Embryology Flashcards
What structure forms by week 5 that the kidneys develop from? What are the 3 overlapping sequences that derive from it?
The urogenital ridge
- Pronephros
- mesonephros
- metanephros
When and where does the pronephros develop? What is its purpose?
Cervical region via divisions of intermediate meso known as “nephrotomes”
How does the pronephric duct induce the mesonephros?
Pronephric
- Continues as mesonephric duct
- induces nearby intermediate meso to form mesonephric tubules
What are the 2 components of the embryonic kidney?
Mesonephric duct + the mesonephric tubules
What does the mesonephric duct give rise to that induces the development of the definite kidney?
Ureteric bud
What does the ureteric bud form?
Metanephric blastema and collecting ducts/system
What does the blastema do collectively?
Forms the metanephric system:
- Collecting ducts derived from the ureteric bud: dilate to create the ureter, renal pelvis, calyces, CTs and terminates at the DCT
- Excretory system derived from the metanephric blastema: Each CT covered by metanephric tissue and gives rise to the proximal nephron (LOH, PCT and DCT) and bowman’s capsule
Where does the metanephros travel and what stops it from continually ascending? What descends while this is happening?
Ascends from pelvic region -> posterior abdo wall, medially rotates 90 deg
Stopped by adrenal glands
Meanwhile the testis descend
How does the metanephros receive blood supply?
In pelvis: common iliacs
Renal arteries shorten as the metanephros ascends and ureters lengthen
What do the metanephric vesicles form?
Nephrons (nephrogenesis, pre birth) which is eventually invaginated by glomerulus
What is one issue that can occur with a polar renal artery?
Persisting older vessel (off aorta) that supplied kidney when it was in pelvis
If it fails to degenerate and lays across the ureter it can obstruct the flow: resulting in hydronephrosis (calyces may flatten rather than cup)
What are you at risk of if you have a low nephron count when born?
Hypertension and renal insufficiency
Name 3 structures that are inevitably formed thanks to the urorectal septum
Bladder, urethra, anorectal canal
What should the allantois become?
Urachus (drains urinary bladder, runs with umbilical cord) -> should degenerate into medial umbilical ligament
Name the 3 parts of the urogenital sinus and what they form
- Vesicle: forms bladder, continuous with the allantois, receives some mesonephric ducts (form trigone)
- Pelvic: urethra (male: prostatic and membranous, female: some repro tract)
- Phallic:
Female: rest of repro tract
Male: spongy urethra
What is unilateral renal agenesis?
One ureteric bud fails to develop off mesonephric duct -> one fetal kidney
What’s a bifid ureter?
Division of ureteric bud: divided kidney or 2 kidneys that drain into separate ureters which unite before the bladder
Which defect in kidney embryology is oligohydramnios most associated with?
Complete renal agenesis
*both ureteric buds failed to develop
What is a pancake kidney?
2 kidneys fuse in pelvis across midline
What is a horseshoe kidney? What kinds of signs/symptoms could you experience?
Kidneys join at lower poles
Usually asymptomatic, can cause hematuria, kidney stones and recurrent UTIs
Why does polycystic kidney disease occur? What are 2 signs that can occur?
*what is the most common inheritance pattern
Inherited: autosomal dominant, high BP and renal failure
*diagnosed in adulthood
Abnormal nephron dilation -> fluid filled cysts in kidney
What happens in Wilm’s Tumour/nephroblastoma?
Stem cells overproduce, kidney tumour in children
What is an ectopic ureter?
Ureter terminates in urethra and/or vagina (not bladder)
What are the 3 urachal anomalies? Are they a problem?
- Urachal cyst: persisting remnant of urachus epithelia, forms sphere, usually not a problem until inflamed
- Urachus sinus: the urachus seals near bladder but not at umbilicus -> serous fluid from umbilicus discharges
- Urachal fistula: urine can leak out of belly button
What happens in exstrophy of the bladder?
Anterior abdominal wall failed to fuse, bladder opens onto ventral wall
What condition describes a kidney that has migrated to the other side?
crossed renal ectopia
