Urinary System Embryo-cole Flashcards
The urinary and genital systems develop from what embryonic layer?
Intermediate mesoderm
Where is the intermediate mesoderm located initially?
Between the paraxial mesoderm (somites) and lateral mesoderm
At what point does the intermediate mesoderm separate from the lateral and paraxial mesoderm?
When the embryo undergoes lateral folding into a big tube
How do the developing kidneys end up on the posterior abdominal wall?
The embryo laterally folds into a big tube such that the neural tube, notochord, somites, and intermediate mesoderm all lie along the posterior aspect of the “tube”
After lateral folding of the embryo, what does the intermediate mesoderm form along the posterior aspect of the folded embryo?
Nephrogenic cord
Function of the nephrogenic cord
Sequentially segments from cranial to caudal into the 3 successive types of kidneys
Three types of kidneys stemming form the nephrogenic cord (intermediate mesoderm)?
Pronephros
Mesonephros
Metanephros
Where do the adult kidneys develop?
Why?
In the pelvis near the bladder
Come from the caudal region of the intermediate mesoderm (nephrogenic cord) at first
What structure runs alongside the nephrogenic cord (intermediate mesoderm) in the embryo?
Where is it derived from?
Mesonephric duct
Epithelium
What does the pronephros consist of following segmentation of the cervical nephrogenic cord?
When is the segmentation?
5-7 paired nephrotomes
4th week
What happens to the cervical nephrotomes (pronephros)?
Remain nonfunctional
Disappear around day 24-25
Describe formation of the mesonephros
In 4th week
About 40 mesonephric tubules form out of the nephrogenic cords in craniocaudal succession, then attach to the nephric duct
Where are the mesonephric ducts in relation to the mesonephric tubules?
When do they form?
Dorsolateral
At 24 days
What happens to the mesonephros?
Functional from weeks 6-10
Degenerate after week 10
Ducts used in males as ductus deferens (so NECESSARY for men)
Is the mesonephros used as anything in women?
Some vestigial structures
The region of the nephrogenic cord that eventually becomes the kidneys is initially called what?
This region is more formally called what?
Renogenic region
Metanephric blastema
First step of ureter formation
Metanephric blastema secretes GF’s that induce growth of the ureteric bud from the mesonephric duct
From what layer is the ureteric bud derived from?
Epithelium (from mesonephric duct)
What is required for the ureteric bud to communicate with the metanephric blastema (mesoderm)?
WT1 is expressed in mesoderm and must be turned on to receive signals from growing ureteric bud
What is a Wilms tumor?
Cause?
A kidney tumor caused by mutations in the WT1 gene. Causes poor communication between epithelium and mesoderm during kidney development
What is needed for the start of formation of the regions of the kidney?
Causes what?
PAX2 and WNT4 signaling from the ureteric bud
PAX2: Condensation of mesenchyme to prepare for tubule formation
WNT4: Mesenchyme epithelializes, getting ready for tubule system
What all is formed from the ureteric bud?
Embryonic layer?
Ureters, collecting ducts, major and minor calyces
Epithelium
What all is formed from the mesenchyme (mesoderm) of the metanephric blastema?
Renal corpuscle, PCT, loop, DCT
At what time does the blood begin to be filtered by the glomeruli?
10th week
What is primary function of urine production in an embryo?
Supplement amniotic fluid production
A fetus is showing signs of oligohydramnios, or insufficient amniotic fluid amounts. What are the most likely causes?
Renal agenesis, urethral obstruction
Urine is not being made (or excreted)
A man dies, and during the autopsy it appears that he seems to have 2 renal arteries. What is the explanation?
During ascension of the kidney, revascularization from the common iliac and/or aorta did not remove the initial renal artery from development, causing an accessory renal artery
It is shown that a patient has fused kidneys that are lower down than normal. What is this condition called?
Where often does the blood supply come from in this case?
Horseshoe kidney
Middle sacral or common iliac aa.
It is shown that a patient has fused kidneys that are lower down than normal. Where is this kidney often found?
Why?
Inferior to the IMA
Gets caught when ascending
Abnormal fusion or ascension of the kidneys can either cause a horseshoe kidney or ____
Ectopic kidneys (out of normal position)
The initial division of the cloaca is done by the formation of what?
