1. Urogenital system

2. The urogenital system can be divided into two entirely different components: the urinary system and the genital system. Two embryonic structures that play an important role in the development of the urogenital system are the intermediate mesoderm and the cloaca.

3. We know that the mesoderm( or intra-embryonic mesoderm is subdivided into:
(a) paraxial mesoderm
(b) an intermediate mesoderm;
(c) lateral mesoderm

8. The development of Urinary System

11. KIDNEY SYSTEMS
Kidney has passed three stages of evolution in a cranial to caudal sequence.
Pronephros
mesonephros
metanephros.

12. Pronephros
At the beginning of the fourth week, the pronephros is represented by 7 to 10 solid cell groups in the cervical region of nephrogenic cord.

13. These groups form vestigial excretory units, which are made up of pronephric tubules and a single desending pronephric duct. The human pronephros have no-function and disappear by the end of the fourth week.
But pronephric duct ending in the cloaca, however, persists. Then it become to mesonephric ducts after development of mesonephros.

15. Mesonephros
The mesonephros consist of a series of excretory tubules that develop in the thoracolumlar region. These tubules (mesonephric tubules ) drain into the nephric duct which may now are called the mesonepheric duct.

16. Mesonephros mesonephric tubules mesonepheric duct Cloaca
( S-shaped )-Bowman’s C+Cap
Mesonephros
mesonepheric duct
Cloaca

19. 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.

20. the urogenital ridge

23. Most of the mesonepheric tubules disappear, but most part of them are modified and take part in forming the duct system of the testis. but they disappear in the female.

24. Metanephros
The metanephros, or permanent kidney, appears in the fifth week. It arises from two distinct sources. the metanephric blastema and the ureteric bud

26. The excretory dubules (or nephrons ) are derived from the lower part of the nephrogenic cord.This part is the metanephros, the cells of which form the metanephric blastema.

27. The collecting part of the kidney is derived from a diverticulum called the ureteric bud which arises from the lower part of the mesonephric duct where it close to its entrance to the cloaca.

29. The bud penetrates the metanephric tissue, which cover the distal end of the bud as a cap. Subsequently the bud grows and dilates to form ampulla.The ampulla divides repeatdly. The first three to five generations of branches fuse to from the pelvis of the kidney.the next divisions become the major calyces while further divisions form the minor calyces and collecting tubules.

32. The ureteric bud gives rise to the ureter, the renal pelvis, the major and minor calyces, and approximately 1 million to 3 million collecting tubules.

33. Each newly formed collecting tubule is covered at its distal end by a metanephric tissue cap. Under the inductive influence of the tubule, cells of the tissue cap form the nephron.

35. A solid clump of cells is converted into a vesicle which soon becomes pear shaped and opens into the ampulla. The visicle now becomes an S-shapd tube. Its distal end comes to be invaginated by a tuft of capillaries which form a glomerulus.The various parts of the nephron are derived from this S-shaped tube.

36. Capillaries grow into the pocket at one end of the S and differentiate into glomeruli. These tubules, together with their glomeruli, form nephrons, or excretory units.

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38. POSITION OF THE KIDNEY
The kidney, initially in the pelvic region, later shifts to a more cranial position in the abdomen. This ascent of the kidney is caused by diminution of body curvature and by growth of the body in the lumbar and sacral regions.

42. BLADDER AND URETHRA
Urinary bladder and urether are derived
from the cloaca.

45. urogenital sinus urorectal septum cloaca Primitive rectum
Between the two, the tip of the urorectal septum forms the perineal body.

46. urogenital membrane
Cloacal
Membrane
urorectal septum
anal membrane

47. The Vessico urethral canal
Derivatives of two parts of Primitive urogenital sinus
urinary bladder
The Vessico urethral canal
Primitive urethra
The pelvic part
Definitive UGS
The phallic part

48. urinary bladder urinary bladder Primitive urethra The pelvic part
Derivatives of two parts of Primitive urogenital sinus
urinary bladder
urinary bladder
The prostatic and membranous parts of the urethra in male
Urethra in female
Primitive urethra
The pelvic part
Penile urthra in male
The phallic part
Vestibule in female

49. The upper and largest part is the urinary bladder
The upper and largest part is the urinary bladder.Initially the bladder is continuous with the allantois, but when the lumen of the allantois is obliterated, a thick fibrous cord, the urachus, remains and
connects the apex of the bladder with the umbilicus. In the adult, it is known as the median umbilical ligament.

51. During differentiation of the cloaca, the caudal portions of the mesonephric
ducts are absorbed into the wall of the urinary bladder. Consequently, the ureters, initially outgrowths from the mesonephric ducts, enter the bladder separately.

53. 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.

57. Anomalies of kidneys: 1. Agenesis 2. Duplication:
3. Anomalies of shape:Horseshoe kidney
4. Abnormal of position:
5. Congenital polycystic kindney:

58. Congenital polycystic kindney:
Failure of the excretory tubules of the metanephros to establish contact with the collecting tubules, leads to the formation of cysts. Isolated cysts are commonly seen,but sometimes the whole kidney is a mass of such cysts.The cysts press upon normal renal tissue and destroy it.

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