Embryology of the Urinary System

Question 1

When does the development of the urinary system begin?

Answer 1

During week 4

Question 2

Where does the urinary system develop from?

Answer 2

The urogenital ridges in the intermediate mesoderm on either side of the primitive aorta

Question 3

What are the three overlapping systems that the kidneys develop from?

Answer 3

The pronephros, mesonephros and metanephros

Question 4

Where does development of the pronephros begin?

Answer 4

The cervical region of the embryo

Question 5

What system do the nephrotomes belong to?

Answer 5

The pronephros

Question 6

What are the nephrotomes?

Answer 6

Segmented divisions of intermediate mesoderm = between 6 and 10 pairs are formed in total

Question 7

What structure do the nephrotomes join with?

Answer 7

Join into the pronephric duct

Question 8

What is the pronephric duct?

Answer 8

Duct that extends from the cervical region to the cloaca of the embryo

Question 9

What is the fate of the pronephros?

Answer 9

Non-functional and regresses completely by the end of week 4

Question 10

Where does the mesonephros develop?

Answer 10

Caudally to the pronephros

Question 11

What does the presence of the pronephric duct induce in the mesonephros?

Answer 11

Induces the nearby intermediate mesoderm in the thoracolumbar region to form mesonephric tubules

Question 12

How is filtration of blood by the mesonephros facilitated?

Answer 12

Mesonephric tubules receive a tuft of capillaries from the dorsal aorta

Question 13

Where do the capillaries that supply the mesonephric tubules drain into?

Answer 13

The mesonephric duct = continuation of the pronephrotic duct

Question 14

What do the mesonephric tubules act as?

Answer 14

A primitive excretory system = most tubules regress by end of month 2

Question 15

What structure does the mesonephric duct give rise to?

Answer 15

Sprouts the ureteric bud caudally, which induces the development of the definitive kidney

Question 16

What does the metanephros form?

Answer 16

The definitive kidney

Question 17

When does the metanephros begin to develop?

Answer 17

Appears in week 5 and becomes functional around weeks 9-11

Question 18

What are the components of the metanephros?

Answer 18

Ureteric bud and the metanephric blastema = consists of a collecting system and an excretory system

Question 19

Where is the collecting system of the metanephros derived from?

Answer 19

The ureteric bud

Question 20

What does the collecting system of the metanephros go on to form?

Answer 20

Dilates to create the ureter, renal pelvis, major and minor calyces, and collecting tubules

Question 21

Where does the collecting system of the metanephros terminate?

Answer 21

At the distal convoluted tubule

Question 22

What happens if the ureteric bud splits too early?

Answer 22

May cause two ureters, or two renal pelvices connecting to one ureter

Question 23

Where is the excretory system of the metanephros derived from?

Answer 23

The metanephric blastema

Question 24

What is each collecting tubule from the collecting system of the metanephros covered by?

Answer 24

A metanephric tissue cap = gives rise to the excretory tubules

Question 25

What structures go on to form the nephrons?

Answer 25

The excretory tubules of the metanephros along with the developing glomeruli

Question 26

What does the proximal end of the excretory tubule form?

Answer 26

The Bowman's capsule around the glomerulus

Question 27

What does the distal end of the excretory tubule form?

Answer 27

Elongates to form the proximal convoluted tubule, loop of Henle and distal convoluted tubule

Question 28

Where does the definitive kidney develop?

Answer 28

Initially develops in the pelvic region before ascending in to the abdomen to L1 level during weeks 6-9

Question 29

Where does the kidney receive blood from when it's in the pelvis?

Answer 29

From a pelvic branch of the abdominal aorta

Question 30

What happens to the blood supply to the kidney as it ascends?

Answer 30

New arteries from the abdominal aorta supply the kidney

Question 31

What happens to the pelvic vessels that used to supply the kidney once it has ascended?

Answer 31

Pelvic vessels usually regress but can persist as accessory renal arteries

Question 32

What causes a horseshoe kidney?

Answer 32

Inferior poles of the metanephroi meet and fuse before ascent = kidney becomes trapped beneath the IVC

Question 33

Where are the bladder and the urethra derived from?

Answer 33

The cloaca

Question 34

When does the urorectal septum divide the cloaca into two parts?

Answer 34

During weeks 4-7

Question 35

What are the two part that the cloaca is divided into by the urorectal septum?

Answer 35

Anal canal (posterior) and the urogenital sinus (anterior)

Question 36

What are the three parts of the urogenital sinus?

Answer 36

Upper part = forms bladder | Pelvic part and phallic/caudal part

Question 37

What does the pelvic part of the urogenital sinus form?

Answer 37

Entire urethra and some of the reproductive tract in females | Prostatic and membranous urethras in males

Question 38

What does the phallic/caudal part of the urogenital sinus form?

Answer 38

Part of the reproductive tract in females | Spongy urethra in males

Question 39

What initially drains the bladder?

Answer 39

The allantois = obliterated during foetal development and become the urachus

Question 40

What does the urachus become in adults?

Answer 40

Remnant exists as the median umbilical ligament = connects apex of bladder to umbilicus

Question 41

What happens as the bladder develops from the urogenital sinus?

Answer 41

It absorbs the Wolffian ducts to become the trigone of the bladder

Question 42

What are the Wolffian ducts?

Answer 42

Caudal parts of the mesonephric ducts

Question 43

Where do the ureters enter the bladder?

Answer 43

At the base of the trigone

Question 44

Where do the ureters form from?

Answer 44

Form as outgrowths of the mesonephric ducts

Question 45

How do the bladder and urethra develop in males?

Answer 45

As kidneys ascend the ureteric openings move cranially | Wolffian ducts move caudally and closer together and enter the prostatic urethra

Question 46

What do the Wolffian ducts form in men?

Answer 46

The ejaculatory ducts

Question 47

How do the bladder and urethra develop in women?

Answer 47

As kidneys ascend the ureteric openings move cranially

Question 48

What happens to the mesonephric ducts in women?

Answer 48

They degenerate due to a lack of testicular androgens

Question 49

What are some defects that can occur in the bladder?

Answer 49

Urachal fistula, urachal cysts, urachal sinus

Question 50

What happens to the ureteric buds at 28 days of development?

Answer 50

They sprout from the distal mesonephric ducts

Question 51

When do the ureteric buds penetrate the metanephric blastema?

Answer 51

At 32 days of development