URINARY SYSTEM URINARY SYSTEM Dr. Mujahid Khan Dr. Mujahid Khan
URINARY SYSTEMURINARY SYSTEM
Dr. Mujahid KhanDr. Mujahid Khan
Urinary SystemUrinary System
It consists of:It consists of:
The kidneys, which excrete urineThe kidneys, which excrete urine
The ureters, which convey urine from the The ureters, which convey urine from the kidneys to the bladderkidneys to the bladder
The urinary bladder, which stores urine The urinary bladder, which stores urine temporarilytemporarily
The urethra, which carries urine from the bladder The urethra, which carries urine from the bladder to the exteriorto the exterior
Development of Kidneys and Development of Kidneys and UretersUreters
Three sets of kidneys develop in human Three sets of kidneys develop in human embryosembryos
The first set is pronephroi, are rudimentaryThe first set is pronephroi, are rudimentary
The second set is mesonephroi, well developed The second set is mesonephroi, well developed but function brieflybut function briefly
The third set is metanephroi, become the The third set is metanephroi, become the permanent kidneyspermanent kidneys
PronephroiPronephroi
These transitory, non functional structures These transitory, non functional structures appear early in the fourth week in the neck appear early in the fourth week in the neck regionregion
The pronephric ducts run caudally and The pronephric ducts run caudally and open into the cloacaopen into the cloaca
They soon degenerate but most of the They soon degenerate but most of the pronephric ducts persist and are utilized pronephric ducts persist and are utilized by the next set of kidneysby the next set of kidneys
MesonephroiMesonephroi
Large, elongated, excretory organ appear Large, elongated, excretory organ appear late in the fourth week, caudal to the late in the fourth week, caudal to the rudimentary pronephroirudimentary pronephroi
Are well developed and function as interim Are well developed and function as interim kidneys for about four weeks, until kidneys for about four weeks, until permanent kidneys developpermanent kidneys develop
They consist of glomeruli and mesonephric They consist of glomeruli and mesonephric tubulestubules
MesonephroiMesonephroi
The tubules open into the mesonephric ductsThe tubules open into the mesonephric ducts
The mesonephric ducts open into the cloacaThe mesonephric ducts open into the cloaca
They degenerate toward the end of the first They degenerate toward the end of the first trimester trimester
Their tubules become the efferent ductules of the Their tubules become the efferent ductules of the testes testes
Mesonephric ducts have several adult derivatives Mesonephric ducts have several adult derivatives in malein male
MetanephroiMetanephroi
These are primordia of permanent kidneysThese are primordia of permanent kidneys
Begin to develop early in the fifth weekBegin to develop early in the fifth week
Start to function about four weeks laterStart to function about four weeks later
Urine formation continues throughout fetal lifeUrine formation continues throughout fetal life
Urine is excreted into the amniotic cavity and Urine is excreted into the amniotic cavity and mixes with amniotic fluidmixes with amniotic fluid
MetanephroiMetanephroi
A mature fetus swallows several hundred ml of A mature fetus swallows several hundred ml of amniotic fluid each day, which is absorbed by amniotic fluid each day, which is absorbed by the intestinethe intestine
The waste products are transferred through the The waste products are transferred through the placental membrane into the maternal blood for placental membrane into the maternal blood for elimination by kidneyselimination by kidneys
They develop from metanephric diverticulum and They develop from metanephric diverticulum and metanephric mass of intermediate mesodermmetanephric mass of intermediate mesoderm
MetanephroiMetanephroi
It is an outgrowth from the mesonephric It is an outgrowth from the mesonephric duct near its entrance into the cloacaduct near its entrance into the cloaca
The metanephric mass of intermediate The metanephric mass of intermediate mesoderm is derived from the caudal part mesoderm is derived from the caudal part of the nephrogenic cordof the nephrogenic cord
Both primordia of the metanephros are of Both primordia of the metanephros are of mesodermal originmesodermal origin
Metanephric DiverticulumMetanephric Diverticulum
It is the primordium of the ureter, renal It is the primordium of the ureter, renal pelvis, calices, and collecting tubulespelvis, calices, and collecting tubules
As it elongates, the metanephric As it elongates, the metanephric diverticulum penetrates the metanephric diverticulum penetrates the metanephric mass of intermediate mesodermmass of intermediate mesoderm
The stalk of the metanephric diverticulum The stalk of the metanephric diverticulum becomes the ureter and its expanded becomes the ureter and its expanded cranial end forms the renal pelviscranial end forms the renal pelvis
Metanephric DiverticulumMetanephric Diverticulum
The straight collecting tubules undergo repeated The straight collecting tubules undergo repeated branching, forming successive generations of branching, forming successive generations of collecting tubulescollecting tubules
First four generations of tubules enlarge to form First four generations of tubules enlarge to form the major calicesthe major calices
Second four generations coalesce to form the Second four generations coalesce to form the minor calicesminor calices
