Development of the Reproductive System

Question 1

when does sexual differentiation begin?

Answer 1

week 7

Question 2

when can male and female genitalia be recognized?

Answer 2

week 12

Question 3

when is phenotypic differentiation complete?

Answer 3

week 20

Question 4

how do the primordial germ cells get to the genital ridge?

Answer 4

they will migrate up through the yolk sac wall and enter through the dorsal mesentery

Question 5

where is the genital ridge found?

Answer 5

within the urinary genital region within the intermediate mesoderm

Question 6

where does kidney and gonadal development take place?

Answer 6

in the intermediate mesoderm

Question 7

what are the precursors of the oogonia and the spermatogonia?

Answer 7

the primordial germ cells

Question 8

what do the primordial germ cells stimulate?

Answer 8

the proliferation and delamination of cells from the coelomic epithelium of the genital ridge to form somatic support cells

Question 9

what do the somatic support cells eventually become?

Answer 9

in males: Sertoli cells in females: follicle cells

Question 10

what are the two sets of reproductive ducts that form within the intermediate mesoderm?

Answer 10

the mesonephric tubules/mesonephric duct and the paramesonephric ducts

Question 11

what serves as the early collecting ducts for the mesonephric kidney?

Answer 11

the mesonephric tubules and ducts

Question 12

what structures are later derived from the mesonephric ducts?

Answer 12

the epididymis, vas deferens, seminal vesicle, and ejaculatory duct

Question 13

what structures are later derived from the paramesonephric duct?

Answer 13

oviduct, uterus, and upper vagina

Question 14

what is sexual dimorphism dependent on?

Answer 14

the Y chromosome but also autosomes as well

Question 15

what does the Y chromosome contain that is ket to sexual dimorphism?

Answer 15

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

Question 16

when is the SRY gene active if present?

Answer 16

only active ~10-11 days- days 41-52

Question 17

where is the SRY gene expressed?

Answer 17

in somatic support cells (pre-sertoli cells)

Question 18

what does SRY gene expression turn on?

Answer 18

SOX9 expression in somatic support cells (drives them towards Sertoli differentiation)

Question 19

what does SRY gene expression suppress?

Answer 19

Wnt4 (the pro-female gene)

Question 20

what does expression of Sox9 result in?

Answer 20

expression of anti-mullerian hormone (AMH)

Question 21

what happens when AMH is expressed?

Answer 21

there is regression of the Mullerian (paramesonephric) ducts

Question 22

when does the regression of the paramesonephric ducts occur?

Answer 22

between weeks 8-10

Question 23

what are the remnants of the paramesonephric ducts?

Answer 23

appendix testis and the prostatic utricle

Question 24

what drives the mesonephric duct development into different structures?

Answer 24

leydig cell-derived testosterone(driven by hCG of placenta)

Question 25

what does the mesonephric duct differentiate into?

Answer 25

the efferent ductules, the epididymis, the vas deferens, and the seminal vesicles

Question 26

when does the mesonephric duct differentiate into different structures?

Answer 26

week 9

Question 27

what is a portion of the testosterone that is derived from the fetal leydig cells converted into?

Answer 27

DHT

Question 28

what converts testosterone into DHT?

Answer 28

5-alpha reductase

Question 29

what is the purpose of the DHT?

Answer 29

it drives the development of external genitalia (penis, scrotum) prostate)

Question 30

what is the purpose of adult leydig cells?

Answer 30

they are going to secrete androgens, which are important for initiation of spermatogenesis, masculinization of the brain, and male sexual behavior

Question 31

what are seminal vesicles?

Answer 31

they are buds that are formed from the mesonephric duct

Question 32

what are seminal vesicles derived from?

Answer 32

intermediate mesoderm of the urogenital ridge

Question 33

what is the prostate gland?

Answer 33

buds from endoderm of urogenital sinus in the region of the pelvic urethra

Question 34

when is the prostate gland formed?

Answer 34

around week 10

Question 35

what do the bulbourethral glands form from?

Answer 35

also endoderm buds

Question 36

what is the genital tubercle?

Answer 36

it is an ectodermal-covered mesodermal swelling at the distal end of the phallic portion of the urogenital plate

Question 37

what is the extend of the growth of the genital tubercle dependent on?

Answer 37

DHT levels

Question 38

what is the urogenital plate?

Answer 38

with rupture of the cloacal membrane, the floor of the phallic segment of the urogenital sinus is lost, but the roff expands along the lower surface of the genital tubercle as it enlarges

Question 39

what germ layer makes up the urogenital plate?

Answer 39

endoderm

Question 40

what is the glans plate?

Answer 40

the very tip of where the cloacal membrane used to be, there is a remnant there and that is the glans plate

Question 41

how do the urogenital folds appear?

