Lecture 11: Renal Embryology

Question 1

Which layer does the renal system come from?

Answer 1

Intermediate mesoderm

Question 2

Describe the initial development of the kidney

Answer 2

Intermediate mesoderm > urogenital ridge in each side of the dorsal aorta > nephrogenic cord > pronephros/mesonephros/metanephros

Question 3

Which sets of nephric structures degenerate and which don’t?

Answer 3

Pronephros and Mesonephros mostly degenerate

Metanephros becomes the permanent kidney

Question 4

Pronephros:
What happens at week 4?
What happens at Day 24-25?

Answer 4

• 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

Question 5

Mesonephros:

What happens at late Wk4?

Answer 5

Mesonephric duct continues downward and develops its own horizontal tubules

Question 6

What do the medial mesonephric tubules form?

Answer 6

Glomerular capsule that wraps around the developing glomerulus (capillaries)

Question 7

Mesonephric tubules:
What happens at Wk6-10?
What happens at Wk 12?

Answer 7

• acts as primitive kidney that filters fetal blood

- stops function and degeneration (complete in females, stays at efferent ductules in males)

Question 8

What happens during Wk 5?

Answer 8

Mesonephric duct at cloacal junction induces formation of the ureteric bud

Question 9

How does the metanephros develop?

When does this happen?

Answer 9

Ureteric bud (from mesonephric duct) grows cranially and meets metanephric blastema/kidney bean (from nephrogenic cord) = form the permanent kidney
Wk 9 -10

Question 10

How do the renal pelvis and ureters form from the ureteric bud?

Answer 10

Ureteric bud meets the blastema and penetrates it to form the renal pelvis
Stalk of the ureteric bud becomes the ureter

Question 11

How do the collecting tubules and the calices form from the ureteric bud?

Answer 11

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

Question 12

How do nephrons develop?

Answer 12

Collecting tubule arches and induces the blastema to form metanephric vesicles on both sides > vesicles form the metanephric tubules

Question 13

What happens to the proximal end of the metanephric tubules?

What happens to the distal end of the metanephric tubules?

Answer 13

• attaches to glomerulus

- elongates to form the PCT, DCT and loop of henle

Question 14

How does the blood supply of the kidney develop?

Answer 14

1st branches from common iliacs > disintegrates

Renal arteries form from the abdominal aorta

Question 15

What is the embryological cause of renal agenesis?

Answer 15

Ureteric bud and blastema did not interact properly

Question 16

Unilateral renal agenesis vs bilateral renal agenesis

Answer 16

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

Question 17

Horseshoe kidney:
Cause
Clinical

Answer 17

• Inferior poles fuse = horseshoe shape

- usually asymptomatic and low laying because ascent is prevented by the IMA

Question 18

Clinical significance of accessory renal vessels?

Clinical significance of end artery damage/ligation?

Answer 18

• 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

Question 19

Autosomal recessive polycystic kidney disease

Multicystic dysplastic kidney disease

Answer 19

• PKHD1 mutation leading to cysts in both kidneys and renal insufficiency
• cysts in the loop of henle that formed from dilations, usually unilateral

Question 20

How does the urogenital sinus (bladder) and the anorectal (rectum) form and separated?

Answer 20

Ventral cloaca (distal hindgut) has both and urorectal septum separates them

Question 21

Vesical part of the urogenital sinus forms _____
Pelvic part forms _____
Phallic part forms _____

Answer 21

• most of bladder
• bladder neck, prostate urethra (m), urethra (f)
• spongy urethra (m) and vaginal vestibule lining (f)

Question 22

How is the trigone formed at the bladder?

When does this happen?

Answer 22

• Bilateral mesonephric and ureteric buds penetrate posterior part of the bladder and form the trigone
• Wk 4 -6

Question 23

Trigone comes from what embryological layer?
Bladder epithelium comes from what embryological layer?
Submucosa and muscularis m. come from what embryological layer?

Answer 23

• intermediate mesoderm
• endoderm
• splanchnic mesoderm

Question 24

How is the allantois related to the bladder?

Answer 24

Connects with bladder and the umbilicus and constricts to form the urachus (drains fetal urine)
Also forms the median umbilical ligament

Question 25

Exstrophy of the bladder:
Cause
Clinical

Answer 25

• Ventral abdominal wall did not close so bladder isn’t separated from abdomen and is also exposed/unfused
• Pelvic hemisection (hemipenis, hemiscrotum)

Question 26

Epispadias

Answer 26

Urethral opening on dorsal genital tubercle rather than ventral
Usually accompanies exstrophy

Question 27

Urachal cysts
Urachal sinus
Urachal fistula

Answer 27

• 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

Question 28

How does the Suprarenal gland initially form (cortex and medulla)?
When does this happen?

Answer 28

• 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

Question 29

What happens to the fetal cortex after initial formation?

Answer 29

• 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