Embryology of Pancreas, Kidney and Ureter😊

Embryology of Pancreas

• Pancreas develops from:
• Ventral Pancreatic Bud (VPB).
• Dorsal Pancreatic Bud (DPB).
• Process:
• Axial rotation of the embryo due to different growth of the duodenum wall.
• Fusion of VPB and DPB.





Origin	Structures derived
Ventral Pancreatic Duct + Distal part of Dorsal Pancreatic Duct	Duct of Wirsung (Main Pancreatic Duct)
Proximal part of Dorsal Pancreatic Duct	Duct of Santorini (Accessory Pancreatic Duct)
VPB	Lower head & uncinate pancreas
DPB	Upper head, neck, body, & tail of pancreas.

Most Common Developmental Anomaly of Pancreas

Pancreatic Divisum

 

• M/c congenital anomaly of pancreas.

• Mechanism: 
• Failure of fusion of dorsal & ventral ducts
• leading to ineffective drainage.
• Increased risk of pancreatitis.

• Management: ERCP + Sphincterotomy.

Development of Kidney and Ureter

Embryological Origin

• Mesoderm → Intermediate Mesoderm → Nephrogenic Cord →
• Kidney, mesonephric duct, paramesonephric duct.

Three Stages of Kidney Development (Cranial → Caudal)

Key Structures

• Metanephric blastema + Ureteric bud = Permanent kidney

Ureteric Bud

• Outgrowth from mesonephric duct

• Begins around 5th week

• Epithelium of ureteric bud
• Forms collecting system:
• Collecting ducts
• Major & minor calyces
• Renal pelvis
• Ureter

Metanephric Blastema (aka Metanephric Mesenchyme)

• Secretory portion of the kidney:
• Bowman’s Capsule (BC)
• Proximal Convoluted Tubule (PCT)
• Loop of Henle (LOH)
• Distal Convoluted Tubule (DCT)
• Connecting tubules

• Interacts with ureteric bud → induces nephron formation

Epithelial-Mesenchymal Interaction (EMI)

• Occurs between 6–8 weeks

• Interaction between:
• Epithelium of ureteric bud
• Mesenchyme of metanephric blastema

• Essential for adult kidney formation

Nephron Development

• First fully formed nephrons → end of 8 weeks

• Urine formation begins at 9–10th week (12 weeks)

• Nephrogenesis completes by 32–36 weeks

• Nephrons cannot be formed after birth
• Lost nephrons are not replaced

• Only postnatal change = increase in concentrating capacity
• Adult concentrating capacity is achieved by 18 months

Epithelium and Lower Urinary Tract Development

Applied Aspects:

WT 1 Gene

• Located on chromosome 11p13

• Most important gene for epithelial mesenchymal interaction in urogenital tract

• Mutation in WTI gene causes:
• WAGR syndrome
• Denys Drash syndrome

WAGR Syndrome

• Wilms tumor

• Aniridia: Absence of iris.

• Genitourinary abnormalities

• Mental retardation

Denys Drash Syndrome

• Denys–Drash = WT1 mutation → Congenital nephrotic syndrome (diffuse mesangial sclerosis) + Gonadal dysgenesis + Wilms tumor risk

• Male pseudo hermaphroditism

• Denys rash driving → loss kidney, and genitalia

• DD → gonadal Dysghenesis, Diffuse mesangial sclerosis

PRK-A Gene

• U/L renal agenesis

• PRK → Partial

RET/GDNF Pathway

• B/L Kidney agenesis

• GDNF → global reath (RET) → b/l

WT-2 gene (11p 15) mutation:

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Beckwith-Wiedemann syndrome.

• BWS = 11p15 imprinting defect → Overgrowth + Macroglossia + Omphalocele + Tumor risk (Wilms, Hepatoblastoma).

• Cause: ↑ copies of imprinted genes (placental overgrowth).

• LGA baby with hemihypertrophy.

• Macroglossia / Protruding tongue

• Omphalocele.

• Organomegaly (liver/spleen).

• Horseshoe kidney

• Double → Ear lobe creases.

• Increased risk of embryonal Tumors:
• Wilms tumor (nephroblastoma)
• Hepatoblastoma
• Neuroblastoma, rhabdomyosarcoma (less common)

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