Embryology Of Urinary System

Question 1

Development of the Urinary System
• Urinary & genital systems are closely associated
• Both develop from ——— mesoderm
– — th- —th somite level(— week)
– Nephrogenic mass (cord)
• At the dorsal side of coelom each cord produces a bulge into the coelom called the —— ridge
• Urogenital Ridge
– Form the —— & —— structures
– ——— : a zone of segmented mesodermal tissue between the somite-forming dorsal mesoderm & the unsegmented lateral plate.

Answer 1

Development of the Urinary System
• Urinary & genital systems are closely associated
• Both develop from intermediate mesoderm
– 7th- 28th somite level(3rd-d week)
– Nephrogenic mass (cord)
• At the dorsal side of coelom each cord produces a bulge into the coelom called the urogenital ridge
• Urogenital Ridge
– Form the urinary & genital structures
– Nephrotomes : a zone of segmented mesodermal tissue between the somite-forming dorsal mesoderm & the unsegmented lateral plate.

Question 2

• Urinary tract develops from the —rd wk of the embryonic period from the —— mesoderm as well as from the —— sinus.
• The kidneys develop from the —th week from three overlapping sequential systems:

Answer 2

• Urinary tract develops from the 3rd wk of the embryonic period from the intermediate mesoderm as well as from the urogenital sinus.
• The kidneys develop from the 4th week from three overlapping sequential systems:
the pronephros, (a cranial anlage) -atrophies in the 4th week
the mesonephros, 6th and 10th weeks, but is only transitory
the metanephros, anlage of the definitive kidneys. They develop from a metanephric anlage (mesodermal origin) & the ureter anlage (that has its origin in the caudal part of the wolffian duct).

Question 3

the pronephros, (a cranial anlage) -atrophies in the —th week
the mesonephros, —th and —th weeks, but is only transitory
the metanephros, anlage of the definitive kidneys. They develop from a ———& the ——

Answer 3

• Urinary tract develops from the 3rd wk of the embryonic period from the intermediate mesoderm as well as from the urogenital sinus.
• The kidneys develop from the 4th week from three overlapping sequential systems:
the pronephros, (a cranial anlage) -atrophies in the 4th week
the mesonephros, 6th and 10th weeks, but is only transitory
the metanephros, anlage of the definitive kidneys. They develop from a metanephric anlage (mesodermal origin) & the ureter anlage (that has its origin in the caudal part of the wolffian duct).

Question 4

the mesonephros, 6th and 10th weeks, but is only transitory
the metanephros, anlage of the definitive kidneys. They develop from a metanephric anlage (—— origin) & the ureter anlage (that has its origin in the ——).

Answer 4

the metanephros, anlage of the definitive kidneys. They develop from a metanephric anlage (mesodermal origin) & the ureter anlage (that has its origin in the caudal part of the wolffian duct).

Question 5

• The nephron, mainly arises from the ——— (glomerulus, proximal, intermediate & distal tubules),
• the rest of the upper urinary tract (collecting ducts, calices, renal pelvis and ureter) develop from the ———.

Answer 5

• The nephron, mainly arises from the metanephric anlage (glomerulus, proximal, intermediate & distal tubules),
• the rest of the upper urinary tract (collecting ducts, calices, renal pelvis and ureter) develop from the ureter anlage.

Question 6

The lower urinary tract differentiates from the cloaca btw the —th & —th wks by the ——— septum.
• The ventral part of the cloaca forms the ———, out of which the —— forms in the lower part & the —— in the upper part.
• The ureter anlage discharges into the ——— wall of the urogenital sinus.

Answer 6

The lower urinary tract differentiates from the cloaca btw the 5th & 8th wks by the urorectal septum.
• The ventral part of the cloaca forms the primary urogenital sinus, out of which the urethra forms in the lower part & the bladder in the upper part.
• The ureter anlage discharges into the upper posterior wall of the urogenital sinus.

