Development of the Urinary System Flashcards
Precursor Tissues for the Kidney and Urinary Tract:
- Intermediate Mesoderm
- Endoderm
-
Intermediate Mesoderm
- Kidney
- Caylces
- Pelvis
- Ureter
-
Endoderm
- Epithelial Lining of:
- Urinary Bladder
- Urethra
- Epithelial Lining of:
What parts of the urinary system come from the splanchnic mesoderm?
Smooth Muscle & CT in the walls of urinary system organs are derived from Splanchnic Mesoderm
Developmental History of the Intermediate Mesoderm
- Intermediate Mesoderm is observable at …
- It eventually separates from the …
- It forms the …
- Intermediate Mesoderm is Observable at day 18-20
- It eventually separates from the paraxial mesoderm
- It forms the Nephrogenic Cord
What paraxial mesoderm transcription factors, expressed in intermediate Mesoderm, direct kidney formation?
Pax2, Pax8 & Lim1
Urogenital Derivatives from Intermediate Mesoderm:
- Kidneys
- Ureters
- Gonads
- Genital Ducts
A __________ Kidney Forms Within the Nephrogenic Cord in the Thoracolumbar Region of the Embryo
A **Mesonephric **Kidney Forms Within the Nephrogenic Cord in the Thoracolumbar Region of the Embryo
What are the 2 components of the mesonephric kidney?
- Mesonephric Duct
- Mesonephric Tubules
Why is the mesonephric duct important?
Important Source of Inductive Signals for Kidney Structures:
- A solid cell cord which eventually canalizes
- Extends caudally through nephrogenic cord
- Fuses with Cloaca (day 26)
What is the cloaca?
- The dilated, caudal end of the primitive hindgut
- A transient, common outlet for the UG & GI systems
What are the immature nephrons?
- Describe their differentiation:
Mesonephric Tubules = Immature Nephrons
- Inductive signals from the mesonephric duct induce tubule formation
- Differentiation occurs in a cranial to caudal direction along the nephrogenic cord
- All tubules induced are not present at same time
The _________ (Mature) Kidney forms in the Pelvic Region of the Embryo from the Caudal Aspect of the Nephrogenic Cord
- What are the 2 precursors for this structure?
The Metanephric (Mature) Kidney Forms in the Pelvic Region of the Embryo from the Caudal Aspect of the Nephrogenic Cord
-
2 precursors: Both derived from the Intermediate Mesoderm
- Metanephric Diverticuclum (ureteric bud)
- Metanephrogenic Mesenchyme (metanephric lastema)
What are the reciprocal inductive interactions in the metanephric kidney?
What can lead to Renal Agenesis?
If the inductive interactions between the metanephric diverticulum and metanephrogenic mesenchyme are altered or absent
- When is Renal Agenesis usually asymptomatic?
- When is Renal Agenesis symptomatic? What syndrome is this associated with?
- Unilateral, is usually asymptomatic
-
Bilateral
- Incompatible with extrauterine life
- Key features include oligohydramnios and pulmonary hypoplasia
- Compression of the face due to decreased amniotic fluid
- Characteristic of Potter’s syndrome
Oligohydramnios vs. Polyhydramnios
-
Oligohydramnios
-
Too little amniotic fluid
- Associated with renal agenesis, polycystic kidney disease, urethral obstruction
- Chronic amniotic leak
-
Too little amniotic fluid
-
Polyhydramnios
-
Excessive amniotic fluid
- Associated with diabetes, multiple gestation, anencephaly, esophageal atresia
-
Excessive amniotic fluid
- What can lead to oligohydramnios?
- What can oligohyramnios lead to?
- What can fetal compression lead to?
- defect of urinary output & chronic leak of amniotic fluid ⇒ oligohydramnios
- oligohydramnios ⇒ fetal compression, growth deficiency, pulmonary hypoplasia
- fetal compression ⇒ Potter’s facies, limb positioning defect, growth deficiency, pulmonary hypoplasia
Describe the signals that guide formation of the nephron:
What prevents cell apoptosis?
- Signals from the MM [GDNF, RA] induce formation of MD
- MD branches [cells express Ret a GDNF receptor]
- Expanded tips of MD called Ampulla
- key signaling center for nephron induction
- Varying nature of signals from the ampulla directs the arrangement of nephrons and collecting ducts
- Ampullae begin to disappear at about 32 weeks
- No new nephrons are formed after all ampullae disappear
- MD signals [Fgf2, Bmp7] prevents MM cell apoptosis
- induces a subset of MM cells to aggregate around ampulla
What are the stages of nephron formation?
Signals via the ampulla cause:
Segregation ⇒ Compaction ⇒ Vesicle Fusion ⇒ S-Shaped Tubule
Nephron Derivatives of the S-Shaped Tubule Include:
- From the Proximal Part (P)
- From the Middle Part (M)
- From the Distal Part (D)
- From the Proximal Part (P)
- Distal Tubule & loop of Henle
- From the Middle Part (M)
- Proximal Tubule
- From the Distal Part (D)
- Renal Corpuscle
Vascular Spouts From ___________ _______ are Induced to Grow Toward the Forming Kidney
Vascular Spouts From Intersegmental Arteries are Induced to Grow Toward the Forming Kidney
- They form the vasculature of the kidney
- Only induced mesenchyme secretes angiogenic growth factors [VEGF] that attracts the vascular sprouts to the forming kidney
- What is hydronephrosis?
- What are two types of cystic kidney disease?
-
Hydronephrosis
- Obstruction of the urinary tract
-
Cystic Kidney disease
- Polycystic kidney disease
- Multicystic dysplastic kidney disease
What are the characteristics of Multicystic Dysplastic Kidney?
