Embryology of Sexual Development Flashcards
What does the bipotential gonad arise from?
the genital ridge
What role do the primordial germ cells (PGCs) have in the development of the gonadal ridge?
Wks 4-6: They migrate along hindgut into the genital ridges and exert inductive effect on ovary/testis
epithelial cells penetrate the mesenchyme to form what?
primary sex cords
What 3 hormones induce male internal genitalia development?
testosterone, AMH, Insl3
What embryological structure forms the efferent ducts of the testes?
the Mesonephric tubules
What embryological structure forms the epididymas, ductus deferens, seminal vesicle, and ejaculatory duct?
the Mesonephric (Wolffian) duct
What embryological structure forms the uterine tubes, uterus, and vagina?
the Paramesonephric (Mullerian) duct
What two hormones determine male or female external genitalia development?
testosterone and dihydrotestosterone (DHT)
When does external genitalia differentiate into male/female?
10-12 weeks
what does the genital tubercle give rise to in both sexes?
Male -> glans penis
Female -> glans clitoris
what do the urethral folds give rise to in both sexes?
Male -> penile urethra
Female -> labia minora
what do the labioscrotal swellings give rise to in both sexes?
Male -> scrotum
Female -> labia majora
the SRY gene gives rise to what initial male cell type?
Sertoli cells
What does testosterone induce differentiation of in fetal life?
epididymas, ductus deferens, and seminal vesicle
What is the primary function of the 5-alpha reductase enzyme?
Convert testosterone to DHT
What cell produces AMH?
Sertoli cells
What is the function of DHT in fetal life?
To induce differentiation of penis and scrotum, as well as prostate budding from urethra
What is the relationship between the SRY and Sox9 gene?
SRY upregulates Sox9
What is the primary function of the Sox9 gene?
To suppress ovary development and induce Sertoli cell formation
What components form the medullary sex cords?
Wk 6: Sertoli cells, germ cells, and myoepithelial precursor cells
What do the outer medullary sex cords give rise to?
the seminiferous tubules
In what week does the tunica albunginea form?
Week 7
When do the medullary sex cords re-canalize?
During puberty
What are the main functions of Sertoli cells?
Secrete AMH, organize testis, and act as a critical component of the blood-testis barrier
What induces the degeneration of the paramesonephric ducts?
Anti-Mullerian hormone
What gives rise to the rete testis and efferent ductules?
Portions of the mesonephric tubules
Which two male reproductive glands require DHT to develop?
The prostate and bulbourethral glands
What condition is the result of improper urethral fold fusion?
Hypospadias or Epispadias
What is Hypospadias?
Instead of at the tip, the meatus is found any place along the ventral side of the penis
What is Epispadias? What other malformation is commonly seen in conjuction with Epispadias?
The urethral orifice is found on the dorsal side of the penis; often seen with bladder exstrophy
The CFTR gene is necessary for the development of which duct?
the ductus deferens
What structure do the prostate and bulbourethral glands develop from?
the urethra
What is the role of the gubernaculum in the descent of the testis?
the gubernaculum anchors to the inferior pole of the scrotal swelling, and shortens to pull the testis to the level of the inguinal rings
What hormone is especially important in the gubernaculum’s role in transabdominal testis descent?
Insulin-like factor 3 (Insl3)
Which cell type produces Insl3?
Leydig cells
When does the development of the inguinal canals begin?
About 12 weeks
What role does the vaginal process have in development of the inguinal canals?
The vaginal process acts as a hydraulic force to assist in testis descent
When does the descent of the testis into the scrotum occur
7 months (28-30 weeks)
Which nerve mediates shortening of the gubernalulum during testicular descent into the scrotum? What peptide is involved?
the Genitofemoral nerve, via the calcitonin gene-related peptide (CGRP)
What is Cryptochidism? How is it treated?
the failure of the testis to descend into the scrotum; it can be treated with HGH, IGF1, IGF3
In males, which part of the vaginal process disintigrates? What is the remaining structure called?
the proximal end; the vaginal tunic
If remnants of the vaginal tunic remains, what condition may result?
a fluid-filled cyst called a Hydrocele
What is the different between the two types of Hydrocele?
A non-communication hydrocele has no patent connection with the abdomen
If the proximal end of the vaginal process does not disintegrate, what may result?
an indirect Inguinal hernia
In absence of the SRY gene, support cells differentiate into?
Follicle precursor cells
primary oocytes are arrested in which phase of meiosis?
Prophase I
What happens to the Paramesonephric ducts in the absence of AMH?
Paramesonephric ducts between oviductus and uterus
What happens to the mesonephric duct in the absence of testosterone?
the Mesonephric duct regresses
What are the roles of Dax1 and Wnt4 in gonadal differentiation?
Dax1 and Wnt4 exhibit anti-testis activities
What is the effect of HoxA on the menstrual cycle?
the menstrual cycle will not occur without HoxA
What is the loss of HoxA10 associated with?
endometriosis
What are mutation in HoxA13 associated with?
vaginal duplication
In female anatomy, what two structures represent remnants of the gubernaculum?
the round ligament (of the uterus) and the ovarian ligament
Incomplete fusion of caudal end of paramesonephric ducts results in what?
Didelphys (two uteruses)
A proximal fusion defect in the paramesonephric ducts results in what malformation?
Bicornuate uterus (one cervix, but two uterus with two separate chambers)
Failred regression during paramesonephric duct fusion results in what uterine defect?
A septate uterus
the upper vagina is formed from what embryological structure?
the paramesonephric ducts
From what embryological structure is the lower vagina formed?
the uterovaginal plate
When does the canalization of the uterovaginal plate occur?
11-20 weeks
What are the symptoms of an imperforate hymen?
vaginal obstruction, primary amenorrhea and cyclic abdominal pain
How early does external gonadal differentiation begin to occur in a fetus?
About 12 weeks
Which gene is responsible for testis-determing factor?
SRY gene
What concurrent condition is often found in males with hypospadias?
cryptorchidism