Question 7

In (males/females?), the wolffian duct remains present & forms a connection to the genital tract in the lower part of the urogenital sinus.

Answer 7

Males

Question 8

: In males, the wolffian duct remains present & forms a connection to the genital tract in the lower part of the ———.

Answer 8

the lower part of the urogenital sinus.

Question 9

• Numerous induction mechanisms between ———& ——— occurs during:
the development of the renal system,

Answer 9

Ureter anlage
Metanephric mesenchyma

Question 10

the ascent of the kidneys, originating at the level of the —— & moving up to the —— at the end of the development,

Answer 10

the ascent of the kidneys, originating at the level of the sacrum & moving up to the diaphragm at the end of the development,

Question 11

Intermediate Mesoderm
In the Cervical region
– Loses contact with the ——
• Forms ———(— - —pairs) which acquire a lumen & open medially into the ————coelom
• Caudal growth unite & form longitudinal duct called the —— duct
• Branches off dorsal aorta form —— (ext & int)
In the Thoracic, lumbar, sacral regions – Loses contact with ———
• — glomeruli fail to develop
• ——— disappears (nephrogenic cord) – 2 or more ——— per prior segment formed

Answer 11

Intermediate Mesoderm
• Cervical region
– Loses contact with the somite
• Forms nephrotomes(6-10 pairs) which acquire a lumen & open medially into the intra-embryonic coelom
• Caudal growth unite & form longitudinal duct (pronephric duct)
• Branches off dorsal aorta form glomeruli (ext & int)
• Thoracic, lumbar, sacral regions – Loses contact with coelomic cavity
• Ext glomeruli fail to develop
• Segmentation disappears (nephrogenic cord) – 2 or more excretory tubules per prior segment

Question 12

Urinary Tubules
• Associated with a vascular tuft = ———
– Open tubules = —— glomerulus •One end opens into the ——
•Other end opens into the ———
– Closed tubules = ——- glomerulus •Open only into the ———

Answer 12

Urinary Tubules
• Associated with a vascular tuft =
glomerulus
– Open tubules = external glomerulus •One end opens into the coelom
•Other end opens into the collecting duct
– Closed tubules = internal glomerulus •Open only into the collecting ducts

Question 13

Formation of 3 kidney systems • Pronephros (simplest & most primitive)
– how many to how many solid or tubular arranged cell groups in the cervical region (head kidney)
– Gone by the end of the —th week
• Mesonephros (intermediate-more advanced) – Appear during regression of ——
– — to —th somite level
• Metanephros (permanent kidney)
– Begins to develop early in —th week, functions by the —-th week

Answer 13

Formation of 3 kidney systems • Pronephros (simplest & most primitive)
– 7-10 solid or tubular arranged cell groups in the cervical region (head kidney)
– Gone by the end of the 4th week
• Mesonephros (intermediate-more advanced) – Appear during regression of pronephros
– 10-26th somite level
• Metanephros (permanent kidney)
– Begins to develop early in 5th week, functions by the 11th week

Question 14

Mesonephros
• Tubules develop from —— cord (NC)
– Opens into the ———— duct
– Gone by week — in females, in males some tubules persist & become vas deferens
• Approximately — pairs of closed tubules – — -shaped bend
– Surrounds ( internal /external?) glomerulus
• Mesonephric duct develops(laterally/medially?) from NC & extends from—th somite to ———

Answer 14

Mesonephros
• Tubules develop from nephrogenic cord (NC)
– Opens into the excretory/mesonephric duct
– Gone by week 10 in females, in males some tubules persist & become vas deferens
• Approximately 38 pairs of closed tubules – S shaped bend
– Surrounds internal glomerulus
• Mesonephric duct develops laterally from NC & extends from 8th somite to urinogenital sinus

Question 15

Metanephros
• Nephrons/tubules develop from nephrogenic mass (—th-—th somite level)
– Located lateral to —— duct
– Internal dense layer which forms ——- – Outer loose layer forms ———
• Duct system derived from ———

