Urogenital System

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Urogenital System
Ass. Prof. Dr. Malak A. Al-yawer
Urogenital System can be divided into two entirely different components

(a (the urinary system and (b) the genital system.

Embryologically and anatomically, they are intimately interwoven
Urinary System 
Kidney Systems
Three slightly overlapping kidney systems are formed in a cranial to caudal sequence during intrauterine life in humans
(a) pronephros rudimentary and nonfunctional (b) mesonephros may function for a short time during the early fetal period (c) metanephros forms the permanent kidney.
Pronephros
Pronephros
Mesonephros
Mesonephros
The mesonephros and mesonephric ducts are derived from intermediate mesoderm from upper thoracic to upper lumbar (L3) segments.
In the middle of the second month the mesonephros forms a large ovoid organ on each side of the midline. Since the developing gonad is on its medial side, the ridge formed by both organs is known as the Urogenital ridge.
Mesonephros
Mesonephric or wolffian duct
Laterally, the tubule enters the longitudinal collecting duct known as the mesonephric or wolffian duct
The majority of excretory tubules
Metanephros The Definitive Kidney
Metanephros The Definitive Kidney
appears in the fifth week Its excretory units develop from metanephric mesoderm in the same manner as in the mesonephric system. The development of the duct system differs from that of the other kidney systems.
Collecting System
Excretory System
Excretory System
Capillaries grow into the pocket at one end of the S and differentiate into glomeruli. The proximal end of each nephron forms Bowmans capsule, which is deeply indented by a glomerulus.
Excretory System
The distal end forms an open connection with one of the collecting tubules. Continuous lengthening of the excretory tubule results in formation of the proximal convoluted tubule, loop of Henle, and distal convoluted tubule
Hence, the kidney develops from two sources 
(a) metanephric mesoderm, which provides excretory units and (b) the ureteric bud, which gives rise to the collecting system.
There are approximately 1 million nephrons in each kidney.They are formed until birth Urine production begins early in gestation, soon after differentiation of the glomerular capillaries, which start to form by the 10th week.
At birth, the kidneys have a lobulated appearance, but the lobulation disappears during infancy as a result of further growth of the nephrons, although there is no increase in their number.
Clinical Correlates


Renal agenesis
may arise if the interaction between the metanephric mesoderm and the ureteric bud fails to occur
Unilateral renal agenesis 
Bilateral renal agenesis
is associated with oligohydramnios (small amount of amniotic fluid) because little or no urine is excreted into the amniotic cavity. Most infants with bilateral renal agenesis die shortly after birth or during the first months of life.

Congenital polycystic kidney disease

(A) Surface view of a fetal kidney with multiple cysts(B) Section of the kidney in A, showing multiple cysts.
Duplication of the ureter results from
Position of the Kidney
Position of the Kidney
Abnormal Location of the Kidneys
Accessory renal arteries
are common they derive from the persistence of embryonic vessels that formed during ascent of the kidneys. These arteries usually arise from the aorta and enter the superior or inferior poles of the kidneys
Common variations of renal vessels
A and B, Multiple renal arteries. Note the accessory vessels entering the poles of the kidney. The polar renal artery, illustrated in B, has obstructed the ureter and produced an enlarged renal pelvis.
Function of the Kidney
Function of the Kidney
Bladder and Urethra
Bladder and Urethra
Three portions of the urogenital sinus can be distinguished the upper part ( the urinary bladder)
The next part is the pelvic part of the urogenital sinus
is a rather narrow canal, in the male , it gives rise to the prostatic and membranous parts of the urethra.
The last part is the phallic part of the urogenital sinus
It is flattened from side to side, and as the genital tubercle grows, this part of the sinus will be pulled ventrally . Development of the phallic part of the urogenital sinus differs greatly between the two sexes.)
During differentiation of the cloaca, the caudal portions of the mesonephric ducts are absorbed into the wall of the urinary bladder
As a result of ascent of the kidneys,
the orifices of the ureters move farther cranially those of the mesonephric ducts move close together to enter the prostatic urethra and in the male become the ejaculatory ducts
Trigone of the bladder
In infants and children, the urinary bladder, even when empty, is in the abdomen. It begins to enter the greater pelvis at approximately 6 years of age, but it does not enter the lesser pelvis and become a pelvic organ until after puberty.
Urethra
The epithelium of the urethra in both sexes originates in the endoderm the surrounding connective and smooth muscle tissue is derived from splanchnic mesoderm.
Urethra
Clinical Correlates
Bladder Defects Exstrophy of the bladder
Bladder Defects
Exstrophy of the bladder
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