- Most often unilateral (polycystic kidney disease is bilateral)
- Multiple cysts of varying sizes
- Non-functioning
- Pathology—primitive ductules and cartilage seen; atretic ureter
-
Contralateral kidney hypertrophies
- potential abnormalities of the contralateral kidney
- Bilateral disease is rare; fatal
- Hypertension is potential complication
- Failure of a large MCKD to regress may be indication for nephrectomy
- Non-genetic (Polycystic kidney disease is genetic)
Remodeling & Differential Growth of the Branching Metanephric Diverticulum results in ….
Formation of the Collecting Ducts, Calyces, Pelvis and Ureter
- Little growth of early generations
- Faster growth of polar branches
- Expansion of the 3rd-6th generations of branches to form the Calyces, Pelvis and Ureters
- Branches distal to the 5th & 6th generations form Collecting Ducts
- In the kidney, Nephrons and Collecting Ducts are organized into larger structures called _____ _____
- Each kidney lobe ends in a pyramid shaped _____ ______ which empties into a _____ _____
- In the kidney, Nephrons and Collecting Ducts are organized into larger structures called Renal Lobes
- Each kidney lobe ends in a pyramid shaped Renal Papilla which empties into a Minor Caylx
Anomalies That Result in Variations in Kidney Size, Histological Organization or Number:
-
Hypoplastic Kidneys
- May be small & normal
- May be small because of abnormal development
- Dysplastic Kidneys
-
Duplications
- Of the Ureter or Kidney which may be partial or complete
-
Horseshoe Kidney
- Fusion prevents complete ascent
Pelvic or Lumbar Kidneys are due to…
Failed or incomplete ascent
- Ectopic location
- Extra renal vessels result from failure to atrophy during kidney ascent
Polycystic Disease of the Kidneys is an _______ Disorder
Polycystic Disease of the Kidneys is an Inherited Disorder
- Autosomal Recessive Polycystic Kidney Disease
- Autosomal Dominant Polycystic Kidney Disease
What are the characteristics of Nephroblastoma (Wilm’s Tumor)?
- A common neoplasm in children
- The gene is located on chromosome 11
What will enhance a Ureteropelvic Junction (UPJ) Obstruction?
Diuresis (increased water excretion) enhances obstruction of the urinary tract
UPJ Obstruction:
- Clinical Presentation:
- Diagnostic Studies:
- Clinical Presentation:
- Infant: flank mass, UTI, failure to thrive, sepsis
- Older child or adult: flank pain, colicky pain, UTI, hematuria
- Prenatal diagnosis
- Diagnostic studies: ultrasound (anatomy) or renal scan, intravenous pyelogram (functional studies)
What Provides for Separate Outlets for the UG & GI Systems?
Division of the Cloaca
- The Primary (Primitive) UG Sinus is located ventrally
- The Anorectal Canal is located dorsally
What does remodeling of the posterior wall of the bladder result in?
- In males, what happens in this region?
Formation of the Trigone Region
- The trigone is associated with entrance of the ureters & exit of the urethra
- In males, differential growth results in the mesonephric ducts** opening into urethra rather than urinary bladder
- **the mesonephric duct distal to the metanephric diverticulum becomes the vas deferens
How can anomalies of the urinary bladder occur?
-
Anomalies of the Urachus [allantois & urachus]
- Arise from failure of regression of these structures
-
Exstrophy of the Bladder
- A defect of the ventral abdominal wall
- The lining of the bladder and the urethra is open to the surface
- Associated with UG & skeletal anomalies
Ureteral Reflux
- The higher the grade of reflux …
- the greater the risk for scarring
- the more abnormal the anatomy is
- spontaneous resolution is less likely
- surgical intervention may be necessary
- What is the consequence of a lateralized ureter?
- How is it treated?
- A lateralized ureter leads to reflux, which can lead to recurrent kidney infections and subsequent atrophy of the kidney.
- Treatment is antibiotic prophylaxis and/or surgical repair
- What causes bladder exstrophy?
- What is the difference in presentation between males and females?
- How healthy are infants at birth?
- **Failure of medial mesenchymal migration **
- 1 per 30,000 live births
- 1 per hundred if positive FH
-
Male:Female 3:1
- Males with epispadius
- Females with shortened vagina; bifid clitoris
- Gonadal structures normal
- Babies typically healthy
- What should be done to treat bladder exstrophy?
- What are the major long term complications?
-
Surgery performed shortly after birth
- Babies hospitalized for 10-14 days
- Incontinence is a major long term issue
- Upper tracts at risk after repair
The Extent of the Urethra Formed from the Caudal Part of UG Sinus Differs in Males & Females. What is the difference?
-
Male
- Proximal Portion of Prostatic Urethra
-
Female
- Most of It
How does the fate of the definitive UG sinus differ between males and females?
-
Male
-
Pelvic portion:
- Distal Prostatic & Membranous Urethra
-
Phallic portion
- Penile urethra
-
Pelvic portion:
-
Female
-
Pelvic portion:
- lower half of the Vagina
-
Phallic portion:
- Vestibule
-
Pelvic portion:
How can anomalies of the urethra occur?
-
Agenesis & Atresia of the Urethra
- Atresia is associated with urinary obstruction & Prune Belly Syndrome
-
Posterior Urethral Valves
- Mucosal folds which obstruct the lumen of the urethra
- A common cause of renal failure in boys
What are the characteristics of Posterior Urethral Valves?
- Occurs only in males
- 1/5000 male births
- Obstructing valves leads to severe obstruction of urinary tract and irreversible renal dysplasia
