Development of the Kidney

Question 1

Name the original four embryonic structures that are involved in the development of the urinary system

Answer 1

Mesonephric (Wolffian) ducts, paramesonephric (Mullerian) ducts, immature gonads and mesenchyme

Question 2

What is the fate of the mesonephric and paramesonephric ducts in females?

Answer 2

The mesonephric (Wolffian) duct degenerates apart from the lower portion which goes on to form the ureteric bud. The paramesonephric duct goes on to form the oviduct.

Question 3

What is the fate of the mesonephric and paramesonephric ducts in males?

Answer 3

The mesonephric duct forms the male reproductive tract and the uteric bud. The paramesonephric duct degenerates.

Question 4

How many embryonic kidneys are there? How many are functional?

Answer 4

3 embryonic kidneys; pronephric and mesonephric kidneys are non-functional whereas the metanephric kidney is functional

Question 5

Name the three embryonic kidneys

Answer 5

Prenephric, mesonephric and metanephric

Question 6

From which duct do all of the embryonic kidneys develop?

Answer 6

Mesonephric duct

Question 7

What two structures are involved in the formation of the metanephric kidney?

Answer 7

The ureteric bud (from the mesonephric duct) and the metanephric bud/blastema from the mesenchyme

Question 8

What is the fate of the embryologic ureteric bud in adults?

Answer 8

The ureteric bud goes on to form the ureter, renal pelvis, major and minor calyces and the collecting tubules. Therefore, it is mainly involved in the development of the collecting system.

Question 9

What is the fate of the metanephric bud (blastema) in adults?

Answer 9

The metanephric bud (blastemal) goes on to form the renal glomerulus and capillaries, the Bowman’s capsule, the proximal convoluted tubule, loop of Henle and distal convoluted tubule. Therefore, it is mainly involved in the formation of the excretory system.

Question 10

What is an ectopic kidney?

Answer 10

Failure for the kidneys to properly ascend from the sacrum into the upper lumbar region

Question 11

Describe the ascent of the kidneys

Answer 11

The metanephros (the functional embryological kidney) is initially located at ~S1 but as the tail of the embryo unfolds, it ascends upwards to the upper lumbar region (~T12)

Question 12

What is meant by kidney agenesis?

Answer 12

Where there is failure of kidney formation; this can be unilateral or bilateral and is often associated with ureteric bud as that cause insufficient ureteric bud formation prevent the ureteric bud from coming into contact with the mesenchyme and therefore, the further development of the kidney will not occur.

Question 13

What is the ureteric bud?

Answer 13

The differentiated mesonephric duct that goes on to form the collecting aspect of the urinary tract

Question 14

What are the consequences of kidney agenesis?

Answer 14

If there is bilateral genesis the baby will not survive after birth.

In the uterus, the embryological kidney is required for amniotic fluid formation, and therefore if there is renal genesis there will be a reduction in amniotic fluid production which can cause birth defects such as failure of lung development and club foot

Question 15

What is meant by a ‘bifid ureter’?

Answer 15

Where an individual either has a ureteric bud that splits in two to form two kidneys from one bud, or the formation of two ureters from one bud.

Question 16

What is meant by ‘pancake kidney’?

Answer 16

This is a type of ectopic kidney where the kidney remains in the pelvic region, this usually only happens with one of the kidney. However, often the two kidneys fuse and this leads to the development of pancake kidney.

Question 17

What is meant by horseshoe kidney?

Answer 17

Ectopic kidney where the kidneys fuse in the pelvic region to form one pole, and as a result there is formation of a single U-shaped kidney and subsequently the kidney cannot ascend in the abdomen

Question 18

What is meant by polycystic kidney?

Answer 18

This condition occurs when the kidney begins to develop fluid-filled cysts, and this is often originally associated with defects in the formation of the tubules of the nephron. This results form issues in the primary cilia.

Question 19

What is autosomal dominant polycystic kidney disease?

Answer 19

85-90% of polycystic kidneys are associated with mutations in polycystin (PKD-1) and 10-15% are associated with mutations in polycystin-2 (PKD-2). These polycystins are proteins that are localised to the primary cilia which are involved in cellular adhesion, calcium transport and the cell cycle