4: Embryology of the reproductive system Flashcards
Which germ layer is most involved in the renal and urogenital systems?
Mesoderm
In the very initial stages of development, which two germ layers exist?
Epiblast
Hypoblast
Which structure do mesoderm cells migrate through to form the middle germ layer?
Primitive streak
After the mesoderm forms, what three sections does it split into?
Paraxial (medial)
Intermediate
Lateral
mesoderm
After migrating through the primitive streak, the mesoderm forms paraxial, intermediate and lateral sections.
What are the two subdivisions of the lateral mesoderm?
Visceral
Parietal
The urogenital system develops from the ___ mesoderm.
(paraxial, intermediate, lateral, visceral, parietal)
intermediate mesoderm
just remember this
Which type of mesoderm does the urogenital system develop from?
Intermediate mesoderm
Early in development, which common cavity do both the renal and genital systems have?
Cloaca
From cranial to ventral, what are the parts of the early renal tract called?
Pronephros
Mesonephros
Metanephros
finishing at the cloaca
What does the term indifferent gonad mean?
You can’t tell if the embryo is male or female
Which type of cell differentiates into the male and female gametes?
Primordial germ cell
‘gamete mother cell’
In weeks 4 - 6 of development, the primordial germ cells migrate from the ___ ___ to the ___ ___.
yolk sac
to the sex cords
through the dorsal mesentery
Which two ducts are formed by the embryo in Weeks 4 - 6?
Mesonephric (Wollfian) duct
Paramesonephric (Mullerian) duct
What is the other name for the mesonephric duct?
Wollfian duct
What is the other name for the paramesonephric duct?
Mullerian duct
Which ducts develop into the reproductive tract in
a) males
b) females?
a) Mesonephric duct
b) Paramesonephric duct
In terms of sex chromosomes, what determines if an embryo will be male or female?
Male - presence of sex-determining region of Y chromosome
Female - absence of sex-determining region of Y chromosome
What are the two germ cells found in males?
What do they do?
Sertoli cells - sperm support cells; during development they secrete Anti-Mullerian hormone (AMH)
Leydig cells - testosterone-producing cells
What type of male germ cell secretes Anti-Mullerian hormone (AMH)?
Sertoli cells
What is the function of AMH?
Causes degeneration of Mullerian tract (paramesonephric duct) in males
Which structure connects the mesonephric ducts to the sex cord in males?
What is the sex cord called?
Rete testis
Testis cord
What hormone do Leydig cells produce?
Testosterone
What is the function of testosterone during development?
Stimulates development of the male reproductive tract
What is the path of sperm from the testes to the penis?
Seminiferous tubules
Epididymis
Rete testis
Vas deferens
Spermatic –> Ejaculatory ducts
Prostatic –> Spongy urethra
Which specific type of testosterone stimulates the development of the male’s external genitalia?
Dihydrotestosterone
In which condition does a male present with male external genitalia, but both male and female reproductive tracts?
Persistent Mullerian Duct syndrome
Mutations in the genes for which hormone causes persistent Mullerian duct syndrome?
AMH
Anti-Mullerian hormone
Which hormones trigger the development of the
a) male external genitalia
b) epididymis, vas deferens and seminal vesicles?
a) Dihydrotestosterone
b) Testosterone
Where do the testes originate during development?
Posterior abdominal wall, 10th thoracic level
Which developmental structure pulls the testes inferiorly during development?
Gubernaculum
Which layers must the testes pass through on their way to the scrotum?
Parietal peritoneum
Transversalis fascia
Transversus abdominis
Internal oblique
External oblique
Superficial fascia
What are the three layers of the spermatic cord and which abdominal layers are they derived from?
Internal spermatic fascia: from transversalis (deep) fascia
Cremasteric fascia: from internal oblique
External spermatic fascia: from superficial fascia
Which structures do the testes pass through to reach the scrotum?
Deep and superficial inguinal rings
What condition is caused by failure of one or both testes to descend?
Cryptorchidism
Which three accessory glands develop in the male?
Prostate gland
Bulbourethral gland
Seminal vesicle
In which circumstances does an indifferent embryo develop a female genital tract?
Absence of Y chromosome
Which female germ cells
a) support the follicles and convert androgens to oestrogen
b) convert pregnenolone to androgens?
a) Granulosa cells
b) Theca cells
Which hormone triggers the development of the female external genitalia and paramesonephric ducts?
Oestrogen
Oestrogen triggers the development of which duct in the female?
Paramesonephric (Mullerian) duct
Which aspects of the internal female genitalia develop from the paramesonephric ducts?
Uterine tubes
Uterus
Superior vagina
Ovaries descend from posterior abdominal wall in a similar manner to the testes
The paramesonephric ducts ___ to form the uterus and superior vagina.
fuse
What is hypospadias?
Abnormal position of external urethral orifice
Which germ layer is the external genitalia of the female formed from?
Endoderm
