Genital Embryology B&B

Question 1

what must happen during the embryological period for the development of the gonads to begin?

Answer 1

germ cells (derived from epiblast) must invade the gonadal ridges (derived from mesenchyme)

failure to reach gonadal ridges = failure for gonads to develop

Question 2

the _____ gene (Y chromosome) codes for testis determining factor, which forms ____ and ____ cells

Answer 2

the SRY gene (Y chromosome) codes for testis determining factor, which forms SERTOLI and LEYDIG cells

Leydig cells produce testosterone —> medullary (testis) cords form

Question 3

in female embryos, the medullary (testis) cords regress and the ______ develop to form clusters

Answer 3

cortical cords - form clusters which surround germ cells —> oogonia and follicular cells form primordial follicles

Question 4

from what are the male vs female internal genitalia derived?

Answer 4

male - mesonephric (wolffian) duct
female - paramesonephric (mullerian) duct

these will form the internal genitalia that “hook up” to the gonads

[named for their relation to the mesonephros, the interim kidney in the 1st trimester]

Question 5

how do Sertoli and Leydig cells both contribute to the development of male, rather than female, genital ducts?

Answer 5

Sertoli cells - secrete Mullerian inhibitory factor (MIF), which suppresses development of paramesonephric ducts [remnant remains as appendix testis]

Leydig cells - secrete androgens (testosterone) which stimulates development of mesonephric (wolffian) ducts

Question 6

what is the function of the epididymis vs ductus deferens (vas deferens)

Answer 6

epididymis - transports sperm from the seminiferous tubules to vas deferens

ductus (vas) deferens: transports sperm from the epididymis to ejaculatory ducts

Question 7

transports sperm from the seminiferous tubules to vas deferens

Answer 7

epididymis

Question 8

transports sperm from the epididymis to ejaculatory ducts

Answer 8

ductus (vas) deferens

Question 9

what is the function of the seminal vesicles, and where are they found?

Answer 9

glands behind the bladder, secrete ~75% of fluid in semen (remainder from prostate)

connects with ejaculatory ducts

Question 10

Gartner’s Duct

Answer 10

Wolffian/mesonephric remnant in females

found on vaginal walls, may form painful cyst

Question 11

the embryological cloaca divides into _____ and _____

Answer 11

the embryological cloaca divides into urogential sinus and anal canal

[cloaca is like a turn in the end of the gut tube]

Question 12

what does the urogenital sinus (derived from cloaca) become in males vs females?

Answer 12

males - bladder (upper portion), prostate/prostatic urethra (pelvic portion), penile urethra (phallic portion)

females - bladder (upper portion), inferior vagina (pelvic portion - note superior vagina develop from müllerian ducts)

Question 13

from what is the inferior vs superior vagina derived?

Answer 13

inferior vagina derived from urogenital sinus (which is derived form cloaca)

upper 2/3 of vagina is derived from müllerian ducts

Question 14

what is the most common type of uterine anomaly?

Answer 14

“lateral fusion defects”: failed fusion of L/R müllerian ducts —> uterine shape is abnormal

may cause infertility, pregnancy loss

Question 15

what causes a septate uterus to develop?

Answer 15

septate uterus: septum divides uterus into 2 endometrial cavities

due to defect in resorption of the septum between the L/R embryological müllerian ducts

most common uterine anomaly

Question 16

what is the most common uterine anomaly?

Answer 16

septate uterus: septum divides uterus into 2 endometrial cavities

due to defect in resorption of the septum between the L/R embryological müllerian ducts

Question 17

what occurs in the following uterine anomalies?
a. bicornuate
b. unicornuate
c. uterine didelphys

Answer 17

a. bicornuate: partial fusion of müllerian ducts (fundus is indented)
b. unicornuate: uterus connects to only 1 ovary
c. uterine didelphys: müllerian ducts fail to fuse (double uterus)

Question 18

Hysterosalpingography

Answer 18

Imaging study in which dye is injected into the uterus to see the shape

Used to diagnose uterine abnormalities

Question 19

what do the following external genitalia of the indifferent stage become in males?
a. genital tubercle
b. urogenital folds (from cloaca)
c. urogenital sinus (from cloaca)
d. labioscrotal (genital) swellings

Answer 19

a. genital tubercle —> phallus (aka penis)
b. urogenital folds (from cloaca) —> penile urethra
c. urogenital sinus (from cloaca) —> glands (prostate, bulbourethral)
d. labioscrotal (genital) swellings —> scrotum

Question 20

hypospadia vs epispadia

Answer 20

congenital anomalies of the male urethra

hypospadis (more common): failure of the urethral folds to close —> ventral opening of the urethra

epispadia: abnormal position/formation of genital tubercle —> urethral opening on the dorsal side of penis, commonly occurs with bladder extrophy

Question 21

what do the following external genitalia of the indifferent stage become in females?
a. genital tubercle
b. urogenital folds (from cloaca)
c. urogenital sinus (from cloaca)
d. labioscrotal (genital) swellings

Answer 21

a. genital tubercle —> clitoris
b. urogenital folds (from cloaca) —> labia minora
c. urogenital sinus (from cloaca) —> glands (paraurethral/Skene, Bartholin)
d. labioscrotal (genital) swellings —> labia majora

Question 22

In males and females, the caudal end of the mesonephric duct forms the…

Answer 22

… bladder trigone and the ureteric bud that gives rise to the ureters, calyces, and collecting ducts.

In females, the rest of the mesonephric duct regresses while in males the rest of the mesonephric duct forms internal genital ducts. The mesonephric duct that forms the male internal genital ducts is also known as the Wolffian duct.

Question 23

The prostate gland grows off of the ______

The bulbourethral glands grow off of the ________

Answer 23

The prostate gland grows off of the prostatic urethra.

The bulbourethral glands grow off of the membranous urethra or penile urethra.