Flashcards in L15 – Development of the Urinary System Deck (107):
Which phase of development has most susceptibility to teratogens?
Highest in embryonic period (1st trimester = development
of important structures)
What are teratogens?
genes that cause specific malformations
What 4 organs are in the urinary system?
Kidneys, ureter, urinary bladder, urethra
What are the three germ layers?
Endoderm, mesoderm, ectoderm
What are the three divisions of mesoderm?
Paraxial, intermediate, Lateral
What is the central axis of mesoderm?
Name two things that arise from paraxial mesoderm
Where does the urogenital system arise from?
Where along the embryo does the intermediate mesoderm extend along?
Dorsal body wall of embryo
In what direction does the embryo fold?
in horizontal plane
What happens to intermediate mesoderm as the embryo folds?
Intermediate mesoderm is carried ventrally
loses connection with paraxial mesoderm (somite)
How is urogenital ridge formed?
Mesoderm elevates longitudinally on each side of dorsal aorta
forms urogenital ridge / fold
What does urogential ridge give rise to?
Nephrogenic cord / ridge (parts of urinary system)
What happens to nephrogenic cord after its formation?
form 3 sets of tubular nephric structures/ 'nephros'
What are the three sets of nephros?
Pronephros, Mesonephros, Metanephros
Describe direction of nephros formation
Temporally and Spatially- head to tail
When do the three sets of nephros start to appear?
Pronephros = 4th week
Mesonephros= Late 4th - 5th wk
Metanephros = Early 5th wk
Describe the cell group of pronephros and location relative to somites.
7-10 solid cell group (cell clusters, tubular structures)
5th -7th cervical somite region
Describe the cell group of mesonephros and location relative to somites.
Large, elongated, excretory organs
14th-26th somites (cervical-lumbar)
When does mesonephros appear during?
regression of pronephros
In the 5th week which two nephros overlap?
meso and metanephros
What happens to rudimentary pronephros? What structure persists?
Rudimentary pronephros soon degenerate (cervical)
Most of Pronephric ducts persist
How does pronephric duct develop?
Run caudally (to tail) and
open into cloaca
Utilized by the next set of the kidneys (mesonephros, metanephros)
What is the primary function of mesonephros?
Function as interim kidneys for about 4 weeks
Location of mesonephros?
extends from upper thoracic to upper lumbar region
What structures make up mesonephros?
Mesonephric tubules within Nephrogenic cord
What structure extends from Cloaca?
What structures branch from the mesonephric duct?
What structure is between the nephrogenic cord and Cloaca?
Which parts of mesonephric tubules and cords regress?
more cranial mesonephric tubules and cords regress
Which parts of the mesonephric tubules and cords remain?
The distal tubules and
cords differentiate into
final ductal system
How does the aorta connect with the mesonephric duct?
(central) Dorsal aorta > Glomerulus > mesonephric tubule> mesonephric duct (lateral)
In females, when do the mesonephric ducts disappear? How about in males?
Female: ducts disappear by 16th week
Mesonephric ducts (cuboidal epithelium) persist as ductus deferens in adults
What is another name for mesonephric duct in male?
What degenrates along with mesonephric kidney?
What forms part of the permenant kidneys?
Which parts of the mesonephric tubules regress and which parts develop?
Cranial mesonephric tubules and cords regress/ atrophy
Distal tubules and cords differentiate
What gives rise to the drainage system of permanent kidneys? Origin?
Ureteric bud/ metanephric diverticulum
outgrowth/protrusion of distal mesonephric duct near its entrance into cloaca
What are the two functional components/ Primordia in forming permanent kidneys?
ureteric bud (collecting portion)
metanephric blastema (excretory portion)
Compared to ureteric bud, where is metanephric blastema derived from?
Ureteric bud is dervied from distal mesonephric duct
Metanephric blastema is derived from caudal part of nephrogenic cord
How are uterteric bud and metanephrogenic blastema arranged?
Metanephrogenic blastema surrounds ureteric bud
How does the ureteric bud develop whilst surrounded by metanephrogenic blastema?