Urorectal septum
The dorsal (inferior) portion of the cloaca develops into what?
The ventral (superior) portion?
Rectum and anal canal
Urogenital sinus –> bladder, urethrae (or urethra and lower vagina)
What happens to the ureteric buds?
Open into the bladder wall to become the ureters
What happens to the mesonephric ducts?
Move down and open inferior to the bladder into the pelvic urethra
What is the trigone?
This tissue comes from what?
Triangular area on the back of the bladder, made from the openings of the ureters on top and the opening of the ductus deferens down below
Mesonephric duct as it moves inferiorly
A baby is born with her bladder seemingly inverted, with the inner wall exposed to the external environment. What is this called?
Cause?
Exstrophy of the bladder
Failure of midline closure of inferior abdominal wall, musculature fails to form
A baby girl has an exstrophy of the bladder. What is a common secondary developmental defect?
Bifid clitoris and spaced pubic symphysis
A baby has an exstrophy of the bladder due to a failed closure of the anterior abdominal wall. What is the most common treatment?
Stretching the tensor fascia lata from the thigh up to cover the hole and create a sphincter as well
Defects of the urinary bladder usually stem from defects in what structure?
Urachus
4 possible urachus defects
Patent urachus
Urachal sinus
Bladder diverticulum
Urachal cyst
In surgery, it’s found that a man’s bladder has a small tubular outpocketing towards the umbilicus. What is the name of this?
It was a problem with what structure?
Bladder diverticulum
Urachus
A baby seems to be urinating out of its umbilicus. What is the most likely diagnosis?
Patent urachus (allantois)
A patient seems to have a growth within her median umbilical fold. What is this called?
Urachal cyst
A patient’s umbilicus seems to be very deep. He has umbilical discharge with redness around it. He also has a distended abdomen with a mass around the umbilical region. What is the likely diagnosis?
Cause?
Urachal sinus
Urachus only partially obliterates (caudal part)
Cause of a bifid ureter?
Ureteric bud branches abnormally before reaching the metanephric blastema
Ectopic ureters are most often formed how?
The abnormal one open may open where? (4 possible in females)
Two ureteric buds
Vestibule, urethra, vagina, uterus
Ectopic ureters in men may empty where? 4 possible
Prostatic urethra, seminal vesicle, ejaculatory duct, ductus deferens
If an ectopic ureter opens into the inferior neck of the bladder or prostatic urethra, what are the common symptoms?
UTI / Flank pain
Epididymorchitis (if into genital tract)
Common cause of a unilateral renal agenesis
Mutation is what gene? Does what?
What is often a clinical sign?
Absent inductive signals from the ureteric bud
GDNF gene - controls branching and growth of ureteric bud
Absence of a ductus deferens
Why is oligohydramnios so dangerous?
Lack of liquid can compress the fetus and cause facial/cranial defects (Potter Facies)
A baby patient’s kidneys have multiple growths on the surface. What is this called?
Cause of the growths?
Congenital polycystic kidney disease
Lesions of PCT and/or loop of Henle
An adult patient’s kidneys appear to have multiple cysts on them. What is this called?
Cause?
What will eventually happen? When?
Adult polycystic kidney
Disturbed nephron development
Renal failure by middle age
A baby appears to have no anus. In surgery, it’s found that its anal canal ends as a blind sac below the pelvic diaphragm.
Name?
Anal agenesis
A baby appears to have no anus. In surgery, it’s found that its rectum ends as a blind sac above the pelvic diaphragm.
Name?
Anorectal agenesis
In a high anorectal malformation, where might the colon end? Names? (2 possible)
Vagina - rectovaginal fistula
Bladder - rectobladderneck fistula
In a low anorectal malformation, where might the colon end? Names? (2 possible)
Vestibule - vestibular fistula
Urethra - rectourethral bulbar fistula
A patient has EITHER a high or low anorectal malformation. What is the general cause of this?
The anal membrane fails to perforate
What is beneficial about a LOW anorectal malformation as opposed to a HIGH one?
Can use the pelvic diaphragm muscles to make an anal sphincter
