Aug27 M2-Male Urogenital System Gonad and Duct embryogenesis Flashcards
early bipotential embryo def
5-6 first weeks where sex determined (XY or XX) but no structural diff
pelvic steps in the cranio-caudal embryonic dev
- urinary system forms (pro, meso and meta nephros). mesonephros is the kidney. metanephros comes later
- cloaca (pelvic viscera precursor) splits to get hindgut (anorectal region) and urogenital sinus
- pelvis develops later
- note: for these to be normal, neural tube dev, lateral folding and gut dev must be normal*
2 regions formed from splitting the cloaca
- bladder region (urogenital sinus)
- anorectal region (anal canal) (endodermal hindgut)
- NOTE: cloaca is endoderm*
cloaca separates what other thing
external bipotential genitalia (so have early bipotential embryo + bipotential external genitalia)
what splits the cloaca
mesenchyme called urorectal septum
extension of the cloaca
allantois in the umbilical cord
cloacal membrane def
membrane surrounding the urogenital sinus (UROGENITAL MEMBRANE) and the anorectal region (ANAL MEMBRANE) (contains them)
cloacal membrane is made of what
bilevel structure
- ectoderm
- endoderm
gut development completion behind the cloaca requires what
recanalization of the thickened endodermal tube by apoptosis all way down to cloaca
consequence of urorectal septum not splitting right
can have communications between the 3 systems (urinary, genital, anal)
how cloaca relates to the kidneys
the mesonephric duct (from the mesonephros = the functional kidneys in the embryo) goes down into the cloaca
name of the region where the kidney will form (from mesonephros to kidney)
ureteric bud
-the ureteric bud and the mesonephric duct will enter the mesonephric sinus (part of posterior urogenital sinus probably?)
allantois fct
- in gastrulation, primordial germ cells migrate and stay in the allantois. (spermatogonia for example)
- at 6 weeks, migrate into the gonads
what is the genital tubercle
specialized sensitive mesenchyme arising from the UROGENITAL MEMBRANE and that is in the region of the mons pubis.
what is the urogenital fold and the labiosacral fold
swellings and thickenings of the inner side of the cloacal membrane to form the primitive external genitalia (urogenital fold more medial, labioscrotal more lateral)
3 components of the primitive bipotential external genitalia
- genital tubercle
- labioscrotal fold
- urogenital fold
name of the precursor region of the gonads in the embryo
urogenital ridge
what’s the gubernaculum
a part of the urogenital ridge what ends in the labioscrotal fold to form either the scrotum or the labium majora
shape of the urorectal septum splitting the cloaca
like a coronal plate coming down in middle of pelvis
what controls the splitting of the cloaca by the urorectal septum
expression of sonic hedgehog by the gut**
consequence of SHH defect in the pelvis
abnormal deviation and growth of the urogenital septum
-FISTULAS can form between urogenital sinus
what attaches to the posterior urogenital sinus
- mesonephric duct
- ureter
what forms the perineal body
the urorectal septum
mesonephric duct goes to what organ
enters the bladder
possible anorectal anomalies at birth
- fistula between the vagina and anal canal (F) or bladder/urethra in and anal canal (M) bc of deviation of urorectal septum to right or left so it failed to close
- anal canal atresia bc of PERSISTENCE OF THE ANAL MEMBRANE (when it should have died) bc failure of recanalization of the gut by apoptosis
anal membrane cellular components and why it makes sense
ectoderm and endoderm bc the anal canal is endoderm on the inside and ectoderm on the outside
charact of the hindgut endoderm in the anal canal
- simple columnar epith
- ANS inn. (insensitive)
- sup rectal a. from inf mesenteric.
