DEVELOPMENT OF KIDNEY,URETER & BLADDER Lecture by Prof. Dr. Ansari (for MBBS semester I students only) Sunday, April 23, 2017.

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.

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

Pronephros are rudimentary, nonfunctional & regresses completely

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.

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.

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.

Saggittal section of a 5-week-old embryo 1.Nephrogenic cord 2. Mesonephric duct 1+2. Mesonephros 4 Cloaca 5 Atrophied pronephros 7Allontois 9 Ureteric bud

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

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.

Formation of urogenital sinus Urogenital ridge Genital ridge Mesonephric duct Mesonephros Gonad Metanephric tissue Ureter Cloacal membrane Cloaca Allontois Urorectal septum Tail

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.

(Allontois +Bladder) (Prostatic urethra+ membranous Urethra & part of vagina) (Penile urethra and part of vestibule) Urogenital sinus

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.

Pelvic & Pancake kidney

Horse shoe kidney

Polycystic kidney (Due to non communication Between ureteric bud & Metanephros)

Polycystic kidney section

Agenesis of kidney 1;1000 live births incidence of renal agenesis

Renal agenesis

Double Ureters are Developmental defect As a result of earlier Bifurcation of ureteric bud

Bilateral doubling of ureters

Double kidney

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.

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.

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.