6. Development of the Genital System (Brauer) Flashcards
When is the earliest that ultrasound-based sex determination can occur?
Week 12.
Where do the genital ducts form?
Within the intermediate mesoderm of the urogenital ridge.
What reproductive organs form from the mesonephric duct?
Epididymis.
Vas deferens.
Seminal vesicles.
Ejaculatory duct.
What reproductive organs form from the paramesonephric duct?
Uterine Tube
Uterus
Vagina
What gene drives male phenotype?
SRY
What forms from the somatic support cells in males and females respectively?
Male: Sertoli cells.
Female: follicle cells.
When is SRY/testis determining factor active?
Days 41-52
Where is SRY (TDF) expressed?
In the somatic support cells of the male.
What are the functions of the early Sertoli cells in the development of the testis?
The early Sertoli cells surround the primordial germ cells and organize seminiferus tubule.
The early Sertoli cells also recruit a subset of intratubular cells to differentiate into fetal Leydig cells.
How is the paramesonephric duct inhibited in males?
SRY -> SOX9 -> anti-müllerian hormone.
When does the paramesonephric duct regress in males?
Between weeks 8 and 10
What are the remnants of the paramesonephric duct in males?
Appendix testis.
Prostatic utricle.
Testosterone drives mesonephric ducts to form what structures in males?
Efferent ductules.
Epididymis.
Vas deferens.
Seminal vesicles.
What cell type secretes anti-müllerian hormone?
Sertoli cells.
What two hormones are secreted by Sertoli cells?
Anti-müllerian hormone.
Androgen binding factor (initiates spermatogenesis).
What is the function of 5 α-reductase?
Conversion of testosterone to dihydrotestosterone.
Dihydrotestosterone is responsible for which three structural conversions in males?
Genital tubercle -> penis.
Genital swellings -> scrotum.
Urethral epithelium -> prostate.
From which germ layer are the seminal vesicles and vas deferens derived?
Intermediate mesoderm.
From which germ layer is the prostate gland derived?
Endoderm.
During what week is the prostate gland formed?
Week 10.
From which germ layer are the bulbourethral glands derived?
Endoderm.
At what vertebral level do the male and female gonads first develop?
T10
What pro-female gene is expressed in the absence of SRY?
WNT-4
What is the function of FOXL2?
Suppression of SOX9, and thereby maintaining the female gonad by suppressing Sertoli and Leydig cell differentiation.
What embryological layers form the vagina?
The upper vagina (from the paramesonephric/müllerian duct) comes from mesoderm.
The lower vagina (from the sinuvaginal bulb) comes from endoderm.
What structure results from the superior gubernaculum?
What structure results from the inferior gubernaculum?
The round ligament of the ovary.
The round ligament of the uterus.
Describe androgen insensitivity syndrome.
The patient is a male genetically, and has testes.
Testosterone is metabolized to estradiol at puberty, initiating female secondary characteristics.
The paramesonephric system is suppressed due to the presence of anti-müllerian hormone, therefore the patient has no uterus or uterine tube – but does have a short blind ended vagina.
Describe 5 α-reductase deficiency.
Genetically male with a normal testis and duct system due to normal presentation of anti-müllerian hormone and testosterone.
However the patient has underdeveloped mail external genitalia or possibly even an external female phenotype.
This is due to the inability to convert testosterone -> dihydrotestosterone.
What is the most common cause of female sexual ambiguity?
Congenital adrenal hyperplasia.
Describe ovotesticular disorders.
A patient with an ovotesticular disorder has both testicular and ovarian tissue. This could be due to translocation of a piece of a Y chromosome onto the X chromosome, or an inactivation mutation in some Y chromosomes.
For these patients, the “true facts” of these individuals is the one they can best adapt into society.
What embryological layer gives rise to the somatic support cells of the indifferent gonad?
The somatic layer of the lateral plate mesoderm.
Where do the primordial germ cells originally come from?
The epiblast.
Proliferation of the primordial germ cells causes delamination and formation of somatic support cells from what previous cell type?
Coelomic epithelium.
During what week do the primitive germ cells enter the genital ridge?
6th week.
What is a Gartner’s cyst?
A cyst on the lateral wall of the vagina, which is a remnant of the mesonephric duct.
What is the navicular fossa?
An invagination of the surface ectoderm of the penis which allows the urethra to open into the outside environment.
