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Endo-Repro Final > Embryology > Flashcards

Embryology Flashcards

1
Q

At what weeks do sexual differentiation begin and end? At what week can sex be determined?

A
  • begins week 7
  • determined by week 12
  • ends week 20
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2
Q

What happens to primordial germ cells during week 5 of development?

A

end up in yolk sac due to body folding and migrate up dorsal mesentery to enter genital ridge

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3
Q

What happens to primordial germ cells during week 6 of development?

A

move into the genital ridge and stimulate cells to separate from epithelium and migrate into ridge

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4
Q

What do the epithelial cells that migrate into the genital ridge develop into in males and females?

A
  • somatic support cells
  • males: sertoli cells
  • females: follicle cells
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5
Q

What does the mesonephric duct make in males?

A
  • epididymis
  • vas deferens
  • seminal vesicle
  • efferent ductules
  • ejaculatory duct
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6
Q

What does the paramesonephric duct make in females?

A
  • oviduct
  • uterus
  • upper vagina
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7
Q

What gene is considered the sex-determining gene and where is it located?

A

SRY gene found on the sex-determining region of the Y chromosome

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8
Q

In what cells is the TDF (testis determining factor) from the SRY gene expressed?

A

somatic support cells (pre-Sertoli)

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9
Q

What is the function of the sertoli cells during development?

A

organize seminiferous tubules and recruit mesoderm cells to differentiate into fetal Leydig cells

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10
Q

What causes the loss of paramesoneprhic ducts in males? When do the ducts regress?

A

SRY gene -> Sox9 -> anti-mullerian hormone (AMH); regression between weeks 8-10

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11
Q

What do the remnants of paramesonephirc ducts in males produce?

A
  • appendix testis

- prostatic utricle

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12
Q

What drives the mesonephric ducts to develop and what drives it?

A

Leydig-derived testosterone (driven by HCG of placenta)

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13
Q

What 2 things are produced by sertoli cells and what do they cause?

A
  • AMH (regression of paramesonephric ducts)

- androgen binding factor during puberty (spermatogonia -> spermatozoa)

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14
Q

What 2 things are produced by fetal Leydig cells?

A
  • testosterone

- 5 a-reductase (testosterone -> dihydrotestosterone)

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15
Q

When do fetal Leydig cells regress?

A

fetal/early post natal life

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16
Q

What is the function of dihydrotestosterone?

A

development of external genitalia (penis, scrotum, and prostate)

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17
Q

What germ layer does the mesonephric duct and everything it develops come from?

A

intermediate mesoderm

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18
Q

Where does the prostate gland come from?

A

endoderm of UG sinus around week 10

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19
Q

What forms the bulbourethral glands?

A

endodermal buds

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20
Q

What is the urogenital plate?

A

endoderm-lined plate that forms after rupture of the cloacal membrane opens the phallic portion of the UG sinus to the exterior

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21
Q

What is the glans plate?

A

remnants of cloacal membrane at ventral end of the urogenital plate; adjacent to genital tubercle

22
Q

What is the genital tubercle?

A

ectodermal-covered mesodermal swelling at ventral end of urogenital plate

23
Q

What happens to the urogenital folds in males?

A

as the penis develops, the folds behind it close off to develop the scrotum

24
Q

What shortens and becomes the anchoring L. of the testis to the scrotum?

A

gubernaculum

25
Q

What is cryptorchidism?

A

failure of the testis to descend in males

26
Q

What is hypospadias?

A

open penile urethra on ventral side of penis (failure of urogenital folds to close)

27
Q

What is epispadias?

A
  • when the urethra opens on the dorsal side of the penis - associated w/ exstrophy of bladder (bladder exposed to outside)
  • due to genital tubercle developing more dorsally
28
Q

What 2 genes can be expressed in the absence of the SRY gene?

A
  • WNT-4 (pro-female)

- FOXL2 (continually suppresses SOX-9 to prevent sertoli and leydig differentiation)

29
Q

What do primordial germ cells differentiate into in females?

