Physiology of the Micturition (Process of Urination)

1. Micturition
Prof. Dr. Rashid Mahmood

2. 22018 Micturition | © Prof. Dr. Rashid Mahmood
Micturition
© Prof. Dr. Rashid Mahmood

3. Objectives
Goal/Aim:
Describe mechanism of Micturition Process
Specific Objectives:
By the end of this session students should be able to
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 3

4. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 4

5. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 5

6. 6
Micturition
• Process by which Urinary Bladder
empties, when it becomes filled.
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

7. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 7

8. 8
Physiological Anatomy of Urinary bladder
Sensory
Motor
Sacral Plexus
Hypogastric nerves
}
Smooth muscle of bladder:
Detrusor muscle
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

9. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 9

10. 10
Parasympathetic
SympatheticSomatic
Nerve supply
of Urinary bladder
Dotted lines: Sensory fibers1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

11. 11
Nerve supply of Urinary bladder
Sensory
Motor
Sacral Plexus
Hypogastric nerves
}
Involuntary
Voluntary1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

12. 12
Nerve supply of Urinary bladder
A. Sensory
Parasympathetic (Pelvic nerves)
S-1  S-3
i) Bladder wall
ii) Neck
(Posterior Urethra)
B. Motor
i) As above
ii) Skeletal Motor:
Pudendal Nerve
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

13. 13
Nerve supply of Urinary Bladder
C. Sympathetic
Blood Vessel
(L-2,
Hypogastric Nerves)
(Some sensory nerves pass by way
of sympathetic nerves→
fullness and pain)
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

14. Q.1
• Define Micturition
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood 14
• Process by which Urinary Bladder
empties, when it becomes filled.

15. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 15

16. 16
Transport of urine to urinary bladder
Collecting Duct→
Calyces
(Pacemaker activity → peristalsis) →
Pelvis →
Ureter →
Urinary Bladder
No change in composition
Sympathetic stimulation:
↓Peristalsis
Parasympathetic stimulation:
↑Peristalsis
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

17. 17
Flow of urine from ureter into urinary
bladder
• Oblique course
• Prevents Vesicoureteral Reflux
• Peristalsis in ureters forces urine into urinary
bladder
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

18. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 18

19. 19
Pain sensation in Ureters
• Well supplied with pain nerve fibers
• Irritation (e.g. stone) → stimulation of
pain nerve fibers
Intense contraction
of ureters
Sympathetic reflex back to kidney
To ↓the urine output
Ureterorenal reflex
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

20. 20
Micturition
Two Steps
A. Gradual filling  Threshold Level
(Cystometrogram)
B. Emptying / Conscious desire to urinate
(Micturition Reflex)
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

21. 211 May 2018 Micturition | © Prof. Dr. Rashid Mahmood
Name the Two Steps of
Micturition
Q.2

22. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 22

23. 23
Micturition
A. Filling of Bladder:
• Stress relaxation
• Up to 300 ml, little rise in pressure
• Beyond 300-400 ml, rapid ↑in pressure
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

24. 24
Cystometrogram
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

25. 25
Micturition
NoMicturition
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

26. 26
Cystometrogram
Micturition contractions=
Micturition waves
 Periodic acute increases in
pressure
 May last a few seconds to > a
minute
 May rise a few cm to >100 cm of
water
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

27. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 27

28. Q. 3
•What is a Cystometrogram ?
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood 28

29. 29
• Autonomic cord reflex
• Contraction of Detrusor muscle
• Inhibited / facilitated by brain
B. Micturition Reflex
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

30. 30
Components of Micturition Reflex (Stretch Reflex)
i. Stimulus:
ii. Receptors
iii. Afferent N:
iv. C.N.S
v. Efferent Nerve
vi. Effector
vii. Response:
i. Stretch
a. Bladder Wall
b. Neck
ii. Sensory stretch receptors
iii. Sensory Fib. Of Pelvic nerve.
iv. S-2 & S-3
v. Motor Fib. Of Pelvic Nerve
vi. Detrusor
vii. Contraction of Detrusor Muscle
As the bladder continues to fill,
the Micturition reflexes become more
Frequent and Powerful1 May 2018

31. Micturition
reflex
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood 31

32. 32
Self-Regenerative Reflex:
i. Progressive
and Rapid
increase of
Pressure
ii. Sustained
Pressure
iii. Relaxation
Activation
of
Stretch
receptors
↑in sensory
impulses
Contraction
of
Urinary
Bladder
Fatigue
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

33. 33
Micturition Reflex
Fatigue
Powerful enough to
Inhibit External
Sphincter through
Pudendal nerve
Activation
of
Stretch
receptors
↑in sensory
impulses
Contraction
of
Urinary
Bladder
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

34. 34
Micturition Reflexes gradually become more and
more powerful and frequent  Inhibition of
external Sphincter through Pudendal Nerve
Inhibition of External sphincter
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

35. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 35

36. 36
Control by Higher Centers
Pons
Facilitatory (and inhibitory?) centers
Midbrain
Facilitatory center
Posterior hypothalamus
Facilitatory center
Cerebral cortex
Normally inhibits the External sphincter
Voluntary urination
By volunteer contraction of abdominal muscles
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

37. Lesson Contents
1. Micturition
2.Physiological Anatomy of Urinary bladder
3. Nerve supply of Urinary bladder
4.Transport of urine to urinary bladder
5. Two Steps of Micturition
6. Cystometrogram
7.Micturition Reflex
8.Control by Higher Centers
9.Abnormalities of Micturition
Counter-Current Mechanism | © Prof. Dr. Rashid Mahmood1 May 2018 37

38. 38
Abnormalities of Micturition
1. Atonic Bladder
Damage to sensory fibers
1. Bladder filling to maximum capacity
2. Overflow incontinence
2. Automatic bladder
Damage to spinal cord above Sacral Regions
No control by brain
3. Uninhibited neurogenic bladder
Partial damage in spinal cord or brain stem
Facilitative impulses > inhibitory impulses
Frequent Micturition
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood

39. Q.4
•What is meant by Atonic Bladder?
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood 39

40. Learning Resources
• Guyton and Hall (Text book of physiology), 13th
Edition
• Berne & Levy Principles of Physiology (Koeppen
BM), 6th Edition
• Human Physiology, Silverthorn
• Human Physiology : from cells to system,
Lauralee Sherwood, 9th edition
Vascular
distensibility &
Functions of
Arterial and
Venous System |
401-May-18

41. Summary
• Urinary bladder is supplied by Sympathetic (Hypogastric
nerves), Parasympathetic (Pelvic nerves) and Pudendal nerves
• Sensory supply to bladder wall and bladder neck is through
Parasympathetic nerves
• Motor supply to detrusor muscle and posterior urethra is
through Parasympathetic nerves
• Motor supply to external sphincter is through Pudendal nerve
• Process of micturition occurs in two steps: gradual filling upto a
threshold level and emptying through micturition reflex or
conscious desire to urinate
• Micturition can be facilitated or inhibited voluntarily
411-May-18

42. Thank You
1 May 2018 Micturition | © Prof. Dr. Rashid Mahmood 42
Questions ?
Comments ?
drrashid62@gmail.com
rashid.mahmood@rmi.edu.pk
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