Urogenital System Flashcards
Types of germ cells
Ectoderm
Mesoderm
Endoderm
Ectoderm
Skin, CNS,PNS, eyes, internal ear, neural crest cells (bones and connective tissue of the face and skull)
Mesoderm
Bones, connective tissue, urogenital system, cardiovascular system
Endoderm
Gut and gut derivatives (liver, pancreas, lungs)
Urogenital system can be divided functionally into which systems
Urinary system
Genital system
These systems therefore are embryologically and anatomically closely related
Urinary and genital systems both develop from the…which forms a…
Intermediate mesoderm
Longitudinal “Urogenital ridge”
Urinary system consists of
-Kidneys-produce urine
-Ureters-convert urbane from the kidneys to the urinary bladder
-bladder- stores urine
-urethra-excrete urine from the bladder
(Nephrons which are functional units of the kidney)
Three successive sets of kidneys form in human embryos
Proneproi (rudimentary and non functional)
Mesonepheoi (functional for short time)
Metanephroni (forms the permanent kidney)
Pronephroi
When does the pronephros appear
Early in the forth week as segmentally arranged cell and tubular (probephric tubuli) structures in the cervical region of the intermediate mesoderm
Pronephroi
Pronephric ducts run….. and open into the ….
Pronephroi degenerate but…
Caudally and open into the cloaca
The ducts persist and are used by the next set of kidneys
Mesonephroi appear.. and are____ to the ___
Later in the 4th week
Caudal to the pronephroi
Facts about the mesonephroi
- functional for short time
- arise from cell clusters->vesicular-> tubules
- tubules contact pronephric duct which is now called meonephric duct
- ducts and a few tubules persist
Mesonephric kidneys consist of
Glomeruli and tubules
Mesonephric tubules open into ….
Bilateral Mesonephric ducts, which were originally the pronephric ducts
The Mesonephric ducts open into the….
Cloaca
The mesonephroi degenerate toward the_______ however, their tubules_____
Of the first trimester
Become efferent ductules of the testes
Metanephroi
Permanent kidneys
When do metanephroi develop
In the 5th week and begin functioning by week 10
Metanephroi
Urine is produced and excreted into
Fetus drinks…… and wastes are….. and removed by….
Amniotic fluid
Amniotic fluid and wastes are absorbed and removed via the placenta
Level of amniotic fluid is ___
Important
(Oligo or polyhydramnios)
Polyhydramnios-build up of amniotic fluid due to blockage of GI tract
The uretic bud forms as an outgrowth from the
Mesonephric duct
Metanephroi develop from —- sources both of mesodermal origin…
2
- Metanephric diverticulum behind as an outgrowth from the Mesonephric duct near cloaca
- metanephric blastema is located in the caudal part of the nephronogenic cord
Metanephric diverticulum gives rise to
Ureter, renal pelvis, major and minor calices, and collecting ducts and tubules
Metanephric blastema gives rise to
As collecting tubules form, they induce the mesoderm to form clusters->vesicles-> tubules-> nephrons
Metanephric diverticulum
The stalk of the Metanephric diverticulum becomes the ureter
The cranial portion of the diverticulum undergoes repetitive branching events, forming the branches which differentiate into the collecting tubules of the Metanephros
Metanephric diverticulum
First four generation tubules become confluent and form the…..
Second four…
Major Calices
Generation coalesce and from minor calices
Metanephric blastema
End of collecting tubules and proximal ends of tubules
The end of the collecting tubules (from metanephric diverticulum) induces clusters of mesenchymal cells to form small metanephric vesicles that elongate to form metanephric tubules
The proximal ends of the tubules are invaginated by glomeruli
Distal end of nephron (DCT) contacts and joins with
Collecting tubules
Metanephric diverticulum and mesoderm have reciprocal inductive influence…
Differentiation of both primordia depends on inductive signals from the other
Reciprocal induction
Metanephric diverticulum
Nephrons
Branching of the metanephric diverticulum is dependent on induction by the metaneprhic mesenchyme
Differentiation of the nephrons depends on induction by collecting tubules
Metanephric diverticulum and the metanephrogenic blastema interact and include each other, a process known as reciprocal induction to form the permanent kidneys.
