Renal embryology Flashcards
From which germ layers is the renal system derived?
Mesoderm and endoderm
3 layers of mesoderm
Paraxial, intermediate and lateral plate (also divides into somatic and splanchnic)
From which germ layer is the uterine tube derived
Mesoderm
From which germ layer is the uterus and uterine canal derived
Mesoderm
From which germ layer is the vagina derived
Mesoderm and endoderm
From which germ layer is the urethra derived
Endoderm
From which germ layer is the external genitalia
Endoderm
Which structures make up the renal collecting duct system
Ureters, renal pelvis, calyces, collecting tubules
Which structures make up the renal excretory system
Nephron (renal corpuscle, glomerulus, Bowman’s capsule), PCT, LOH, DCT
Which structures are formed by the mesonephric system?
Mesodermal germ layer structures (renal tubules, ureter, reproductive ductal system, uterine canal, vagina)
Which structures are formed from the cloaca?
Ectodermal germ layer (urinary bladder, urethra, vagina, external genitalia)
What is the pronephros?
Functional kidney in primitive fish, derived from intermediate mesoderm
What is the mesonephros?
Functional kidney in advanced fish - intermediate mesoderm, forms mesonephric ducts
- Mesonephros form excretory tubules with glomerular capillaries surrounding which forms Bowman’s capsule - makes renal corpuscle which drains to mesonephric ducts
- Developing gonads lies on medial side of developing mesonephros, forming urogenital ridge
What is the metanephros?
Functional kidney in human
How is the collecting system formed?
- Ureteric bud from mesonephros penetrates the metanephric tissue or blastema
- Gives rise to ureter, renal pelvis, calyces
- Collecting tubules converge on minor calyces forming renal pyramids
How is the excretory system formed?
- Distal end covered by metanephric cap
- Cells of cap form renal vesicles
- Renal vesicles form S-shapes renal tubules
- At one end of tubules, forms glomerulus
- Glomerulus indents to form Bowman’s capsule
- Other end forms pathway from Bowman’s capsule to collecting units
- Renal tubules + glomeruli form nephrons
- Lengthening of excretory tubes forms convoluted tubules
What are the two embryonic structures from which the kidney is derived?
- Ureteric bud from mesonepohric duct gives rise to collecting system
- Metanephric blastema forms excretory units
When does urine production start?
week 12
Why do the kidneys not filter waste in fetus?
Placenta does
Why does the kidney ascend?
Body curvature, growth in lumbar and sacral regions
How does the blood supply to the kidney change as it ascends?
In pelvis = pelvis branch of abdominal aorta
When ascends = higher branches of aorta
Wilm’s tumour
Kidney cancer in kids <5
Caused by mutated WT1 gene on 11p13
WAGR
Wilms, Aniridia, Gondoblastoma and mental retardation, due to deletion in chromosome 11 that includes PAX6 and WT1 genes
Denys-Drash
Congenital nephropathy
renal failure, ambiguous genitalia, Wilm’s tumour
How to treat renal dysplasia and Genesis
Dialysis and transplantation in yr1
What is multicystic dysplastic kidney?
ducts surrounded by undifferentiated cells, nephrons fail to develop and ureteric buds fail to branch so collecting ducts never form
Kidney defect impacts
involution of kidneys and renal agenesis (may also arise if no interaction between metanephric mesoderm and ureteric bud fails)
Potter’s syndrome
anuria, oligohydramnios and hypoplastic lungs, can be with abnormalities of vagina, uterus, vas deferens, seminal vesicles
Oligohydramnios
uterine cavity compressed - flattened face (Potter facies) and club feet
congenital polycystic kidney
may be autosomal recessive or dominant, cysts form from collecting ducts - large kidneys and renal failure
Autosomal recessive polycystic kidney disease
Cysts form in collecting ducts
Kidneys are very large - renal failure
Duplication of the ureter
early splitting of ureteric bud, can be partial or complete, metanephric tissue divides into twi parts with separate renal pelvis - may have some lobes in common. Sometimes, one ureter opens into bladder and other is ectopic, entering vagina, urethra or vestibule
Pelvic kidney
one kidney fails to ascend
Horseshoe kidney
Lower poles of kidneys fuse
- During ascent, horseshoe kidney arrested at lower lumbar vertebrae by inferior mesenteric artery
- Ureters arise from anterior surface of kidneys and pass ventral to isthmus of fused poles
What is the cloaca?
enlarged common sac for lower parts of hind gut and allantois - endoderm
What happens to the cloaca between weeks 4-8
cloaca divided by urorectal septum into urogenital sinus and anal canal
What happens to the urogenital sinus?
- Cloaca: enlarged common sac for lower parts of hind gut and allantois - endoderm
- During week 4-8, cloaca divided by urorectal septum into urogenital sinus and anal canal
- Urogenital sinus forms bladder, which is initially continuous with allantois - leaves urachus behind which connects bladder to umbilicus
- In adults, urachus forms median umbilical ligament
- Pelvic part of urogenital sinus in male forms prostatic and membranous parts of urethra
- Caudal portions of mesonephric ducts absorbed into bladder to form trigone
- Ureters enter bladder separately
- Trigone is mesodermal but is replaces by endodermal epithelium
- Orifices of ureters move farther cranially
- Mesonephric ducts move close together to form urethra and ejaculatory ducts
Exstrophy of the bladder
- Exstrophy of cloaca: ventral body wall defect, closure of lateral wall folds disrupted, anal malformations occur
Urachal fistula
lumen of intraembryonic portion of allantois persists, may cause urine to drain from umbilicus
Urachal cyst
localised area of allantois persists and results in cystic dilation
Urachal sinus
lumen in upper allantois persists, usually continuous with bladder