Distal mesonephric duct/ ureteric bud branches, forming ureteric trunks and ureteric branches
Why does ureteric bud branch?
How long does it take for metanephros to start functioning?
4 weeks of development
What 4 structures of the permanent kidney does ureteric bud give rise to?
Major and minor calyces
What 4 structures of the permanent kidney does metanephric blastema give rise to?
Proximal convoluted tubule
Loop of Henle’s
Distal convoluted tubule
How does ureteric bud and metaphric blastema join?
Canalization with collecting duct to establish link between excretory and collecting system
What are the orders of ureteric bud divisions?
major, then minor calyces
5th order: papillary duct
6th-14th order: collecting
What specific nutrient influence renal organogenesis?
Vitamin A (retinoids)
How does absence of ureteric bud manifest?
renal agenesis (no kidney): unilateral (1 side) / bilateral (2 sides: almost fatal)
How does Incomplete
division of ureteric bud manifest?
divided kidney + bifid ureter
(= 2 ureters)
How does complete division of ureteric bud manifest?
supernumerary kidney + bifid ureter
How does a second ureteric bud manifest?
2 ureteric buds =
supernumerary kidney (3rd kidney)
How does left kidney migration to right side manifest?
Unilateral double kidney
How does fusion abnormalities manifest?
Horseshoe/ Discoid kidney
Interfere inferior mesenteric artery
Rosette kidney (rounded and joined)
Duplex kidney: partially duplicated collecting system (2 ureters)
What is Sequential & Reciprocal Induction in permanent kidney formation?
Ureteric bud and
interact and induce each
other to differentiate
How does sequential and reciprocal induction change the metanephric tissue caps?
mesenchyme to epithelia
Which gene is most essential in sequential and reciprocal induction?
WT1: essential in normal kidney development
Explain how WT1 can malfunction.
Homozygous recessive (rare)
Wilms tumor 1 mutation: incomplete mesenchymal-to-epithelial transformation, but transform into cancerous cells
What is polycystic kidney disease?
Holes between ureteric bud and metanephric blastema
Cysts larger than nephron
There are two kinds of polycystic kidney disease. Name and incidence rate?
polycystic kidney disease
(ADPKD): 1-2 per 1000 births
Autosomal recessive polycystic
kidney disease (ARPKD): ~1 in 20,000-40,000
How does PKD come about?
Mutation of PKD1 & 2 gene
Ureteric bud and metanephric blastema anomaly
How does the kidney transition in the body?
Kidney ascends and rotates from pelvic to lumbar region (L2)
How does the hilum of the kidneys change as it ascends and rotates?
Original hilum is ventral, rotate to medial
What brings about the ascend of the kidneys?
The kidneys do not actually move across body compartments.
Depends on differing growth of Sacral and Lumbar regions
What other structure grows as kidneys ascend and rotate?
Growth of ureter
Explain the change in kidney blood supply as the kidney ascends. *blood vessels do not follow the kidney*
Metanephros at pelvis = middle sacral arteries/common iliac arteries
Transitional vessels that disappear/ degenerate later
Finally upper lumbar arteries
What congenital anomalies can occur with transitionary vessels?
Aberrant renal arteries
Accessory (supernumerary) renal arteries
Polar renal artery may obstruct ureter
What prevents the right kidney from ascending higher?
Right lobe of liver prevents right kidney to ascend as far as that on the left
What is a congenital condition in kidney ascending?
Ectopic kidney or unilateral double kidney
What supplies the suprarenal/ adrenal glands?
Suprarenal arteries (from
What is persistent lobulation?
Fetal kidneys are subdivided into lobes
disappears during infancy
Which 2 types of dysgenesis of kidney is possible?
Renal hypoplasia (undergrowth): unilateral /
Renal dysplasia: renal cysts
What structure is continuous with Cloaca and the lumen is later obliterated?
What divides the cloaca into two portions? When does this occur?
What are the two divded portions of the cloaca?
1. Posterior portion = anorectal canal (hindgut for fecal matter)
2. Anterior portion = primitive urogenital sinus (for urine)
What does urogenital sinus later contribute to ?
How does the urogenital sinus later divide and what if formed from each part?
