Development of urinary system

Question 1

tissue layer urinary and genital systems originate from

Answer 1

intermediate mesoderm (between paraxial and lateral)

Question 2

three sequential kidney systems

Answer 2

pronephros, mesonephros and metanephros

Question 3

signals that help kidney develop

Answer 3

reciprocal inductive interactions leading to branching morphogenesis and mesenchymal to epithelial transformation

Question 4

bladder formation

Answer 4

separation of the cloaca

Question 5

definitive kidney

Answer 5

metanephros

Question 6

action of kidneys before birth

Answer 6

dilute urine, main constituent of amniotic fluid, excretion of urea from fatal blood via the placenta

Question 7

pronephros development

Answer 7

4th week in cervical region of embryo

degrades quickly, only present for a couple of days and not functional

Question 8

mesonephric duct development

Answer 8

mesonephric ducts appear around day 24

paired set of epithelial tubes that run along the head-tail axis of embryo

Question 9

metanephric development

Answer 9

a few days after mesonephric, start of week 5

Question 10

structure of mesonephros

Answer 10

repeating glomerular units
about 40 pairs develop that are constantly being replaced, so 30 present at any one time
glomerular units extend from thoracic to lumbar regions

Question 11

mesonephros attached to

Answer 11

mesonephric duct, which they drain into

Question 12

eventual mesonephric duct structure

Answer 12

retained in males as genital duct, is lost in females

Question 13

when does metanephros begin to develop

Answer 13

end of week 4, while the mesonephros is functional

about day 26, pairs of mesonephric duct join the cloaca

Question 14

initiation of metanephric kidney

Answer 14

uteric bud invaginates from caudal end of the mesonephric duct and grows towards the adjacent mesoderm called the metanephric blastema

Question 15

initiation of branching morphogenesis

Answer 15

mesenchyme induces the uteric bud to begin branching
reciprocal inductive signalling
mesenchyme initiates branching, bud causes mesenchymal cells to form glomerular units

Question 16

result of bud branching

Answer 16

continues to bifurcate until week 32, producing 1-3 million collecting tubules and ducts

Question 17

what does the first bifurcation produce

Answer 17

renal pelvis

Question 18

what happens after 4 generations of branching

Answer 18

branches coalesce to form the major calyces

followed by more branching into minor calyces and then collecting ducts

Question 19

what happens at week 10

Answer 19

functional nephric units appear in the distal regions of the metanephros

Question 20

induction of nephron formation

Answer 20

tips of collecting ducts widen to form ampullae
ampullae at the tip of the collecting duct interact with adjacent mesenchyme to induce nephron formation
forms nephric cap and nephric vesicles
nephrogenic vesicles fuse with the collecting duct to form a continuous nephron

Question 21

important gene

Answer 21

wt 1 gene

expressed in early metanephric duct, responsible for initial outgrowth of uteric bud

Question 22

where in the embryo to kidneys form

Answer 22

caudally, near developing bladder

Question 23

what is kidney ascent

Answer 23

6-9 weeks

metanephric kidney ascends to the lumbar region

Question 24

position of kidneys

Answer 24

retroperitoneal

Question 25

why does ascent occur

Answer 25

primarily by differential growth, kidneys stay in place while embryo lengthens

Question 26

problems associated with ascension

Answer 26

pelvic kidney if left behind

horseshoe kidney if the kidneys fuse before ascent and get caught underneath the inferior mesenteric artery

Question 27

wilms tumour

Answer 27

often due to mutations in wt 1 gene
usually occurs in the first 5 years of life
most common kidney cancer in children

Question 28

congenital polycystic kidney disease

Answer 28

defects of tubule growth
nephrons are functional so form large fluid-filled cysts
need dialysis and transplant

Question 29

where does the bladder form from

Answer 29

from the allantois, which is a diverticulum from the hindgut
superior part of the urogenital sinus, continuous with the allantois, forms the bladder

Question 30

what does the urorectal septum do

Answer 30

separates the urogenital sinus from the anorectal canal

Question 31

how does the trigone form

Answer 31

distal parts of the mesonephric duct and forming ureter are absorbed into the endoderm-lined bladder, forming the mesodermal trigone

Question 32

features of trigone development

Answer 32

brings opening of ureter into bladder
opening of mesonephric duct travels inferiorly to the level of the urethra
triangle of mesospheric duct tissue -> trigone of bladder

Question 33

what is the urachus

Answer 33

remnant of the allantoic duct, forms the median vesicle-umbillical ligament

Question 34

urethra development

Answer 34

pelvic urethra forms the membranous urethra in females and membranous prostatic urethra in males
distal expansion of urogenital sinus forms the vestibule of the vagina in females and penile urethra in males

Question 35

when are kidneys functional by

Answer 35

12 weeks

Question 36

loop of hence function before/ after birth

Answer 36

before birth - lots of dilute urine

after birth - loops of Henley lengthen and urine more concentrated