Part of the development of the urinary system
The ascent of the kidney, stages of development of kidney
discussion about pronephros, mesonephros, metanephros.
5. Subdivisions of cloaca and
development of urinary bladder
CLOACA
primitive
rectum
primitive
urogenital
sinus
Definitive
urogenital
sinus
Vesicourethral
canal
Urorectal
septum
Pelvic part
Phallic part
Urinary bladder
Primitive urethra
Absorbed
part of
Mesonephric
duct
Splanchno-
pleuric
mesoderm
9. Evolutionary History of
kidney
◦ Kidney develops from nephrogenic cord of intermediate
mesoderm
◦ Ontogeny repeats phylogeny
◦ Humans have metanephric kidney
◦ Nephrogenic cord forms:
ØPronephros
ØMesonephros
Ømetanephros
10. ◦ Pronephros:
◦ Appears in cervical region at beginning of 4th
week of I.U.L.
◦ Later it regresses
◦ Pronephric duct continues as mesonephric
duct
◦ Mesonephros:
◦ Thoracolumbar region at end of 4th week
◦ Completely regresses
◦ Forms collecting part of kidney and other
parts of male reproductive system.
◦ Metanephros:
◦ Sacral region
◦ Start of 3rd month
◦ Forms secretory part of kidney
13. DEVELOPMENT OF A COLLECTING
SYSTEM
URETERIC BUDS ARISE
FROM CAUDAL REGION
OF MESONEPHRIC DUCT
AND GROW TOWARDS
METANEPHROS
(NEPHROGENIC CORD)
METANEPHRIC
BLASTEMA CAPS
GROWING DILATED END
(pull) OF URETERIC BUD.
14. DEVELOPMENT
OF SECRETORY
PART
CELLS OF METANEPHROS
FORM METANEPHRIC
BLASTEMA THAT CAPS
DIVIDING URETERIC BUD
METANEPHRIC CAP DILATES
TO FORM A PEAR-SHAPED
METANEPHRIC VESICLE THAT
LATER FORMS S-shaped
primitive renal tubule
One end dilates to forms
bowman’s capsule
Other end communicates
with collecting tubules
Metanephros give rise to
secretory unit or nephron
15. Ascent of kidney
Kidney ascends from sacral to thoracolumbar
region
Causes: (A)in search of better blood supply, (B)due to smaller pelvic
cavity that fails to accommodate enlarging kidney, (C)differential
growth of P.A.W.,(D) Reduction of foetal curvature
By 9th week kidney ascends to their adult position
within abdomen.