– Ureteric bud elongates & makes contact with nephrogenic mass which surrounds bud like a cap
• Tubules are (closed/open?) (——glomerulus)
• Migrate from —— to —— as fetus grows – Blood supply from aorta changes as ascent occurs
• Becomes functional in (first/second?) 1⁄2 of pregnancy

Answer 15

Metanephros
• Nephrons/tubules develop from nephrogenic mass (26th-28th somite level)
– Located lateral to mesonephric duct
– Internal dense layer which forms tubules/nephrons – Outer loose layer forms connective tissue capsule
• Duct system derived from ureteric bud
– Ureter, renal pelvis, calyces, collecting ducts
– Ureteric bud elongates & makes contact with nephrogenic mass which surrounds bud like a cap
• Tubules are closed (internal glomerulus)
• Migrate from pelvis to abdomen as fetus grows – Blood supply from aorta changes as ascent occurs
• Becomes functional in second 1⁄2 of pregnancy

Question 16

Cloaca
• —— end of the hindgut (dilated)
• In 3 week old embryo the hindgut ends blindly at the ——membrane
• —— and ——— open into cloaca
• Cloaca is latin for ——, a system of pipes used to transport human waste
• During —th to—th week cloaca subdivided
– —— portion = anorectal canal
– ——- portion = primitive urogenital sinus

Answer 16

Cloaca
• Caudal end of the hindgut (dilated)
• In 3 week old embryo the hindgut ends blindly at the cloacal membrane
• Blind end = cloaca
• Allantois and mesonephric ducts open into cloaca
• Cloaca is latin for sewer, a system of pipes used to transport human waste
• During 4th to 7th week cloaca subdivided – Posterior portion = anorectal canal
– Anterior portion = primitive urogenital sinus

Question 17

Urinary Bladder
• Bladder is formed from primitive ——
• Initially bladder is continuous with the ——
– Allantois lumen obilterated & —— formed connecting ——— with ———
– In adult urachus = ——ligament
• Ureter is outgrowth of —— duct
– Terminal ends of mesonephric ducts become part of ———
– Ureter obtains separate entrance into bladder with time

Answer 17

Urinary Bladder
• Bladder is formed from primitive urogenital sinus
– Bladder is upper & largest part of urogenital sinus
• Initially bladder is continuous with the allantois
– Allantois lumen obilterated & urachus formed connecting apex of bladder with umbilicus
– In adult urachus = median umbilical ligament
• Ureter is outgrowth of mesonephric duct
– Terminal ends of mesonephric ducts become part of bladder wall
– Ureter obtains separate entrance into bladder with time

Question 18

Ascent of Kidneys
• During the —— & —— weeks of development, the mature kidneys lie in the —- with their hila pointed ——.
• As the pelvis & abdomen grow, the kidneys slowly move upward.
• By the —— week, the hilum points —— & the kidneys are located in the ——.
• As the embryo continues to grow in a caudal direction, the kidneys are left behind and eventually come to lie in a —— position at the level of L— by the —— week of development.
• In the meantime, the kidneys have completed rotation & the hila now face ————.

Answer 18

Ascent of Kidneys
• During the fifth & sixth weeks of development, the mature kidneys lie in the pelvis with their hila pointed anteriorly.
• As the pelvis & abdomen grow, the kidneys slowly move upward.
• By the seventh week, the hilum points medially & the kidneys are located in the abdomen.
• As the embryo continues to grow in a caudal direction, the kidneys are left behind and eventually come to lie in a retroperitoneal position at the level of L1 by the ninth week of development.
• In the meantime, the kidneys have completed rotation & the hila now face anteromedially.

Question 19

, the kidney does maintain its —— appearance throughout development.

Answer 19

Lobulated

Question 20

List abnormalities that could occur

Answer 20

APPIED ANATOMY
• Duplication of the urinary tract
• Polycystic kidney disease
• Pelvic kidney (A)
• Horseshoe kidney (B)