Lecture 6 & 7 - Urogenital System I & II Flashcards
What germ layers gives rise to the urogenital organs?
Almost only mesoderm, except:
- Adrenal medulla: ectoderm
- Labioscrotal swelling and urogenital sinus: endoderm
Embryological origin of the male parts and trigone? 3 names.
What does this include?
Mesonephric duct = Wolffian duct = male duct
Trigone Efferent ducts of the testes Epididymis Vas deferens Seminal vesicles Ejaculatory ducts
Embryological origin of the female parts? 3 names
What does this include?
Paramesonephric duct = Mullerian duct = female duct
Fallopian tubes
Uterus
Cervix
Upper 2/3rds of vagina
Embryological origin of the ureters and collecting system? Describe the development of this structure
Ureteric bud
Most caudal mesonephric tubule is surrounded by metanephric blastema => differentiates into ureteric bud arising as a diverticulum of the mesonephric duct (bud grows laterally/dorsally and induces the metanephros)
Embryological origin of urogenital system from the bladder down (excluding gonads and their tubing)?
Urogenital sinus
What is the cloaca?
Common chamber into which urinary, genital, and GIT converge
What is Potter syndrome? Pathology?
P = pulmonary hypoplasia O = oligohydramnios T = twisted face T = twister skin E = extermity defects R = renal failure
Pathology: oligohydramnios => not enough amniotic fluid => fetus does not produce urine => compression of developing fetus
5 causes of Potter syndrome?
- PCKD
- Obstructive uropathy (valves)
- Esophageal atresia
- Bilateral UPJO
- Megaureter
List 7 potential renal congenital abnormalities?
- Horseshoe kidney
- Renal agenesis
- MCDK = Multicystic dysplastic kidney
- Duplicated Collecting System
- UPJO = Ureteropelvic Junction Obstruction
- Pelvic kidney
- ARPKD = Autosomal Recessive Polycystic Kidney Disease
What is the trigone’s embryological origin?
Connection between the mesonephros to the cloaca through the mesonephric ducts
When does the pronephros disappear during embryological development?
Gone after week 4
When does the mesonephros disappear during embryological development?
Gone after 1st trimester
What does the pronephros give rise to when it disappears?
Mesonephric ducts
What gives rise to the trigone in females?
Mesonephric ducts
From what germ layer do the kidneys develop?
Anterior intermediate mesoderm
When does the metanephros develop?
After 8 weeks
What connects the metanephros to the ureteric bud?
Ureteropelvic junction
What connects the ureteric bud to the UG sinus/cloaca?
Ureteral orifice of trigone
What is UPJO (Ureteropelvic Junction Obstruction)?
Abnormal placement of the ureteropelvic junction leading to obstruction
What induces the metanephros to become the kidney?
Ureteric bud
What is MCDK (Multicystic dysplastic kidney)?
Failure of ureteric bud to get to and induce the metanephros to become the kidney causing failure of formation of the kidney as a functional set of glomeruli
What connects the gonad to the mesonephric duct in the male?
Efferent Ducts => epididymus => vas Deferens
What connects the gonad to the paramesonephric duct in the female?
Fallopian tube => uterus => cervix
Describe the steps of kidney formation.
- Step 1: ureteric bud and metanephros induce each other to create the kidney and collecting system
- Step 2: ascendance of kidney from sacrum up the chest while ureteric bud bifurcates/branches 14-15 times into calyces, infundibula, and collecting ducts
- Rotation/Revascularization: as the kidney ascends it gains and loses blood supplies: iliacs => aorta
What EXACTLY does the metanephros develop into?
- Glomerulus
- Proximal tubule
- Loop of Henle
- Distal tubule
What EXACTLY does the ureteric bud develop into?
- Collecting ducts
- Calyces
- Renal pelvis
- Ureter
What are the 2 insertions of the ureteric bud?
- Cloaca
2. Metanephros
What is the most common cause of an abdominal mass in a child?
MCDK = multicystic dysplastic kidney
What is hydronephrosis?
Swelling of a kidney due to a build-up of urine
What does MCDK look like on an ultrasound?
Beehive
What is the renal infundibulum?
Passage from the calyx to the renal pelvis
What anomalies can result from abnormal step 2 of kidney development, aka ascendance?
Duplications of collecting system if ureteric bud bifurcation happens too soon:
- Complete duplication: 2 ureters on one side
- Partial duplication: split ureter half-way between kidney and bladder
- Bifid pelvis: split ureter at the renal pelvis
What are 3 potential road blocks to the kidney’s ascendance?
