W04: RENAL EMBRYOLOGY Flashcards
Describe the embryological development of the urinary tract and relate this to developmental anomalies
(intermediate plate mesoderm) = folding
- peritoneum sits anteriorly to the intermediate mesoderm thus the GU system is retroperitoneal
- cloacal separation producing rectum and urogenital sinus which separate completely
- URACHUS & UROGENITAL SINUS = URINARY BLADDER
- kidneys arise from 2 intermediate plate mesoderms
Folding of the embryo
endoderm = gut tube
lateral plate mesoderm fusion = visceral and parietal pleura
ectoderm = amniotic cavity
intermediate mesoderm = GU system
head and tail folding, allantoic sac develops (caudal end of gut tube) = waste products
Significance of horseshoe kidney
Kidneys cannot ascent up the abdomen thus end up at lower levels within the adult cavity.
Allantois & Cloaca Development
endoderm outpouching @ hindgut extending into the body stalk (which forms into the umbilical cord); allantois combines w/ umbillical cord
\+Cloaca (embryological Vs birds) = same hole (gross); develops as allantois develops; and becomes divided via URORECTAL SEPTUM = anterior cloaca - UROGENITAL posterior cloaca - RECTUM
once umbillical cord severed = allantois remnant becomes fibrous.
What mbryological origins are the bladder and urethra
Endodermal origin
Kidney embryological origin
intermediate plate mesoderm
Kidney development
1) PRONEPHROS @ W4
intermediate plate neck region,
pronephric duct + tubules opens into cloaca
degenerates @ W5
2) MESONEPHROS @ late W4
tubules + duct drain to cloaca / anterior urogenital sinus
(duct originally the pronephric duct - recycled structure)
degenerate @ W9
3) METONEPHRIC KIDNEY @ late W9
ureteric bud buds off mesonephric duct = metanephric mesoderm which gives rise to definitive kidney
*meanwhile MESONEPHROS incorporated into gonad
+mesonephric duct = spermatic cord / vas deferens
+ mesonephros = ovary + tubules and duct degenerate
+paramesonephric (females) = uterus fallopian tubes etc
a
a
METANEPHROS / DEFINITIVE KIDNEY DEVELOPMENT
ureteric bud comes off the mesonephric duct = metanephric mesoderm (most caudal part of intermediate mesoderm)
*reciprocal induction
URETERIC BUD
- ureteric stalk/bud develops into ureters as it branches continually as well as pelvis (proximal end of ureteric bud)
- major calyces arise from first 4 generations of branches
- minor calyces arise from next 4 generations
- remaining = collecting tubules
METANEPHRIC MESODERM
*surrounding a ureteric bud, where the mesoderm buds off and forms ducts and vessels
What does the metanephric mesoderm form?
Kidney parenchyma = medulla and cortex = definitive kidney
*surrounding a ureteric bud, where the mesoderm buds off and forms ducts and vessels
= medullary loops etc.
*ascension of the kidneys = so hilum @L1-L2
kidneys generally lie at T12-L3
*suprarenal gland arrests any further ascent, during ascent vasculature is continually broken down and recycled
What does the ureteric bud form?
collecting system = calyces, pelvis, ureter
- ureteric stalk/bud develops into ureters as it branches continually as well as pelvis (proximal end of ureteric bud)
- major calyces arise from first 4 generations of branches
- minor calyces arise from next 4 generations
- remaining = collecting tubules
Difference between nephron and uniferous tubule
embryologically = nephron exclusively arises from metaneph. mesoderm. whereas the uriniferous tubule arises from both as it also involves the collecting duct (of ureteric bud origin)
Congenital Abnormalities
1) Dysfunctional vascularisation during ascent = extra artery at lower pole of kidney exerting pressure on ureter
=enlarged renal pelvis
2) Bifid kidneys
3) abnormal ureter opening sites
4) horseshoe kidney = IMA, SMA and branches
5) polycystic kidneys
