4 – Development of Urinary System I

Question 1

What is the intermediate mesoderm between?

Answer 1

-somites
-lateral plate mesoderm
*where urinary and reproductive systems are derived from

Question 2

What induces the intermediate mesoderm to become kidney-forming?

Answer 2

-paraxial mesoderm
*leads to expression of transcription factors that drive nephric tubule development

Question 3

What are the 3 ‘generations’ of nephric tubules?

Answer 3

-pronephros
-mesonephros
-metanephors

Question 4

Pronephros:

Answer 4

-least complex
-cervical region of embryo

Question 5

Pronephros development:

Answer 5

-at time of somite presence (2-3 weeks) cells of intermediate mesoderm in cervical region give rise to
>INNER VISCERAL LAYER
>OUTER PARIETAL LAYER (dorsal)
*cavity between them=nephrocele

Question 6

Nephrotomes:

Answer 6

*cords of cells that grow out from parietal (dorsal) wall and form PRONEPHRIC TUBULES

Question 7

Pronephric tubules:

Answer 7

*distal end of each grows and extends laterally, then moves caudally to fuse with same region of growing cells of the tubule right behind it
*where they all fuse=PRONEPHRIC DUCT

Question 8

Pronephric duct:

Answer 8

-as more caudal pronephric tubules grow they fuse with it
*grows toward cloaca and becomes canalised

Question 9

First glomeruli to form are in the pronephros:

Answer 9

-start as tufts of capillaries branching from dorsal aorta in pronephros
-tufts push and invaginate into wall of pronephric tubule to form internal glomeruli
>found in HIGHER vertebrates
*example of angiogenesis

Question 10

‘bowman’s capsule’ forms from:

Answer 10

-invaginated epithelium around each glomerulus

Question 11

What is the function of the pronephros?

Answer 11

-internal glomerular filtration produces a filtrate that moves to pronephric tubule
-water and electrolytes are re-absorbed
-waste products move to pronephric duct then cloaca
*suitable because of the basic metabolism and not fully developed organs

Question 12

Mesonephros:

Answer 12

-second generation
-develops in thoraco-lumbar region

Question 13

Post-somite stage (after 3 weeks) of development in higher vertebrates:

Answer 13

-column of tissue grows=UROGENITAL RIDGE
>proliferation of intermediate mesoderm in T-L region
>projects into peritoneal cavity

Question 14

Pronephric duct in early developing mesonephros:

Answer 14

-extends to cloaca, but induces mesonephric tissue to form nephric vesicle and then mesonephric tubule

Question 15

Renal corpuscle (mesonephros):

Answer 15

*more intimate relationship
-glomerular tufts from dorsal aorta push into invaginating mesonephric tubule to form Bowman’s capsule

Question 16

What develops around each mesonephric tubule?

Answer 16

-peri-tubular capillary network
>aids a greater capability of reabsorption of water and electrolytes

Question 17

Pronephros vs. mesonephros size:

Answer 17

-pronephros: 1 tubule at each somite
-mesonephros: multiple mesonephric tubules at each somite

Question 18

Mesonephros size:

Answer 18

-large enough that it projects into abdominal cavity
>especially in PIGS

Question 19

Metanephros:

Answer 19

-third generation
-develops in sacral region
*what forms the adult kidney

Question 20

What are the 2 structures that give rise to form the excretory organ (metanephros)?

Answer 20

-ureteric bud
-metanephric mass or blastema

Question 21

Ureteric bud:

Answer 21

-outgrowth of the mesonephric duct
-extends cranially into metanephric mass and widen=then surrounded by metanephric tissue
>way it widens influences final arrangement of kidney

Question 22

Metanephric mass (blastema):

Answer 22

-region of urinary ridge

Question 23

Diluted or widened portion of ureteric bud gives rise to:

Answer 23

-pelvis in kidney
>undergoes branching to produce collecting ducts of kidney

Question 24

The collecting ducts induce:

Answer 24

-metanephric tissue to give rise to metanephric tubules

Question 25

‘age of nephrons’:

Answer 25

-grows from medullary to cortex
-YOUNGEST are in the cortex

Question 26

Molecular mechanisms of metanephros development:

Answer 26

-metanephric mass is composed of mesenchyme and is needed for ureteric bud formation
-ureteric bud is need for survival of metanephric mesenchyme
>without it=mesenchyme dies

Question 27

What secretions from the mesenchyme induce the bud to branch?

Answer 27

-retinoic acid (RA)
-glial-derived neurotrophic factor (GDNF)

Question 28

What will the branch secrete to create a primitive tubule?

Answer 28

-Wnt6 or Wnt9b

Question 29

What does the comma shaped part of the tubule secrete and start to develop?

Answer 29

-secretes vascular endothelial growth factor (VEGF)
>get blood vessels and tufts that are derived from the renal artery (vs. the dorsal aorta)

Question 30

Metanephros position during differentiation:

Answer 30

-pelvic to the lumbar region
>definitive kidney occupy a position dorsal to degenerating mesonephros

Question 31

Kidney position:

Answer 31

-right migrates more cranially than left
>except in pigs
*Left is Last and Lagging

Question 32

Kidney cortex contains:

Answer 32

-renal corpuscles
-proximal and distal convoluted tubules

Question 33

Kidney medulla contains:

Answer 33

-loops of Henle
-collecting ducts

Question 34

Medullary pyramid:

Answer 34

-conical arrange of loops of Henle and collecting ducts
-base of pyramid covered by cortex of kidney
-apex as a papilla projecting into the pelvis of kidney

Question 35

Renal lobe=

Answer 35

-medullary pyramid with cortical covering