Genital Embryology: Wilson: Video Flashcards
When do renal and genital systems deviate in development?
At the urogenital ridge: middle part is gonads
What has to move into the gonad to make sperm and ova?
Primordial germ cells: become gametes
Where do the primordial germ cells that eventually become gametes come from originally?
Yolk sac (extraembryonic mesoderm)
What cells do not come from the three classic germ layers that form at gastrulation?
Priordial germ cells from yolk sac
Where do primordial germ cells land when they come in from the yolk sac?
Line the posterior allantois
When do primordial germ cells leave the yolk sac?
4th or 5th week
What is the only cell to undergo meiosis?
Gametes from primordial germ cells
When are primordial germ cells fully populated in the gonad?
6th week
What happens to the MALE primordial germ cells when they reach the gonad?
They go dormant. No meiosis at all until PUBERTY… 12 whole years of napping until endocrine system wakes it up.
What happens to the FEMALE primordial germ cells when they reach the gonad?
They immediately go into MEIOSIS 1 to become gametes.
How are gonads classified in the 4th-7th week?
Indifferent gonad… indistinguishable between sexes
What 3 things are in an indifferent gonad?
- Primordial germ cells from yolk sac
- Sex cords of connective tissue
male: seminiferous tubules
female: primordial follicles - Two Duct Systems:
male: Mesonephric/woffian–>genitals
females: Paramesonephric/mullerian–>genitals
What does the woffian duct become?
Male genitals: epidydimus, vas deferens, seminiferous tubules
What does the mullerian duct become?
Female genitals
What is another name for the woffian duct?
Mesonephric duct (male)
What is another name for the mulerian duct?
Paramesonephric duct (female)
What do the vas deferens, seminal vesicles, ejaculatory duct come from?
Woffian duct (Mesonephric)
What do the oviduct, uterus, upper vagina come from?
Mullerian duct (Paramesonephric)
Why is it harder to make a testes than an ovary?
Testes need 4 events:
- Testes determining factor (TDF) from SRY of Y chromosome
- Testosterone from Leydig cells/LH
- Mullerian Inhibiting Factor from Sertoli cells
- DHT from external genitalia from 5 a redutase
Sumary testes development?
- TDF from SRY of Y crx
- T from Leydig
- MIF from sertoli
- DHT from external 5 a reductase
When does the testes develop?
8th week
Do you have more male or female genitalia errors?
Male… more complicated
Low DHT causes what?
Microgenitalia: no external penis/scrotum growth
Due to low 5a reductase
What if you have low MIF?
Male with female vagina +/- uterus
How do ovaries develop?
No Y crx, no TDF
- breakdown of woofian/mesonephric
- breakdown of cords
- primordial follicle growth
What do female gonads have instead of seminiferous tubules?
Primordial follicles
What is the male remnant of the mullein duct?
Blind sac utricus prostaticus on backside of prostate
What drives female external development?
Estrogens
What is the upper vagina derived from?
Mullerian paramesoderm
What does the lower vagina derive from?
Urogenital sinus
What two derivations form the vagina?
UG sinus: lower (endoderm)
Mullerian: upper (mesoderm)
What is the remnant of the woofian/mesonephric duct?
Epoopheron
Paraoopheron
In the broad ligament (can get infected)
Garner’s cyst: in vaginal wall
What is a garner’s cyst?
Woofian/mesonephric reminanat in vaginal wall that makes a cyst
What is the most common mullerian/paramesonephric error?
Bicornate uterus
What are the three components of the indifferent stage of external genitalia?
- Genital tubercal
- Urethral groove
- Genital swelling
What forms the scrotum?
Genital swelling movement from lateral to fuse in middle
What forms the glans and most of the shaft of the penis?
The genital tubercle
What forms the ventral shaft of the penis?
Fusion of genital folds
Summary of male external genitalia development?
Shaft/Glans=tubercal
Ventral shaft=folds
scrotum=swelling
Summary of female genitalia?
Clitoris=tubercle
Labia minora=folds
Labia majora=swelling
What is the most common male genital defect?
Hypospadias
Failure of genital folds to close
What is another failing of fusion that is more concerning in the male?
Epispadias: Can have extrosphy of bladder
What time do testes and ovary descend?
Third trimester
Where does testes travel?
Through and out inguinal canal
What goes in front of testes as it travels?
Gubernaculum Processus vaginalis (parietal peritoneum)
What is the GPS system of the testes?
Gubernaculum
When is peritoneum open to scrotum, when does it close?
7th: open through processes vaginalis
8th and 9th: closes
What is the piece of peritoneum retained in testes in scrotum?
Tunica vaginalis
What is the difference between tunica vaginalis and processes vaginalis?
Tunica: post descent
Processus: Pre descent
What is the function of the tunica vaginalis?
Prevent friction
EXAM: What happens if processes vaginalis stays patent?
Indirect hernia into scrotum
EXAM: What happens if fluid collects in scrotum?
Adult: hydrocele.
Fluid filled: transmits light.
Vein fluid (vericocoel) will not transmit light
What is the most common cause of female intersexuality?
Congenital adrenal hyperplasia (21 and 11) causes excess androgens to be formed that masculinize external genitalia
What are the most common causes of male intersexuality?
MIF deficiency
5 a reductase deficiency
Microgenitalia/low DHT
What is a male that looks fully female on the outside?
Androgen insensitivity syndrome/Testicular feminization syndrome
Testes in labia majora
No receptors to respond to normal androgen levels
