Sexual Differentiation: How to make a boy or girl Flashcards
Where do primordial germ cells originate?
Arise from epiblast week 2
-PGCs are pluripotent
Differentiation of PGCs
- MIgrate to yolk sac to prevent becoming imprinted
2, Later returns next to genital ridge (next to kidneys) and become the indifferent gonad
XX replicate at cortex
XY replicate at medulla
Gender decisions is dependant on genetic switches and hormones
Genetic switches
-all
General transcription factors
-Wt1, Sf1
Specific promoters of testis development
-Sry, Sox9
Specific promoters of ovarian development
-Wnt-4, FoxL2
Specific promoters of testis development
Sry
Sox9
Specific promoters of ovarian development
Wnt-4
FoxL2
Supporting precursor cells
Urogenital ridge>Bipotential gonad
Supporting cell precusors develop into
- Follicular cells in ovaries
- Seroli cells in testis
Primordial germ cells develop into?
Oocytes in ovaries
Pro-spermatogonia in testis
Steroidogenic precursors develop into?
Develop into internal theca cells in ovaries
Leydig cells in testis
Outline the differentiation of the
- Female PGCs
- Sex cord cells
- Cortex
Female PGCs => oogonia (primary oocytes)
Sex cord cells => granulosa (support and nutrifying the ovum)
Cortex => layer of thecal cells => secrete androgens before those generated by the follicles
Sry
Specific genetic promoter of testis development
Influences definition and identity of Sertoli cells
Stimulates AMH secretion
AMH
Anti-mullerian hormone
Produced from sertoli cells under Sry gene stimulation
- Suppresses female development pathway
- Induces Leydig differentiation (from intermediate mesoderm)
Where do the kidneys originate?
intermediate mesoderm (as the reproductive organs)
between somites and lateral plate (each side of the aorta)
Outline the 3 stages of development of the kidneys
- Pronephros - disappears soon after
- Mesonephros - leaves remnants and ducts that become integral to development of reproductive organs
- Metanephros - becomes kidney
When do internal genital organs begin differentiation?
Week 8
Female pseudohermaphrodite
- description
- cause
46 XX female with virilization
internally they are female, with male external genitals
Features: enlarged clit, fusion of labia
possibly due to exposure of male hormone prior to birth e.g in congenital virilizing adrenal hyperplasia
True hermaphrodite
Both ovaries and testis (fused)
Male pseudohermaphrodite
- description
- cause
- features
46 XY male with undervirilization
external genitalia- ambiguous or female
testis can be underdeveloped, normal or absent
Cause- defective androgen synthesis
defective androgen action (e.g receptor dysfunction)
features- no breast development, primary amenorrhea, blind ending vagina
Male pseudohermaphrodite
-types of conditions
- Androgen insensitivity syndrome
- leydig cells HYpoplasia (body insensitive to LH)
Gonadal dysfunction
-XY gonadal dysgenesis, a.k.a. Swyer’s Syndrome
Associated with XY karyotype
Cause: alteration to Sry gene
External appearance: female (no menstruation)
No functional gonads (no testicular differentiation)
Gonad may develop into malignancy
Tract abnormalities
-examples
uterine (unicornuate uterus)
Vagina agenesis
Ductus Deferens: unilateral or bilateral absence, failure of mesonephric duct to differentiate
What duct develops into female internal genital organs?
Paramesonephric duct
What duct develops into male internal genital organs?
Mesonephric duct
Gonadal descent
undescended ovaries in females
-detected in fertility assessments
cryptorchidism- hidden tests (common in premature babies 30%)
What is male hypospadia?
external genitalia problem where there is failure of urogenital folds to fuse
leads to proximal displaced urethral meatus
What structure is produced by the fusion of the urethral folds in the male?
The spongy urethra
What structure forms in the female when the urethral folds remain open?
labia minora
What structure forms in female when labioscrotal swellings remain open?
labia majora
When does differentiation of gonads occur?
Week 5
When does differentiation of internal and external genital organs occur?
after week 5
Where are ovaries derived from?
XX PGCs replicate at cortex
Where are testes derived from?
XY PGCs replicate at medulla
