development and sexual differentiation Flashcards
what are the parts to sexual development?
genetic sex - determined at fertilisation
gonadal development
development of sex-specific internal ducts and external genitalia
secondary sexual characteristics
when is sex determined?
fertilisation
when do we develop male or female characteristics?
until week 6 or 7
how do the gonads appear when they’re indifferent?
genital ridges
where are primitive sex cords and how are they formed?
outside the ridges (formed by proliferating epithelium from ridge invades underlying mesenchyme)
what is the cloaca?
unseparated bladder and bottom end of the GI system (hindgut, anus, rectum)
what is the mesonephros?
embryonic kidney. Produces urine during fetal development and produces amniotic fluid.
what is the Wolffian duct?
takes urine produced from the mesonephros to the cloaca
what is the metanephros?
definitive kidney
what are the types of cells in the ridge?
primordial germ cells
what do PGCs form?
future gametes
when and how do PGCs migrate to the genital ridges?
start to migrate to genital ridges via GI system and peritoneum at week 4
what do the mesothelial cells form?
seminiferous tubules - men
ovarian follicles - women
what do the mesenchymal cells form?
supporting cells (connective tissue)
what are the mullerian ducts?
future female ducts
what are the wolffian ducts?
future male ducts
what do the mullerian ducts form?
the uterus, fallopian tuves, cervix and upper 1/3 of the vagina
what do the wolffian ducts form?
the epididymis, vas deferens and seminal vesicles
what do the wolffian and mullerian ducts empty into?
common cloaca
what happens to the genital ducts in XX chromosomes?
Women keep Mullerian and get rid of the Wolffian in XX
what does the Y chromosome do?
ensures you produce testes from the gonadal ridge
ensures you produce Leydig and Sertoli cells
what do Leydig cells produce?
testosterone
can be turned into DHT
what do testosterone and DHT do?
Testosterone maintains the Wolffian duct to join with the epididymis
DHT helps with prostate, penis and scrotum development
what do Sertoli cells produce?
MIF (Mullerian Inhibitory Factor)
what does MIF do?
inhibits the Mullerian duct, causing it to shrink and disappear
what causes XY DSD?
- Testosterone isn’t produced so Wolffian duct isn’t formed or isn’t formed completely
- DHT might also not be made bc its made from testosterone male external genitalia aren’t made so more female genitalia are made
- MIF may still be produced no Mullerian tube No uterus, FP, cervix etc.
how does XY DSD present?
- Patient presents as female with female external genitalia
- Primary amenorrhea
- No genital ducts/associated structures
- Undescended testes as genetically male XY
what is the urogenital sinus?
general outflow
what does the genital swelling of the indifferent gonad become?
external genitalia
what is the gubernaculum?
ligament
describes what happens in weeks 7-8 of male development?
- Mullerian duct degenerates and disappears
- Wolfian duct becomes the vas deferens
- Out-swelling becomes the seminal vesicles
- Gubernaculum – important in the descent of the testes to the scrotum
describe what happens in weeks 7-8 of female development?
- Mullerian duct fuses in the midline to form the uterus, with the uterine tubes being the two ends of the Mullerian duct
- Lower gubernaculum becomes ligaments that attach to the ovary and the labia, helping to support the uterus and ovaries in later life
what happens in the 4th month of female development?
- Ovarian ligament – upper gubernaculum which attaches ovaries to the uterus
- Round ligament - caudal part of the gubernaculum goes down to the labia
- Hymen separates the Mullerian duct from the urogenital sinus
what does the ovarian ligament attach to?
upper gubernaculum which attaches ovaries to the uterus
what does the round ligament attach to?
caudal part of the gubernaculum goes down to the labia
what does the hymen separate/
separates the Mullerian duct from the urogenital sinus
what are the causes of a double uterus or a bicornuate/unicornuate uterus?
o Incomplete fusion of Mullerian ducts inferiorly
o Incomplete development of ducts
o Failure of one of the ducts
at 8 weeks, what structures do fetuses have?
genital tubercle
urogenital fold
labioscrotal fold/swelling
what does the genital tubercle become?
clitoris in females
glans in males
what does the urogenital fold become?
labia majora in females
shaft of the penis in males
what does the labioscrotal fold become?
becomes labia minora in females and forms part of the scrotum in men
what does a fetus become distinctly male or female?
week 12
how do the testes descend?
