Development of the Renal System

Question 1

What 3 systems develop craniocaudally?

Answer 1

Pronephros
Mesonephros
Metanephros

Question 2

Where do the 3 systems develop from?

Answer 2

Intermediate mesoderm - either side of midline during gastrulation
- between paraxial and lateral plate mesoderm

Question 3

Describe the Pronephros?

Answer 3

5-7 paired cervical segments of intermediate mesoderm produce nephric vesicles called nephrotomes

Question 4

Describe nephrotomes?

Answer 4

Hollow epithelial balls
non-functional
formed in week 4 disappear by end

Question 5

Describe mesonephros?

Answer 5

Wk4 thoracolumbar region
Mesonephric tubules from swellings
Mesonephric ridges either side of intermediate mesoderm
40 pairs produced craniocaudally

Question 6

What forms 30 pairs?

Answer 6

Cranial regression during caudal diffrentiation

Question 7

What happens in wk 5/6 to mesonephros?

Answer 7

Massive cranial regression leaves 20 pairs of lumbar mesonephric tubules

Question 8

What are the mesonephric excretory units?

Answer 8

Menonephric tubules diffrentiatite into Bowmans capsule and glomerulas (from dorsal aorta)

Question 9

What froms the MEU?

Answer 9

renal corpuscle and mesonephric tubule

Question 10

What are the mesonephric wolffian ducts?

Answer 10

thoracic region wk.4
longitudial intermediate mesoderm rods condense dorsolaterally to mesonephric tubules
Grow caudally
diverge from intermediate mesoderm in lumbar region
Fuse with ventrolateral walls of cloaca by d.26 (future bladder)
Cavitate at distal end to produce lumen

Question 11

Describe the MEU?

Answer 11

Lateral tips fuse with mesonephric duct
Allows passage from meu to cloaca
function in wk 6/10 for urine
Regress after wk10 - mesonephric regress in Female too
In male, mesonephric duct part of genital system SEED

Question 12

Describe the Metanephros?

Answer 12

Formed in sacral by pair of urteric buds

Question 13

describe ureteric buds?

Answer 13

sprout from distal mesonephric duct at wk4 end

Penetrate sacral intermediate mesoderm called metanephric blastema to encourage bifurcation of ureteric bud

Question 14

What is the Ureteric growing tip called?

Answer 14

Ampulla
Caplike aggregation near ampulla brancing bud causes lobe formation seperate by sulcus
14-16 lobes formed by wk16
sulci eventually filled obscure lobulated appearance

Question 15

What is the reciprocal interaction?

Answer 15

Diffrentiation of ureters and collecting ducts depend on metanephric blastema
Differentiation of nephrons depend on ureteric bud

Question 16

What does the collecting system have?

Answer 16

Major calyx
Minor Clayx (plurals)

Question 17

Describe nephron formation?

Answer 17

Wk 6 metanephric tissue caps form around ampulla of bifurcating collecting ducts (embroyological distinct)

Question 18

When do Distal tubules connect fully to collecting tubules?

Answer 18

Wk 10 - functional MEU

Question 19

What is fetal urine function for?

Answer 19

Supplementing production of amniotic fluid

Question 20

When is the normal ascent of kidneys?

Answer 20

Wk 9

Transient inferior arteries sometimes fail to regress causing accessory renal arteries (pelvic kidney, horseshoe kidney)

Question 21

Describe Urinary tract formation?

Answer 21

Cloaca split by urorectal septum between wk 4 and 6 to form:
PUS (primitive urogenital sinus)
Rectum

Question 22

What does superior part of PUS and allantois become?

Answer 22

The bladder

Question 23

What does constricted pelvic urethra and membranous prostatic become?

Answer 23

Constricted - female urethra

Membranous - male urethra

Question 24

What does the Distal part of PUS expand and become?

Answer 24

Vaginal vestibule in Females

Penile Urethra - males

Question 25

Describe bladder formation?

Answer 25

Week 6 - root of mesonephric duct exstrophies into wall of bladder
Completed by week 12

Question 26

What does mesonephric duct do to form the bladder?

Answer 26

Pushes the origin of ureteric buds into bladder walls creating ureteric openings
Opening of mesonephric duct to be pushed inferiorly to level of pelvic urethra
Exstrophied wall of mesonephric duct incorporated to bladder forming trigone