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COM: Endocrine - Final COPY > Lecture 5: Development of Genitalia > Flashcards

Lecture 5: Development of Genitalia Flashcards

1
Q

During embryological development, for what time period if the sex of the embryo indifferent and when does sexual differentiation begin?

A

Weeks 1-6 = indifferent embryo

Week 7 = sexual differentiation begins

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2
Q

When during embryological development can female and male genitalia be recognized and when is phenotypic differentiation complete?

A

Week 12 = genitalia recognized

Week 20 = phenotypic differentiation complete

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3
Q

What 2 things does the intermediate mesoderm give rise to?

A

Nephrogenic cord

Urogenital ridge mesenchyme

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4
Q

What gives rise to the primary sex cords?

A

Coelomic epithelium

**Sex cords will become the cortex and medulla of the gonads

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5
Q

Where are primordial germ cells found?

A

Allantois/yolk sac endoderm

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6
Q

Primordial germ cells are found in the allantois/yolk sac endoderm. Where do they come from and when?

A

The epiblast during week 2

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7
Q

Gametes arise from the epiblast during week 2. Why dont they arise any later?

A

Because at this week we only have 2 germ cell layers and week 3 we get the 3rd germ cell layer which we dont want in these cells

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8
Q

What tissue type gives rise to Sertoli cells?

A

Coelomic epithelium

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9
Q

What tissue type gives rise to interstitial (leydig) cells?

A

Intermediate mesoderm

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10
Q

What tissue type gives rise to follicle cells in females?

A

Coelomic epithelium

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11
Q

What tissue type gives rise to thecal cells in females?

A

Intermediate mesoderm

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12
Q

What are the somatic support cells in males versus females?

A

Males = Sertoli cells

Females = follicle cells

**Both cell types come from coelomic epithelium

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13
Q

Gametes arise front he epiblast during week 2 and migrate through the primitive streak and reside in the yolk sac and allantois. What happens during week 5 and 6?

A

They migrate via dorsal mesentery during the 5th week to the primary sex cords where they colonize during week 6

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14
Q

When do meiosis I and meiosis II of oogenesis occur?

A

Meiosis I occurs at ovulation

Meiosis II occurs at fertilization

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15
Q

How does the number of oogonia change throughout the life of a female?

A

They extremely decrease -> during week 5 of embryogenesis there are 6 million, then 1 million at birth, then 40,000 at puberty

**About 400 released during lifetime*8

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16
Q

What are the central and secondary events of sex determination?

A

Central event = differentiation of testes

Secondary events = production of humoral factors by gonads

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17
Q

What gene determines the sex of the embryo?

A

SRY gene -> male if present and female if absent

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18
Q

What is the pathway to internal and external genetalia production if the SRY gene is present?

A

If present, leydig and Sertoli cells are made

Leydig cells secrete testosterone which causes mesonephric ducts to persist and secrete DHT which forms the male external genitalia

Sertoli cells secrete AMH (MIF) which causes paramesonephric ducts to generate forming male internal genitalia

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19
Q

What is the pathway for internal and external genitalia formation when the SRY gene is absent?

A

Thecal and follical cells are formed

Thecal cells DONT produce testosterone, causing the mesonephric ducts to degenerate and female external genitalia to form

Follical cells DONT secrete AMH so the paramesonephric ducts persist and female internal genitalia forms

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20
Q

What is 46, XX testicular DSD?

A

Female genotype but male genitalia -> they look male but need testosterone supplement at puberty to develop male secondary characteristics

**Usually due to SRY somehow getting on the X chromosome so you get male phenotype with female genotype

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21
Q

What is 46, XY complete gonadal dysgenesis?

A

Male genotype but female phenotype -> need hormone supplementation once they reach puberty

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22
Q

What is ovotesticular DSD?

A

True gonadal intersex

Have both testicular and ovarian tissue and an ovotestis -> not functional

Phenotype may be male or female but external genitalia is ambiguous

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23
Q

What is 46, XX DSD caused by?

A

Caused by exposure of female fetus to excessive androgens

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24
Q

What is seen iin 46, XX DSD?

A

Ovaries present but external genitalia masculinized -> clitoral hypertrophy, partial fusion of labia majora, and persistent urogenital sinus

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25
Q

What condition is common in pts with 46, XX DSD?

