Urinary System Dev

Question 1

Functional units of kidneys

Answer 1

1. Nephrons
   A. Renal corpuscle = glomerulus + glomerular capsule -> filtrate
   B. Renal tubules: process filtrate
   
   1. Divided -> 5 regions after Bowman’s capsule (specific fxns)
2. Collecting system -> final steps urine production
   A. Connecting tubule connects nephron and collection duct
   B. Filtrate connecting tubules -> collecting ducts -> collecting duct (modified)
   C. Several collecting ducts -> minor calyx -> major
   D. Major calyx -> renal pelvis -> ureter

Question 2

Urogenital ridge

Answer 2

On sides of dorsal aorta

1. Nephrogenic cord -> urinary
2. Gonadal ridge -> reproductive

Question 3

Kidney development

Answer 3

1. Pronophroi
2. Mesonephroi
3. Metanephroi

Question 4

Pronephroi

Answer 4

1st set of kidneys

1. Never functional
2. Dev needed for 2nd set to dev
3. Originate cervical region and grow caudally
4. Degenerate but ducts persist and used by mesonephroi

Question 5

Mesonephroi

Answer 5

Intermediate (2nd) set of kidneys
1. Functional weeks 6-10
2. Glomeruli (10-50/kidney) + mesonephric tubules
3. Pronephroic duct -> mesonephric (wolffian) duct week 4
4. Signals from wolffian -> mesonephric tubules in thoracic and lumbar regions
A. Tubules lengthen -> S-shaped loop
1. Acquire capillaries -> glomerulus
2. Tubules -> Bowman’s capsule
3. Glomerulus + Bowman’s = renal corpuscle
4. Distal end tubule fuses mesonephric duct
5. Mesonephric duct fuses w/ cloaca
6. Mesonephric duct and tubules degenerate cranial to caudal
A. Distal ends absorbed into dev. Bladder -> trigone

Question 6

Metanephroi

Answer 6

3rd set, permanent
1. Primordia appear week 5
2. Functional week 10
3. Urine -> amnion -> swallowed -> recycled
4. Fused metanephric duct -> ureteric bud -> collecting system
5. Metanephrogenic blastema from sacral region -> nephrons
6. Ureteric buds lengthen and grow into metanephrogenic blastema -> initiates dev
A. Collecting system
1. Renal pelvis from coalescence of 1st bifurcation
2. Major calyces from 2nd generation bifurcations
3. Minor calyces from 3rd and 4th generation bifurcations
4. Collecting ducts from 5th and all subsequent generations bifurcations-> renal pyramids
B. Nephrogenesis
1. Renal vesicles in mesenchyme after signal from ureteric bud
2. Primordial blood vessels dev
3. Renal vesicle -> renal tubule (S-shaped elongation and lumen formation)
4. Proximal end -> Bowman’s capsule surrounding dev glomerulus
5. Middle portion lengthens and becomes convoluted
6. Distal nephron fuses -> connection w/ collecting tubules
A. Pathway Bowman’s capsule -> collecting unit

Question 7

Bladder and urethra dev from UG sinus

Answer 7

1. Urogenital sinus from allantois and cloaca -> differentiates
   A. Vesical part
   B. Pelvic part
   C. Phallic part
2. Epithelium bladder and urethra from endoderm
3. Urinary trigone

Question 8

Vesical part UG sinus

Answer 8

1. Superior portion
  A. Initially continuous w/ allantois
  B. Allantois obliterated -> urachus
     1. Connects bladder and umbilicus 
     2. Remnant = median umbilical lig (in medial umbilical fold)

Question 9

Pelvic part UG sinus

Answer 9

1. Middle portion
   A. Dev -> urethra
   
   1. Just prostatic and membranous in males
      A. Epithelium prostatic -> prostate
      B. Cranial portion -> urethral and paraurethral glands in females

Question 10

Phallic part UG sinus

Answer 10

1. Inf portion
   A. Grows toward genital tuberacle
   B. Spongy urethra (males)
   C. Vestibule of vagina

Question 11

Urinary trigone dev

Answer 11

Two ureter and urethra opening inside bladder
1. After fusing bladder portion UG sinus mesonephric ducts -> caudally
A. Ureteric bud forms connection w/ bladder
2. Mesonephric duct -> urethra portion UG sinus
A. Cells proliferate and add to bladder wall
B. Wall of trigone
1. CT and smooth m. From intermediate mesoderm
2. Doesn’t stretch when bladder fills
C. Males: mesonephric ducts -> ejaculatory ducts

Question 12

Suprarenal gland dev

Answer 12

1. Cortex from intermediate mesoderm and some lateral plate mesoderm
   A. 1st wave delaminating cells -> fetal suprarenal cortex
   
   1. Imp for maintaining pregnancy
      B. 2nd wave -> definitive cortex
   2. Surrounds fetal cortex
   3. Not fully functional until birth
      C. After birth fetal cortex regresses, definitive functional
2. Medulla from neural crest ectoderm
   A. Post-synaptic symp n. -> chromaffin cells
   
   1. Lack axon and secrete epinephrine and NE into blood

Question 13

Migration and rotation of kidneys

Answer 13

1. Metanephric kidneys in sacral region
  A. Hilum ventral
  B. Renal a. = branches common iliac a.
2. Trunk growth -> kidney in abdominal region
  A. Rotate 90 medially
  B. New blood supply
3. Migration complete
  A. Kidneys at T12-L3 region, rt. Lower
  B. Hilum medial
  C. Renal a. Branches off aorta