Intermediate mesoderm will give rise to:
GU
Intermediate mesoderm will later be called:
urogenital ridge (2, on either side of midline)
*name change once arranged cranial-caudally
How does GU develop in earlier stages?
cranial-caudal, along full length of UG ridge
How do gonadal/genital parts develop in earlier stages?
along medial + central portion of UG ridge
What are the 3 stages of kidney development (start in 4th week)?
- pronephros (non-functional, disappears early)
- mesonephros (functional from week 5 to ~week 9)
- metanephros (functional begining in 2nd trimester)
mesonephros consist of:
nephron
mesonephric duct
During kidney development, as _____ portion is developing, ____ portion is regressing.
caudal
crainial
Separate draining systems that exist during kidney development?
mesonephrus
Mesonephric duct is aka
Wollfian duct
What portion of the mesonephros does NOT regress?
mesonephric duct
What are the 2 parts of metanephros?
ureteric bud (grows out of mesonephric duct)
metanephric blastema/mass
Metanephric duct drains into
cloaca
What would causes congenital absence of kidney on 1 side?
ureteric bud or metanephric blastema/mass fail to develop
Ureteric bud develops to form:
calyces, pelvis, ureter
all the parts that drain urine!
Doubling of ureteric bud results in:
doubling of ureters
What is an ectopic ureter?
ureter develops abnormally and misdirects urine to area other than bladder, causes incontinence
(Female commonly = vagina, urethra, vestibule; Male commonly = bladder neck, prostatic urethra)
What structure forms the nephron?
metanephric blastema (mass) **forms cortex/medullary
Metanephric blastema develops from:
metanephric caps on ureteric buds
3 conditions related to abn renal development?
unilateral renal agenesis (most commonly M + L side)
unilateral hypoplastic kidney
supernumerary kidney
What condition results from bil renal agenesis, and why is it so bad?
Potter’s sequence
Most common cause of oligohydroaminos (fetus takes in amniotic fluid, but can’t send it back out)
**also causes facial abn, clubbing of hand, hypoplastic lungs
What causes the movement of kidneys during development?
“body grows out from under them”
some upward pull PLUS they do not descend along with pelvis + trunk, which grow downward and disproportionately (relative to upper trunk)
What causes a “pelvic kidney?”
Why would this be a problem?
kidney is “caught” and descends with the pelvis abnormally
if it were to rotate, ureter may become obstructed
What is a horseshoe kidney?
renal poles fuse, causing grossly abn but functionally normal kidney; get stuck at inferior mesenteric artery
What divides UG sinus from anorectal canal?
urorectal septum
What was the original space which is divided into the UG sinus + anorectal canal?
cloaca (hindgut)
The urogenital sinus forms:
bladder, urethra, prostate, lower vagina
What layer is distal urethra originally derived from?
ectoderm
How does the positioning of the ureter and vas deferens develop?
- -mesonephric duct and ureteric bud eventually separate
- -the ureteric duct connects directly/independently to the posterior bladder
- -mesonephric duct descends downward, but remains hooked over the ureter
What path do primordial germ cells talk to reach gonad?
- originate in yolk sac
- migrate through connecting stalk
- pass through dorsal body wall
- populate gonads (bilaterally at urogenital ridge)
What does the yolk sac originate from?
extra-embryonic tissue
When do germ cells migrate?
4th-6th week
What occurs once the germ cells reach the gonads (male vs female)?
males: remain dormant until puberty, then meiosis
female: immediate meiosis I
What occurs to the gonad following primordial germ cell migration?
remains in “indifferent” stage, does not have M or F characteristics
What are the 3 components of an indifferent gonad?
- primordial germ cells present
- primary sex cords (grow from surface epith)
- 2 duct system (mesonephric + paramesonephric)
What effect does the absence of testerone have on sex cords?
primordial follicles = regress, break into segments
What effect does testosterone have on sex cords?
Become semeniferous tubules = length, coil, form lumen
Each follicle in an ovary contains:
one primordial germ cell
Wolffian ducts form…
Mullerian ducts form…
M genital tract
F genital tract
**only keep 1 duct
4 classic proteins/hormones in 7,8,9th week, which drive male development:
- Testes determining factor
- T (Leydig cells)
- MIF (Sertoli cells)
- DHT (requires 5aR)
Early production of ___ drives male development.
T
Where does testes determining factor develop?
short arm of Y chromosome
SRY gene codes for TDF
Why is it easier to develop an ovary?
develop by the ABSENCE of Y chromosome, which = absence of TDF
What is the function of MIH?
secreted by testes to drive suppression fo paramesonephric ducts
What drives female duct development?
E
Paramesonephric ducts ultimately become:
uterine tubes
uterus
upper part of vagina (two portions fuse)
(all from mesoderm)
What layer does the lower part of the vagina develop from?
ectoderm
Remnant of mesonephric duct which may become infected?
Gertner’s cyst
Congenital abn are usually resultant from:
abn fusion of paramesonephric ducts
How does male external genitalia develop from the indifferent stage?
- genital swellings fuse into midline = scrotum
- genital tubercle forms glans
- UG fold fuses along ventral shaft
How does female external genitalia develop from the indifferent stage?
- genital tubercle forms clitoris
- genital swelling becomes labia majora
- UG folds form labia minora
Hypospadias is caused by…
Epispadias is caused by…
failure of UG folds to fuse:
ventrally = hypo
dorsally = epi (can extend along abd)
How/when do testis/ovary migrate?
in last trimester, ovary/testes departs from UG ridge in lateral body wall
What is processus vaginalis?
piece of peritoneum captured during descent, remains in scrotum with testis (later called tunica vaginalis, reduces ball friction)
What is the gubernaculum?
CT that = pathway of testis into scrotum
What does a patent processus vaginalis cause?
congenital indirect inguinal hernia
What does excess fluid of tunica vaginalis cause?
hydrocele
Ovarian tissue with masculinization of female ext genitalia =
female intersexuality due to congenital adrenal hyperplasia
Testicular tissue with stunted male ext genitalia =
female intersexuality caused by inadequate T/MIH by testes
XY but develops testes located within labia majora, has female ext genitalia =
androgen R mutation