Formation of uriniferous tubule
The metanephric tubules, the primordia of the nephrons, become continuous with the collecting tubules and form uriniferous tubules
A uriniferous tubule consists of two embryologically different parts:
- a nephron deceived from the metanephrogenic blastema
- a collecting tubule deceived from the metanephric diverticulum (ureteric bud)
Where are your kidneys?
What blood vessel is present and when?
- position of kidneys changes
- formed in the pelvis but come to lie in the abdomen due to growth of body caudal to kidneys
- as kidneys ascend, their blood supply changes
- definitive renal arteries are present at about 9 weeks
- variations in arterial supply to kidneys are very common (25%)
Abnormalities of kidneys and ureters
- occur in 3-4% of the population
- renal agenesis (unilateral or bilateral): missing of one or both kidneys
- ectopic kidneys (in abnormal position)
- horseshoe kidney (inferior poles are fused)
- duplications of upper urinary tract
Cloaca is divided by
Urorectal septum into dorsal rectum and venteal Urogenital sinus
Bladder and urethra are derived from
UG sinus and adjacent mesoderm
As bladder enlarges, caudal parts of Mesonephric ducts are incorporated into the wall therefore ureters enter bladder directly.
Initially the bladder is continuous with..
_____ becomes median umbilical ligament
Allantois
Allantois constricts ->urachus that is attached to apex of bladder and umbilicus
Urachus becomes median umbilical ligament (urachal sinus or fistula if remains patent)
Urethra develops from
Caudal portion of UG sinus
Exstrophy of bladder results from
Failure of mesoderm to migrate and improper formation of anterior abdominal wall
Steps of Reciprocal Induction and Genes involved
- MB induces branching of MD which induces MB to form cluster of cells which condense to form vesicles
- In MB where cells cluster up=metanephric tissue caps
- tissue caps have expression of WT1 (TF)
- when invaginating to prevent MB from apoptosis, MD expresses BMP7 and FGF2
- In MD there are RTK receptors (RET for GDNF and MET for HGF)
- MB expression of WT1 causes increased expression of GDNF (glial derives neurotrophic factor) and HGF (hepatocyte growth factor)
- MD release WNT9B and WNT6 to increase Pax2 and WNT4
- Pax2 causes condensation of mesenchymal cells and WNT4 causes epithelialization into vesicles and tubes
Mesenchymal to epithelial transformation reauires increased expression of what?
E-Cadherin (adhesion moleucles)
Genetic sex of an embryo is determined when? And depends on what?
At the time of fertilization and depends on the type of sperm that fertilized the secondary oocyte
The early genital systems in the teo sexes are similar; therefore the inital perood of genital development is reffedred to as the
Indefferent stage of sexual develpment
The gonads (testes and ovaries) are derived from which sources?
- Mesothelium (mesodermal epithelium), lining the posterior abdominal wall
- underlying mesenchyme (embryonic connective tissue)
- primordial germ cells
Indifferent gonads in embryos
- with an xx sex chromosome complex: the cortex of the indifferent gonad differentiaties into an ovary
- with an xy sex chromosome complex: the medulla differentiates into a testis, and thr cortex regresses, except for vestigial remnants
Primordial germ cells
Where do they migrate?
Large, spherical sex cells visible early in the 4th week among the endodermal cells of the umbilical vesicle (yolk sac) near the origin of the allantois.
Migrate along rhe dorsal mesentery of the hindgut to the gonadal ridges
Paramesonephric duct becomes the??
Fallopian/uterine tube
During the 6th week of development, the primordial germ cells enter the underlying mesenchyme and are incorporated in the _____
Gonadal cords
The migration of the primordial germ cells is regulated by which genes?