The remaining generations of tubules form the The remaining generations of tubules form the collecting tubulescollecting tubules
Metanephric DiverticulumMetanephric Diverticulum
The end of each arched collecting tubule The end of each arched collecting tubule induces clusters of mesenchymal cells in the induces clusters of mesenchymal cells in the metanephric mass of mesoderm to form small metanephric mass of mesoderm to form small metanephric vesiclesmetanephric vesicles
These vesicles elongate and become These vesicles elongate and become metanephric tubulesmetanephric tubules
As these renal tubules develop, their proximal As these renal tubules develop, their proximal ends are invaginated by glomeruliends are invaginated by glomeruli
Metanephric DiverticulumMetanephric Diverticulum
The renal corpuscle and its proximal convoluted The renal corpuscle and its proximal convoluted tubule, loop of Henle, and distal convoluted tubule, loop of Henle, and distal convoluted tubule constitute a nephrontubule constitute a nephron
Between the tenth and eighteenth weeks of Between the tenth and eighteenth weeks of gestation, the number of glomeruli increases gestation, the number of glomeruli increases graduallygradually
They increase rapidly until the thirty second They increase rapidly until the thirty second
weekweek
Uriniferous TubuleUriniferous Tubule
It consists of two embryologically different It consists of two embryologically different parts:parts:
A nephron derived from the metanephric A nephron derived from the metanephric mass of intermediate mesodermmass of intermediate mesoderm
A collecting tubule derived from the A collecting tubule derived from the metanephric diverticulummetanephric diverticulum
Fetal KidneysFetal Kidneys
They are subdivided into lobesThey are subdivided into lobes
This lobulation diminishes toward the end of the This lobulation diminishes toward the end of the fetal periodfetal period
The lobulation usually disappear during infancy The lobulation usually disappear during infancy as the nephrons increase and growas the nephrons increase and grow
The lobulated character of kidneys is normally The lobulated character of kidneys is normally obscured in adultsobscured in adults
Fetal KidneysFetal Kidneys
At term each kidneys contains 800,000 to At term each kidneys contains 800,000 to 1,000,000 nephrons1,000,000 nephrons
The increase in kidney size after birth The increase in kidney size after birth results mainly from the elongation of the results mainly from the elongation of the proximal convoluted tubules, as well as an proximal convoluted tubules, as well as an increase in interstitial tissueincrease in interstitial tissue
Fetal KidneysFetal Kidneys
Nephron formation is complete at birth, Nephron formation is complete at birth, except in premature infantsexcept in premature infants
Functional maturation of kidneys occurs Functional maturation of kidneys occurs after birthafter birth
Glomerular filtration begins around the Glomerular filtration begins around the ninth week and the rate of filtration ninth week and the rate of filtration increases after birthincreases after birth
Positional Changes of KidneysPositional Changes of Kidneys
Initially the metanephric kidneys lie close Initially the metanephric kidneys lie close to each other in the pelvisto each other in the pelvis
As the abdomen and pelvis grow, the As the abdomen and pelvis grow, the kidneys gradually come to lie in the kidneys gradually come to lie in the abdomen and move apartabdomen and move apart
They attain there adult position by the They attain there adult position by the ninth weekninth week
Positional Changes of KidneysPositional Changes of Kidneys
Initially the hilum of the kidneys lie Initially the hilum of the kidneys lie ventrallyventrally
As the kidney ascends, it rotates medially As the kidney ascends, it rotates medially almost 90 degreesalmost 90 degrees
By the ninth week the hilum is directed By the ninth week the hilum is directed anteromediallyanteromedially
Changes in the Blood Supply of Changes in the Blood Supply of KidneysKidneys
As the kidneys ascend from the pelvis, they As the kidneys ascend from the pelvis, they receive their blood supply from vessels that are receive their blood supply from vessels that are close to themclose to them
Initially the renal arteries are branches of the Initially the renal arteries are branches of the common iliac arteriescommon iliac arteries
As they ascend further, the kidneys receive their As they ascend further, the kidneys receive their blood supply from the distal end of the aortablood supply from the distal end of the aorta
As they reach higher level, they receive new As they reach higher level, they receive new branches from the aortabranches from the aorta
Changes in the Blood Supply of Changes in the Blood Supply of KidneysKidneys
Normally the caudal branches disappearNormally the caudal branches disappear
Their ascent stops when they come in contact Their ascent stops when they come in contact with suprarenal glands in the ninth weekwith suprarenal glands in the ninth week
The kidneys receive their most cranial branches The kidneys receive their most cranial branches from abdominal aorta, which becomes the from abdominal aorta, which becomes the permanent renal arteries permanent renal arteries
The right renal artery is longer and often more The right renal artery is longer and often more superiorsuperior
Urinary BladderUrinary Bladder
The urogenital sinus is divided into three The urogenital sinus is divided into three parts:parts:
