Embryology

Question 1

What structure forms by week 5 that the kidneys develop from? What are the 3 overlapping sequences that derive from it?

Answer 1

The urogenital ridge

1. Pronephros
2. mesonephros
3. metanephros

Question 2

When and where does the pronephros develop? What is its purpose?

Answer 2

Cervical region via divisions of intermediate meso known as “nephrotomes”

Question 3

How does the pronephric duct induce the mesonephros?

Answer 3

Pronephric

1. Continues as mesonephric duct
2. induces nearby intermediate meso to form mesonephric tubules

Question 4

What are the 2 components of the embryonic kidney?

Answer 4

Mesonephric duct + the mesonephric tubules

Question 5

What does the mesonephric duct give rise to that induces the development of the definite kidney?

Answer 5

Ureteric bud

Question 6

What does the ureteric bud form?

Answer 6

Metanephric blastema and collecting ducts/system

Question 7

What does the blastema do collectively?

Answer 7

Forms the metanephric system:

1. Collecting ducts derived from the ureteric bud: dilate to create the ureter, renal pelvis, calyces, CTs and terminates at the DCT
2. 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

Question 8

Where does the metanephros travel and what stops it from continually ascending? What descends while this is happening?

Answer 8

Ascends from pelvic region -> posterior abdo wall, medially rotates 90 deg

Stopped by adrenal glands

Meanwhile the testis descend

Question 9

How does the metanephros receive blood supply?

Answer 9

In pelvis: common iliacs

Renal arteries shorten as the metanephros ascends and ureters lengthen

Question 10

What do the metanephric vesicles form?

Answer 10

Nephrons (nephrogenesis, pre birth) which is eventually invaginated by glomerulus

Question 11

What is one issue that can occur with a polar renal artery?

Answer 11

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)

Question 12

What are you at risk of if you have a low nephron count when born?

Answer 12

Hypertension and renal insufficiency

Question 13

Name 3 structures that are inevitably formed thanks to the urorectal septum

Answer 13

Bladder, urethra, anorectal canal

Question 14

What should the allantois become?

Answer 14

Urachus (drains urinary bladder, runs with umbilical cord) -> should degenerate into medial umbilical ligament

Question 15

Name the 3 parts of the urogenital sinus and what they form

Answer 15

1. Vesicle: forms bladder, continuous with the allantois, receives some mesonephric ducts (form trigone)
2. Pelvic: urethra (male: prostatic and membranous, female: some repro tract)
3. Phallic:
   Female: rest of repro tract
   Male: spongy urethra

Question 16

What is unilateral renal agenesis?

Answer 16

One ureteric bud fails to develop off mesonephric duct -> one fetal kidney

Question 17

What’s a bifid ureter?

Answer 17

Division of ureteric bud: divided kidney or 2 kidneys that drain into separate ureters which unite before the bladder

Question 18

Which defect in kidney embryology is oligohydramnios most associated with?

Answer 18

Complete renal agenesis

*both ureteric buds failed to develop

Question 19

What is a pancake kidney?

Answer 19

2 kidneys fuse in pelvis across midline

Question 20

What is a horseshoe kidney? What kinds of signs/symptoms could you experience?

Answer 20

Kidneys join at lower poles

Usually asymptomatic, can cause hematuria, kidney stones and recurrent UTIs

Question 21

Why does polycystic kidney disease occur? What are 2 signs that can occur?

*what is the most common inheritance pattern

Answer 21

Inherited: autosomal dominant, high BP and renal failure
*diagnosed in adulthood

Abnormal nephron dilation -> fluid filled cysts in kidney

Question 22

What happens in Wilm’s Tumour/nephroblastoma?

Answer 22

Stem cells overproduce, kidney tumour in children

Question 23

What is an ectopic ureter?

Answer 23

Ureter terminates in urethra and/or vagina (not bladder)

Question 24

What are the 3 urachal anomalies? Are they a problem?

Answer 24

1. Urachal cyst: persisting remnant of urachus epithelia, forms sphere, usually not a problem until inflamed
2. Urachus sinus: the urachus seals near bladder but not at umbilicus -> serous fluid from umbilicus discharges
3. Urachal fistula: urine can leak out of belly button

Question 25

What happens in exstrophy of the bladder?

Answer 25

Anterior abdominal wall failed to fuse, bladder opens onto ventral wall

Question 26

What condition describes a kidney that has migrated to the other side?

Answer 26

crossed renal ectopia