week 12 for genital system of embryo?

A

Male and female external genitalia can be recognizd

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4
Q

What happens at week 20 for genital system of embryo?

A

phenotypic differentiation complete

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5
Q

Where are primordial germ cells derived from, and where do they go?

A

From endoderm of yolk sac

Invade dorsal mesentery and migrate to urogenital ridges

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6
Q

What guides the migration of the primordial germ cells?

A

C-kit receptor

Stem-cell factor (c-kit ligand) on PGCs

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7
Q

What happens when primordial germ cells fail to reach genital ridges?

A

Gonadal dysgenesis

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8
Q

Describe pure gonadal dysgenesis (PGD)

A

a normal set of chromosomes but nonfunctional gonads
Normal karyotype but may have defects of a specific gene on chromosome
Swyer syndrome PGD 46 XY
XX gonadal dysgenesis PGD 46 XX

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9
Q

Describe gonadal dysgenesis that results from missing all or part of second sex chromosome

A 
Turner syndrome (45 X)
46XY/45X
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10
Q

What are primary sex cords? Describe the gonad at this point

A

Aggregates of supporting cells (hormone secreting cells)

Gonad now has an outer cortex and inner medulla

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11
Q

What ducts play the most important role for male genital development?

A

Mesonephric ducts

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12
Q

What ducts play the most important role in female genital development?

A

Paramesonephric ducts

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13
Q

Describe fetal sex development

A

Encoded on sex-determining region of Y-chromosome (SRY)
Synthesis of SRY protein (testis-determining factor, TDF) triggers male development
If not expressed (absent of defective), female path is followed
Female: basic (default) development pathway

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14
Q

What is SOX9?

A

Transcriptional regulator for testes differentiation vis steroidogenic factor 1 or SF1

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15
Q

What is the transcriptional regulator for testes differentiation?

A

SOX9 via SF1

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16
Q

What is required for proper sexual differentiation and chrondrogenesis?

A

SOX9

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17
Q

What results from a mutation in SOX9?

A

Campomelic dysplasia

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18
Q

What is campomelic dysplasia?

A

Mutation in SOX9
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
Characteristic feature is male t female sex reversal
Almost fatal outcome

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19
Q

Describe the progression to regression of paramesonephric ducts in males

A

Activation of SRY gene
TDF -> Differentiation of bipotential gonad into testis
SOX9 via SF1 -> Sertoli Cell differentiation
Mullerian inhibitory substance (anti-Mullerian hormone or Mullerian inhibitory factor)
Regression of paramesonephric (Mullerian) ducts

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20
Q

Describe the production of testosterone in male

A

Activation of SRY gene
TDF -> Differentiation of bipotential gonad into testis
SOX9 via SF1 -> Interstitial (Leydig) cell differentiation
Steroid synthesis
Testosterone -> 5alpha-reductae-Dihydrotestosterone

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21
Q

What does dihydrotestosterone do?

A

Influences differentiation of external genitalia and development of prostate

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22
Q

Where is 5-alpha-reductase I made?

A

Liver and skin

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23
Q

Where is 5-alpha-reductase II made?

A

By parts of male reproductive tract (epididymis, seminal vesicle, prostate)

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24
Q

Which enzyme is deficient in 5 ARD (->intersexuality)?

A

5-alpha-reductase II

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25
Q

What effect does testosterone have on mesonephric ducts?

A

Influences differentiation into ductus deferens and epididymis

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26
Q

What hormone influences the masculinization of the mesonephric ducts?

A

Testosterone

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27
Q

What effect does DHT have on urogenital sinus?

A

Closes urethra and prostate

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28
Q

What hormone influences the urogenital sinus to close urethra and prostate?

A

DHT

29
Q

What does DHT do to genital tubercle?

A

Masculinizes it into a penis

30
Q

What hormone influences the genital tubercle to become the penis?

A

DHT

31
Q

What effect does DHT have on labioscrotal swellings?

A

Closes scrotum

32
Q

What hormone acts on labioscrotal swellings to close the scrotum?

A

DHT

33
Q

Describe the primary and secondary cords for the development of the ovaries

A

Primary (medullary) cords degenerate by 10th week
Secondary (cortical) cords develop and are invaded by primoridal germ cells
Cords form groups of primordial follicles (oogonium and follicular cells)

34
Q

In females, the mesonephric ducts degenerate except for what?

A

Epoophoron and paroophoron found in mesentery of ovary

Portions may exist as Gartner’s duct

35
Q

Describe the persistence of the paramesonephric duct

A

WTN4 (which also regulates other genes that control ovarian developmet) upregulates DAX1
DAX1 suppresses SOX9 and AMH expression

36
Q

What suppresses SOX9 and AMH expression?

A

DAX1 (which is upregulated by WTN4)

37
Q

Describe relationship between DAX1 and SRY

A

DAX1 is found on X chromosome in both sexes
SRY expression represses DAX1 expression
DAX1 duplicated in male prevents testis formation, resulting in a 46XY female

38
Q

Describe development of Paramesonephric ducts

A

Develop during 6th week as invaginations of epithelium lateral to mesonephros
Cranial end opens into peritoneal cavity
Distal ends join to form uterovaginal primordium (connects to urogenital sinus)
Inhibited in male by AMH secreted by Sertoli cells

39
Q

What do the paired portions of paramesonephric ducts become?

A

Uterine tubes

40
Q

Uterine tubes develop from what?

A

Paired portions of paramesonephric ducts

41
Q

What does the uterovaginal primordium become?

A

Epithelium and glands of uterus
Epithelium of upper 1/3 of vagina
Muscular wall of vagina

42
Q

What do the epithelium and glands of uterus, epithelium of upper 1/3 of vagina, and muscular wall of vagina develop from?

