Reproductive Flashcards
What is chromosomal sex?
Chromosomes of correct complement
What is gonadal sex?
Functional testis or ovaries containing germ cells
What is phenotypic sex?
Possessing the correct internal and external anatomical male or female genitalia
What is behavioral sex?
Demonstrating appropriate sexual behaviour patterns
What leads to the male phenotype?
Presence of a functional Y chromosome
What about the Y chromosome makes someone male?
SRY (sex determining region of the Y chromosome)
Is it always the case that chromosomal sex will give rise to correct gonadal sex?
No
What part of mesoderm do the gonads develop from?
Intermediate in region of mesonephros
What do gonads initially develop as?
A gonadal ridge
What differences between sexes are there when the gonadal ridge first develops?
None
Which gene is only switched on in males?
SRY
What does the gonadal ridge mesoderm first differentiate into in males?
Coelomic epithelium (mesoderm) covers ridge and forms somatic support cells which then forms Sertoli cells
Sertoli cells lead to differentiation of a testis (AMF and testosterone due to SRY) with testis tubule and interstitial cell formation.
What does the gonadal ridge mesoderm (coelomic epithelium) first differentiate into in females?
Granulosa cells which surround the oocytes.
What happens to gonadal ridge in 5th week?
Descends into abdomen and reaches it’s final position in 7th week before differentiating
What genes are needed for testis formation?
Sox9 of SRY
Where do the germ cells develop?
In the embryonic epiblast
Where do the primordial germ cells migrate to?
To gonadal ridge via yolk sac and hind gut
Describe how testis develop
Primitive germ cells concentrate in medulla (cortex regresses)
Medullary cords develop and contain spermatogonia and Sertoli cells
Leydig cells make testosterone
Describe how ovaries develop
No SRY - Primitive germ cells (oogonia) concentrate in cortex, medulla degenerates
Cortex form cortical cords through surface epithelium and primitive sex cords degenerate
Cortical cells differentiate as follicular cells and oogonia proliferate before arresting in prophase
What are primitive sex cords?
Structures that develop from the gonadal ridges, in response to germ cells
What happens to sex cords in female?
Germ cells send signals to promote differentiation of epithelial cells in gonadal ridge to granulosa cells
Sex cords dissociate so primitive germ cells are in nests (primordial follicles)
Primitive follicles develop but undergo atresia until puberty
What happens to testis cords (sex cords)?
Composed of primitive germ cells and Sertoli cells
Forming primitive seminiferous tubules connected to rete testis
Leydig cells differentiate between cords (mesenchyme) (week 7)
What do the two ducts originate from?
Paramesonephric (Müllerian) duct
Mesonephric (Wolffian) duct
Which duct is retained in females?
Mullerian
Which duct is retained in males?
Wolffian
What happens to the Mullerian duct in females?
Cranially become fallopian tube
Caudally: draws broad ligament across pelvis
Other structures from Mullerian duct are oviducts, uterus and cervix
What happens to the Wolffian duct in males?
Contacts rete testis
Form the epididymis, vas deferens and seminal vesicles
Where does the prostate develop from?
Urogenital sinus
What hormone is needed to stimulate development of male external genitalia, how is it formed?
5alpha-dihydrotestosterone (DHT) converted from testosterone by the enzyme 5alpha-reductase.
Why is 5alpha-dihydrotestosterone (DHT) used over testosterone?
It is more active
What is the indifferent stage of the tubes at week 7?
2 ductile system:
Wolffian duct
Mullerian duct
Which duct drains to enter the bladder?
Wolffian
Why does the Mullerian duct not drain into the bladder?
It is fused caudally
What hormones in males drive the degredation of Mullerian duct and growth of Wolffian duct?
MIF/AMH (anti-mullerian hormone) and MIS secreted by Sertoli cells - Mullerian duct degenerate
Testosterone from Leydig cells stimulates growth and differentiation of Wolffian ducts (into epipdymis, vas deferens, ejaculatory duct, seminal vesicles)
Why does the Wolffian duct degenerate in females?
No testosterone
Describe arrangement of external genatalia in indifferent stage
Genital gubercle divides into genital/urethral folds flanking urogenital sinus all surrounded by genital swelling
Urethral groove present
When does external genitalia first begin to differentiate and develop?
Week 9
How does masculine genitalia differentiate?
Genital tubercle - phallus -penis
Urethral folds close urogenital sinus
Genital swellings become scrotal swellings
Prostate develops
How does penile urethra form?
Fusion of urethral folds and canalisation of glands at tip of tubercle
Describe how female external genitalia form?
Genital tubercle - clitoris Urethral folds - labia minora Urogenital sinus - remains open Genital swellings - major labora Urethral groove remains open between labia minora
What does the gubernaculum become in females?
From ovary to labora majora, forms round ligament attaching uterus to anterior abdominal wall
What is the cortex and medulla of the genital ridge?
Cortex - edge
Medulla - centre
In males what separates the developing seminiferous tubules from surface epithelium?
Tunica albuginea
In females does anything separate the follicles from germinal epithelium?
No
Where are granulosa cells derived from?
Are derived from mesodermal cells of the gonadal ridge
What are sertoli cells generated from?
Coelomic epithelium forms somatic support cells which then form Sertoli/ follicular cells
What does the endometrium derived from?
Paramesonephric duct
How do XY individuals with androgen insensitivity syndrome develop?
Like a female
