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Questions and Answers
What is the correct sequence of kidney development stages from earliest to latest?
What is the correct sequence of kidney development stages from earliest to latest?
Which structure gives rise to the definitive kidney?
Which structure gives rise to the definitive kidney?
At what gestational week does the pronephros appear?
At what gestational week does the pronephros appear?
How long does the mesonephros remain functionally transient?
How long does the mesonephros remain functionally transient?
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What is the primary tissue origin of the kidneys?
What is the primary tissue origin of the kidneys?
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What abnormality is characterized by the failure of one or both kidneys to develop?
What abnormality is characterized by the failure of one or both kidneys to develop?
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Which embryonic structure is the precursor for glomeruli and nephric tubules?
Which embryonic structure is the precursor for glomeruli and nephric tubules?
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What is the role of mesenchymal-epithelial transitions in kidney development?
What is the role of mesenchymal-epithelial transitions in kidney development?
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What does the urorectal septum separate during embryonic development?
What does the urorectal septum separate during embryonic development?
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Which developmental stage is characterized by segments of nonfunctional kidney formations?
Which developmental stage is characterized by segments of nonfunctional kidney formations?
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What role does Glial-derived Neurotrophic Factor (GDNF) play in renal development?
What role does Glial-derived Neurotrophic Factor (GDNF) play in renal development?
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Which of the following is NOT a consequence of oligohydramnios in fetal development?
Which of the following is NOT a consequence of oligohydramnios in fetal development?
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Which molecular signal is responsible for inducing the expression of PAX2 during nephron formation?
Which molecular signal is responsible for inducing the expression of PAX2 during nephron formation?
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What is the primary consequence of a loss-of-function mutation in GDNF related to renal development?
What is the primary consequence of a loss-of-function mutation in GDNF related to renal development?
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In the context of renal agenesis, which syndrome includes the complications of pulmonary hypoplasia and anuria?
In the context of renal agenesis, which syndrome includes the complications of pulmonary hypoplasia and anuria?
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Which of the following factors is known to stimulate proliferation of metanephric mesoderm?
Which of the following factors is known to stimulate proliferation of metanephric mesoderm?
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What is a characteristic feature of Potter facies resulting from in utero compression?
What is a characteristic feature of Potter facies resulting from in utero compression?
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Which factor primarily induces the filtration tubule formation in renal epithelium during nephron development?
Which factor primarily induces the filtration tubule formation in renal epithelium during nephron development?
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What is the main function of the pronephros during its development?
What is the main function of the pronephros during its development?
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During which gestational week does the metanephros first appear?
During which gestational week does the metanephros first appear?
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Which structure induces the differentiation of the metanephric blastema?
Which structure induces the differentiation of the metanephric blastema?
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What is the renal corpuscle composed of?
What is the renal corpuscle composed of?
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What is the significance of the WT1 gene in kidney development?
What is the significance of the WT1 gene in kidney development?
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At what gestational week does the mesonephros begin to disappear?
At what gestational week does the mesonephros begin to disappear?
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Which ducts are involved in female reproductive structure development?
Which ducts are involved in female reproductive structure development?
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What type of tissue caps does the metanephric blastema initially consist of?
What type of tissue caps does the metanephric blastema initially consist of?
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How many collecting tubules are formed from the ureteric bud?
How many collecting tubules are formed from the ureteric bud?
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What is the main function of the mesonephric duct?
What is the main function of the mesonephric duct?
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Study Notes
Urinary System Embryology
- The urinary system develops from intermediate mesoderm, also called the nephrogenic cord.
- Kidney development occurs in a cranio-caudal gradient
- Three distinct kidney structures appear sequentially: pronephros, mesonephros, and metanephros.
- Pronephros: forms in the cervical region, is non-functional, and regresses by week 5.
- Mesonephros: forms in the thoracolumbar region, is transiently functional, appearing in the 4th week and disappearing around the end of the 2nd month (except for the mesonephric duct in males). It is considered a "transitory kidney"
- Metanephros: forms in the sacral or pelvic region in the 5th week, and is the "definitive kidney".
Germ Tissues
- The chordamesoderm and paraxial mesoderm create the axial skeleton, while the intermediate mesoderm gives rise to the kidneys and gonads.
- Lateral plate mesoderm forms the circulatory system, body wall, and limbs.
Embryonic Renal Origins
- The kidney develops from intermediate mesoderm.
- The nephron, glomerulus, renal corpuscle, urorectal septum, pronephros, mesonephros, and metanephros are all components of the urinary system during development.
- The ureteric bud and metanephric mesoderm contribute to kidney development.
- Mesenchymal-epithelial transitions are crucial in kidney development.
- Defects like renal agenesis, cystic kidney, double ureter, horseshoe kidney, and bladder exstrophy have embryonic origins.
Pronephros
- Appears during week 4.
- Disappears by week 5.
- Located in the neck region.
- A non-functional structure.
- Made of nephrogenic cord, nephrotomes, pronephric tubules, and glomeruli
- Develops from nephrotomes after the 13-14th somite.
Mesonephros
- Appears during week 4.
- Forms the mesonephric tubules and duct.
- Has its own nephrons and tubules.