- valveless inferior mesenteric vein to portal system
- inf mesenteric lymph nodes
significance of the portal veins being valveless (for hindgut ectoderm of anal canal)
increased portal P = get internal hemorrhoids
anal membrane significance in the adult
the anal membrane used to be at the site of the pectinate line (div between anal canal hindgut endoderm and anal canal ectoderm)
charact of the ectoderm in the anal canal
- stratified squamous epith
- inferior rectal nerve from pudendal nerve (sensitive)
- pudendal a and v (from inf rectal a and v) to internal iliac to IVC
- superior inguinal nodes
name of the region of the urogenital ridge where the gonads will form
gonadal primordial site of the UGR
what forms after the gonads form first in the UGR
the mesonephric duct (from mesonephros = functional kidney of embryo) and the paramesonephric duct (Muellerian duct)
what pelvic structures are common to everyone in the embryo
- mesonephric duct
- paramesonephric duct (Muellerian duct)
- bipotential gonads
- bipotential external genitalia
allantois was created by urogenital sinus. why does it connect to the urogenital ridge
for primordial germ cells to migrate in the urogenital system and to the gonads
level where gonads develop + what is also there
L1, L2
-dorsal mesenteries to the gut are also there
lining of the abdominal cavity in the embryo
primitive multipotential coelomic epithelium (will form many structures) will go around behind the whole UGR and form the dorsal mesentery
mesonephros state before the kidneys form and while they’re forming
the mesonephros is functional and produces urine
what’s the gonadal ridge
a big fold for the gonads formed by the coelomic epithelium (it its lining) where imp structures for M and F gonads will form
steps of migration of PGCs (how they reach gonads)
- allantois
- bladder
- gut
- gonads
neural tube steps formation related to pelvis
- neural tube forms
- NCCs migrate and are pluripotent
- NCCs migrate down the urogenital ridge (high in the ridge, L1, L2)
- NCCs form the renal medulla (ANS) at the bulge
what forms the adrenal cortex
coelomic epithelial cells. migrate and act on NCCs to form the adrenal gland
how the paramesonephric duct (Muellerian duct) is formed
the mesonephric duct induces the coelomic epithelium to form the PMD (Muellerian duct) which then goes all the way down to the cloaca
what makes the mesonephros
renal corpuscule
how urine gets to the cloaca from the mesonephros
- mesonephros
- mesonephric tubules
- mesonephric duct
- cloaca
coelomic epith function in the gonad formation at 4-6 weeks
it migrates to form projections that will be the primary sex cords
function of the gonadal ridge (made by coelomic epith)
- is induced by the mesonephric duct
- it involules, invaginates and closes all the way down on the side of the PMD (Muellerian duct)
- its top forms the Fallopian tube
- its bottom forms the body of the uterus
function of the primary sex cords in the gonads (were formed by a contribution of coelomic epith to the gonads)
form the rete testis or rete ovaries (rete network)
- in the male, will remain as rete testis
- in the female, will disappear and all that remains is a remnant of the rete ovaries in the ovary
how does the coelomic epith maintain the PMD epithelium
coelomic epith produces a TF called Lim-1
consequence of anomaly in Lim-1
abnormal uterus and fall tube formation
embryonic correlate to ectopic endometriosis (why it occurs)
defect in the formation of the coelomic epith (Lim-1 defect) (which forms the PMD which forms the uterus). leads to abnormal formation of the endometrium
which ducts persist and regress in M and F
- M: mesonephric stays. PMD regresses
- F: PMD stays. mesonephric regresses
anomalies related to regressing MD and PMD
cysts and others
what’s near the gonad and its gonadal ridge
- rete network (from primary sex cords which are from coelomic epith contribution in the gonads)
- renal corpuscule leading to mesonephric tubules and mesonephric duct
- PMD on side of MD formed by coelomic epith involuting
where do the PGCs go in the gonad once they reach the gonad
in the primary sex cords which are/will form the rete testis
precise cells that the sex cords in the male gonad will form
Sertoli cells, in close contact with the PGCs
type of cells that are in the sex cords
mesenchyme
other cells produced by the mesenchyme in the sex cords
Leydig cells
function of Leydig cells and Sertoli cells in the embryo
L: produce testo
S: produce AMH
what happens after the rete testis and the medullary region (sex cords = all that’s inside the future tunica albugenia = future STs = S and L cells, PGS, etc.) of the gonads is formed
the renal corpuscule (which would cause fluid to go to the mesonephric duct) degenerates so the mesonephros is no longer important functionally
what happens to the renal corpuscule, mesonephric tubules and duct: what structures will they lead to
no more ‘‘kidney function’’ so
- renal corpuscule and mesonephric tubules form the ductuli efferentes
- mesonephric duct becomes the EDD
- all three together form the vas deferens
new function of the mesonephric duct
carry spermatozoa
what formed the Sertoli cells in the testis
coelomic epithelium
first gene expressed by sertoli cells
SRY gene on the X chromosome
2nd gene expressed by Sertoli cells
Sox9 gene.
function and importance of the Sox9 gene
- fct: maintain Sertoli cells
- MOST IMPORTANT GENE expressed by Sertoli cells
