Lecture 11: Renal Embryology Flashcards
Which layer does the renal system come from?
Intermediate mesoderm
Describe the initial development of the kidney
Intermediate mesoderm > urogenital ridge in each side of the dorsal aorta > nephrogenic cord > pronephros/mesonephros/metanephros
Which sets of nephric structures degenerate and which don’t?
Pronephros and Mesonephros mostly degenerate
Metanephros becomes the permanent kidney
Pronephros:
What happens at week 4?
What happens at Day 24-25?
- Pronephros develops at cervical region and duct grows caudally to connect to the cloaca (future bladder
- Horizontal tubules degenerate and ducts are used as template for mesonephros
Mesonephros:
What happens at late Wk4?
Mesonephric duct continues downward and develops its own horizontal tubules
What do the medial mesonephric tubules form?
Glomerular capsule that wraps around the developing glomerulus (capillaries)
Mesonephric tubules:
What happens at Wk6-10?
What happens at Wk 12?
- acts as primitive kidney that filters fetal blood
- stops function and degeneration (complete in females, stays at efferent ductules in males)
What happens during Wk 5?
Mesonephric duct at cloacal junction induces formation of the ureteric bud
How does the metanephros develop?
When does this happen?
Ureteric bud (from mesonephric duct) grows cranially and meets metanephric blastema/kidney bean (from nephrogenic cord) = form the permanent kidney Wk 9 -10
How do the renal pelvis and ureters form from the ureteric bud?
Ureteric bud meets the blastema and penetrates it to form the renal pelvis
Stalk of the ureteric bud becomes the ureter
How do the collecting tubules and the calices form from the ureteric bud?
Cranial ureteric bud forms the collecting tubules
1st 4 generations of the collecting tubules become major calices
2nd 4 generations of the collecting tubules form the minor calices
How do nephrons develop?
Collecting tubule arches and induces the blastema to form metanephric vesicles on both sides > vesicles form the metanephric tubules
What happens to the proximal end of the metanephric tubules?
What happens to the distal end of the metanephric tubules?
- attaches to glomerulus
- elongates to form the PCT, DCT and loop of henle
How does the blood supply of the kidney develop?
1st branches from common iliacs > disintegrates
Renal arteries form from the abdominal aorta
What is the embryological cause of renal agenesis?
Ureteric bud and blastema did not interact properly
Unilateral renal agenesis vs bilateral renal agenesis
Unilateral: One kidney did not form, typically asymptomatic and more common in males
Bilateral: Both kidneys did not form due to oligohydramnios. Associated with pulmonary hypoplasia
Horseshoe kidney:
Cause
Clinical
- Inferior poles fuse = horseshoe shape
- usually asymptomatic and low laying because ascent is prevented by the IMA
Clinical significance of accessory renal vessels?
Clinical significance of end artery damage/ligation?
- Extra renal vessels can obstuct ureter and cause hydronephrosis (kidney swelling)
- usually serves as the only blood supply of certain parts of the kidney ischemia to those parts if ligated or damaged
Autosomal recessive polycystic kidney disease
Multicystic dysplastic kidney disease
- PKHD1 mutation leading to cysts in both kidneys and renal insufficiency
- cysts in the loop of henle that formed from dilations, usually unilateral
How does the urogenital sinus (bladder) and the anorectal (rectum) form and separated?
Ventral cloaca (distal hindgut) has both and urorectal septum separates them
Vesical part of the urogenital sinus forms _____
Pelvic part forms _____
Phallic part forms _____
- most of bladder
- bladder neck, prostate urethra (m), urethra (f)
- spongy urethra (m) and vaginal vestibule lining (f)
How is the trigone formed at the bladder?
When does this happen?
- Bilateral mesonephric and ureteric buds penetrate posterior part of the bladder and form the trigone
- Wk 4 -6
Trigone comes from what embryological layer?
Bladder epithelium comes from what embryological layer?
Submucosa and muscularis m. come from what embryological layer?
- intermediate mesoderm
- endoderm
- splanchnic mesoderm
How is the allantois related to the bladder?
Connects with bladder and the umbilicus and constricts to form the urachus (drains fetal urine)
Also forms the median umbilical ligament
Exstrophy of the bladder:
Cause
Clinical
- Ventral abdominal wall did not close so bladder isn’t separated from abdomen and is also exposed/unfused
- Pelvic hemisection (hemipenis, hemiscrotum)
Epispadias
Urethral opening on dorsal genital tubercle rather than ventral
Usually accompanies exstrophy
Urachal cysts
Urachal sinus
Urachal fistula
- remnant epithelium of urachus infected and enlarged
- urachus end remains open and discharges into umbilicus (superiorly) or bladder (inferiorly)
- patent urachus causing urine to escape umbilical orifice
How does the Suprarenal gland initially form (cortex and medulla)?
When does this happen?
- Fetal cortical cells (future adrenals) form at the edges of the urogenital ridge to form the adrenal cortex. NCC migrate into medulla to form the chromaffin cells
- Wk 5
What happens to the fetal cortex after initial formation?
- Organizes the layers (glomerulosa, fasciculata and reticularis) and starts secreting ACTH and glucocorticoids
- Will start secreting DHEA which is converted to estradiol by placenta to maintain pregnancy
