Development of the Genital System _ PV Flashcards
Timeline of Genital System
- Week 1
- Week 7
- Week 12
- Week 20
Week 1: indifferent embryo
Week 7: sexual differentiation begins
Week 12: Female and male genitalia can be recognized
week 20: phenotypic differentiation complete
What happens in Genital system at week 5?
Indifferent Gonad
primordial germ cells specified within epiblast
- end up in yolk sac wall after gastrulation and body folding
migrate up dorsal mesentery to enter genital
What happens to genital system at week 6?
indifferent gonad
somatic support cells
Male: sertoli cells
Female: follicle cells
Where do the genital ducts form?
intermediate mesoderm of the urogenital ridge
Mesonephric duct
- aka
- what it makes
wolffian duct
- part of early kidney development
- epididymis, vas deferens, seminal vesicle, ejaculatory duct
Paramesonephric duct
- aka
- what it make
Mullerian Duct
- uterine tube, uterus, upper vagina
What is the gene that determines sex?
- what happens when you do not have it>
SRY gene on Y chromosome
w/o SRY- development is female
Describe SRY
- aka
- how long is it active
- where is it expressed
transcription factor
Testis determining factor
active from 41-52 days
expressed in somatic support cells (pre-sertoli)
Pathway of SRY
- paramesenphric duct
Sertoli cells-> SRY-> SOX9-> AMH and ABF-> regression of Mullerian duct bte week 8-10-> remnants are appendix testis and prostatic utricle
Pathway of SRY
- mesonephric duct
Leydig cells-> SRY-> testosterone-> Wolffian duct-> ductus deferens, epipdidymis, vas deferens, seminal vesicles
What are the two things Sertoli cells secrete?
- AMH ( regression of paramesonephric ducts)
2. Androgen binding factor ( spermatogonia-> spermatozoa)
Leydigs Cells
1. Fetal
FATESS
2.adult
- Fetal
a. testosterone
- week 8-12 driven by HCG of placenta
- mesonephric duct-> ductus deferens, epididymis, seminal vesicle
b. 5 a reductase
- testosterone-> DHT
- Genital tubercle-> penis
- genital swelling-> scrotum
- urethral epithelium-> prostate - Adult Leydig cells
- androgens-> initiation of spermatogenesis, masculinzation of brain, male sexual behavior
Parts of External Genetalia
- Urogenital plate
- Glans Plate
- Genital Tubercle
Urogenital Plate
rupture of cloacal membrane opens phallic portion of urogenital sinus to exterior; forming endodermally-lined plate
Glans plate
remnants of cloacal membrane at the ventral end of urogenital plate and adjacent genital tubercle
Genital tubercle
ectodermal-covered mesodermal swelling at ventral and cranial end of phallic portion of urogenital plate
Role of DHT
lengthen genital tubercle and fusion of labioscrotal swellings to form scrotum
Testis descent
- when
- 2 component
week 10
supspensory= gonada; vessels, nerves, lymphatics
gubernaculum- shortens and becomes anchoring ligament of testis of scrotum
Hypospadias
most common birth defect after cyrptochidism
- failure of neural tube folding
- get penile shaft
Episadias
rare
- extrophy of bladder
- ventral body fold defect
Ovary development
- genes
- cell maturation pathway
WNT4-> FOXL2 suppresses SOX 9
primordiall germ cells -> oogonia-> oocytes-> follicle cells surround oocytes
no sertoli or leydig cells
- paramesonephric persist
- mesonephric duct system lost
FOXL2 pathway
FOXL2-> inhibit SRY to AMH-> persistence of Mullerian (paramesonephric) duct-> fallopian tubes, uterus, vagina ( upper portion)
Uterus formation
- when
- describe
week 9-10
- endoderm form sinovaginal bulb
- fusion of inferior paramesonephric ducts form the uterus
- uterine tubes are the unfused superior portion of the paramesonephric ducts
Uterus anomalies
didelphys- term for double uterus
Embryological layer of upper vagina, lower vagina
upper vagina= mesoderm
lower vagina= endoderm
vaginal plate eventually canalized
Vaginal agenesis
failure of normal sinovaginal bulb to development or failed canalization
Female external genitalia development
no testosterone= no DHT=> no lengthening of genital tubercle and no fusion of urogenital folds or labioscrotal swellings
Formation of Broad Ligament
- midline fusion of paramesonephric ducts brings lower urogenital ridge within pelvic cavity and it is covered with peritoneum
- upon completion of uterus and oviduct formation, the remaining tissue thins forming a double fold of peritoneum ( broad ligament) support uterus and ovary
Round Ligament of Ovary and Uterus
Superior gubernaculum= round ligament of ovary ( connects ovary to uterus)
Inferior gubernaculum= round ligament of uterus ( connects uterus to labia majora)
Indifferent gonad
- male
- female
Male: Testis
Female: ovary
Primordial germ cells
- male
- female
male: spermatogonia
female: oocytes
Somatic support cells
- male
- female
male: sertoli cells
female: follicular cells
Stromal cells
- male
- female
male: leydig cells
female: thecal cells
Gubernaculum
- male
- female
Male: gubernaculum testis
Female:
- round ligament of ovary
- round ligament of uterus
Mesonephric tubules
- male
- female
male: efferent ducts
female: epoophoron, paroophoron
Mesonephric duct
- male
- female
Male:
- epididymis
- vas deferens
- seminal vesicle
- ejaculatory duct
female:
gartner duct
Paramesonephric duct
- male
- female
Male:
- testis
- prostatic utricle
Female
- fallopian tube
- uterus
- vagina
Urogenital Sinus
- Male
- Female
Male
- prostatic urethra
- prostatic gland
- BU gland
Female:
- membranous urethra
- paraurethral gland
- greater vestibular gland
Genital tubercle
- male
- female
male:
- glans penis
- corpus cavernousa
- corpus spongiosum
Female:
- glans clitoris
- corpus cavernousa of clit
- bulbospongiosum
Urogenital folds and glans plate
- male
- female
male:
penile urethra
female:
labia minora
labioscrotal fold
- male
- female
male
- scrotum
female
- labia majora
Pseudohermaphroditism
intersex
genotypic sex masked by phenotypic appearance resembling the opposite sec or having opposite reproductive organs
46 XY DSD ( male)
testis but phenotype female
- inadequate testosterone synthesis ( 17 B hydrosteroid DH)
- androgen insensitivity syndrome
- 5a reductase deficiency
- mutation in AMH or AMH receptor
Androgen insensitivity Syndrome
x linked recessive
-testis but no spermatogenesis= testosterone levels may be high
testerone is metabolized to estradiol=> female secondary characteris but amenorrhea
- produce AMH so paramesonephric system is suppressed
5 a reductase deficiency
46 XY
autosome recessive
normal testis and duct system
underdeveloped male external genitalia
- short penis
no effect on mesonephric system and gonadal development
Female DSD
46 XX genotypes
have ovaries
excessive androgens=> fusion of labia, giving appearance of scrotum
Congenital adrenal hyperplasia
- 21 hydroxylase deficiency
Ovotesticular Disorders
true intersexuality
both testicular and ovarian tissue
ambiguos external genital and predominantly female
causes:
- translocation of piece of Y onto X
- subset may have mutation in Y
- anomaly in sex determination and differentiation of primordial germ cells
