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DEVELOPMENT OF KIDNEY,URETER & BLADDER

Lecture by Prof. Dr. Ansari

(for MBBS semester I students only)

Wednesday, April 19, 2023.

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Objectives

• The three generations of kidney development, pronephros, mesonephros & metanephros.

• The ureter development and their developmental anomalies.

• The urinary bladder development and anomalies.

• The kidney developmental anomalies.

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The first generation kidney develops during 4th week of development from intermediate mesoderm/urogenital ridge

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Pronephros are rudimentary, nonfunctional & regresses completely

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The mesonephros

• The mesonephros is functional for short period & remains as the mesonephric duct/Wolffian duct.

• Urine formation begins between 11 –12 weeks &

• Continues throughout fetal life.

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The metanephric blastema (intermediate mesoderm)

The ureteric bud grows out from the mesonephric duct and induces changes into the metanephric blastema.

• The metanephric blastema differentiates into the functional units of the kidneys - the nephrons (approximately 1-2 million per kidney).

• The mesonephric duct drains into the allantois close to the cloaca.

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The ureteric bud

• From the ureteric bud develops the collecting duct system, including the collecting tubules which link with the nephrons, the major and minor calyces, the renal pelvis, and the ureter.

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Saggittal section of a 5-week-old embryo

1.Nephrogenic cord

2. Mesonephric duct1+2. Mesonephros

4 Cloaca

5 Atrophied pronephros

7Allontois

9 Ureteric bud

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The metanephros develops from the intermediate mesoderm (5) of the sacral

region:

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The ‘ascent’ of the kidneys

• Each metanephric kidney 'ascends' from the pelvic region, where it originates, to its final position on the posterior wall of the abdomen.

• It reaches T12 – L3 vertebral level by 9th week of intra-uterine life.

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Formation of urogenital sinus

1. Urogenital ridge2. Genital ridge3. Mesonephric duct4. Mesonephros5. Gonad6. Metanephric tissue7. Ureter8. Cloacal membrane9. Cloaca10.Allontois11.Urorectal septum12.Tail

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The uro-genital sinus may be divided into three component parts

The first of these is the cranial portion which is continuous with the allantois and forms the bladder proper.

• The pelvic part of the sinus forms the prostatic urethra in the male and the membranous urethra and part of the vagina in females.

• Thirdly, the caudal portion, or definitive uro-genital sinus, forms the penile urethra in males and the vestibule in females.

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Urogenital sinus

(Allontois +Bladder)

(Prostatic urethra+ membranousUrethra & part of vagina)

(Penile urethra and part of vestibule)

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Urinary bladder sources of development

• 1. Urogenital sinus

• 2.Allontois

• 3. Endoderm

• 4. Trigone from metanephric ducts

• 5. Connective tissue + Muscles from Splanchnic mesoderm

• 6. Allontois will form Urachus and later median umbilical ligament.

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Pelvic & Pancake kidney

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Horse shoe kidney

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Polycystic kidney

(Due to non communicationBetween ureteric bud &Metanephros)

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Polycystic kidney section

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Agenesis of kidney

1;1000 live births incidence of renal agenesis

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Renal agenesis

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Double Ureters areDevelopmental defectAs a result of earlierBifurcation of ureteric bud

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Bilateral doubling of ureters

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Double kidney

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Urachal fistula (4)

• It is a congenital defect due to persistence of allontoic canal/patent urachus.

• It opens at the umbilicus.

• Urine dribbling out from the umbilicus.

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Adult derivatives of embryonic kidney

• 1. Ureteric bud…….Ureter, renal pelvis, major/minor calyces, & collecting tubules.

• 2. Metanephric mesoderm….Renal glomeruli + capillaries + Bowman’s capsule + PCT + loops of Henle +DCT.

• 3. Mesonephric duct derivatives are epidydimis, vas deferens, trigone of bladder, ureter.

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Exstrophy of bladder

• The urinary bladder is exposed out side on the anterior abdominal wall.

• It is due to non development of infra umbilical part of abdominal wall.