Embryology. Development of the Kidneys and Urinary Tract

Question 1

What are the three sets of excretory organs in development of the kidneys?

Answer 1

Pronephros, mesonephro, metanephros.

Question 2

When does the pronephros appear and regress in kidney development?

Answer 2

Appears at the start of week 4 and regresses at the end of week 4.

Question 3

Is the pronephros functional?

Answer 3

No.

Question 4

When does the mesonephros appear and regress in kidney development?

Answer 4

Appears at the end week 4 and regresses at the end of week 8.

Question 5

Is the mesonephros functional?

Answer 5

Yes but no water conserving mechanism.

Question 6

Aside from kidney development, what is the mesonephros duct important for?

Answer 6

Development of the male reproductive tract.

Question 7

What sprouts from the mesonehric duct in kidney development?

Answer 7

Ureteric bud, the primordium of the collecting system of the definitive kidney.

Question 8

When does the metanephros appear and regress?

Answer 8

Appears in week 5 and doesn’t regress.

Question 9

Is the metanephros functional?

Answer 9

Yes, from the end of the first trimester.

Question 10

What does the collecting system develop from?

Answer 10

The ureteric bud.

Question 11

What does excretory system develop from?

Answer 11

Metanephric tissue cap.

Question 12

What does the embryonic kidney originate from?

Answer 12

The urogenital ridge - a region of the intermediate mesoderm.

Question 13

What does the pronephros produce?

Answer 13

The pronephric duct.

Question 14

Where is the pronephric duct?

Answer 14

Extends from the cervical region of the cloaca.

Question 15

What is the role of the pronephric duct?

Answer 15

Drives development of the next stage - mesonephric duct.

Question 16

Where do the tubules sprouted by the mesonephros develop?

Answer 16

Caudal to the pronephric region.

Question 17

What makes up the embryonic kidney?

Answer 17

The mesonephric tubules and the mesonephric duct.

Question 18

What does the ureteric bud induce?

Answer 18

Development of the definitive kidney.

Question 19

Where does the definitive kidney develop?

Answer 19

Within the intermediate mesoderm of the caudal region of the embryo.

Question 20

Where does the metanephric kidney first appear?

Answer 20

In the pelvic region.

Question 21

How do the kidneys end up more caudal than the pelvic region?

Answer 21

They don’t move themselves, but the trunk distends downwards so the kidneys effectively move caudally.

Question 22

What do the kidneys cross in their ascent?

Answer 22

The arterial fork formed by vessels returning blood from the foetus to the placenta.

Question 23

What is renal agenesis?

Answer 23

The ureteric bud fails to interact with the intermediate mesoderm.

Question 24

What is a risk of a migration defect of the kidney?

Answer 24

The kidneys lie extremely close to each other so they can get stuck on the arterial fold and fuse to form a horseshoe kidney.

Question 25

What is a horseshoe kidney?

Answer 25

A result of a migration defect where both kidneys get stuck on the arterial fold and fuse.

Question 26

What are duplication defects of the kidney due to?

Answer 26

Splitting of the ureteric bud, either partial or complete.

Question 27

What is the systemic consequence of duplication defects of the kidneys?

Answer 27

Ectopic openings into the vagina or urethra, so the urine bypasses the bladder and there is incontinence.

Question 28

What is the normal arterial supply development of the kidneys?

Answer 28

As the kidneys 'ascend' they require new arterial supply, and the previous supply disappears.

Question 29

What causes supernumerary arteries to the kidneys?

Answer 29

When the original arterial supply doesn't disappear on ascent of the kidneys.

Question 30

What is the bladder derived from?

Answer 30

The hindgut, the caudal portion of the primitive gut tube from the fourth week of development.

Question 31

What is the cloaca?

Answer 31

A blind pouch dilation of the caudal portion of the gut tube.

Question 32

What separates the cloaca from the outside?

Answer 32

The cloacal membrane - one of the two mesoderm-less regions left present after gastrulation.

Question 33

What is the cloaca divided into and what by?

Answer 33

The urogenital sinus (future bladder and urethra) and anorectal canal (future rectum and anal canal) by the urorectal septum.

Question 34

Where does the bladder develop?

Answer 34

In the allantois - superoventral diverticulum of the hindgut that extends into the umbilical cord.

Question 35

What is the allantois?

Answer 35

Superoventral diveriticulum of the hindgut that extends into the umbilical cord.

Question 36

What is the fate of the allantois?

Answer 36

Its lumen is obliterated to become the urachus, the median umbilical ligament in adults.

Question 37

Describe the development of the male bladder.

Answer 37

Mesonephric ducts reach urogenital sinus, ureteric bud sprouts from mesonephric ducts. Smooth musculature begins to appear and urogenital sinus expands. Ureteric bud and mesonephric ducts make independent opening in the urogenital sinus. Prostate and prostatic formed from mesonephric ducts.

Question 38

Describe the development of the female bladder.

Answer 38

Mesonephric ducts reach the urogenital sinus, ureteric bud sprouts from the mesonephric ducts. The urogenital sinus begins to expand and mesonephric duct regresses. This regression continues, the ureteric duct opens into the urogenital sinus.

Question 39

What is the female urethra formed by?

Answer 39

The pelvic part of the urogenital sinus.

Question 40

What are the four parts of the male urethra?

Answer 40

Pre-prostatic, prostatic, membranous, spongy.

Question 41

What is exstrophy of the bladder/ urachal anomalies?

Answer 41

A congenital anomaly in which part of the urinary bladder is present outside the body.

Question 42

What causes exstrophy of the bladder?

Answer 42

Maldevelopment of the lower abdominal wall, leading to rupture that causes the bladder to communicate with amniotic fluid. Or urachal fistula - patent urachus.

Question 43

What happens if the urachus remains as a duct?

Answer 43

It will connect the bladder to the umbilicus.

Question 44

What is hypospadias?

Answer 44

A defect in fusion of urethral folds. The urethral opens onto the ventral surface, rather than at the end of the glans.