Urinary System Embryo

Question 1

Review the development of the intermediate mesoderm and identify its location through the process of body folding

Answer 1

becomes retroperitoneal in postion

• Starts between to paraxial mesoderm and lateral plate mesoderm
• Lateral body folding pushes intermediate mesoderm posteriorly
  
  • Disrupted and pushed behind peritoneum

Question 2

Identify the urogenital ridge and describe the regions that will give rise to the pronephroi, mesonephroi, and the metanephroi

Answer 2

Urogenital ridge

• Made of intermediate mesoderm
• Two parts
  
  • Nephrogenic cord
  • Genital cord

Nephrogenic cord gives off urinary system

• Pronephroi
  
  • C5-C7 (cranial region)
• Mesonephroi
  
  • thoracic/lumbar region
• Metanephric
  
  • most caudal portion of cord

Question 3

Name and briefly describe the three sets of kidneys

Answer 3

• Pronephros
  
  • rudimentary, nonfunctional
• Mesonephros
  
  • function for a short time during early fetal period
• Metanephros
  
  • forms the permanent kidney

Question 4

Identify the derivatives of the metanephric diverticulum vs. those of the metanephrogenic blastema

Answer 4

metanephric diverticulum/urteric bud

• Collecting portions
  
  • ureter
  • renal pelvis
  • major and minor calyces

metanephrogenic blastema

• Excretory portions
• Bowman’s capsule
• PCT
• Loop of Henle
• DCT

Question 5

Describe the positional changes of the kidneys and understand how congenital anomalies of position and renal vessels occur

Answer 5

postion change:

• kidneys begin in the caudal end of the embryo around week 6-9
• ascend because embryo grows in length
• as they ascend they send out more rostral blood supply,
  
  • don’t bring supply with them

Pelvic kidney

Divided kidney

• 2 ureteric buds
• forms 2 blastemas
  
  • leads to 2 ureters or 1 bifurcated

Horseshoe kidney

• kidneys fuse together at the caudal end to form 1 large kidney
• Can’t ascend higher than IMA

Supernumerary vessels

• Caudal vessels don’t retract as kidney ascend
• Not usually a problem unless ureter is pinched

Question 6

Describe the formation of the urinary bladder and urethra

Answer 6

Urorectal septum divides cloaca into 2 parts

• Ventral portion: urogenital sinus
  
  • Vesicle part
    
    • bladder
    • superior portion of urogential sinus
  • Pelvic part
    
    • inferior portion of sinus
    • female: urethra
    • male: membraneous and prostatic urethra
  • Phallic part
    
    • penile or sponge urethra
• Dorsal portio: anal rectal canal

Question 7

Describe the formation of the pronephros

Answer 7

Pronephroi

• Not actually functional
• Form primitive duct system
• Day 21-24
• Start to degenerate and mesonephroi begin to develop

Question 8

Describe the formation of the mesonephros

Answer 8

• Semi-functional
• Urine is produced and drains and along now mesonephric duct to cloaca/amniotic cavity
  
  • Mesonephric vesicles:lumen of nephrogenic cord
    
    • Primordial nephron
    • tubules
• Blood vessels start penetrating
  
  • 1. Nephrogenic cord has a lumen called mesonephric vesicle
  • 2. Mesonephric vesicle grows outward to join mesonephric duct
  • 3. Once they merge called mesonephric tubule
  • 4. Blood vessels branch out from dorsal aorta
       * Forces invagination of mesonephric tubule to form glomerulus –bowman’s capsule
  • 5. Blood vessels continue to penetrate area and tubule becomes convuluted
• Week 4 -10
• Most rostral segments start to degenerate at week 5
• Canalization of mesonephric duct cadual to cranial
• Intiation of ureteric bud
  
  • week 5/ day 28

Question 9

Describe the formation of the metanephros

Answer 9

• Ureteric bud grow outward
  
  • initiates formation of metanephric blastema (which forms from intermediate mesoderm in the sacral region)
• Ureteric bud forms collecting portion
• Blastema form excretory portion
• Then kidneys ascend along w/ embryo growth
  
  • weeks 6-9
  • Don’t drag blood supply
    
    • Send out more cranial branches while caudal regress

Question 10

Describe the different persistent intraembryonic allantoises

Answer 10

• urachal cyst
  
  • dialation
• urachal sinus
  
  • opening at one end
• urachal fistula
  
  • open at both ends, from bladder to umbilicus

Question 11

Describe extrophy of bladder

Answer 11

• bladder comes out of body wall
• results in lack of mesoderm/rectus abdominus forming
  
  • muscles not strong enough to hold bladder in