Renal Embryology Flashcards
Dermal origin of urinary system and parts of genital system
Intermediate mesoderm
Urogenital ridge
Forms urinary and genital regions
Nephrogenic cord
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
Pronephros
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)
Mesonephros
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
Metanephros
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
Ureteric bud
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
Nephron formation
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
Vasculature of kidneys
First suprarenal vessels form from common iliacs
Definitive renal arteries are from abdominal aorta
Unilateral renal agenesis
Suspected in infants with 1 umbilical artery
Both unilateral and bilateral renal agenesis occurs because ureteric bud never branches off of mesonephric duct
Bilateral renal agenesis
Oligohydramnios develops because of no amniotic fluid production
Pulmonary hypoplasia then results
Potter syndrome sometimes
Duplication/incomplete division/complete division
Duplication- abnormal division of ureteric bud
Incomplete division- divided kidney and bifid ureter
Complete division- double kidney and bifid or separate ureter
Horseshoe kidney
Fusion of inferior poles
Kidney lies lower because inferior mesenteric artery impedes ascent
Accessory renal vessels
Can obstruct the ureter causing hydronephrosis End arteries (only artery feeding certain portion of kidney) - if ligated can cause ischemia of that tissue
Polycystic kidney disease
Cysts in both kidneys
Renal insufficiency
25% associated with pulmonary hypoplasia
Multicystic dysplastic kidney disease
Cysts are likely dilations of loop of Henle
Usually only affects one side
Urogenital sinus
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)
Urogenital sinus and anorectal canal separated by
Urorectal septum
Connection of kidney and bladder
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
Bladder development
Develops from vesicle part of urogenital sinus
Epithelium: endoderm (urogenital sinus)
Submucosa and muscularis: splanchnic mesoderm
Trigone: intermediate mesoderm (mesonephric ducts)
Allantois
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
Exstrophy of bladder
Arises during body folding
Defective closure of ventral abdominal wall
Exposure of mucosa of posterior wall of bladder
Epispadias
Urethral opening is on the dorsum of the genital tubercle rather than on its ventral side
Exstrophy of the bladder frequently occurs as well
Urachal cysts
Remnants of epithelial lining of urachus that can become infected and enlarged
Urachal sinus
End of urachus remains open into the bladder (inferior region) or umbilicus (superior region)
Urachal fistula
Entire urachus remains patent and allows urine to escape from umbilical orifice- leak urine from belly
Suprarenal medulla
Neural crest cell derived, cells migrate down from sympathetic ganglia, form chromaffin cells
Suprarenal cortex
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
Fetal cortex secretions
Secretes DHEA which tells placenta to form estradiol
This is critical for maintaining pregnancy
Also secretes ACTH and glucocorticoids