- Mesonephric tubules are S-shaped loops.
- The mesonephric (Wolffian) duct is involved in the development of the male reproductive system (collecting duct) and can contribute also to excretion..
- The mesonephric ducts are involved in part of the male reproductive structures, but degenerate in the female.
Paramesonephric (Müllerian) Duct
- Not part of the mesonephros, but derived from intermediate mesoderm.
- No role in the kidneys, instead plays a role in the reproductive system.
Mesonephros - Mostly Disappears
- Disappears after week 8-10.
- Except:
- Mesonephric ducts - Give rise to male reproductive structures.
- Degenerate in females.
- Analogous to Paramesonephric Ducts (also known as Müllerian ducts).
Metanephros
- Appears in week 5 and becomes functional by week 10.
- Metanephric blastema(i.e. tissue) is differentiated by the ureteric bud(metanephrogenic diverticulum)(outgrowth of mesonephric ducts)
- Formation of nephrons begins
- Becomes the functional kidneys, the "definitive kidney"
Collecting System
- The ureteric bud (which is a derivative of the mesonephros) subdivides into 1-3 million collecting tubules.
- Major and minor calyces act as convergence points for collecting tubules.
- Pelvis is the convergence point for major calyces.
- The ureter is the main tube that carries urine to the bladder.
Filtration System
- It comprises of the primordial metanephric mesoderm.
- This tissue initially exists as undifferentiated tissue caps.
- Ureteric bud influences the formation of renal vesicles and subsequently nephrons.
- Final development culminates into nephrons, basic structures of the kidney
Nephron (Excretory Unit)
- Renal corpuscle (glomerulus and Bowman's capsule).
- Proximal convoluted tubule.
- Loop of Henle.
- Distal convoluted tubule.
- Connect to collecting ducts.
- Formed until birth, ~1e6 nephrons
- Urine production begins by week 10
Filtering System Derivation
- Nephrons develop from metanephros.
- Collecting duct system (ureter, pelvis, calyx) is formed from the ureteric bud, a mesonephric derivative.
Molecular Signals
- WT1 gene is expressed in metanephric mesenchyme, maintaining nephron development competence.
- Mesenchymal signals affect the ureteric bud, influencing branching and division.
- Ureteric bud signals to metanephric mesoderm, inducing proliferation, blocking cell death, and inducing the formation of the renal epithelium.
- Several proteins and signaling pathways are involved in these developmental processes.
Renal Agenesis
- A developmental defect where one or both kidneys fail to develop, Often associated with other abnormalities.
- Possible causes include mutations in Genes like WT1 or GDNF or other developmental defects or errors.
Congenital Cystic Kidney
- Autosomal recessive polycystic kidney disease (ARPKD) involves cyst formation in collecting tubules and hypertrophy of surrounding nephrons, which can cause early kidney failure.
- Autosomal dominant polycystic kidney disease (ADPKD) sees cyst formation impacting all parts of the nephron, causing renal failure in adulthood.
Ciliopathies
- Defects in primary cilia, involved in fluid transport signal transduction, are associated with congenital cystic diseases affecting the kidneys.
- Primary cilia defects interfere with renal function.
Ureter Duplication
- A common renal abnormality.
- It can present either as a partial or complete splitting of the ureteric bud.
- Ectopic ureter termination into the vagina, urethra, or vestibule may occur.
Kidney Ascent
- Kidneys move from their pelvic to their abdominal position (T12-L3).
- Factors contributing to their movement include changes in body curvature and growth.
Kidney Positioning Defects
- Pelvic kidney: one kidney is retained in the pelvic region.
- Horseshoe kidney: fusion of kidney at upper or lower poles (90 percent). This is often caused by the isthmus of the kidneys getting trapped beneath the inferior mesenteric artery.
Cloaca
- The common embryonic cavity initially recieves urine and feces.
- Eventually divides and forms the urogenital sinus (anterior part) and anorectal canal (posterior part).
Urogenital Sinus (endoderm)
- Develops into the urinary bladder, and parts of the urethra.
Urachal Defects
- Urachal defects involve abnormalities in the development of the urachus, which is located between the urinary bladder and the umbilicus.
- These defects can result in the urachus remaining patent, forming a fistula, developing into a cyst, or a serous discharge from the umbilicus..
Bladder Formation
- The urinary bladder develops from the allantois-derived endoderm. and from the urogenital sinus.
- The urogenital sinus will develop into the pelvic, spongy, and phallic regions of the urethra in males and the urethra in females.
Trigone Formation
- The trigone is the posterior part of the urinary bladder.
- The mesonephric ducts and ureter play a role in its development as they incorporate into the posterior part of the bladder, forming the trigone region during embryonic development.
- The trigone's lining develops from the endoderm, replacing the mesodermal origin.
Epispadias
- A condition where the urethra opens dorsally on the penis or clitoris.
Exstrophy
- A condition where the abdominal wall fails to close around the developing bladder.
- Often associated with other structural anomalies
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Description
Test your knowledge on the development of the urinary system and its embryological origins. This quiz covers the stages of kidney development, including pronephros, mesonephros, and metanephros, as well as the germ tissues involved. Dive into the fascinating process of renal development during embryogenesis.
