Topic 49 - The urinary tract and the process of urination

Question 1

Words to include in the urinary tract

Answer 1

Upper urinary tract

• Calix renalis
• Pelvis renalis
• Ureter
• Urine
  
  • Continuously produced in the kidney
• Rhytmical contractions of the calix
  
  • Periodically
  • Calix → pelvis renalis
    
    • Urinal reflux (ø)
• Peristalsis of ureter
• Ureter
  
  • Wall is shrunk, opens periodically
  • Urine backstream to kidney (ø)
    
    • Autmatically closes

Lower urinary tract

• Urinary bladder
  
  • Smooth muscle
    
    • M. derusor
  • Elastic fibers
  • Stretch → relaxation
  • Filling
    
    • Mechano-receptor activity ↑
      
      • Urination induced
  • Storage of urine
    
    • Periodical emptying
  • Sympathetic efferentation (during filling)
    
    • Bladder wall: loosened
    • Sphicter: contracted stage
  • Parasympathetic dominance (during urination)
    
    • Bladder wall: contracted
    • Sphincter: dilates
• Urethra

Question 2

Words to include in the process of urination

Answer 2

• Urinary center in pons
• Mechanoreceptors of the bladder
• Lumbal motor system
  
  • Sympathetic
  • L1-3
• Sacral motor system
  
  • Parasympathetic
  • S1-3
• Somatic motor system
  
  • Abdominal muscles
  • Perineum
  • Outer sphicter
  • N. pudendus
• Phase of filling
  
  • Parasympathetic activity
    
    • m-ACh-R
      
      • Contraction of bladder walls
        
        • M. detrusor
      • Parasympathetic inhibited
        
        • Sympathetic activity (by)
  • Sympathetic basic tone
    
    • Beta-2 receptor
      
      • Relaxes m. detrusor
    • Alpha-1 receptor
      
      • Contracts smooth muscles of bladder neck
• Urination
  
  • Mechanoreceptive activity ↑
    
    • Center in pons
      
      • Parasympathetic activatin ↑
      • Somatic activity (ø)
      • Sympathetic activity (ø)
    • Bladder wall: contract
    • Sphincter: relax
  • Inhibition of urination:
    
    • Center in pons connected to the cortex
• Diagram:
  
  • ​Wall tension
  • Bladder volume
  • Maximal stretch and mechnoreceptor activity
  • Reflex relaxation
  • Stimulus of urination
  • Urination

Question 3

Topics to include in the essay

Answer 3

1. Urinary tract
   
   • Upper urinary tract
   • Lower urinary tract
2. The process of urination
   
   • Location
   • Phase of filling
   • Urination
3. Excreted volume (interspecies) (ikke nødvendig)

Question 4

The urinary tract

Give the division and compartments of the urinary tract

Answer 4

• Upper urinary tract
  
  • ​Calix renailis
  • Pelvis renalis
  • Ureter
• Lower urinary tract
  
  • ​Urinary bladder
  • Urethra

Question 5

The urinary tract

Upper urinary tract

Answer 5

• Compartments:
  
  • Calix renalis
  • Pelvis renalis
  • Ureter​
• Urine is produced continously in the kidney
• Rhytmical periodical contraction of the calix renalis forwards the urine into the pelvis renalis
  
  • ​No urinal reflux in normal cases
• Peristalsis of the ureter forwards the urine with a speed of 2-3 cm/s
• Under normal urine formation speed the wall of ureter is shrunk, collapsed and only periodically opens
  
  • ​One “bolus” at a time is forwarded to the bladder
• The ureter enters the bladder wall in such an angle, which automatically closes the way of urine backstream to the kidney from the filling bladder

Question 6

The urinary tract

Lower urinary tract

Answer 6

• Compartments
  
  • Urinary bladder
  • Urethra
• Urinary bladder:
  
  • ​Its wall consists of smooth muscle (m. derusor) and elastic fibers
    
    • ​Reacts to stretch by relaxation
  • ​At a certain point of filling the activity of mechano-receptors increase
    
    • Urination is induced
  • Urine is stored in the urinary bladder
    
    • Emptying from the organism is periodical
  • During filling the muscles of the bladder are under sympathetic efferentation:
    
    • Bladder wall: loosened
    • Sphincter: contracted
  • During urination the parasympathetic dominance prevails:
    
    • Bladder wall: contracted
    • Sphicter: dilates

Question 7

The process of urination

How is the nervous system linked to urination?

Answer 7

• The emptying of the bladder is controlled by the urinary center in the pons, based upon the information arriving from the mechanoreceptors of the bladder
• The execution is carried out via the:
  • Lumbal motor system (L1-3)
    
    • ​Sympathetic
  • Sacral motor system (S1-3)
    
    • ​Parasympathetic
  • Somatic motor system (n. pudendus)​

Question 8

The process of urination

Phase of filling

Answer 8

• The parasympathetic activity (m-ACh-R) responsible for the contraction of the bladder wall (m. detrusor) is presynaptically inhibited by the continoud sympathetic acitvity
• The same sympathetic basic tone (beta-2-receptor) relaxes the m. detrusor, and contracts the smooth muscles of the bladder neck via the alpha-1-receptor

Question 9

The process of urination

Urination

Answer 9

• The increased mechanoreceptor activity during urination affects the center in the pons, which:
  
  • Increases the parasympathetic activation
  • inhibits both the somatic and sympathetic activity
• Result:
  
  • Bladder wall: contracts
  • Sphincters: relax
• ​Urination begins
• The center in the pons is connected to the cortex and hypothalamus, which can exert a inhibition on its activity: the retention of urine can be achieved under certain bladder tension, earlier causing urination

Question 10

Give the diagram for wall tension / bladder volume

Answer 10