Lecture 28: Development of Reproductive System Flashcards
When does sexual differentiation begin?
Week 7
When is phenotypic differentiation complete?
Week 20
Primordial germ cells migrate up dorsal mesentery to enter the genital ridge, which is what type of mesoderm?
Intermediate Mesoderm
What do the primordial germ cells become?
Primordial germ cells: undergo meiosis
- spermatozoa
- ova
What do the somatic support cells become?
Support cells: undergo mitosis
- Sertoli cells
- Follicle cells
What two ducts form in the intermediate mesoderm of urogenital ridge?
1) Mesonephric/Wolffian Ducts
2) Paramesonephric/Mullerian Ducts
What does the Mesonephric/Wolffian ducts eventually become?
Male Genital System
- epididymis
- vas deferens
- seminal vesicles
- ejaculatory duct
What does the Paramesonephric/Mullerian ducts eventually become?
Female Genital System
- oviduct
- uterus
- upper vagina
What gene on the Y chromosome determines the sex?
SRY gene
Where is the SRY gene expressed?
Somatic support cells (pre-Sertoli)
-helps organize seminiferous tubules
How do males lose the Paramesonephric/Mullerian ducts?
SRY –> SOX 9 –> Anti-Mullerian hormone
-regression of duct between weeks 8-10
What drives the mesonephric ducts to develop into the male reproductive system?
Testosterone from Leydig cells
What hormones are produced by Sertoli cells, and what do they do?
1) AMH: regression of Paramesonephric/Mullerian duct
2) Androgen binding factor: spermatogonia into spermatozoa
What hormones are produced by fetal Leydig cells, and what do they do?
1) Testosterone: drives the mesonephric ducts to develop into the male reproductive system
2) 5 α-reductase:
- testosterone –> dihydrotestosterone
- genital tubercle –> penis
- genital swellings –> scrotum
- urethral epithelium –> prostate
What hormones are produced by adult Leydig cells, and what do they do?
Androgens:
- initiate spermatogenesis
- male sexual behavior
Where does the seminal vesicle come from?
Buds of mesonephric duct
-intermediate mesoderm
Where does the prostate gland come from?
Endoderm of UG sinus in pelvic urethra
Where does the bulbourethral gland come from?
Endodermal buds
How does the urogenital plate form?
Rupture of cloacal membrane
-endoderm
How does the glans plate form?
Remnants of cloacal membrane at ventral end of urogenital place
-adjacent to genital tubercle
How does the genital tubercle form?
Swelling at ventral and cranial end of phallic portion of urogenital plate
- mesoderm
- ectoderm covered
What drives the folding along the penis and folding/fusion of scrotum?
DHT
What is hypospadias?
Failure of urogenital folds to close around penis or scrotum
What is epispadias?
Exstrophy of bladder
-opening on dorsal side of penis instead of ventral side
In females, what gene is expressed and promotes the female reproductive system?
WNT-4
What suppresses SOX-9 in females?
FOXL2
What blocks oocytes in meiosis-1?
Follicle cells
How does the uterus form?
Fusion of inferior paramesonephric ducts
- do not enter urogenital sinus
- stimulate differentiation of sinuvaginal bulb from urogenital sinus
What is the term for a double uterus?
Didelphys
-failure of inferior part of duct to fuse
How does the vagina form?
Lengthening of sinuvaginal bulb, which is eventually canalized
What is the broad ligament?
Peritoneal fold that attaches the uterus, fallopian tubes, and ovaries to the pelvis
How does the broad ligament form?
Remaining tissue from the uterus and oviduct forms a double fold of peritoneum
What does the round ligament of ovary connect?
Ovary to uterus
What is the embryological origin of the round ligament of ovary?
Superior gubernaculum
What does the round ligament of uterus connect?
Uterus to labia majora
What is the embryological origin of the round ligament of uterus?
Inferior gubernaculum
What causes a 46 XY DSD?
-outwardly female, but has a testes
- Inadequate testosterone synthesis
- Androgen insensitivity syndrome
- 5 α-reductase deficiency
- Mutations in AMH or its receptor
Describe Androgen insensitivity syndrome.
- X linked recessive
- have testes
- no spermatogenesis
- female secondary characteristics
Describe 5 α-reductase DSD.
- Autosomal recessive
- 46 XY
- underdeveloped male external genitalia
Describe congenital adrenal hyperplasia.
Mutations in 21-hydroxylase
- excess androgen production
- masculinization of female external genitalia
