Lecture 8 - Embryology Reproductive System 2

Question 1

what occurs at 6 weeks

Answer 1

indifferent genital ducts form

Question 2

what is the difference in genital ducts in male and female

Answer 2

Female - develop paramesonephric ducts (Mullerian) whereas in males they depress
Male - mesonephric ducts (Wolffian) - develop and in females they regress

Question 3

What drives the development of the genital ducts

Answer 3

SRY gene

Question 4

What does the SRY gene do?

Answer 4

encodes for testis determining factor (TDF)

somatic cells invest PGC’s (Proliferating Germ Cells) with SRY gene and differentiate into sertoli cells

Question 5

What do sertoli cells do?

Answer 5

secrete anti-mullerian hormone

which causes degeration of the paramesonephric ducts

Question 6

what are the derivatives of the mesonephric duct

Answer 6

vas deferens
epididymis
seminal vesicle

Question 7

What are the remnants of the paramesonephric duct?

Answer 7

Appendix testis

Utriculus prostaticus

Question 8

How do genital ducts form?

Answer 8

in the absence of SRY
no anti- mullerian hormone - paramesonephric ducts remain
No testosterone - mesonephric ducts degenerate

Question 9

What are the 3 parts of the paramesonephric duct

Answer 9

cranial and horizontal - become uterine tubes

caudal - fuse to form uterine canal

Question 10

Remnants of the mesophrenic duct

Answer 10

epophoron
paraoophoron
gartners cyst

Question 11

how does the uterus and the vagina form?

Answer 11

cloaca divides into urogenital sinus and anus

urogenital sinus develops into sinovaginal bulbs that fuse with caudal tips of paramesonephric ducts to form vagina

Question 12

abnormalities of the uterus

Answer 12

Failure of paramesonephric tubes to fuse
failure of uterine septum to degenerate
failure of one paramesonephric duct to elongate
affect 1% of non-fertile women - higher rates of miscarriage, premature delivery or dystocia

Question 13

Persistent mullerian duct syndrome

Answer 13

affect genetic males
mutation in AMH gene
No AMH production - paramesonephric ducts persist
both mesonephric and paramesonephric duct derivatives develop
normal external genitalia but associated with crytorchidism

Question 14

Indifferent stage of development of external genitalia

Answer 14

mesoderm cells migrate to surround cloacal membrane and form elevated cloacal folds
cloacal folds unite anteriorly to form genital tubercle - future penis or clitoris
fold - divide into anal and urethral divisions
genital swellings - appear next to folds - future scrotum or labia majora

Question 15

what does development of male external genitalia depend on?

Answer 15

androgens
genital tubercle elongates to form phallus
genital swellings enlarge and move caudally

Question 16

When does formation of the penile urethra occur?

Answer 16

9-10 weeks

Question 17

formation of the penile urethra

Answer 17

urethral folds pull forward and form lateral walls of the urethral groove
urethral groove is lined by epithelium and form urethral plate
end of 3rd month - urethral folds close over urethral plate to form penile urethra
scrotal swellings fuse in midline

Question 18

What is hypospadias

Answer 18

incomplete fusion of urethral folds - urethra opens on ventral surface of penis
occurs in 3-5/1000 births
difficulty urinating
can be repaired surgically using foreskin

Question 19

Epispadias

Answer 19

opening in dorsal surface of penis
often associated with exstrophy of the bladder
incidence - 1 in 30,000
results from improper location of the genital tubercle posterior to urogenital sinus - urethral groove on dorsal surface

Question 20

What is development of female genitalia dependent on

Answer 20

oestrogens
genital tubercle elongates slightly to form clitoris
urethral folds do not fuse - form labia minora
genital swellings - labia majora
urogenital groove - remains open

Question 21

When can you tell the difference between males and females

Answer 21

13 weeks

size of phallus and clitoris are similar until 12 weeks