Development of the Reproductive System (Brauer) Flashcards
What are primordial germ cells
Cells of the epiblast that are initially localized w/in the walls of the yolk sac but migrate up the dorsal mesentery into the genital ridge of the intermediate mesoderm. They develop into oogonia and spermatogonia.
How are somatic support cells formed
Primordial germ cells stimulate cells from the coelomic epithelium of the genital ridge to proliferate and delaminate into Somatic support cells
What do somatic support cells develop into in males & females
Males - Sertoli cells
Females - Follicle cells
What are the two sets of reproductive ducts that form within the intermediate mesoderm
Mesonephric ducts (Wolffian) & Paramesonephric ducts (Mullerian)
What structures are derived from the mesonephric duct
Epididymis
Vas Deferens
Seminal Vesicle
Ejaculatory duct
Mesonephric duct is lost in females so only male structures formed
What structures are derived from the Parameonephric duct
Oviduct
Uterus
Upper Vagina
Parameonephric duct is lost in males so only female structures formed
What is the role of SRY in sex determination
It is the testis-determining factor gene which is located on the Y chromosome. In it’s absence, development is female.
What is the effects of SRY in males
- Turns on SOX9 expression in somatic support cells which triggers them to differentiate into Sertoli cells
- Suppresses Wnt4 (pro-female gene)
What is the effects of the abscent of SRY in females
Since the SRY gene is abscent, somatic support cells express Wnt4 and FOXL2 (supresses SOX-9)
What do a subset of intertubular cells differentiate into in males
Leydig cells (recruited by Sertoli cells)
What is the role of Sertoli cells in male development
They express Anti-Mullerian hormone (AMH) which causes the paramesonephric duct to degenerate
What are the remnants of the paramesonephric duct
Appendix testis & proststic utricle
What do Fetal Leydig cells do
They produce testosterone which triggers the mesonphric tubules and ducts to form:
- Effernet ductules
- Epididymis
- Vas deferens
- Seminal vesicles
How are external male genitalia developed
(penis, scrotum, prostate & testicular descent)
Testosterone is converted to dihyrotestosterone (DHT) by 5-alpha-reductase
What is the role of adult Leydig cells
Produce androgens that initiate and maintain:
Spermatogenesis
Masculinization of the brain
Male sexual behavior
What germ layers are semial vesicles formed from
Intermediate mesoderm of urogenital ridge
Seminal vesicles are buds coming of the mesonephric duct hence deried from intermediate mesoderm
What germ layers are prostate glands from
Endoderm buds of urogenital sinus
What is the urogenital plate
The roof of the phallic portion of the urogenital sinus that is lined by endoderm. It expands along the lower surface of the genital tubercle as the genital tubercle enlarges
What germ layer are the bulourethral glands formed from
Endodermal buds
How is the genital tubercle form?
Ectodermal-covered mesoderm swelling at ventral and cranial end of phallic portion of urogenital plate.
What is the glans plate?
Remnants of cloacal membrane at the ventral end of urogenital place and adjacent genital tubercle
What are the pair of swellings that develop on either side of the urogenital plate through aan expansion of mesoderm underlying the ectoderm
Urogenital folds
Fusing of the urogenital folds with each other forms what structure
Urethra
What promotes lengthening and growth of the genital tubercle to form the penis & fusion of labioscrotal swellings to form the scrotum
dihydrotestosterone (DHT)
What is hypospadias
A common male birth defect that is a result of the failure of the urogenital (urethral) folds to close properly
What is Epispadias
Opening of the urethra on the superior aspect of the penis. Cause is unknown but may be due to improper ventral body closure or formation of too large of a cloacal membrane to be covered when it ruptures
In females, what gene is expressed and promotes the female reproductive system?
WNT-4 & FOXL2
What suppresses SOX-9 in females?
FOXL2
What is the effect of the suppression of SOX-9
No SOX-9 = No Sertoli cells = No AMH = paramesonephric ducts retained
What blocks oocytes in meiosis-1?
Follicle cells
Absence of Leydig cells in females means what?
Mesonephric duct system is lost
Fusion of the inferior paramesonephric ducts form what
Uterus
The unfused superior portion of the paramesonephric ducts form what
Uterine tubes
What is didelphys
Double uterus
How is the vagina formed
Contact of paramesonephric duct to the urogenital sinus stimulates proliferation and formation of sinuvaginal bulb which is eventually canalized
What germ layer is the vagina derived from
Whole thing is endodermally derived with the exception of the upper vaginal fornix which is mesodermally derived.
What is vagina agensesis
Lack of a vagina due to failure of normal sinuvaginal bulb development and/or canalization
What do the urogenital folds and labiosacral folds develop into in females
Urogenital folds - labia minora
Labioscrotal folds - labia majora
What does the phallic segment of the urogenital sinus contain in females
Urogenital plate
Glans plate
Genital tubercle
Same as in males
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 is the term for the congenital condition in which development of chromosomal, gonadal and anatomical sex is atypical
Disorders of sex development (DSDs)
What is it called when an individual has testes but their phenotype appears female
46, XY DSDs
What are some causes of 46, XY DSDs
- Inadequate testosterone synthesis
- Androgen insensitivity syndrome
- 5 alpha-reductase deficiency
- Mutation in AMH or AMH receptor
What are the characteristics of androgen insensitvity syndrome
- Common cause is loss of functional androgen receptors (X linked recessive)
- They have testes but no spermatogensis. Testosterone levels may be high due to a lack of negative feedback.
- At puberty, the testosterone is metabolized to estradiol initiating female secondary sexual characteristics
- Produce AMH so paramesonephric system is supressed = no uterus or uterine tube and the vagina is short and ends blindly.
- Testes usually found in inguinal or labial regions
- Increased risk of tumor formation in gonads
What are the characteristics of 5- alpha-reducatse deficiency
- Autosomal recessive
- Have a 46 XY genotype
- Normal testis and duct system since there is AMH and testosterone
- Underdeveloped male external genitalia due to deficieny in DHT
What are the characteristics of 46 XX DSDs
- Presence of ovaries
- Fetus produces excess androgens
- Maculinzation of the female external genitalia; may even exhibit fusion of labia giving appearance of a scrotum.
- Most common cause is congenital adrenal hyperplasia
How does Congenital adrenal hyperplasia cause of 46 XX DSDs?
Deficiency in 21-hydroxylase leads to excess ACTH production (lack of negative feedback). Excess ACTH causes an excessive production of androgens.
