development of urinary system Flashcards
from where does the urinary system develop?
Intermediate mesoderm
describe the stages of development of urinary system?
3 stages
appear in succession
caudal to the proceeding one in position and after it in time
what are 3 stages of development of urinary system?
Pronephros ( fore kidney )
Mesonephros
Metanephros —–> permanent kidney
when does the pronephros start?
beginning of 4th week
describe pronephros ?
functionless transitory structure
PERMANENT kidney in some fishes
about 5-7 pairs of horizontally arranged segments ( NEPHROTOMES )
where do pronephrons appear?
opposite to the cervical segments
what are the components of pronephros ?
each pronephric tubule has 2 ends
describe the first end?
Open into the :
Intraembyronic coelom and is invaginated by small branches of the dorsal aorta forming internal and external renal corpuscles
describe the other end?
bends caudally and all of them unit together and become canalized to form longitudinal duct called PRONEPHRIC DUCT
what is the fate of pronephric tubules?
disappear at the end of 4th week of development
whats the fate of pronephric duct?
grows :
Caudally beyond the level of the tubules
until it opens into the CLOACA and receive the openings of mesonephric tubules and BECOME MESONEPHRIC DUCT
SO: mesonephric tubules + pronephric duct = mesonephric duct
what is the main purpose of pronephros ?
only function is to form the mesonephric duct for the next stage —> MESONEPHROS
hence the structure of pronephros are temporary functionless structures
no secretion of urine at this stage
what is mesonephrons?
second kidney to appear at 4th week ( the tubules disappear at 4th week )
Temporary functioning structure
it is the stage as where the kidneys start functioning and produce urine
(AKA MIDKIDNEY )
describe the development of mesonephros ?
masses of cells called MESONEPHRIC MASSES
where do the mesonephric masses appear at?
opposite the thoracic region
L3
what happens to the mesonephric masses ?
in wollfian body stage
the masses become HOLLOWED INTO VESICLES
ELONGATE to form tubule and BEND TO BE S SHAPE
and has lateral end and medial end
what happens to lateral end of the mesonephric tubule in S shape?
joins the mesonephric duct
( continuation of the pronephric duct in the previous stage after the cloaces )
what happens to the medial end of the mesonephric tubule ?
Becomes invaginated by blood capillaries to form renal corpuscles
( bowman capsule )
what is the function of mesonephros?
permanent kidney of amphibians
in human;
mesonephros may function and produce small amount of urine between the :
6th and 10th weeks
the duct contribute to the formation of the duct system in both males and females but they play more in significate role in males
what does the mesonephric structure give rise to in MALES?
Vasa efferentia
Vas deferens
Seminal vesicles
Ejaculatory duct
what does the mesonephric structure give rise to in females?
Largely regress leaving behind :
Epoophoron
Paraophoron
both located near the ovary
what happens the to the mesonephros ?
degenerate by the end of 10th week
what is metanephrons ?
HIND KINDEYS
permanent kidney
when does the metanephros appear?
end at the 4th weeks
what is the origin of the metanephros ( HIND KIDNEY )?
Ureteric bud –> Give rise to collecting system
Metanephric cap —-> give rise to excretory unit
where does ureteric bud come from?
Distal end of mesonephric duct close to THE CLOACA ( where the pronephric become mesonephric duct )
appear as diverticulum
elongate up through the intermediate mesoderm
what happens to ureteric bud ?
Upper end dilates to form : PELVIS OF THE URETER
Proximal part —> GREATER PART forms URETER
What happens to the pelvis of the ureter from upper end of ureteric bud?
divide into 2 or 3 MAJOR calyces
then to :
Minor calyces
Minor calyces which branch into a great number of collecting TUBULES
where does the ureteric bud opens into?
Ureter originally opens into :
Mesonephric duct (end of 1st stage )
BUT AT LATER STAGE :
the lower part of mesonephric duct becomes absorbed into the wall of the developing urinary bladder
So due to that the ureter will open directly into urinary bladder
what gives rise to the trigone region?
part of mesonephric duct that get absorbed into the cloaca
what is the origin of the urinary bladder ?
primarily derived from the endoderm
EXCEPT THE TRIGONE FROM THE INTERMEDIATE MESODERM
what is the origin of metanephric cap?
Mesoderm of the metanephros surrounds the upper part of the ureteric bud
what happens to the metanephric cap?
Segmented into cell clusters
in relation to the termination of collecting tubules
These cell clusters change into VESICLES KNOWN AS RENAL VESICLES
what happens to the renal vesicles (From the cap )?
elongate greatly to form different part of the nephron which :
Bowmans capsule
Proximal convoluted tubules
Loop of henle
Distal convoluted tubules
what happens to the distal convoluted tubule?
Joins the nearest collecting tubule
together to form a complete uriniferous tubules
what is the first location of the kidney?
sacral region
why does the kidney ascend to the lumbar region ?