A cranial visceral part that forms most of A cranial visceral part that forms most of the bladder, continuous with the allantoisthe bladder, continuous with the allantois
Middle pelvic part becomes the urethraMiddle pelvic part becomes the urethra
A caudal phallic part that grows toward the A caudal phallic part that grows toward the genital tuberclegenital tubercle
Urinary BladderUrinary Bladder
The bladder develops mainly from the vesical The bladder develops mainly from the vesical part of the urogenital sinuspart of the urogenital sinus
Its trigone region is derived from the caudal Its trigone region is derived from the caudal ends of the mesonephric ducts ends of the mesonephric ducts
Its epithelium is derived from the endoderm of Its epithelium is derived from the endoderm of vesical part of urogenital sinusvesical part of urogenital sinus
Other layers of its wall develop from adjacent Other layers of its wall develop from adjacent splanchnic mesenchyme splanchnic mesenchyme
Urinary BladderUrinary Bladder
Initially it is continuous with the allantoisInitially it is continuous with the allantois
The allantois soon constricts and becomes The allantois soon constricts and becomes a thick fibrous cord, called urachusa thick fibrous cord, called urachus
Urachus extends from the apex of the Urachus extends from the apex of the bladder to the umbilicusbladder to the umbilicus
In the adult the urachus is represented by In the adult the urachus is represented by the median umbilical ligament the median umbilical ligament
Urinary BladderUrinary Bladder
As the bladder enlarges, distal parts of the As the bladder enlarges, distal parts of the mesonephric ducts are incorporated into mesonephric ducts are incorporated into its dorsal wallits dorsal wall
Epithelium of the entire bladder is derived Epithelium of the entire bladder is derived from the endoderm of the urogenital sinusfrom the endoderm of the urogenital sinus
As the mesonephric ducts are absorbed, As the mesonephric ducts are absorbed, the ureters come to open separately into the ureters come to open separately into the urinary bladderthe urinary bladder
Urinary BladderUrinary Bladder
The orifices of the mesonephric ducts The orifices of the mesonephric ducts move close together and enter the move close together and enter the prostatic part of the urethra prostatic part of the urethra
Caudal ends of these ducts become the Caudal ends of these ducts become the ejaculatory ductsejaculatory ducts
The distal ends of the mesonephric ducts The distal ends of the mesonephric ducts in females degeneratein females degenerate
Urinary BladderUrinary Bladder
In infants and children, the urinary bladder In infants and children, the urinary bladder is in the abdomenis in the abdomen
It begins to enter the greater pelvis at It begins to enter the greater pelvis at about six years of ageabout six years of age
Does not enter the lesser pelvis and Does not enter the lesser pelvis and become a pelvic organ until after puberty become a pelvic organ until after puberty
UrethraUrethra
The epithelium of most of the male urethra and The epithelium of most of the male urethra and the entire female urethra is derived from the entire female urethra is derived from endoderm of the urogenital sinusendoderm of the urogenital sinus
The epithelium of the terminal part of the urethra The epithelium of the terminal part of the urethra is derived from the surface ectodermis derived from the surface ectoderm
The connective tissue and smooth muscle of the The connective tissue and smooth muscle of the urethra in both sexes are derived from urethra in both sexes are derived from splanchnic mesenchymesplanchnic mesenchyme
Suprarenal Glands Suprarenal Glands
The cortex develops from the mesodermThe cortex develops from the mesoderm
The medulla differentiates from neural crest cellsThe medulla differentiates from neural crest cells
Cortex appears during the sixth week from the Cortex appears during the sixth week from the mesothelium lining the posterior abdomnal wallmesothelium lining the posterior abdomnal wall
The cells that form the medulla are derived from The cells that form the medulla are derived from an adjacent sympathetic ganglion, derived from an adjacent sympathetic ganglion, derived from neural crest cellsneural crest cells
Suprarenal GlandsSuprarenal Glands
Differentiation of the characteristic Differentiation of the characteristic suprarenal cortical zones begins during suprarenal cortical zones begins during the late fetal periodthe late fetal period
The zona glomerulosa and zona The zona glomerulosa and zona fasciculata are present at birthfasciculata are present at birth
The zona reticularis is not recognizable The zona reticularis is not recognizable until the end of the third year until the end of the third year
Suprarenal GlandsSuprarenal Glands
The suprarenal glands of human fetus are 10 to The suprarenal glands of human fetus are 10 to 20 times larger than adult glands relative to body 20 times larger than adult glands relative to body weightweight
This is due to the extensive size of the fetal This is due to the extensive size of the fetal cortex cortex
The glands lose about one-third of their weight The glands lose about one-third of their weight during the first 2 or 3 weeks after birth and do during the first 2 or 3 weeks after birth and do not regain their original weight until the end of not regain their original weight until the end of the second yearthe second year