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GIGU test! > Development of the Reproductive system > Flashcards

Development of the Reproductive system Flashcards

1
Q

Timeline for the reproductive system development

A

Weeks 1-6: indifferent embryo

Week 7: sexual differentiation begins

week 12: Female and male genitalia can be recognized

week 20: Phenotypic differentiation complete

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2
Q

what are the primordial germ cells and their characteristics

A

Progenitor cells of the oogonia and spermatogonia

Primordial germ cells are specified within the epiblast

after gastrulation and body folding, primordial germ cells end up within the yolk sac wall

Primordial germ cells migrate up the dorsal mesentary of developing gut to enter the genital ridge of the intermediate mesoderm in week 5

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3
Q

what happens in the indifferent gonad during week 6

A

Primitive gonads appear initially as pair of longitudinal swellings in the urogenital ridges of the intermediate mesoderm at about axial level T10

formed by proliferation and delamination of coelomic epithelium and condensation of underlying mesenchyme

Primordial germs stimulate the proliferation and delamination of cells from the coelomic epithelium of the genital ridge to form the somatic support cells (primitive sex cords)

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4
Q

What do the somatic support cells differentiate into in males and females?

A

Males the somatic support cells become the sertoli cells

in females they become the follicle cells

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5
Q

what are the two sets of reproductive ducts that form eary in development?

A

Mesonephric tubules and mesonephric duct:
-these tubules and ducts form within the urogenital ridge and serve as early collecting ducts for the mesonephric kidney. Mesonephric ducts open into the urogenital sinus

Paramesonephric (mullerian) ducts

  • new ducts form on both sides from an invadignation along the anteriolateral surface of the urogenital ridge
  • cranially they open to the coelomic cavity and caudally they meet with each other when attaching to the urogenital sinus
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6
Q

What is critical for sexual dimorphism

A

the key to sexual dimorphism is the Y chromosome

this chromosome contains the testis determining factor gene SRY

presence or absence of this factor has a direct effect on gonadal differentiation and acts as a switch to initiate a cascade of many downstream genes that determine the fate of rudimentary sexual organs

in the absence of it the development is female

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7
Q

Development of the testis

A

SRY gene is transcribed on days 42-52 which then turns on the gene expression for SOX9 in somatic support cells and suppresses WNT4 (pro-female gene)

Sertoli cells surround the primordial germ cells, and on the 4th month with the sertoli, germ, and myoepithelial cells they organize into the testis cords and eventually develop into the seminiferous tubules

The testis cords become connected to the rete testis and the rete testis becomes connected to the efferent ductules (remnants of mesonephric tubules) thereby linking the testis cords to the developing epididymis and vas deferens (mesonephric duct)

Primordial germ cells proliferate and differentiate into Type A spermatogonia 3 months postnatal

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8
Q

what does a subset of intratubular cells differentiate into?

A

Leydig cells that are recruited by the sertoli cells

the leydig cells begin producing testosterone during the 9-10th week and begin influencing differentiation of genital ducts and external genitalia

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9
Q

What happens to the paramesonephric ducts at week 8-10

A

The seroteli cells express anti-Mullerian hormone (AMH) or also known as Mullerian inhibitor substance that drives the regression of paramesonephric ducts at week 8-10

the remenants of paramesonephric duct in males include appendix testis and prostatic utricle

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10
Q

what does the Leydig cell derived testosterone drive to form?

A

Leydig cell derived testosterone drives the mesonephric tubules to form:

  • Effernt ductules: paradidymis
  • Epididymis
  • Vas deferens
  • Seminal vesicle
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11
Q

what is the importance of DHT

A

a portion of testosterone is converted to duhydrotestosterone (DHT) by 5a reductase

this is important for driving the development of the external genitalia (penis, scrotum, prostate, testicular descent)

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12
Q

How do seminal vesicles form?

A

Seminal vesicle formed from the buds emanating from the mesonephric duct, hence they are derived from intermediate mesoderm of urogenital ridge

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13
Q

how does the gland form?

A

forms from buds emanating from endoderm of urogenital sinus within future membranous region of the pelvic urethra (week 10)

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14
Q

how does the bulbourethral glands form?

A

also from the endoderm buds of urogenital sinus

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15
Q

Development of genital tubercle?

A

Ectodermal covered mesodermal swelling at the ventral end of the phallic portion of the urogenital plate

how extensive it outgrows depends on the DHT levels

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16
Q

development of the Urogenital plate and what forms ventral to it?