- Vasculature
- Malformation: horseshoe kidney, where the inferior poles of the kidneys fuse, forming a horseshoe kidney that crosses over the ventral side of the aorta until it is blocked by the IMA
- Masses
Consequence of horseshoe kidney on collecting system?
Ureteropelvic junction obstruction due to abnormal angle between the 2
In a person with a right pelvic kidney, where is the right adrenal located?
Normal spot
What anomalies can result from abnormal step 3 of kidney development, aka revascularization? How common is this? What happens exactly?
Kidneys have multiple arteries/veins
15% of people
When the vessels do not involute along the way, you get multiple arteries/veins
How does the urogenital sinus form? When?
At 30 days the urorectal septum splits the cloaca into the urogenital sinus and the anorectal canal
How does the trigone of the bladder form?
Urogenital sinus grows and absorbs part of the Wolffian duct distal to the ureteric bud - this part of the Wolffian duct becomes the trigone
Where is the trigone of the bladder located?
Middle bottom
What does the connection between the Wolffian duct and the ureteric bud become? Does this occur laterally or medially?
Ureteral orifice
Laterally
What does the insertion of the mesonephric ducts into the urogenital sinus become? Does this occur laterally or medially?
Ejaculatory duct
Medially
What is vesicoureteral reflux? What can this lead to?
Urine moves from bladder to ureter
Can lead to hydronephrosis, cystitis, or pyelonephritis
What is cystitis?
Bladder infection
What are UVJ obstructions?
Ureterovesicular junction obstructions
What is a ureterocele?
Obstruction of the ureteral orifice during embryogenesis, with incomplete dissolution of the Chwalla membrane, which is a primitive, thin membrane that separates the ureteral bud from the developing urogenital sinus
What is special about the trigone of the bladder?
Develops, looks, and acts differently compared to the rest of the bladder
Full of receptors and is where the ureter plugs into the bladder
What is an ectopic ureter? In this more prominent in males or females?
Uterer does not insert into the trigone:
- ureter inserts distal to the bladder neck (e.g. in UG sinus), leading to incontinence (continence mechanism in neck of bladder)
- ureter inserts in a more obstructed region than the trigone => obstruction of urethral orifice
More common in females
What rule do ectopic ureters follow? Explain.
Weigert-Meyer rule: when a collecting system is duplicated, ureters insert separately into the bladder and the upper pole is the ectopic one that inserts medially and is obstructed
Do ectopic ureters in men often result in incontinence? Explain.
NOPE because their continence mechanism is the external urinary sphincter in the penile urethra
6 potential causes of hydronephrosis in children?
- Vesicoureteral reflux
- UPJO
- Megaureter
- Ureterocele
- Urinary obstruction with posterior urethral valves
- MCDK/ARPKD
What is a megaureter?
Congenital abnormality in which the ureter is very big and distended and cannot conduct peristalsis, therefore cannot eject urine
What is ARPKD?
Genetic disease with abnormal cyst growth in kidneys
What would bilateral UPJO or megaureter cause?
Potter syndrome
Most common cause of Potter syndrome?
Posterior urethral valve leading to obstruction => obstructing membrane in the posterior urethra, which causes the ENTIRE urinary system to be obstructed
2 potential causes of hydronephrosis in adults?
- Kidney stones
2. Cancer
4 most common places where kidney stones lodge?
- UPJ
- Over the iliacs
- UVJ
- Ureteral orifice
What are the first 2 steps in the differentiation of the genitals? When does each occur? What are the next steps dependent on?
- 5 weeks: genital ridges next to the developing mesonephros (by having primordial germ cells migrate from yolk sac) and the primitive sex cord from mesenchymal cells
- 6 weeks: paramesonephric ducts form lateral to the nephric ducts
Next steps depend on the presence or absence of the SRY gene on the Y chromosome = sex-determining region Y
Describe the genital development in the presence of the SRY gene in males. 4 steps
- Primitive sex cord enlarge and are populated by Sertoli cells/germ cells and the genital ridges become testes
- Sex chords are separated further from their surface by tunica albuginea => become the seminiferous tubules, which eventually join the efferent ducts
- Sertoli cells secrete Mullerian Inhibiting Substance (MIS) starting at week 8 => Mullerian duct involutes and its cells undergo apoptosis + keeps Wolffian duct intact
- Leydig cells differentiate within the sex chords and produce testosterone by week 8 and shut down at week 18 until puberty
- 5-alpha reductase makes DHT from testosterone => DHT causes the development of the external genitalia: penis, scrotum, penile urethra