Urinary System Development

Question 1

What part of the mesoderm is most important for the development of the urogenital system?

Answer 1

the intermediate mesoderm

Question 2

What are the two parts of the urogenital ridge of the intermediate mesoderm?

Answer 2

1. nephrogenic ridge (gives rise to urinary system)

2. Gonadal or genital ridge (gives rise to genital system)

Question 3

The developing urinary system consists of three successive development phases, which are:

Answer 3

1. pronephros
2. mesonephros
3. metanephros

Question 4

When does the pronephric kidney develop? How long does it last?

Answer 4

Around the 2nd week of conception and really only lasts about a week.

Question 5

THe pronephric kidney doesn’t last very long, but what part of it is super important?

Answer 5

the pronephric duct, which drains the pronephric kidney into the cloaca

Question 6

WHat happens to the pronephric duct?

Answer 6

it remains and becomes the mesonephric duct (or Wolffian duct)

Question 7

The mesonephros gives rise to what structures that eventually become really important in the male testis?

Answer 7

the mesonephric tubule - they become the efferent ductules of the male testis

Question 8

What does the mesonephric duct gives rise to in the male only?

Answer 8

the ductus deferens

Question 9

What does the mesonephric duct give rise to in both males and females?

Answer 9

the ureteric bud

Question 10

What is another name for the ureteric bud?

Answer 10

metanephric diverticulum

Question 11

What does the ureteric bud do?

Answer 11

It grows out from the mesonephric duct into the intermediate mesoderm (metanephrogenic mesoderm) to initiate the formation of the definitive kidney (the metanephros)

Question 12

What does the ureteric bud give rise to?

Answer 12

ureter
renal pelvis
minor and major calyces
colecting ducts (tubules) up to the arch of the collecting duct

Question 13

What is the rest of the nephron derived from?

Answer 13

the metanephric mesoderm that the ureteric bud grows to join

Question 14

WHat induces the metanephric mesoderm to form the nephron?

Answer 14

signalling from the arched collecting duct (derivative of the ureteric bud)

Question 15

Where are the metanephric kidneys initially located?

Answer 15

deep in the pelvic region

Question 16

How do they get up into the abdominal region?

Answer 16

they appear to “ascend”, but in reality, the caudal embryo just rapidly grows away from them

Question 17

How does this “ascent” affect blood supply?

Answer 17

They initially receive blood supply from the common iliac arteries, but as the caudal region of the body grows, the kidneys receive their blood supply from progressively more superior parts of the abdominal aorta

Question 18

What does this mean in terms of anatomic variations?

Answer 18

this means it’s relatively common to have a kidney receive blood from multiple arteries off the aorta - some just don’t undergo apoptosis like they should.

Question 19

What will result in renal agenesis?

Answer 19

failure of the ureteric bud and metanephric mesoderm to interact

Question 20

Renal agenesis is unilateral on what side? in what gender?

Answer 20

left side

males

Question 21

What newborn exam finding should make you concerned about renal agenesis?

Answer 21

having only one umbilical artery

Question 22

What will result in a duplicated or branched ureter?

Answer 22

if the ureteric bud bifurcates prior to interaction with the metanephric mesoderm

note - this can also result in a divided kidney or multiple kidneys on one side (supernumerary kidney)

Question 23

What can non-rotation or abnormal rotation of the kidney result in?

Answer 23

a kidney with a hilus that faces laterally instead of medially - doesn’t cause any issues

Question 24

What is a pelvic kidney?

Answer 24

When the metanephric kidneys fails to migrate from the pelvis and thus fuses to form on epelvic kidney - functions normally

Question 25

What is a crossed ectopic kidney?

Answer 25

it’s when one kidney migrates over to the other side and fuses with the other

Question 26

What blocks the ascent of a horseshoe kidney?

Answer 26

the IMA

Question 27

What structure will divide the cloaca into the rectum and urogenital sinus?

Answer 27

urorectal septum

Question 28

The urogenital sinus is continuous with what structure that extends into the umbilical cord?

Answer 28

the allantois

Question 29

The allantois will eventually form what?

Answer 29

the urachus

Question 30

Describe the urachus

Answer 30

it’s a fibrous cord that extends from the bladder to the umbilicus

Question 31

What does the urachus form in the adult?

Answer 31

the mediaN umbilical fold (covered by peritoneum

Question 32

What are the three parts of the urogenital sinus?

Answer 32

vesicle part
pelvic (middle) part
phallic part

Question 33

What does the vesicle part of the urogenital sinus form?

Answer 33

the urinary bladder (continuous with the allantois)

Question 34

What does the pelvic part of the urogenital sinus form?

Answer 34

the bladder neck
prostatic urethra in males
entire urethra in females

Question 35

What does the phallic part of the urogenital sinus form?

Answer 35

the penile urethra in males

Question 36

What is the term for the region where the urorectal septum fuses with the tissue of the proctodeum?

Answer 36

the perineal body

Question 37

What forms the trigone of the bladder?

Answer 37

the incorporation of the mesonephric ducts into the bladder wall

as the mesonephric ducts are incorporated into the posterior wall of the urogenital sinus, they ultimately reach the pelvic part that gives rise to the prostatic urethra. the ureters terminate in the posterior lateral wall of the vesical portion.

Question 38

The proximal male urethra is part of the original urogenital sinus, but what is the distal male urethra derived from?

Answer 38

ectoderm - there is an ectodermal cord that grows inward form the glans

Question 39

The connective tissue and smooth muscle of the urinary bladder is derived from what?

Answer 39

splanchnic (visceral) mesenchyme (mesoderm)

Question 40

What is a urachal cyst?

Answer 40

when the chord of tissue that comprises the urachus has a region that doesn’t close completely, the epithelium will secrete per usual and a cyst will develop

these cysts can become infected

Question 41

What is a urachal sinus?

Answer 41

when the urachus remains open in the region of the umbilicus - the epithelium will secrete out of it

Question 42

What is a urachal fistula?

Answer 42

this is when the urachus remains open all the way from the bladder to the umbilicus - this means urine will come out

Question 43

Failure of lateral plate mesoderm folding will cause what?

Answer 43

extrophy of the bladder in severe cases

epispadias in the male fetus

Question 44

What causes megacystis in male infants?

Answer 44

they can have posteior urethral valves in the area hwere the ejaculatory ducts enter the prostatic urethra and they can block the outflow of urine from the bladder

this causes the bladder to enlarge and you get hydronephrosis and renal failure

Question 45

What other developmental issue will be seen in megacystis?

Answer 45

lung hypoplasia because they’re not peeing so there is not amniotic fluid to cushing them

Question 46

What region of mesoderm will give rise to the adrenocortical primordia?

Answer 46

the cranial part of the urogenital ridge (intermediate mesoderm)

Question 47

What will migrate down into this region to form the adrenal medulla?

Answer 47

neural crest cells

Question 48

What accounts for the relatively large size of the fetal adrenal gland compared to that of adults?

Answer 48

there is a fetal cortex that is really big and then regresses during the first year after birth to give way to the permanent cortex