A

oogonia (stem cells) -> differentiate into oocytes

30
Q

What do follicle cells do to oocytes?

A

surround them and block them in meiosis I

31
Q

Why do females retain paramesonephric ducts and lose mesonephric ducts?

A
  • no sertoli cells -> no AMH -> paramesonephric retained

- no Leydig cells -> no testosterone -> lose mesonephric

32
Q

How are the uterus and uterine tubes formed? During which weeks?

A
  • weeks 9-10
  • uterus = fusion of inferior portion of paramesonephric ducts
  • uterine tubes = unfused superior portion of paramesonephric ducts
33
Q

What is vaginal agenesis?

A

failure of normal sinovaginal bulb to develop or failed canalization of vaginal plate

34
Q

What are the upper/lower portions of the vagina derived from?

A 
upper = mesoderm
lower = endoderm
35
Q

What does the lack of dihydrotestosterone in females cause?

A

lack of lengthening of the genital tubercle and no fusion of urogenital folds or labioscrotal swellings

36
Q

What forms the broad L.?

A

peritoneum that is dragged into the pelvic cavity by the fusing paramesonephric ducts

37
Q

What do the superior/inferior portions of the gubernaculum form in females?

A
  • superior = round L. of ovary

- inferior = round L. of uterus

38
Q

What is 46, XY DSD?

A

genotype of male and has testis but phenotype is female

39
Q

What are 4 causes of 46, XY DSD?

A
  • inadequate testosterone synthesis
  • androgen insensitivity syndrome (can’t respond to testosterone)
  • 5 a-reductase deficiency
  • mutations n AMH receptor
40
Q

What is androgen insensitivity syndrome? What happens at puberty?

A
  • loss of functional androgen receptors -> high testosterone but body can’t respond to it
  • at puberty, testosterone -> estradiol (female secondary sex characteristics); amenorrhea due to lack of uterus
41
Q

Do pts with androgen insensitivity syndrome have a uterus or testis?

A

will have testis in inguinal or labial regions but no uterus (produce AMH from sertoli cells so no paramesonephric system)

42
Q

What is 5 a-reductase deficiency?

A

AR disorder in 46, XY genotype w/ underdeveloped male external genitalia (no dihydrotestosterone)

43
Q

What will still develop in pt’s with 5 a-reductase deficiency?

A

normal testis and duct system (due to AMH and testosterone)

44
Q

What is a common cause of female DSD?

A

congenital adrenal hyperplasia (CAH) - virilization of female external genitalia due to excess androgen production

45
Q

What are ovotesticular disorders?

A

true intersexuality disorders - have both testicular and ovarian tissue

46
Q

What are some causes of ovotesticular disorders?

A
  • translocation of piece of Y onto X (Barr body causes mosaicism)
  • subset of cells may have mutation in Y
  • anomaly in sex determination of primordial germ cells
47
Q

What is the decidua?

A

functional layer of endometrium that separates from remainder of uterus after childbirth

48
Q

Describe each of the parts of the decidua: decidua basalis, decidua capsularis, and decidua parietalis

A
  • decidua basalis: deep to conceptus (part where embryo embedded)
  • decidua capsularis: superficial to conceptus (closest to uterine cavity)
  • decidua parietalis: remaining part of decidua
49
Q

Describe syncytiotrophoblasts structurally. What do they produce?

A
  • large grouping of nuclei with no detectable cell membrane (invade and displace decidual cells)
  • produce hCG
50
Q

What is the amnion and what creates it?

A
  • thin tough membrane surrounding embryo and amniotic fluid

- derived from amnioblasts that separate from epiblasts

51
Q

How does the embryo receive nutrients/O2 before complete production of the placenta?

A

primordial uteroplacental circulation where nutrients pass to embryo via diffusion through lacunar networks (maternal side of placenta)

52
Q

What establishes the fetal part of the placenta?

A

the chorionic sac

Endo-Repro Final (7 decks)

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