A

Congenital adrenal hyperplasia (CAH) which is a deficiency in 21 hydroxylase that causes a reduction in cortisol and excess production of androgens

**Excess androgens cause female genitalia to become masculinized

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26
Q

What is 46, XY DSD cuased by?

A
  • Inadequate production of testosterone and/or AMH

- Androgen insensitivity syndrome (no receptors for AMH or testosterone)

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27
Q

What is seen in 46, XY DSD?

A
  • Testicular development rudimentary to normal and may have persistent paramesonephric ducts
  • External genitalia are female or ambiguous
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28
Q

What is seen in androgen insensitivity syndrome?

A

Normal appearing female external genitalia

Blind end vagina

Absent or rudimentary uterus and uterine tubes

At puberty normal breast development and female characteristics, but no mensturation -> many time condition is diagnosed at puberty

46, XY genotype and testes are present

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29
Q

What genotype does a pt with androgen insensitivity syndrome have?

A

46, XY genotype and testes are present

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30
Q

What would happen in an embryo with the SRY gene present but not enough or no AMH?

A

Develop both male and female internal genitalia and male external genitalia

**Testosterone still working fine to develop normal male external genitalia but the low AMH causes paramesonephric to not fully degenerate giving you internal genitalia of both sexes

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31
Q

What would happen in an embryo with the SRY gene present but a 5alpha-reductase deficiency?

A

Cant convert testosterone to DHT

Develop female external genitalia or ambiguous and male internal genitalia

**AMH still working fine so paramesonephric ducts degenerate creating male internal genitalia but having not DHT causes female or ambiguous external genitalia

32
Q

In what sexes do the primary sex cords persist in?

A

Males only! Degenerate in females

Primary sexy cords = medulla

33
Q

In what sexes do the secondary sex cords persist in?

A

Both!

secondary sex cords = cortex

34
Q

_______________ cells invade gonadal ridges by the 6th week migrating along the dorsal mesentery

A

Primordial germ cells

35
Q

During week 5, the gonadal ridge appears where on the mesonephros?

A

Medial side

36
Q

What do the primary sex cords in males become?

A

Seminiferous cords

Sertoli cells

37
Q

What does the connective tissue (gonadal ridge) of the testis become?

A

Leydig cells and tunica albuginea

Derived from intermediate mesoderm

38
Q

What do secondary sex cords give rise to in females?

A

Primordial follicles and granulosa cells

**Secodnary sex cords are derived from coelomic epithelium

39
Q

What ducts persist and degenerate in females versus males?

A

Mesonephric duct persists in males and degenerates in females

Paramesonephric (Mullerian) duct persists in females and degenerates in males

40
Q

What 2 things can be found in females as the remnants of the mesonephric duct?

A

Epoophoron and paroophoron

**also Gartner’s cyst

41
Q

What do Sertoli cells secrete during male embryological development, what does this cause to happen and when does this happen?

A

Secrete AMH which causes the paramesonephric duct to degenerate -> happens in week 9

42
Q

What do leydig cells secrete in male embryologic development and what does this cause to happen?

A

They secrete testosterone (DHT) that causes the mesonephric duct to be retained

43
Q

Leydig cells in male embryos secrete testosterone which causes the mesonephric duct to be retained, giving rise to what 4 structures?

A

Epididymis
Ductus deferens
Seminal vesicle
Ejaculatory duct

44
Q

What 2 structures do the mesonephric tubules in the male embryo give rise to?

A

Efferent ducts and rete testis

45
Q

What 2 structures can be found in a male as remnants of the paramesonephric duct?

A

Utriculus prostaticus

Appendix testis

46
Q

What structures of the female do the paramesonephric ducts give rise to?

A

Cranial portion gives rise to uterine tubes

Caudal portion gives rise to uterovaginal primordium

47
Q

In female embryologic development, what structure do the paramesonephric ducts project to during differentiation of the female duct system and what does this produce?