• Attached via the gubernaculum – shortens and contracts and pulls on the testes into the scrotum
what do the testes bring with them when they descend?
o Brings spermatic cord filled with vas deferens, fascia, cremaster muscle, transversus abdominis, internal and external oblique
what is the tunica vaginalis?
serous fluid filled cavity in front of the testes. Essentially a pinched off part of the peritoneum
what can happen if the testes remain in the abdomen?
sterility bc of the body heat
increases risk of testicular cancer
how do ectopic testes occur?
Occurs when the gubernaculum passes to an abnormal location
how does a persistent processus vaginalis occur?
• If communication between tunica vaginalis and the peritoneal cavity fails to close
what is a persistent processus vaginalis?
- Loop of intestine may herniate through
* Herniation passes through the deep inguinal ring and passes through the inguinal canal
how is the common ejaculatory duct formed?
Ductus deferens joins duct of seminal vesicle to form common ejaculatory duct
where does the common ejaculatory duct go?
penetrates through prostate to connect with urethra at seminal colliculus
where are the seminal vesicles?
Coiled, sacculated swellings between bladder and rectum
how are the seminal vesicles separated from the rectum?
Separated from rectum behind by rectovesical fascia and rectovesical pouch
why are patients not sterile for 3-6 months after a vasectomy?
because sperm in the vesicles can still mature
where is the prostate found?
sits under the bladder and surrounds the urethra
what is the function of the alkaline fluid in ejaculate?
neutralises acid of the vagina
contains anticoagulant to keep seminal fluid liquid
contains glucose to supply the sperm
describe the structure of the prostate
1 median lobe and 2 lateral lobes
what transverses the prostate?
Traversed by urethra and ejaculatory duct
what happens in prostatic hypertrophy?
o Enlarges esp. median lode – disturbs vesicular sphincter action and makes micturition difficult.
what does cancer of the prostate affect?
lateral lobes of the prostate
where are the ovaries found initially and where do they relocate to?
Superior lumbar region - Relocate to the lateral wall of the pelvis
what does the cranial gubernaculum become?
ovarian ligament
what does the caudal gubernaculum become?
round ligament of the uterus
where does the ovarian ligament attach?
ovary to uterus
where does the round ligament of the uterus attach?
Uterus to labium majorum via inguinal canal
where does the pouch of douglas attach?
between the uterus and rectum
why is the vesiculouterine pouch so narrow?
bc the uterus sits on top of the bladder
what are the supports of the uterus and where do they attach?
- Levator ani muscles and the perineal body
- Sacrocervical ligaments - Fibro musc bands cervix to sacrum
- Transverse cervical (cardinal) ligaments - Fibromusc from lat. Pelvic walls to cervix and upper vagina
- Pubocervical Ligaments - 2 firm bands CT from pubis to cervix (either side of bladder
what is the vagina?
Thin muscular tube extending backwards from vulva to uterus
describe the structure of the vagina
• Upper half above pelvic floor, lower perineum
• Upper end of vagina pierced by cervix
o The lumen surrounding cervix divided into fornices
Anterior,
Posterior
2 lateral
describe the relations and supports of the vagina
- Ant – bladder/urethra
- Post – pouch of douglas, ampulla of rectum, perineal body
- Lat – ureters,levator ani, urogenital diaphragm and bulb of vestibule
- Upper –the transverse cervical, pubocervical and sacrocervical ligaments
- Middle- the levator ani and the urogenital diaphragm
- Lower – perineal body
where are the ureters found?
- Pass over the pelvic brim at bifurcation of common iliac arteries in front of the sacroiliac joint
- Run on lateral walls of pelvis
- Opposite ischial spine, curve anteromedially
where do gonadal vessels originate from?
abdominal aorta or renal vessels
where are testicular vessels found?
retroperitoneally around pelvic rim to deep inguinal ring
where are ovarian vessels found?
in suspensory ligament of ovary