Answer 41

they develop on either side of the urogenital plate through an expansion of the mesoderm underlying the ectoderm

Question 42

what forms along the ventral surface of the urogenital plate as the genital tubercle elongates?

Answer 42

a urethral groove

Question 43

what do the urethral groove and the urogenital plate terminate as distally?

Answer 43

the glans plate

Question 44

how do the urogenital folds grow towards one another?

Answer 44

the grow towards one another and fuse in the midline- beginning proximally in the perineal region and extending distally towards the glans penis

Question 45

what drives the lengthening and growth of the genital tubercle and fusion of the labioscrotal swellings forming the scrotum?

Answer 45

DHT

Question 46

what is hypospadias?

Answer 46

failure of the urethral folds to close properly (ventral aka underneath)

Question 47

what is epispadias?

Answer 47

opens on the dorsal shaft of the penis

Question 48

when is the urethra closed by?

Answer 48

week 14

Question 49

in absence of the SRY gene, what do somatic support cells express?

Answer 49

wnt-4 and FOXL2

Question 50

what is the purpose of the FOXL2 gene?

Answer 50

it continually suppresses any SOX-9 expression and thereby maintains female gonad differentiation

Question 51

in females, what do primordial germ cells differentiate into?

Answer 51

oogonia

Question 52

what happens to the oogonia?

Answer 52

they are going to proliferate and differentiate into oocytes

Question 53

what do the developing oocytes induce?

Answer 53

the surrounding somatic support cells to become follicular cells

Question 54

what is the role of the follicular cells?

Answer 54

they surround individual oocytes and are responsible for arresting the primary oocytes in prophase I of meiosis until puberty

Question 55

what do the paramesonephric ducts become in the absence of AMH?

Answer 55

Fallopian tubes, uterus, and the upper most portion of the vagina

Question 56

what are the remnants of the lost mesonephric duct system?

Answer 56

the epoophoron and paraoophoron

Question 57

when does uterus formation occur?

Answer 57

weeks 9-10

Question 58

how is the uterus formed?

Answer 58

there is fusion of the inferior paramesonephric ducts

Question 59

what are the uterine tubes?

Answer 59

the unfused superior portion of the paramesonephric ducts

Question 60

what is the term for a double uterus?

Answer 60

didelphys

Question 61

how does the vagina form and what germ layer is it derived from?

Answer 61

it forms from the lengthening of the solid sinuvaginal bulb ; endodermally derived; this is eventually canalized

Question 62

What is the upper portion of the vagina aka the vaginal fornices formed from? and what germ layer is it derived from?

Answer 62

fusion of the paramesonephric ducts (mesoderm)

Question 63

what is vaginal agenesis most often due to?

Answer 63

failed sinovaginal bulb development and/or canalization

Question 64

what stimulates the proliferation and formation of the sinovaginal bulb?

Answer 64

contact of the paramesonephric duct to the urogenital sinus

Question 65

in females, what does the phallic segment of the urogenital sinus contain?

Answer 65

just like males- the glans plate, the urogenital plate, and the genital tubercle

Question 66

why is there no lengthening of the genital tubercle and no fusion of the urogenital folds or labioscrotal swellings in females?

Answer 66

there is no testosterone and therefore no DHT

Question 67

what do the urogenital folds in females form?

Answer 67

labia minora

Question 68

what do the labioscrotal swellings in females form?

Answer 68

labia majora

Question 69

upon completion of the uterus and oviduct formation, what happens to the remaining tissue?

Answer 69

it thins and forms a golf fold in peritoneum (the broad ligament, mesovarian, and mesosalpinx), which supports the uterus and the ovary

Question 70

what is the round ligament of the ovary?

Answer 70

it connects the ovary to the uterus; from the superior gubernaculum

Question 71

what is the round ligament of the uterus?

Answer 71

it connects the uterus to the labia majora; from the inferior gubernaculum

Question 72

what do the urogenital folds and urogenital plate and glans plate become in the male?

Answer 72

the penile urethra/ ventral part of the penis

Question 73

what is androgen insensitivity syndrome?

Answer 73

when a person has testis but no spermatogenesis; testosterone levels may be high

Question 74

what happens at puberty in patients with androgen insensitivity syndrome?

Answer 74

testosterone is metabolized to estradiol- initiates female secondary characteristics but patients exhibit amenorrhea

Question 75

what is a common cause of androgen insensitivity syndrome?

Answer 75

loss of functional androgen receptors (x-linked recessive)

Question 76

what is congenital adrenal hyperplasia

Answer 76

the most common cause of female sexual ambiguity; the fetus produces excess androgens; they still have ovaries, but there is masculinization of the female external genitalia

Question 77

what mutation could lead to congenital adrenal hyperplasia?

Answer 77

mutations in genes involved in adrenocortical steroid biosynthesis (deficiency in 21-hydroxylase)