Embryology Urinary tract

Question 1

what is the primary origin of the urinary system

Answer 1

intermediate mesoderm

Question 2

what is the first set of kidneys that form

Answer 2

pronephros

form in thorax (from nephrogenic ridge)
these form during beginning of week 4 and are gone at the end of week 4

not very important at all b/c no congenital abnormalities come from this

Question 3

what is the second set of kidneys

Answer 3

Mesonephros

form week 4 and become functional nephrons and function until about month 3

these tubules drain into the mesonephric duct

from in lower thoracic upper lumbar region

excrete products into mesenphric duct

Question 4

what in males does the mesonehric duct contribute to form

Answer 4

genitalia of males

Question 5

what is the third set of kidneys

when does it form

Answer 5

Metanephros
forms week 5, functional by end of third month

this is the definitive kidney (adult kidney)

forms in the pelvic region

has both the metanephric blastema (from intermediate mesoderm in the pelvis)
AND the ureteric bud (forms ureter which is a diverticulum that forms from the mesonephric duct)

at the 3rd month

Question 6

what does the metanephric blastema form?

Answer 6

Nephron (excretory units of the kidney)

bowman’s capsule
proximal convoluted tubules
loops of henle
distal convoluted tubules

Question 7

what does the ureteric bud form?

Answer 7

the ureteric bud is an evagination of mesonephric duct and penetrates the metanephric blastema

Forms:
collecting tubules
minor and major calyces
renal pelvis
ureter

Question 8

WT1

Answer 8

wilm’s tumor protein 1

one of the most important proteins involved in the development of the kidney (reciprocal stimulation)

if the ureteric bud or the nephron don’t signally properly the kidney WONT form correctly

Question 9

what movement do the kidneys undergo around 6 weeks - 9 weeks

what happens to their blood supply as they ascend

Answer 9

ascent and rotation from the pelvis into the abdomen (upper part)

in the pelvis the hilum is directed anterior then these rotate about 90 degrees medially as they ascend so that the hilum faces anteromedially

as they ascend they receive new blood vessels, lymphatics, and nerves*** (only organ that does this)

orginal blood supply is from the common iliac arteries
The permanent renal arteries are branches of the aorta
caudal arterial branches typically degenerate

Question 10

LV1 LV2

Answer 10

renal artery

Question 11

what is the shape of the fetal kidney

Answer 11

lobulated

when the infant is born these will be smooth

Question 12

what does the cloaca form

Answer 12

the urinary bladder and urethra

Question 13

what does the urorectal septum divide

Answer 13

divides the cloaca into the anterior urogenital sinus and the posterior rectum/anal canal

Question 14

the allantois forms what?

Answer 14

has attachment to the urogenital (Cranial portion) part of the cloaca (but is endoderm derived)

eventually it forms the urachus (more fibrous)

the urachus will form the median umbilical ligament which remains attached to the urinary bladder

Question 15

where does the trigone come from

what is its function in the bladder

Answer 15

the mesonephric duct

this is because the mesenephric duct grows to become part of the bladder itself

trigone then acts as a sphincter mechanism for the ureter!!

Question 16

what is the cause of accessory renal arteries/veins

what happens if this is symptomatic

how do you fix

Answer 16

more caudal vessels fail to regress during ascent of the kidney

usually asymptomatic

(these arteries are end arteries so they must be transposed and cannot just be removed b/c then you would lose blood supply to an entire segment of the kidney)

accessory vessels can cause compression of ureter and become symptomatic

Question 17

what is the cause of renal hypoplasia

when is the symptomatic

Answer 17

Inadequate branching of ureteric bud and lack of differentiation of nephrons

(underdevelopment of the kidney)

symptomatic if this is bilateral!!

