Reproductive embryology 2 Flashcards
How many sets of kidneys do we have throughout development and which set is the mesonephros?
3, mesonephros is the 2nd set
What forms the male reproductive system (other than the testis)?
Mesonephric ducts
What forms the female reproductive system (other than the ovaries)?
Paramesonephric duct
What are the mullerian and wolffian ducts?
Mullerian = paramesonephric Wolffian = mesonephric
Sertoli cells are derived from what part of the developing gonad and what hormone stimulates their development?
TDF stimulates the differentiation of the epithelium surrounding the primordial germ cells into sertoli cells
What hormone is produced by the sertoli cells and what does this cause?
Sertoli cells secrete anti mullerian hormone
This causes degeneration of paramesonephric ducts
From what part of the gonad are leydig cells derived?
Mesoderm
What causes the development of the leydig cells?
Sertoli cells stimulate the formation of leydig cells from the mesoderm of the gonad
What hormone do the leydig cells produce and what does this cause?
Testosterone
Promotes survival and further development of the mesonephric ducts
What connects the mesonephric ducts to the rete testis?
Epigenital tubules
What do the epigenital tubules form in the testis?
Efferent ductules
What is the appendix epididymis a remnant of?
The cranial part of the mesonephric duct above the testis
What is the Paradidymis a remnant of?
The paragenital tubules below the gonad
What forms the seminal vesicle?
Outpouching of the mesonephric duct
What 2 structures are found in the male reproductive system which are remnants of parts of the paramesonephric duct?
Utriculus prostaticus
Appendix testis
What hormones control the degeneration of the mesonephric duct and development of the paramesonephric duct in the female?
In the absence of TDF no sertoli cells and therefore no anti mullerian hormone is produced so the paramesonephric duct does not degenerate
In the absence of sertoli cells no leydig cells and thus no testosterone are produced so the mesonephric duct degenerates
What part of the paramesonephric duct forms the uterine tubes?
The cranial and middle parts
What part of the paramesonephric duct forms the uterus?
The caudal parts which fuse to form the uterine canal
From what is the cervix formed?
The caudal tip of the paramesonephric ducts
From what is the vagina formed?
Cranial part - from the caudal tip of the paramesonephric ducts
Caudal part - urogenital sinus (anterior part of the cloaca) forms sinovaginal bulbs which fuse with the caudal tips of the paramesonephric ducts to form the vagina
Why may a hymen seperate the vaginal canal from the external environment?
Vagina and cervix form as a solid piece of tissue
The cells must undergo apoptosis to form an opening
A hymen is a membrane that may remain due to incomplete apoptosis of the vagina - it degenerates to varying degrees in different people
What are sinovaginal bulbs?
Formed from the urogenital sinus, they fuse with the caudal tips of the paramesonephric ducts to form the vagina
What 3 structures persist in the female as remnants of the mesonephric duct and where are they?
Epoophoron and Paroophoron are bits of tissue that are found in the broad ligament next to the ovary
Gartner’s cyst is a caudal remnant of the mesonephric duct next to the vagina
What 2 abnormalities of the uterus can occur due to failure of the 2 paramesonephric ducts to fuse?
1) Double uterus
2) Double uterus double vagina
What abnormality of the uterus can occur due to failure of one paramesonephric duct to elongate?
Unicornate uterus (like half a uterus with only 1 uterine tube)
What 3 abnormalities of the uterus can occur due to failure of the uterine septum to degenerate?
Bicornate uterus (2 horned uterus) Cervical atresia Septated uterus (1 uterus with a septum down the middle - but not all the way)
What percentage of fertile women are affected by a uterine abnormality?
1%
What do abnormalities of the uterus increase the risk of?
Miscarriage
Premature delivery
Dystocia (difficult birth)
These uteruses also tend to be smaller so can reduce growth of the foetus
What happens in persisitent mullerian duct syndrome and who does it affect?
Affects genetic males
Mutation in the gene for AMH - paramesonephric ducts do not degenerate
Both mesonephric ducts and paramesonephric ducts develop
Normal male external genitalia but associated with cryptorchidism
What is persistent mullerian duct syndrome associated with increased risk of?
Cryptorchidism
What are the cloacal fold?
Formed from mesodermal cells which migrate to surround the cloacal membrane and form these elevated cloacal folds
What do the cloacal folds unite anteriorly to form and what develops from this?
Unite to form the genital tubercle which will go on to form the penis or clitoris
What subdivides the cloaca and what happens to the cloacal folds when this happens?
The urorectal septum (mesoderm derivative meets the cloacal membrane) to divide the cloacal into the anorectal canal posteriorly and the urogenital sinus anteriorly
This divides the cloacal folds into urethral folds and anal folds
From what germ are the cloacal folds derived?
Mesoderm
What are the genital swellings and what do they go on to forms?
Swellings either side of the urethral folds
Go on to form the scrotum or labia majora
What hormones are needed fro male external genitalia to develop?
Androgens ie. testosterone
What happens to the genital swellings in the male?
They move caudally and fuse in the midline (testis still separated by a scrotal septum)
What is the urethral plate in the male?
Epithelium lining the urethral groove inbetween the urethral folds
How is the penile urethra formed in the 3rd month?
Urethral folds fuse over the urethral plate to form the penile urethra
What is hypospadias?
Incomplete fusion of the urethral folds means the penile urethra is open on the ventral surface
What does hypospadias cause and how can it be corrected?
Causes difficulty urinating
Occurs in 3-5/1000 births
Can be repaired surgically using the foreskin (Penile urethra was made from the epithelium, the foreskin is effectively extra epithelium)
What is epispadias?
Urethra opening on the dorsal surface of the penis
What is epispadias commonly associated with?
exstrophy of the bladder (bladder outside the body wall)
What does epispadias result from?
Improper location of the genital tubercle - posterior to the urogenital sinus rather than anterior The urethral groove then ends up positioned on the dorsal surface of the penis
What hormone determines the development of the female external genitalia?
Estrogens
What happens to the urogenital folds in the female?
They do not fuse, they form the labia minora
What happens to the genital swellings in the female?
They form the labia majora
What happens to the urogenital groove in females?>
It remains open
From what weeks can you tell the difference between male and female external genitalia?
From week 13 - up until week 12 the penis and the clitoris are similar in size
