development of the reproductive system Flashcards
what are the three primitive germ layers?
ectoderm - develops in skin
mesoderm- (paraxial- vertebrae, intermediate - urogenital structures, lateral)
endoderm- GIT and respiratory tubes
when does gastrulation occur?
day 16
what happens to the intermediate mesoderm?
condenses to form cylindrical structures creating the urogenital ridges.
They then organise into the nephrogenic cord which gives rise to urinary structures and the gonads
where does gonad development begin
in the yolk sac- lined with endoderm cells
how is the yolk sac connected to the embryo
via the vitelline duct
how to endoderm cells in the yolk sac become the primitive sex cords?
differentiate to primitive germ cells.
migrate along vitelline duct to the dorsal mesentery.
In week 6 they go to the genital ridge and settle in the epithelium
send signals to the ridge to self organise into an undifferentiated gonad of which the epithelium layer forms the primitive sex cords.
at what week does gonal differentiation occur
week 7
how do male gonads differentiate?
SRY region of the Y chromosome codes for testes determining factor
up regulating SOX9 which initiates testes development.
what happens to the primitive sex cords in males?
they become the medullary cords which carry germ cells into the mesoderm.
The medullary cord become 3 ductal structures: seminiferous tubules, straight tubules and the rete testes.
primordial germ cells into the seminiferous tubules and mature to become spermatogonia which then become sperm during puberty.
at what week do the cells in the walls of the seminiferous tubules become sertoli cells?
week 8
what do sertoli cells secrete
mullerian inhibiting factor
what do leydig cells secrete
testosterone
how do female gonads differentiate?
no SRY gene so no testes determining factor
WNT4 gene develops undifferentiated gonads into ovaries
what happens to the primitive sex cords in females?
they degenerate
the surface epithelium becomes cortical cords which form nests of follicular cells surrounding each primordial germ cell.
this is called a primordial follicle which becomes a primary then secondary oocyte.
from which embryological structure do the genital ducts originate from
nephrogenic duct
which embryological duct forms the male genital duct
mesonephric
which embryological duct forms the female genital duct
paramesonephric (mullerien)
how do the male genital ducts develop
mullerian inhibiting factor secreted from the sertoli cells degenerate the paramesonephric duct into the appendix testes
the mesonephric duct grows under the influence of testosterone forming: efferent ductules epididymus vas deferens seminal gland ejaculatory duct
what is the appendix testes
the degenerated paramesonephric duct
how do the female genital ducts develop
there is no testosterone so the mesonephric duct degenerates
no mullein inhibiting factor so the paramesonephric duct persists to form: fallopian tubes uterus cervix 1/3 vagina
what are the two sets of folds that form the undifferentiated external genetalia
urethral folds and labioscrotal swellings
there is also the genital tubercle which forms the primordial phallus
how does the male external genetalia develop
there are high levels of testosterone due to leydig cells
5-alpha-reductase converts testosterone to dihydrotestosterone (more potent) which masculinises the genetalia
urethral folds fuse along the midline to form the penile urethra
the primordial phallus elongates
the labioscrotal swellings fuse to form the scrotum
how does the female external genetalia develop
no testosterone so the urethral folds stay unfused forming the labia minora
the labioscrotal swellings fuse anteriorly to form the mons pubis and the labia majora
the primordial phallus shrinks to form the clitoris
what what week are the external genetalia done differentiating
week 12
what does the gubernaculum anchor
the testes to the scrotum
where do the testes originally develop
near the anterior abdominal wall
what does the gubernaculum do
it shortens to pull the testes down towards the scrotum forming the inguinal canal (where the processes vaginalis herniates through the abdominal wall
what are the contents of the spermatic cord
3 arteries 3 nerves 3 other
testicular artery, vas deferens artery and cremaster artery(+vein)
genital branch of the genitofemoral nerve, creasteric nerve and sympathetic nerve fibres
vas deferens
pampiniform plexus
lymph vessels
what are the layers of the scrotum
Some- skin Damn- dartos fascia Englishman- external spermatic fascia Called- cremaster muscle It- internal spermatic fascia The- tunica vaginalis Testes- tunica albuginea
External spermatic fascia was originally the external clique aponeurosis
Cremaster was the internal oblique
Internal was the transversalis fascia
what does the gubernaculum join in females
the inferior ovary to the labia majora
what does the gubernaculum do in females
it shortens and the middle joins to the uterus forming two ligaments- the ovarian ligament and the round ligament
what is cryptorchidism
undescended testes
can be anywhere along the path of descent: abdominal, inguinal, prescrotal
what are the complications of undescended testes
TESTIS
T-trauma E-epididymo-orchitis S-sterility T-torsion I-intestinal hernia S- seminoma
what is hypospadias
congenital disorder of the urethra
the urinary opening is not at the head of the penis
failure of the urethral folds to close
what other abnormalities is hypospadias associated with
undescended testicle, cleft lip/palate, congenital heart disease, inguinal hernia
what is the venous drainage of the testes
the pampiniform plexus become a single vein as it ascends through the inguinal canal
right testicular vein drains into the IVC
the left testicular vein drains to the left renal vein
what is varicocele
dilation of the pampiniform plexus
why is varicocele seen more commonly on the left side
- the left testicular vein is longer
- it enters at a right angle to the renal vein
- the left testicular artery arches over it
- a loaded sigmoid colon can compress it
what is testicular torsion
when the testicle rotates, twisting the spermatic cord thus stopping blood flow to the testicle
what are the attachments of the inguinal ligament?
the anterior superior iliac spine (ASIS) and the pubic tubercle
what are the boundaries of the inguinal canal
anterior- aponeurosis of the external oblique
posterior- transversals fascia
roof- internal oblique and transverse abdomenus
floor- inguinal ligament
what are the openings of the inguinal canal
the deep ring: found above the midpoint of the inguinal ligament (created by transversals fascia)
the superficial ring: just superior to the pubic tubercle (created by evagination of the external oblique)
what are the contents of the inguinal canal
spermatic cord (males) round ligament (females) ilioinguina nerve (only passes through superficial ring not through the deep) genital branch of the genitofemoral nerve
what is an indirect hernia
where the peritoneal sac enters the inguinal canal through the deep ring
(hernia will be lateral to the epigastric vessels)
what is a direct hernia
where the peritoneal sac enters the inguinal canal through the posterior wall
(hernia will be medial to epigastric vessels)
what is a bicornate uterus
a ‘heart shaped uterus’
failure of the fusion of the user parts of the paramesonephric ducts
has a risk of recurrent miscarriage