Question 18

what are the cystic disease and when are they present?

in autosomal recessive cyst form from what

in autsomal dominant cyst forms from what

Answer 18

the functional part of the kidney is replaced by cysts

Both of the following are types of this that are PRESENT AT BIRTH ***

Multicystic dysplastic

Polycystic kidneys

recessive –> from from collecting ducts
dominant–> from collecting ducts and nephrons

Question 19

what is the cause of renal agenesis

Answer 19

No kidney formation BUT with most of these the adrenal gland is fine b/c it has a different embryological origin

cause:
Ureteric bud fails to form and/or induce differentiation of the metanephric blastema.

unilateral –> asymptomatic

Question 20

what are the of horseshoe kidney and pelvic kidney

Answer 20

pelvic (ectopic) kidney- fails to ascend

horsehoe kidney–> Inferior poles of left and right kidneys fuse in the pelvis. Ascent is blocked by inferior mesenteric artery.

usually these are asymptomatic!
completely functional kidneys just in a different spot

Question 21

what is Wilm’s tumor

Answer 21

presents by year 5 ( very malignant)

metastases to the lung

caused by mutation in the WT1 (which is expressed in the metanephric blastema)

this results in metablatic blastima that is very underdifferentiated but very rapidly dividing tissue (cancer tissue)

will also see gonad that doesn’t form b/c of Deny’s -Drash syndrome which is what wilm’s tumor is part of

Question 22

WAGR syndrome

Answer 22

mutation of WT1 and PAX6 (even more severe than WIlm’s tumor)

Pax6 is involved in brain and eye development

aniridia (no eye) and mental retardation

Question 23

what is the cause of the duplication of the ureter

Answer 23

splitting of the ureteric bud causing a y-shaped ureter

can lead to duplication of the kidney

Question 24

what is the cause of an ectopic ureter

Answer 24

two ureteric buds form

usually the lower portion is normal

the upper of the two ureters is often abnormal (dilated, less smooth muscle, drains to abnormal site)

Question 25

what is the cause of urachal anomalies

Answer 25

urachus remains patent (open)
(lumen of the allantois persists!)

called a urachul fistula (abnormal opening from urinary bladder to umbilicus)

present with urine dripping from their umbilicus

Question 26

what is the cause of the exstrophy of the bladder/cloaca

which one is more severe?

Answer 26

Ventral body wall defect (left open)

bladder or cloaca form externally

often presents with epispadias

extrophy of the cloaca is even more severe
(bladder mucosa (inner epithelium) is exposed)
the urorectal septum is also deficient, thus exposure of the rectum is also present
imperforate anus

Question 27

Deny’s Drash syndrome

Answer 27

mutation of the WT1 gene ???

Question 28

what ridge does the urinary system develop from

Answer 28

nephrogenic ridge

extensive ridge
forms functioning nephrons

Question 29

what ridge does the reproductive system develop from

Answer 29

gonadal ridge

Question 30

mesenephric duct and tissue form what

Answer 30

kidneys and ureters

Question 31

what does the cranial portion of the urogenital sinus form (urogenital sinus is formed from the cloaca splitting)

Answer 31

forms bladder NOT trigone region

Question 32

what does the middle (pelvic portion) of the urogenital sinus form in females. males.

Answer 32

females- urethra

males - prostatic and membranous urethra in males

Question 33

what does the caudal portion of the urogenital sinus form in males

Answer 33

forms penile urethra

only in males

Question 34

where does the ureter originally bud off?

what is its eventual development?

Answer 34

originally it buds off the mesonephric duct
but the mesonephric duct develops and eventually grows to become part of the urinary bladder (trigone)

the ureter then has its own pathway into the urinary bladder

Question 35

WHAT is potter sequence

what are the symptoms

Answer 35

bilateral renal agenesis (complete lack of kidney formation)

This results in oligohydraminos b/c fetus is not producing amniotic fluid (which usually happens around week 5)

This causes fetal constraint

3. Secondary symptoms are caused by oligohydramnios.
   a. Hypoplastic lungs
   b. Potter facies: broad, flat nose; wide-set eyes; low-set ears; micrognathia.
   c. Sometimes limb malformation as well (club foot)