A

Projects to the urogenital sinus (urinary bladder) which produces the sinus tubercle

48
Q

The uterine tubes, uterus and superior part of the vagina come from the ___________________ and the lumen of the vagina comes from _________________, specifically the ________________

A

Paramesonephric ducts (mesoderm); endoderm; urogenital sinus

49
Q

Explain the differentiation of the uterus and vagina

A

1) The uterovaginal primordium (fused paramesonephric ducts) contacts the urogenital sinus forming the sinus tubercle
2) The sinus tubercle induces formation of the sinovaginal bulbs (endodermal outgrowths) which fuse to form the vaginal plate
3) Epithelium of vaginal plate proliferates and later breaks down forming the lumen of the vagina

50
Q

Sinovaginal bulbs are endodermal outgrowths that extend from the ___________________ to the ________________

A

Urogenital sinus; uterovaginal plate

51
Q

What does teh prostate develop from?

A

Pelvic part of urogenital sinus (endoderm) and smooth muscle and CT from splanchnic mesoderm

52
Q

What do the male bulbourethral glands develop from?

A

Phallic part of urogenital sinus (endoderm) and smooth muscle and CT from splanchnic mesoderm

53
Q

During male embryological development of the external genitalia, what 3 structures develop under the influence of DHT?

A

Genital tubercle
Urethral (urogenital) folds
Labioscrotal swellings

54
Q

What do male labioscrotal swellings give rise to?

A

Scrotum

55
Q

What do male urethral (urogenital) folds give rise to?

A

Lateral walls of urethra
Spongy urethra
Penile raphe

56
Q

What does the male genital tubercle give rise to?

A

Glans penis

57
Q

What does the female genital tubercle give rise to?

A

Glans clitoris

58
Q

What do the female urethral (urogenital) folds give rise to?

A

Frenulum of labia minora

59
Q

What do the female labioscrotal swellings give rise to?

A

Labium majus

Mons pubis

60
Q

During female embryological development of external genitalia, what 3 structures form under the influence of estrogen?

A

Genital tubercle
Urethral (urogenital) folds
Labioscrotal swellings

61
Q

How does the navicular fossa of the penis develop?

A

Surface ectoderm proliferates and concaves inward creating the external urethral orifice which enlarges to become the navicular fossa

62
Q

On what surface of the penis do hypospadias occur on?

A

Ventral surface

63
Q

What developmental defect causes a glanular hypospadia?

A

Navicular fossa doesnt migrate to the right place so the opening of the glans penis is in a slightly ventral spot

64
Q

What developmental defect causes penile hypospadia?

A

Urogenital/urethral folds dont fuse (causes opening on ventral shaft of penis)

65
Q

What developmental defect causes penoscrotal hypospadia?

A

Labial scrotal swellings dont fuse properly (Causes abnormal opening on scrotum)

66
Q

What is epispadias?

A

Improper location of genital tubercles to the cloacal membrane causing abnormal opening on the dorsal side of the penis

67
Q

What condition is almost always associated with epispadias?

A

Estrophy of the bladder

68
Q

What artery is housed in the suspensory ligament of the ovary?

A

Ovarian artery

69
Q

Where is the ovarian ligament derived from?

A

Cranial part of the gubernaculum

70
Q

What germ layer is the suspensory ligament of the ovary derived from?

A

Mesoderm

71
Q

What is the broad ligament of the uterus derived from?

A

Fusion of paramesonephric ducts bring along a peritoneal fold separating the pelvic cavity -> rectouterine pouch and vesicouterine pouch

72
Q

What is the round ligament of the uterus derived from?

A

Caudal part of the gubernaculum

73
Q

What female ligament is formed from the fusion of the paramesonephric ducts bringing along a peritoneal fold separating the pelvic cavity? What 2 pouches are created by this?

A

Broad ligament; rectouterine pouch and vesicouterine pouch

74
Q

What are considered the gonads in males versus females?

A

Males = testis

Females = ovary

75
Q

What are considered germ cells in males versus females?

A

Males = sperm

Females = ova

76
Q

What are considered interstitial cells in males versus females?

A

Males = leydig cells

Females = thecal cells

77
Q

What does the urogenital sinus give rise to in males versus females?

A

Males = bladder, urethra, prostate gland, bulbourethral gland

Females = bladder, urethra, inferior vagina, greater and lesser vestibular glands, vestibule, hymen

COM: Endocrine - Final COPY (15 decks)

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