A

With rupture of the cloacal membrane, the floor of the phallic segement of the urogenital sinus is lost

where as the roof of the phallic segment expands along the lower surface of the genital tubercle
-as the genital tubercle enlarges this endodermal extension will form the urogenital plate

A urethral groove forms along the vental surface of the urogenital plate as the genital tubercle elongates

distally the urethral groove and urogenital plate terminate at the solid glans plate

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17
Q

what do the urogenital folds form?

A

A pair of swellings called the urogenital folds (or cloacal folds) develop on either side of the urogenital plate through an expansion of mesoderm underlying the ectoderm

at the distal end of the urogenital folds, remenants of the cloacal membrane adjacent to the genital tubercle remain as the glans plate

a new pair of swellings, the labioscrotal swellings will appear on either side of the urethral folds

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18
Q

Development of the male external genitalia

A

Initially the urethral groove and urogenital folds extend part of the way along the shaft of the elongating phallus

As the phallus and urogenital plate continue to elongate the urogenital folds grow toward one another and fuse in the midline beginning proximally in the perineal region and extending distally toward the glans penis
-this converts the urethral groove into the tubular penile urethra

Solid glans plate canalizes and joins the developing penile urethra to form the glans urethra and external penile meatus

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19
Q

What drives the legthening and growth of the genital tubercle or labioscrotal swellings forming the scrotum?

A

DHT

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20
Q

How do the testis descent?

A

Suspensory ligament contains gonadal vessels, nerves, and lymphatics and connections are made at T 10

the gubernaculum which is a structure connecting the gonad to base of the labioscrotal swellings will shorten eventually pulling the testes into the scrotum

21
Q

What is it called if the testis fail to descend?

A

Failure to descend leads to cryptorchidism

most self resolve within a year but must be watched as incidence of testicular cancer is greatly increased

22
Q

what is Hypospadias and Epispadias

A

Hypospadias is the most common male birth defect after cryptorchidism
-due to failure of urethral folds to close properly

Epispadias: uretra on top of the penis, cause is unknown but may be due to improper ventral body closure or formation of too large of a cloacal membrane to be covered when it ruptures

23
Q

How does the ovary initiate its differentiation?

A

In the absence of the SRY gene, somatic support cells express WNT4 and FOXL2

FOXL2 continually suppresses SOX9 expression thereby maintaining female gonad differentiation

Primordial germ cells differentiate into the oogonia, proliferate ad differentiate into oocytes

the developing oocytes induce the surrounding somatic support cells to become follicular cells

the follicle cells surrounding individual oocytes are responsible for arresting the primary oocyte in prophase I of meiosis until puberty

24
Q

what are the duct system in females

A

Since no Sertoli cells the Paramesonephric ducts are retained

absence of Leydig cells the mesonephric duct system is lost
-remnants include epoophoron and paraoophoron near the ovary and gartners cyst

the Paramesonephric duct will fuse at week 9-10 at the inferior proximal end and form the uterus and the un-fused portion forms the uterine tubes

25
Q

what are some uterus anomalies?

A

all due to improper or failed fusion of paramesonephric ducts

  • Didelphys: double uterus
  • Bicornate: two bodies one cervix
  • Double uterus and double vagina
  • Double uterus
  • Unicornate uterus: only one uterine tube formed
  • sepated uterus
26
Q

Formation of the Vagina

A

Contact of paramesonephric duct to urogenital sinus stimulates proliferation and formation of sinuvaginal bulb (endodermal thickening)

Sinuvaginal plate will proliferate and lengthen and is eventually canalized

The entire vagina with possible exception of the upper vagina fornix is derived from endoderm

27
Q

Vaginal agenesis?

A

due to failure of normal sinuvaginal bulb development or canalization or due to agenesis of the parasmesonephric ducts

28
Q

Female external genitalia developmen

A

Phallic segment of urogenital sinus has a urogenital plate, glans plate, and genital tubercle

in the absence of testosterone and DHT, there is no lengthening of genital tubercle and no fusion of urogenital folds or labioscrotal swellings

the urogenital folds in female form the labia minora

labioscrotal folds in female form the labia majora

differential growth and expansion separates the urethra from the vaginal opening

29
Q

Formation of broad ligament

A

MIdline fusion of paramesonephric ducts drags the lower urogenital ridge, which is covered with developing peritoneum into the pelvic cavity

with completion of uterus and uterine tube development, the remaining tissue thins and forms a double peritoneum fold that supports the uterus and the ovary

30
Q

How does the descent of the ovary occur and what makes up those structures associated with the process

