Development Of The Reproductive System Flashcards
Week 5 Indifferent Gonads
Primordial germ cells in epiblast migrate to yolk sac wall, after gastrulation and body folding
——> up the dorsal mesentery to the genital ridge
What enters and surrounds the primordial cells in the genital ridge
F : Follicle cels
M : Sertoli Cells
What duct runs in the mesoderm to join the urogenital sinus
The Mesonephric Duct
Kidneys and Gonads form form
Intermediate mesoderm
Both Mesonephric duct and paramesonephric duct
Mesonephric Duct (wolffian duct)
Part of kidney development
- Epididymis
- Vas Deferens
- Seminal Vesicle
- Ejaculatory Duct
Paramesonephric Duct (Müllerian duct)
Travels dorsal to open into ABD cavity
- Oviduct
- Uterus
- Upper vagina
Presence of SRY gene
Sex determining gene (also called TDF)
= male (Ychr)
Active on day 41-52
1. Express somatic support cells (pre-Sertoli cells)
2. Sertoli cells surround the primordial germ cells = seminiferous tubules
3. Intertubular cells (in mesoderm) differentiate into Leydig cells
Absence of SRY gene
Female development
What do the primordial cells become
Spermatogonia just before birth
How does the SRY gene transcribe ——> male features
SRY gene on Y chr ——> Sox9 protein in the Sertoli cells
——> transcribes AMH (anti-Müllerian H.)
= regression of mullerian paramesonephric duct
Degenerate paramesonephric duct remnants
Utricle, appendix, epididymis
Leydig cells in the mesoderm do what
Start releasing TESTOSTERONE form hGC signals from placenta
= activates the synthesis of Mesonephric ducts
What do Sertoli cells release
2 Hs.
- AMH = degeneration do paramesonephric duct
2. Androgen binding factor = spermatogonia ——> Spermatozoa (puberty)
What 2 things do fetal Leydig cells release
Week 8-12
- Testosterone (driven by hCG) =Mesonephric duct ——> vas defernes, epididymis, seminal vesicle
- 5 a-reductase : Testosterone——> Dihydrotestosterone
What does dihydroestosterone do
- Genital tubercle —> PENIS
- Genital swellings —> SCROTUM
- Urethral epithelium —> PROSTATE
* drives the lengthening of genital tubercle + fusion of labioscrotal swellings to for scrotum
What do adult Leydig cells release
Androgens
- Initiation of spermatogenesis
- Brain Masculation
- Male sexual behavior
Vas deference has what on it and connects to what
Derived from
Has seminal vesicle on it
Runs into the prostate gland (from endoderm of UG sinus)
Derived from Mesonephric duct (intermediate mesoderm)
*Ns from ectoderm
When does the cloaca disappear from the urogenital sinus and rectum holes
When urorectal septum runs down to separate them
Endoderm tissue becomes
Prostate tissue
The glandular epithelial part of the male genital and the bulbourethral gland come from
Endoderm
Developing penis
Some remanent of cloaca on tip ——>
Under Side has some endoderm ——>
Roof top part ——>
Glans plate (endoderm) Urogenital plate (endoderm lines plate) - week early 7 Genital tubercle (covered by ectoderm)
Urogenital plate late week 7
Becomes urogenital groove in the middle that becomes the urethra
When is urethral closed
Week 14
Hypospadias
Most common birth defect of male
The urethra does not close all the way
Epispadias
The urethra forms above the genital tubercle and so forms a open canal on top of the penis
Can also cause bladder to be unclosed and stuck out from ABD wall
WNT-4 gene
PRO FEMALE gene ——> FOXL2 ——I Sox9
= suppress Sertoli and Leydig cells
= maintain female gonads
Primordial cells of the female go where
To the genital ridge and ——> OOGONIA that proliferate ——> OOCYTES
Support cells of the female
Somatic cells ——> follicle cells around the oocytes
They ——I meiosis 1 in oocytes
(No Sertoli = no AMH = paramesonephric duct stays)
(No Leydig cells = no testosterone = no Mesonephric duct)
What do females continually transcribe throughout life
FOXL2 to ———I Sox9
=NO SERTOLI
= YES FOLLICLE
When does the uterus fuse
Week 9-10
How is the uterus developed
The paramesonephric ducts on each side fuse which forms the uterus and on top (dorsally) are the 2 uterine tubes unfused
Didelphys
Double uterus The uterus (paramesonephric ducts) don’t fuse right or all the way
Vagina forms from what
The lengthening of the solid sinuvaginal bulb (endoderm)
Eventually becoming a canal
Vaginal agenesis
Failed sinovaginal bulb or canalizations of it
Where is the sinovaginal bulb
Right under the uterus
The phallic segment (developing female genital) becomes three parts
(Under the genital tubercle, endoderm)
(Remnants of cloaca on tip)
(Top part, ectoderm)
- urogenital plate
- Glans Plate
- Genital Tubercle
Reason there is no fusion of the labiosacral swellings that are lateral to the urogenital plate and groove
No testosterone = no dihydrotestosterone = no lengthening of genital tubercle + no fusion of the labialscrotum swellings
What do the urogenital folds that fuse become
The labial minora
The unfused labioscrotal swellings become
The labial majora
Gentian tubercle forms the
Glands clitoris
Outside of the paramesonephric ducts that have fused
Forms a mesentery that is of peritoneum so lower urogenital ridge is in the pelvic cavity
When the uterus and oviduct are completes formation the remaining tissue does what
What is the function of this
Thins and forms the double fold peritoneum = Mesentery
= supports broad lig, mesovarian, and mesosalphinx
Superior gubernaculum forms
Round ligament of Ovarian lig
From ovary to uterus
Inferior gubernaclum forms
The round ligament of the uterus
Connects uterus to labia majora
stromal cells of males and females
Males = Leydig cells Female = thecal cells
DSD Disorders of Sex Development
Genotype sex is masked by the phenotype of the person , which resembles opposite sex (anatomical differences happen)
46 XY male DSD
Testis with female phenotype
X TESTOSTERONE
(NO 17 B-hydroxysteroid dehydrogenase-3 = no testosterone)
X Androgen sensitive (testosterone is made only can’t be seen)
X 5 a reductase = no dihydrotestosterone
Mutated AMH or AMHR
Androgen Insensitivity Syndrome
MaleDSD
X Androgen Receptors
X-linked recessive
YES : testis, high testosterone, short vagina, AMH
NO : spermaptogenesis, uterus, uterine tubes
Puberty = testosterone—> estradiol —> female secondary features (breast, wide hips)+amenorrhea
* increase risk of gonadal tumor
X 5 a-reductase
Male DSD
46 XY
YES : normal testis, normal duct system, AMH, testosterone
NO : external male genitalia
Can have some external female features
*no lengthening of penis, fusion of scrotum
Female DSD
Features and most common cause
46XX
YES : ovaries, excess androgens
NO :
Masculine external genitalia, can have labial fusion
* MOST COMMON CAUSE = congenital adrenal hyperplasia (X21-hydroxylase)
Week what : Indifferent embryo
Week 1-6
Week what : sexual differentiation begins
Week 7
Week what : female and male genitalia can be recognized
Week 12
Week what : Phenotypic differentiation is complete
Week 20