A

Uterovaginal primordium

43
Q

What does the inferior portion of the vagina develop from?

A

Posterior wall of the urogenital sinus (urinary bladder & urethra)

44
Q

What is Mullerian (paramesonephric) agenesis?

A

Failure of paramesonephric ducts to develop
Results in missing uterine tubes, uterus, and variable malformations of upper portion of vagina
Mayer-Rokitansky-Kuster-Hauser Syndrome (MRKH)

45
Q

What causes hematosalpinx?

A

Retrograde passage of blood into uterine tubes

Can lead to endometriosis and adhesion formation

46
Q

Cloaca divides into __ and __

A

Urogenital sinus

Rectum

47
Q

Urorectal septum divides cloacal membrane into __ and __

A

Urogenital membrane

Anal membrane

48
Q

What do urogenital and anal membranes form?

A

Sphincter urethrae and external anal sphincter

Also forms urethral folds anteriorly and folds posteriorly

49
Q

Describe development of male external genitalia

A

Enlargement of genital tubercle forms phallus
Urethral folds become urethral groove, then fuse to form penile urethra
Labioscrotal swellings become scrotum

50
Q

Describe development of female external genitalia

A

Genital tubercle elongates and bends inferiorly to become clitoris
Urethral folds become labia minora
Labioscrotal swellings become labia majora
Urethra and vagina open into vestibule

51
Q

What is cryptorchidism?

A

Unilateral or bilateral agenesis
Undescended testes. Testes usually descend within first year
Associated with increased incidence of testicular CA
Ectopic testes or ovary (rare)

52
Q

What is the term for undescended testes?

A

Cryptorchidism

53
Q

What s hypospadias?

A

Incomplete fusion of urethral folds
Urethra opens onto ventral aspect of penis
Can result from inadequate androgen production or inadequate receptor sites for DHT

54
Q

What is incomplete fusion of urethral folds with the urethra opening on the ventral aspect of the penis?

A

Hypospadias

55
Q

What is epispadias?

A

Urethral meatus opens on dorsum of penis

Often occurs with bladder exstrophy

56
Q

What is the term for urethral meatus opening on dorsum of penis that often occurs with bladder exstrophy?

A

Epispadias

57
Q

Describe Klinefelter syndrome

A

47 XXY
Small testes, low levels of testosterone
Poorly developed secondary sexual characteristics and gynecomastia
Risk for osteoporosis, 20x increased risk of breast cancer
Elongate limbs
Testosterone replacement therapy

58
Q

Name the disorder. 47 XXY. Small testes, low levels of testosterone, poorly developed secondary sexual characteristics and gynecomastia, risk for osteoporosis, 20x increased risk of breast cancer, elongate limbs, testosterone replacement therapy

A

Klinefelter syndrome

59
Q

Describe Turner’s syndrome

A

45X
Short stature, no adolescent growth spurt, broad chest, webbed neck, congenital heart disease
Ovary development is abortive
Secondary sex characteristics do not develop
Growth hormone and estrogen replacement therapy

60
Q

Name the disorder. 45X. Short stature, no adolescent growth spurt, broad chest, webbed neck, congenital heart disease. Ovary development is abortive. Secondary sex characteristics do not develop.

A

Turner’s syndrome

61
Q

Describe pseudointersexuality, 46 XX DSD, 46 XY DSD

A

External genitalia of one sex accompanies gonads of other sex

62
Q

Describe mechanism of 46 XX DSD

A

Induced by prenatal exposure to androgens
Exposure after 12th fetal week leads only to clitoral hypertrophy
Exposure at progressively earlier stages of differentiation leads to retention of urogenital sinus and labioscrotal fusion
If exposure occurs sufficiently early, labia will fuse to form a penile urethra

63
Q

Describe classic virilizing adrenal hyperplasia (46 XX DSD)

A

Female intersex
Females with severe forms of adrenal hyperplasia have ambiguous genitalia at birth due to excess adrenal androgen production in utero
Ambiguous genitalia ranges from complete fusion of labioscrotal folds and phallic urethra to only cltiromegaly, parial fusion of labiascrotal folds, or both
No abnormalities of ovaries

64
Q

Name the disorder. Female intersex (46 XX DSD) with ambiguous genitalia at birth due to excess adrenal androgen production in utero

A

Classic virilizing adrenal hyperplasia

65
Q

Describe androgen insensitivity syndrome (AIS), 46 XY DSD

A

X-linked disorder in which receptors remain unresponsive to androgens
Despite normal levels of testosterone, male fetus fails to masculinize
External genitalia are feminine. Internally, they possess non-functioning undescended testes
At puberty, secondary female sexual characteristics may appear due to estradiol from testosterone aromatization

66
Q

Name the disorder. X-linked disorder in which receptors remain unresponsive to androgens. Despite normal levels of testosterone, male fetus fails to masculinize. External genitalia are feminine, while testes are undescended and non-functional. At puberty, secondary female sexual characteristics may appear due to estradiol from testosterone aromatization.

A

Androgen insensitivity syndrome (AIS)

46 XY DSD

67
Q

Describe 5-alpha reductase deficiency (5-ARD)

A

46 XY DSD
Autosomal recessive condition resulting in inability to convert testosterone to more physiologically active DHT
Genetic males with 5-ARD are born with ambiguous genitalia (underdevelopment of penis & scrotum or pseudovaginal perineoscrotal hypospadias)
Derivative of mesonephric duct are normal
Often misdiagnosed as AIS

68
Q

Name the disorder. Autosomal recessive condition resulting in inability to convert testosterone to more physiologically active DHT. Genetic males have ambiguous genitalia but normal derivatives of mesonephric duct.

A

5-alpha reductase deficiency

69
Q

When is the genotype of the embryo (46 XX or 46 XY) established?

A

At fertilization

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