Reproductive System (embryology) Flashcards
What do Leydig cells secrete?
Testosterone
What doe Sertoli cells secrete?
Mullerian inhibiting hormone (MIH)
Female genitalia develop by __________, meaning in the absence of ________ and _________
- Default
- Testosterone
- MIH
Male genitalia development
- XY chromo has SRY gene –> leydig and sertoli cells
- Leydigs secrete T and Sertoli secretes MIH
- T causes differentiation of mesonephric ducts into male ducts
- MIH causes regression of Mullerian duct
Female genitalia development
- XX chromo
- Mesonephric duct fail to develop (no T)
- Mullerian ducts differentiate into female ducts (no MIH)
Differentiation of indifferent gonad into testis
With Y influence:
1. Medullary cords develop
2. No cortical cords
3. Thick tunica albuginea
Differentiation of indifferent gonad into ovary
Absence of Y:
1. Medullary cords degenerate
2. Cortical cords develop
3. No tunica albuginea
What does the differentiation of mesonephric ducts and external male genitalia depend on?
Depends on T and DHT (5a reductase converts T into DHT), respectively
Where do gonads develop from?
Genital ridge, thickened intermediate mesoderm
What cells do gonads contain?
Germ cells and supporting cells
Primordial germ cells
Arise from yolk sac and migrate along the gut wall into the genital ridge
Proliferate and get into the sex cords (medullary in males, cortical in females)
Medullary cords in males
Differentiate into seminiferous cords with:
1. Primordial germ cells –> spermatogonia
2. Supporting cells–> sertoli (MIH)
Cortical cords in females
Contain primary oocytes surrounded by follicular cells
primordials differentiate into oogonia and have entered meiosis 1
What do mesonephric tubules turn into in males?
Efferent ductules
What do mesonephric ducts turn into in males?
Epididymus, ductus deferens, ampulla, ejaculatory duct, seminal vesicle
What does the urogenital sinus develop into in males?
Urethra –> bulbourethral glands and prostate
___________ is the remnant of the cranial end of the mesonephric duct in males
Appendix epididymus
What does the paramesonephric duct turn into in females?
Uterus, cervix, cranial 1/3 of the vagina
The remaining vagina and vestibule develop from ___________
urogenital system
What are remnants of the mesonephric tubules of females?
Epoophoron and Paroophoron
Gartner’s cyst
Remnant of the mesonephric duct
Found in vestibule or vagina
Prone to become a cyst
Where does the male external genitalia develop from?
Three swellings:
Genital tubercle –> penis
Bilateral urethral folds –> penile urethra
Bilateral scrotal swelling (genital) –> scrotum
Finasteride/ DHT blocker
Used to treat hair loss, prostate hypertrophy and contraindicated in pregnant women
Where does the female external genitalia develop from?
Genital tubercle –> clitoris
Bilateral urethral folds –> labia of vulva
Urethral groove –> opens and forms vestibule
Bilateral scrotal swelling (genital) –> degenerate
Hermaphrodite
Genital organs of both sexes present
True hermaphrodite rare (with both male and female gonads)
Pseudo-hermaphrodite
Most common form (esp. in dogs)
Have gonads of one sex and genital organs with some characteristics of both sexes
Male: testes with some female genitalia
Female: Ovary with some male genitalia
Klinefelter Syndrome (XXX, 47 chromos)
In cats (tricolor cat), dogs, boars, bulls
Testis atrophy, spermatogenesis inhibited, T present @ low concentration
Cryptorchidism
Intra-abdominal or inguinal retention of one of both testes (inherited condition)
Freemartin disease
Females born as twin to males and transfer T and MIH from males to females
External and internal genitalia in free martin
Female-like (vagina is under developed)
Some development of epididymus, ductus deferens and seminal vesicle
Some underdevelopment of the uterus and vagina
Hypospadias and Epispadias
Abnormal fusion of the urethral folds on the ventral side of the penis
… dorsal side
Androgen insensitivity syndrome (46, XY)- Testicular feminization, male pseudo-hermaphrodite
Testes present and produce androgens but androgen receptors lacking
External genitalia fail to masculinize and develop as short blind vagina
Male ducts underdeveloped and female ducts absent
Congenital Adrenal Hyperplasia (Female pseudo-hermaphrodite)- 46, XX
Absence of adrenal cortical hormone gene –> overproduction of adrenal androgens
External gen: male like
Internal gen: Female ducts fully develop, male ducts partially developed
