Embryo/Teratogenesis Flashcards
Where does the urinary system develop from?
Intermediate mesoderm along posterior wall of abdominal cavity
What are the 3 developmental kidney systems (cranial to caudal)?
1) Pronephros
2) Mesonephros
3) Metanephros
Is the pronephros functional?
No, it is rudimentary and non-functional
How long does the pronephros exist for?
1 week (beginning to end of 4th week)
What arises from the pronephros?
Vestigial excretory units (nephrotomes)
When does the pronephros develop?
Beginning of 4th week
When does the mesonephros develop?
Middle of 2nd month
Where are both the mesonephros and mesonephric ducts derived from?
Intermediate mesoderm from Upper thoracic to L3 segment
The mesonephros form ______ on each side of the midline and the ________ ridge.
Form large ovoid organ
and urogenital ridge
When do the 1st excretory tubules of the mesonephros appear?
Early in 4th week
The 1st excretory tubules of mesonephros acquire _____________ at the _____ end. Tubules enter the ______________.
Acquire glomerular capillary tuft at medial end
Tubules enter longitudinal mesonephric (wolffian) duct laterally
True or false: Caudal tubules will differentiate into functional tubules before the cranial tubules degenerate.
False.
Cranial tubules start degenerating while caudal tubules are still differentiating
Most disappear by end of 2nd month
The metanephros forms the permanent kidney and appears in the ____ week.
5th week
Where do nephrons develop from?
Metanephric mesoderm
Where does the collecting system of kidneys develop from?
Ureteric bud
How are metanephric tubules formed?
From metanephric tissue cap (induced by collecting tubule)
- forms small renal vesicles
→ comma-shaped → S-shaped
→ metanephric tubules
How do metanephric tubules develop into functional nephrons?
Proximal end deeply indented by glomerulus and forms Bowman’s capsule
Distal end in open connection with collecting tubules
Nephron lengthen → PCT, LOH, DCT
How does the collecting system of the kidneys form?
From ureteric bud
1) Bud penetrates metanephric tissue
2) Dilates to form renal pelvis
3) Branches repeatedly → Ureter, pelvis, major/minor, calyces, collecting tubules
True or false: The maximum number of nephrons a person has is determined at birth.
True.
There is no increase in number of nephrons postnatally. (~1 mil)
True or false: The kidneys are lobulated only at birth.
True.
The lobulations disappear with the growth of nephrons (gaps filled with tissue)
True or false: The kidneys are located in the pelvic region throughout life.
False.
Kidneys initially located in pelvic region but ascend to more cranial position in abdomen.
How does the blood supply of the kidneys change throughout development?
1) Initially supplied by pelvic branch of aorta
2) Shifts to more cranial position in abdomen
3) Supplied by arteries from higher levels of aorta → lower vessels degenerate
What causes the ascent of the kidneys?
1) Diminution of body curvature
2) Growth of body in lumbar and sacral regions
When does the metanephros become functional?
End of 1st trimester
Where is fetal urine passed into after the 1st trimester?
Amniotic cavity
(mixes with amniotic fluid and swallowed to be excreted over and over)
True or false: The kidneys are functional by the end of the 1st trimester and are responsible for homeostasis of ions, water, blood pressure, excretion of waste products etc.
False.
Excretion of waste products is done by placenta
What are the forms of renal agenesis?
1) Unilateral (1 functional)
2) Bilateral (die)
What is an ectopic kidney?
Pelvic kidney (did not ascend)
What is a horseshoe kidney?
Fusion of kidneys
In which condition would more than 2 renal pelvises be seen?
Duplication of urinary tract (eg. complete division of ureteric bud)
What is a possible complication of accessory renal arteries formed as a result of developmental anormalities?
Compression/obstruction of ureter
Where does the urinary bladder form from?
The upper (largest) part of urogenital sinus
What does the pelvic part of the urogenital sinus form?
Forms prostatic and membranous parts of urethra in males
What is the urorectal septum?
Divides cloaca into anorectal canal and urogenital sinus
When does the cloaca divide into the anorectal canal and urogenital sinus?
Between 4th-7th week
The _______ membrane divides into the urogenital and anal membrane.
Cloacal
What are 2 structures that the urogenital sinus gives rise to?
Bladder and urethra
The caudal portions of the mesonephric duct are absorbed into _________.
The urinary bladder wall
What forms the ejaculatory ducts in males?
Orifices of the mesonephric ducts that move close together and enter the prostatic urethra
What is the embryological origin of the mesonephric ducts and ureters?
Mesoderm
What is the embryological origin of the trigone?
Mesoderm
What is the embryological origin of the bladder lining?
Mostly endoderm
(only trigone mesoderm left, rest replaced)