A

Descent of the ovary: it has a suspensory ligament superiorly containing vessels, nerves, and lymphatics

also has a gubernaculum connecting the gonad to the labioscrotal swelling, the gubernaculum becomes attached to developing uterus restricting the furthur ovarian descent

Round ligament of ovary is the portion of gubernaculum between the gonad and uterus

Round ligament of uterus is the portion of the gubernaculum between the uterus and base of labioscrotal swellings (future labia majora)

31
Q

17B Hydroxysteroid dehydrogenase deficiency

A

inadequate testosterone synthesis

17B hydroxysteroid dehydrogenase is important for converting androstenedione to testosterone

has testes but phenotype appears female

32
Q

Androgen insensitivity syndrome

A

Loss of functional androgen receptors: X linked recessive

Have testes but no spermatogeneis, testosterone levels may be elevated due to lack of negative feedback

At puberty, the testosterone is metabolized to estradiol initiating female secondary sexual characteristics

They produce AMH so the paramesonephric system is suppressed resulting in the absence of a uterus or uterine tubes and the vagina is short and ends blindly

Testis usually found in inguinal or labial regions increasing risk of tumor formation in the gonads

33
Q

5alpha-reductase deficiency

A

inability to convert testosterone to DHT, autosomal recessive

Normal testis and duct system development as there is AMH and testosterone

however there is underdeveloped male external genitalia, the gdegree of which depends on level of deficiency of DHT but they can exhibit an external female phenotype

34
Q

Mutation in AMH or AMH receptor

A

retention of paramesonephric ducts so individual has a uterus and uterine tubes along with male ducts and external genitalia

35
Q

Congenital adrenal hyperplasia

A

XX DSD

mutation in genes involved in adrenocortical steroid biosynthesis such as deficiency in 21-hydroxlase leading to excess ACTH production causing adrenal hyperplasia and excessive production of androgens

have ovaries but female genitalia is masculinization and depending on androgen levels can exhibit fusion of labioscrotal swellings and an enlarged clitoris with what may look like hypospadias

36
Q

Ovotesticular disorders

A

Have both testicular and ovarian tissue
-karyotype is 46XX

AMbiguous external genitalia or predominatly female

Usually have a uterus

Causes:

  • translocation of piece of Y chromosome onto X chromosome (barr body causes mosaicism)
  • subset of cells may have mutation in Y chromosome
  • anomaly in sex determination and differentiation of primordial germ cells
37
Q

What is the male and female structure based on the presumptive rudiments: Indifferent gonad

A

Testis

Ovary

38
Q

What is the male and female structure based on the presumptive rudiments: Primordial germ cell

A

Spermatogonia

Oocyte

39
Q

What is the male and female structure based on the presumptive rudiments:Somatic support cell

A

Sertoli cell

Follicle cell

40
Q

What is the male and female structure based on the presumptive rudiments: Stromal cell

A

Leydig cell

Thecal cell

41
Q

What is the male and female structure based on the presumptive rudiments: Gubernaculum

A

Gubernaculum testis

Round ligament of ovary
Round ligament of uterus

42
Q

What is the male and female structure based on the presumptive rudiments: MEsonephric tubules

A

Effernt ducts of testis
Paradidymis

Epoophoron
Paroophoron

43
Q

What is the male and female structure based on the presumptive rudiments: Mesonephric duct

A 
Appendix of Epidiymis
Epididymis
Vas deferens
Seminal vesicle
Ejaculatory duct

Appendix vesciculosa
Duct of epoophoron
Gartners duct

44
Q

What is the male and female structure based on the presumptive rudiments: Paramesonephric duct

A

Appendix of testis

Fallopian tubes
uterus
vagina

45
Q

What is the male and female structure based on the presumptive rudiments: Urogenital sinus

A

Prostatic and membranous urethra
prostatic utricle
prostatic gland
Bulbourethral glands

Membranous urethra
Urethral/paraurethral glands
greater vestibular glands

46
Q

What is the male and female structure based on the presumptive rudiments: Genital tubercle

A

Glans penis
corpus cavernosa of penis
corpus spongiosum of penis

glans clitoris
corpus cavernoisa of clitoris
bulbospongiosum of vestibule

47
Q

What is the male and female structure based on the presumptive rudiments: Urogenital folds and urogenital and glans plate

A

Penile urethra/ventral part of penis

Labia minora

48
Q

What is the male and female structure based on the presumptive rudiments: Labioscrotal folds

A

Scrotum

Labia majora

GIGU test! (40 decks)

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