1. Vesical (proximal) part (upper,largest) = forms part of bladder
2. Pelvic (middle) part forms prostatic, membranous urethra
3. Phallic (distal / lower) part forms penile urethra
What 2 things is allantois subdivided into?
What is the fate of the two subdivisions of the allantois?
vesico-urethra canal forms urinary bladder
Urachus becomes obliterated and becomes thick fibrous cord- median umbilical ligament
Where is urachus attached to on the bladder?
connected to apex of bladder
Extends along posterior
surface of anterior abdominal wall
What structure outgrows to form ureter? What part of it dilate to form a part of bladder wall?
Outgrowth / extension of mesonephric duct
Terminal ends of mesonephric ducts dilate > become trigone (triangular, smooth part of bladder wall)
What is trigone later covered by?
covered by ENDODERMAL***
from surrounding cloaca and
allantois > sensitive to
expansion and signal urination
What three congenital anomalies of the urachus are there?
(most common to least)
Urachal sinus (hollow cavity)
Urachal fistula (abnormal connection)
How do the three urachus anomalies come about?
Arise from remnants of epithelial lining of urachus
Urachal sinus (hollow cavity):
Superior part of urachus lumen may remain patent
Inferior part maybe patent
Urachal fistula (abnormal connection):
Entire urachus remains patent > allows urine to escape from its umbilical orifice
When does urorectal septum completely seperate cloaca?
Complete separation of liquid and solid into 2 cloaca compartments at 8 weeks
What is female perineal body?
central tendon of perineum
mass of interlocking muscular, fascial, and fibrous components lying between vagina and anorectum
What three components are there that form bladder?
Primitive urogential canal from divided cloaca
Extending mesophrenic duct forming trigone
Vesico-urethral canal from divided Allantois
Why is female perineal body important?
Essential for integrity of pelvic floor
Provides attachment to muscles
There are 6 congenital anomalies to ureter development. Try and name a few?
Double pelvis of ureter
Ectopic ureteric orifice
Postcaval ureter (behind vena cava)
Atresia of ureter(absence)
Ureterocele: distal ureter balloons at its opening into bladder > sac-like pouch
The connective tissue and smooth muscle of both sexes' urethra are derived from where?
splanchnic mesenchyme (endoderm, mesoderm)
What are the three parts to male urethra? Where are these parts developed from?
Vesical part - bladder
Pelvic part- prostatic and membranous
Phallic part- penile, enclosed by urethral fold
from urogenital sinus
+ glans urethra from ectoderm
What part of the adult spongy/ penile urethra is not derived from urogenital sinus?
How does the phallic urethra become continous with external environment?
Glans urethra, solid cord of ectodermal cells, ingrowth and canalize with terminal phallic urethra
How does the female urethra and male urethra differ in germ layer origin?
Male= endoderm and ectoderm
Female= only endoderm
Female urethra is formed how?
neck of primitive bladder elongates to form entire urethra
oligohydramnios (low amniotic fluid volume) causing Potter sequence anomalies is a result of what dysfunction?
renal agenesis, hypoplasia, or dysfunction in utero
Unlike other parts of the urinary system, the urethra is not...? (in origin)
Not originate from the mesoderm
What are 2 features at the terminal end of the spongy penile urethra in male?
Navicular fossa = pouch like end of urethra
What does the MEDIAN umblilcal ligament lie between?
MEDIAL umbilical ligaments which are fibrous remnants of umbilical arteries
What causes exstrophy of bladder?
Ventral body wall defect, exposing urinary bladder mucosa on abdominal wall
What are the three congenital anomalies to urethra development in male?
Narrow opening of external meatus, urethral stenosis
Urethral Openings on the underside of penis instead of at tip
Urethral opening on top of penis. Wide seperation of pubic bone and complete exstrophy of bladder
Summarize the origin of kidneys.
Ureteric bud and metanephric blastema
Outgrowth of mesnephric duct
Urinary bladder origin?
Extending mesophrenic duct
Urethra: female and male origin?
Female = endoderm, elongation of primitive bladder
Male: urogenital sinus, surface ectoderm