Renal Embryology Flashcards
Intermediate mesoderm separates from?
Lateral and paraxial mesoderm during folding
2 components that give rise to the urogenital system?
Nephrogenic cord and urogenital ridge
Nephrogenic cord leads to?
3 kidneys
Cervical nephrotomes (pronephros)
- In the 4th week, 5-7 paired nephrotomes appear in cervical region
- Their development is abortive
- Remain nonfunctional until disappearance (day 24/25)
Mesonephros
- During the 4th week, a second primitive kidney develops
- Mesonephric tubules form within nephrogenic cords
- About 40 tubules develop in craniocaudal succession
Mesonephric tubules
- Very primitive nephrons
- Regression of cranial tubules occurs with formation of distal ones
- By 5th week, 20 pair of tubules are found in lumbar region
- Differentiate into functional nephric units with glomeruli
Mesonephric ducts
- Form at 24 days from cords dorsolateral to mesonephric tubules
- Run caudally to empty into ventrolateral portion of cloaca
- Fusion of tubule tip with duct provides passage from excretory unit–>cloaca
Mesonephros
- When is it present and functional?
- What happens after?
- Present and functional from the 6th to the 10th weeks
- After week 10, it degenerates
Mesonephros
- In the male?
- In the female?
- In the male, its duct system will contribute to part of the genital system
- Also contributes to vestigial structures in the female
Summarize the normal epithelial-mesenchymal interactions that are involved in differentiation of the kidney (Figure 16.7 and clinical correlates 255-256)
-Metanephros: steps in renogenesis
- Cranial-caudal patterning establishes a “renogenic” region within the intermediate mesoderm in the tail of the embryo
- This renogenic mesoderm is the METANEPHRIC BLASTEMA
Describe the contributions of the ureteric bud and metanephric blastema or diverticulum to the metanephros (the definitive kidney)
The METANEPHRIC BLASTEMA secretes growth factors that induce growth of the URETERIC BUD from the caudal portion of the mesonephric duct
Metanephros: steps in renogenesis
-Ureteric bud secretes?
-URETERIC BUD secretes PAX2 and WNT4
Metanephros: steps in renogenesis
-PAX2-function?
PAX2 which promotes condensation of the mesenchyme preparatory to tubule formation
Metanephros: steps in renogenesis
-WNT4-function?
Causes the condensed mesenchyme to epithelialize and form tubules
Metanephros: steps in renogenesis
Modifications in the ECM also occur with change to laminin and type 4 collagen, characteristic of an epithelial basal lamina
Metanephros: steps in renogenesis
CAMs syndecan and E-cadherin are essential for condensation of the mesenchyme into an epithelium
In utero function of metanephros
- When does blood plasma begin to be filtered?
- Primary function?
- Blood plasma from glomerular capillaries begins to be filtered by 10th week
- Urine is produced, but the primary function is not to clear waste (placenta) but to supplement production of amniotic fluid
Oligohydramnios (insufficient amount of amniotic fluid) may indicate?
Bilateral renal agenesis or urethral obstruction
Describe the developmental changes in kidney position (figure 16.10)
?
How does ‘ascent’ of the kidneys explain accessory renal arteries and ectopic kidneys? (Clinical correlates 257-258)
Kidneys are formed in pelvis but ascend to lumbar region with progressive revascularization from common iliac and aorta-accessory renal arteries are common
Renal fusion
- Prevents normal rotation
- Abnormal blood supply-usually from middle sacral or common iliac arteries
- Ectopic kidney-may also be crossed with/without fusion
- Horseshoe kidney
Horseshoe kidney
- Most common
- 90% fused at lower pole
Horseshoe kidney
-Usually found?
Usually found inferior to the inferior mesenteric artery
Describe the partitioning of the cloaca into the urogenital sinus and anal canal.(Figure 16.12)What changes, especially in the role of the mesonephric ducts, are made to the urogenital sinus to create the urinary bladder? (Figure 16.14)
-Cloaca is divided by the?
Urorectal septum
Development of the urinary bladder
- The cloaca is divided by the urorectal septum
- The dorsal (inferior) portion develops into?
The dorsal (inferior) portion develops into the rectum and anal canal