Stella, fragilis, BMP-4
Before 7the week gonads of teo sexes are identical in appearance and are called
Indifferent gonads
Testis-determining factor (TDF)
A protein product of the gene SRY located in the Y chromsome which determines testicular differentiation
Therefore absence of Y chromosome results in formatiom of the ovary
Presence of _____ is responsible for differentiation of testes from indifferent gonad
TDF
Gonadal sex cords become ____________ when TDF is present
Seminiferous tubules, tubuli recti, and rete testes as they branch and anastomose (tube fusion)
Gonadal cords to seminiferous tubules has which other genes involved
Sox9 and FGF9
Walls of seminiferous tubules include ____ and _____ derived from ____ and _____
Spermatogonia dereived from primordial germ cells
Sertoli cells derived from surface mesothelium
Interstitial cells of Leydig are derived from ______ and lie between seminiferous tubues
Mesoderm
Interstitial cells begin to secrete ______ in the _____ week which influences development of _____ and ____
Testosterone
8th
Indifferent ducts
External genitalia
Compare testes and ovaries development
Testis:
- medullary cord develop
- no cortical cords
- thick tunica albuginea
Ovary:
- medullary cords degenerate
- cortical cords develop
- no tunica albuginea
Genetic signals from XY chromosme
SRY—->SOX9—>SF1 and other genes—->Testes
Steroidogenesis factor 1
SRY produces TDF (TF)
SOX9 is an autosomal gene
SOX9 induces testes to produce ____ which acts as a ____
FGF9
Chemotactic factor that causes tubules from mesonephruc ducts to penetrate gonadal ridges
SF1 influences _____ and _____
Sertoli cells to produce AMH/MIS/PIH
Leydig cells to produce testosterone
What inhibits paramesoneprhuc duct?
AMI
What inhibts WNT4
SOX9
Genetic signals from XX chromosome
WNT4->DAX1 and other genes->ovaries
WNT4
Master gene for ovary development
What inhibts SOX9
DAX1
AMH/MIS/PIH
Anti müllerian hormone
Müllerian inhibiting hormone
Paramesoneprhic inhibiting hormone
-suppresses paramesonephric duct =Fallopian tube
Testosterone from leydig cells stimulates which ducts to form vas deferns and epididymis
Mesonephric
Dihydrotestosterone stimulates what
External genitalia to grow (penis, scrotum, and prostate)
Paramesonephric ducts are stimulated by…
Absence of SRY and presence of WNT4 along with estrogen from maternal and placental sources
Stimulated paramesonephric ducts form what
Uterine tube, upper portion of vagina, cervix, uterus
Development of ovary from indifferent gonad
- develops slower than testes
- gonadal sex cords degenerate
- cortical cords form and incorporate primordial germ cells
- break up into clusters to form primordial follicles
- oogonia divide during fetal life producing 2M primary oocytes
Indifferent duct sustem
-2 pairs of genital ducts form:
- mesonephric ducts
- paramesonephric ducts-lateral to mesonephric ducts, and cranial end open into peritoneal cabitt and the caudal ends fused-uterovaginal primordium
Mesonephric ducts into male genital duct system is influences by what
Production of testosterone by fetal testes
Testes also produce _________ from ______ which inhibts decelopment of the paramesonephric ducts
Paramesonephric inhibiting hormone/ Anti Mullerian Hormone/ Mullerian inhibiting substance
Sertoli cells
In females, lack of _____ and _____ results in paramesonephric ducts deceoping and mesonephric ducts regressing
Testosterone
MIS
In males, some mesonephric tubules persists and form___
Efferent ductules
Mesonephric duct gives rise to
Epididymis, ductus deferens, seminal vesicle and ejaculatory duct
Development of female genital ducts from indifferent ducts
- mesonephric ducts regress
- cranial ends of paramesonephric ducts form uterine tubes
- caudal fused portiok forms uterovagonal primordium
Uterovaginal primordium gives rise to
Uterus, upper half of vagina
-reaminser from mesoderm
Sinus tubercle becomes what in men and women
Hymen
Seminal colliculus (elecated part of urethral crest on prostraitc urethra)
Indifferent external genitalia behins to devleop when and include what
4th week
- genital tubercle (phallus)
- labioscrotal swellings
- urogenital folds
What causes masculinization of indifferent external genitalia
Testosterone
In males, the phallus elongates to becomes the
Glans penis
Urogenital folds fuse to form _____ in males
Penile urethra
Corpora cavernosa and spongiosum develop from ____ of penis
Mesoderm
Labioscrotal swellings fuse to form ___ in males
Scrotum
In females the phallus becomes what
Clitoris
In females, urogential folds become what
Labia minora
In females, labioscrotal swellings become what
Labia majora
