Renal Embryology

Question 1

Dermal origin of urinary system and parts of genital system

Answer 1

Intermediate mesoderm

Question 2

Urogenital ridge

Answer 2

Forms urinary and genital regions

Question 3

Nephrogenic cord

Answer 3

Forms from urogenital ridge
Gives rise to pronephros–>mesonephros—>metanephros
Areas of urogenital ridge not coming from the nephrogenic cord will form the reproductive organs

Question 4

Pronephros

Answer 4

Rudimentary kidney
Appears early in week 4 in the neck
Form ducts that run caudal and open into cloaca, which are eventually used by mesonephros (rest of pronephros degenerates)

Question 5

Mesonephros

Answer 5

Late in fourth week
Mesonephric ducts develop, and then induce tubule formation
Function as interim kidney from 6-10 weeks, produces urine
Stops functioning and degenerates in week 10-12

Question 6

Metanephros

Answer 6

Begins forming week 5
Made up of:
Ureteric bud- outgrowth of mesonephric duct (induced to grow by mesonephric duct itself)
Metanephric blastema- from nephrogenic cord
Forms functional and definitive kidney in 10th week
Sole purpose of fetal kidney is to make amniotic fluid

Question 7

Ureteric bud

Answer 7

Elongates and penetrates blastema, to form renal pelvis
Stalk of ureteric bud becomes ureter
Cranial part of ureteric bud branches into collecting tubules- 1st gen tubules form major calices, 2nd gen tubules form minor calices

Question 8

Nephron formation

Answer 8

Ureteric bud–>
Arched collecting tubules
Collecting tubules induce metanephrogenic blastema formation
Metanephrogenic blastema–>
Metanephric vesicles–>
Metanephric tubules–>
Proximal tubule forms glomerular capsule, distal end lengthens and forms PCT, DCT and nephron loop

Question 9

Vasculature of kidneys

Answer 9

First suprarenal vessels form from common iliacs

Definitive renal arteries are from abdominal aorta

Question 10

Unilateral renal agenesis

Answer 10

Suspected in infants with 1 umbilical artery

Both unilateral and bilateral renal agenesis occurs because ureteric bud never branches off of mesonephric duct

Question 11

Bilateral renal agenesis

Answer 11

Oligohydramnios develops because of no amniotic fluid production
Pulmonary hypoplasia then results
Potter syndrome sometimes

Question 12

Duplication/incomplete division/complete division

Answer 12

Duplication- abnormal division of ureteric bud
Incomplete division- divided kidney and bifid ureter
Complete division- double kidney and bifid or separate ureter

Question 13

Horseshoe kidney

Answer 13

Fusion of inferior poles

Kidney lies lower because inferior mesenteric artery impedes ascent

Question 14

Accessory renal vessels

Answer 14

Can obstruct the ureter causing hydronephrosis
End arteries (only artery feeding certain portion of kidney) - if ligated can cause ischemia of that tissue

Question 15

Polycystic kidney disease

Answer 15

Cysts in both kidneys
Renal insufficiency
25% associated with pulmonary hypoplasia

Question 16

Multicystic dysplastic kidney disease

Answer 16

Cysts are likely dilations of loop of Henle

Usually only affects one side

Question 17

Urogenital sinus

Answer 17

Urogenital sinus is critical for bladder and urethra development
Vesical part- forms most of urinary bladder
Pelvic part- forms neck of bladder; prostatic urethra (m) and urethra (f)
Phallic part- forms spongy urethra (m), and lining of vaginal vestibule (f)

Question 18

Urogenital sinus and anorectal canal separated by

Answer 18

Urorectal septum

Question 19

Connection of kidney and bladder

Answer 19

In wks 4-6, mesonephric duct is incorporated into bladder wall with ureteric bud attached
Ureteric bud is using the mesonephric duct to gain access to bladder and eventually attach itself
Openings of mesonephric duct are carried inferiorly to pelvic urethra
Forms trigone- region of mesonephric and ureteric ducts blending into posterior bladder

Question 20

Bladder development

Answer 20

Develops from vesicle part of urogenital sinus
Epithelium: endoderm (urogenital sinus)
Submucosa and muscularis: splanchnic mesoderm
Trigone: intermediate mesoderm (mesonephric ducts)

Question 21

Allantois

Answer 21

It is a fetal membrane developed from the hindgut
Constricts and forms the urachus
Extends from apex of the bladder to umbilicus
Forms the median umbilical ligament

Question 22

Exstrophy of bladder

Answer 22

Arises during body folding
Defective closure of ventral abdominal wall
Exposure of mucosa of posterior wall of bladder

Question 23

Epispadias

Answer 23

Urethral opening is on the dorsum of the genital tubercle rather than on its ventral side
Exstrophy of the bladder frequently occurs as well

Question 24

Urachal cysts

Answer 24

Remnants of epithelial lining of urachus that can become infected and enlarged

Question 25

Urachal sinus

Answer 25

End of urachus remains open into the bladder (inferior region) or umbilicus (superior region)

Question 26

Urachal fistula

Answer 26

Entire urachus remains patent and allows urine to escape from umbilical orifice- leak urine from belly

Question 27

Suprarenal medulla

Answer 27

Neural crest cell derived, cells migrate down from sympathetic ganglia, form chromaffin cells

Question 28

Suprarenal cortex

Answer 28

Coelomic epithelium (from somatic mesoderm) delaminates and enters surrounding mesoderm forming fetal cortical cells
This initial cortex eventually regresses and is replaced by new cells (also from the coelomic epithelium

Question 29

Fetal cortex secretions

Answer 29

Secretes DHEA which tells placenta to form estradiol
This is critical for maintaining pregnancy
Also secretes ACTH and glucocorticoids