Urinary System Development- Articulate Flashcards
From which embryologic germ layer is the urinary system derived?
Intermediate mesoderm
The intermediate mesoderm swells to form
Genital ridge & Nephrogenic Cord/Ridge
As they ascend, the kidneys pass through an arterial fork formed by the _________ arteries?
Umbilical arteries
The definitive kidney arises from?
Metanephros
Appears at the beginning of the 4th week, degenerated by the end of the 4th week
Pronephros
Not functional in humans
Rudimentary
What region is the Pronephros found within
Cervical
Is the Pronephros functional?
No
Appears early in week 4, functional until week 10
Mesonephros
Where does the mesonephros range?
From intermediate mesoderm of upper thoracic to upper lumbar segments
Is the Mesonephros functional?
Yes
When does the metanephros appear?
5th week
Two components of metanephros?
Uteric bud
Metanephric blastema
Derivative of Metanephric blastema
Excretory portion
Derivative or Ureteric bud
Collecting ducts
Derivatives of Ureteric bud
-Collecting tubules
• Major & Minor Calyces
• Renal Pelvis
• Ureter
Derivatives of Metanephric blastema
- Bowmans capsule
- Proximal convoluted tubules
- Loop of Henle
- Distal convoluted tubule
Excretory units
Nephrons
Triangular area of the incorporated mesonephric duct on posterior bladder wall
Trigone of bladder
2 systems of urogenital system
- Urinary system
- Genital system
Where does the urogenital system develop from?
Intermediate mesoderm
Swells to form urogenital ridge
Intermediate mesoderm
What does the urogenital ridge differentiate into
- Genital ridge
- Nephrogenic cord/ridge
Becomes retroperitoneal
as a result of lateral body folding
Nephrogenic cord (ridge)
Rudimentary; never functional in humans
Pronephros
Functional for short time (early fetal period);
most of system disappears
Mesonephros
Forms permanent kidney
Metanephros
How do the kidney systems develop?
Cranial to caudal sequence
Represented by 7-10 solid cell groups in intermediate
mesoderm of cervical region
Pronephros
Degenerated by end of week 4
Pronephric
Derived from intermediate mesoderm of upper thoracic to upper lumbar (L3)
segments
Mesonephros
Characterized by excretory units (nephrons) & collecting duct (mesonephric/Wolffian
duct)
Mesonephros
When are the excretory units of the mesonephros functional?
between weeks 6th-10
Urine produces and drained along ___ to cloaca
Mesonephric (Wolffian) duct
First excretory tubules of mesonephros appear
4th week
Tubules lengthen rapidly; form S-shaped loop; acquire tuft of capillaries
Glomerulus
Tubules surrounding glomerulus form
Bowman’s capsule
Tubules enter longitudinal collecting duct
Mesonephric (Wolffian) duct
First appear as solid longitudinal
rods within intermediate mesoderm
Mesonephric (Wolffian) Ducts
What contributes to posterior wall of future bladder?
Rods of Mesonephric (wolffian) ducts grow caudally & fuse with cloaca
What direction does canalization progress?
Cranially
Rods cavitate at caudal ends and form a
Lumen
What induces the formation of ureteric bud?
Caudal end of mesonephric duct
When does the metanephros appear?
5th week
Sprouts from caudal end of each mesonephric duct
Uteric bud
Metanephric diverticulum
Uteric bud
Ureteric bud grows into surrounding mesenchyme known as the
Metanephric blastema
Becomes molded over bud like a cap
Metanephric blastema
Gives rise to collecting portion of permanent
kidney
Uteric bud
Definitive kidney formed from the metanephros becomes functional
12th week
Swallowed by fetus & recycled through kidneys
Urine
In fetus, main function of kidneys isn’t excretion of wastes à carried
out predominately by
Placent
Fetal urine contributes to
Amniotic fluid
Where is urine passed into in fetus?
Amniotic cavity and mixes with amniotic fluid
Differentiation of metanephric nephrons reliant on interaction (inductive signals) from ureteric bud
Reciprocal Induction
What happens if uteric bud is abnormal or missing?
Nephron does not develop
Where are kidneys initially positioned?
Pelvic region
During ascent, receive blood supply from arteries off aorta at continuously higher levels
The vessels degenerate
During ascent, kidneys pass through arterial ‘fork’ formed by
Umbilical arteries
Complication of kidney formation may lead to
Pelvic kidney or Horseshoe kidney
Kidney remains in pelvis close to
common iliac a
Pelvic kidney
Kidneys pushed so close together during passage through umbilical arterial fork, that lower poles fuse
Horseshoe kidney
Usually at lower lumbar level; ascent prevented by root of inferior mesenteric a.
Horseshoe kidney
What does the Urorectal septum divides the cloaca into?
Urogenital sinus
Anal canal
Three portions of the ureogenital sinus
- Vesical part
- Pelvic part
- Phallic part
Gives rise to the bladder
Vesical part of the urogenital sinus
Caudal ends of mesonephric ducts and attached ureteric buds become incorporated into
Posterior wall of bladder
Process brings opening of utereric buds into
Bladder wall
Opening of mesonephric ducts are carried inferiorly to the level of
Pelvic urethra
Triangular area of the incorporated
mesonephric duct on posterior bladder wall
Trigone of bladder
Give rise to urethra
Pelvic & Phallic part of urogenital sinus
Pelvic part of ureogenital sinus in female
Urethra
Pelvic part of ureogenital sinus in male
- Prostatic urethra
- Membranous urethra
Phallic part of urogenital sinus in female
Contribute to vestibule of vagina
Phallic part of urogenital sinus in male
Penile (spongy) urethra
Is the genital or nephrogenic ridge more lateral in development
nephrogenic ridge