Growth of the body in the lumbar and sacral regions
Straightening of the body curvature
Differential growth of the surrounding organs
why is the right kidney slightly lower than left?
large size of the right lobe of the liver
what is the blood supply of kidney during development ?
Nearest artery as it ascend :
Median sacral
internal iliac
common iliac
FINALLY : renal artery develops at the 2nd lumbar vertebra
Describe lobulation of the kidney?
fetal kidney is lobulated
this lobulation disappear before birth
if persist its considered congenital
describe the rotation of the kidney?
At first :
Hilum is anteriorly
Then :
Kidney rotate 90 degree MEDIALLY so hilum be medially
Describe agenesis of the kidney?
Due to failure of the uretic bud (no bud = no cap )
or failure of development of nephrogenic ridge
Unilateral renal agenesis :
No specific symptoms because the other kidney undergo hypertrophy to compensate
Bilateral renal agenesis :
2 kidneys are absent
Ureters either wholly or partially absent
Trigone is poorly formed
incompatible with postnatal life
Whats associated with agenesis of the kidney?
Oligohydramnios
because little or no urine is excreted into amniotic fluid ( cuz no kidney = no urine = little fluid )
what is supernumerary kidney and what causes it?
multiple kidneys
Due to :
Early splitting of the ureteric bud
Branching from the initial ureteric bud
Theres more than one kidney in one or both sides
additional kidney is normal in shape and caudal to the dominant one
what causes simple renal ectopia ?
abnormal site of kidney
Defective development of METANEPHRIC CAP
Failure of metanephric cap to induce the ascent
what is pelvic kidney?
kidney located opposite to the sacrum
below the aortic bifurcation
what is lumbar kidney?
kidney in ILIAC FOSSA
opposite to the sacral promontry
what is abdominal kidney?
Above iliac crest
opposite to 2nd lumbar vertebrae ( L2 )
what is horse shoe kidney?
abnormal in formation and fusion of kidney
The lower poles of both kidneys are connected together by ISTHMUS
usually renal tissue may pass in front of the aorta and IVC
Hilum usually faces anteriorly ( no rotation )
PRODUCE NO SYMPTOMS AS THE COLLECTING SYSTEM DEVELOPS NORMALLY
what prevents the ascent of horse shoe kidney?
arrested by origin of inferior mesenteric artery
At L3
So the horse show is at L3
describe anomalies in rotation ?
Non rotation : hilum is anteriorly
Incomplete rotation : HILUM is anteromedially
Reverse rotation : hilum is directed antero laterally
what causes renal hypoplasia ?
Incomplete development and differentiation of ureteric bud
kidney are small in one or both sides
what is polycystic kidney?
multiple cysts in the kidney due to accumulation of urine in convoluted tubules results in formation of retention of cysts
results in normal nephrons being compressed by cysts
3 TYPES :
congenital polycystic kidney
adult polycystic kidney
solitary cyst of kidney
what causes congenital polycystic kidney?
hereditary causes
what causes adult polycystic kidney?
failure of connection between collecting and excretory tubules
what is multiple renal arteries ?
anomaly of renal vascular
the kidneys are supplied by multiple arteries due to failure of degeneration of primitive arterial supply
could be
median sacral artery
internal iliac artery
Common iliac artery
what is accessory renal artery?
two or more arterial branches supplying the same renal segment
what causes ureteral agenesis ?
Due to complete failure of ureteral bud development
occurs with bilateral renal agenesis
no kidney = no ureter
what causes duplication of the ureter ?
Premature division of ureter bud
MOST COMMON URTERAL ANOMALY
its hereditary autosomal dominant trait
shows :
Double pelvis of ureter ( due to premature division of ureteric bud near the termination - upper end )
Bifid ureter ( Partial duplication ) :
Double pevlis and double ureter open through a common orifice into urinary bladder
Double ureter ( complete duplication ) :
Development of 2 ureteric buds from single mesonephric duct , two ureters open independently into the bladder
Orifice of the lower uterer occupies more cranial and lateral position and that of upper ureter
what is ectopic ureteric orifice ?
second ureteric bud arising from the as ingle mesonephric duct near its termination
In males :
additional ureter may into the bladder , PROSTATIC URETHRA, EJACULATORY DUCT
in females :
Additional ureter may opens into the urethra or even vagina
what is retrocaval / retroiliac ureter?
development disorder of inferior vena cava
the right ureter TRACES OUT AN S at the level OF L4 behind the THE VENA CAVA ( Retrocaval )
in similar fashion the ureter can also run behind the common iliac artery at the level of L5 ( retero iliac ureter )
can suffer from renal obstruction due ureteric obstruction in cases of INCEASED VENOUS RETURN
what causes anomalies of structure of ureter?
Varying degrees of failure of ureteral bud development and canalization
1- MEGA URETER : CAUSES BY OBSTRUCTION OF RENAL FLOW
2- Atresia and hypoplasia : the ureter has developed proximally and can end blinding distally
3- Ureteral stenosis and stricture
4- folds of the ureters
5- Ureteral valves
6- Ureteral diverticula
