micturition and nursing implications

1. MICTURITION
PRESENTED BY:
M.C.KNIRANDA
ASSISTANT PROFESSOR
SSNSR, SU.

2. MICTURITION
•Micturition is the process of excreting urine from the body.
•Micturition is the process by which the urinary bladder
empties when it becomes filled.

5. PHYSIOLOGY OF MICTURITION
•Micturition is a reflex mechanism which refers to the
process by which the urinary bladder empties when filled.
•It can be described under the following headings –

6. 1. Urine Storage
• Once urine has been formed by the kidneys, it is transmitted
through the ureters to the urinary bladder.
• Peristaltic waves in ureter transmit urine to the bladder at a
rate of 3 cm/sec.
• The physiological capacity of urine storage in adults is about
600 mL.

7. 2. Muscles of Micturition
• Micturition is controlled by three muscles:
the detrusor muscles of the bladder,
the internal, and
external sphincter muscles.
• During filling, the detrusor muscles relax, the internal and external
sphincter muscles remain contracted.

9. INNERVATION OF BLADDER
• Urinary bladder and Internal sphincter are supplied by sympathetic and
parasympathetic nerve fibres.
Sympathetic supply : L1, L2 ( Hypogastric nerve)
Parasympathetic supply : S2,S3,S4 (Pelvic nerve/nervi erigentes)
NOTE - (Pelvic nerve also has sensory fibres, which carry impulse
from the stretch receptors present on the wall of urinary bladder and
urethra.)

10. •External sphincter is supplied: Somatic nerve fibres.
( Pudendal nerve).
INNERVATION OF BLADDER

11. CHARACTERISTICS OF SYMPATHETIC SUPPLY :
Stimulation of hypogastric nerve causes, RELAXATION OF
DETRUSOR MUSCLE and CONSTRICTION OF INTERNAL
SPHINCTER.
It results in filling of bladder.
So, this nerve is called NERVE OF FILLING.
INNERVATION OF BLADDER

12. CHARACTERISTICS OF PARASYMPATHETIC SUPPLY :
Stimulation of pelvic nerve causes CONTRACTION OF
DETRUSOR MUSCLE and RELAXATION OF INTERNAL
SPHINCTER.
It results in emptying of bladder.
So, this nerve is called NERVE OF MICTURITION
INNERVATION OF BLADDER

13. FUNCTION OF PUDENDAL NERVE :
Pudendal nerve always keeps the external sphincter in
CONSTRICTED STATE.
When this nerve is blocked, external sphincter relaxes.
Since it’s a somatic nerve fibre, it can be CONTROLLED
VOLUNTARILY.
INNERVATION OF BLADDER

15. CENTERS FOR MICTURITION
1) SPINAL CENTRES :
• Located in sacral and lumbar segments.
• Controlled by higher centers of brain.
2) HIGHER CENTERS :
• Has facilitatory and inhibitory centers.
Facilitatory center : Pontine region, Posterior hypothalamus (The pons is the
largest part of the brainstem, located above the medulla and below the midbrain).
Inhibitory center : Mid brain.

16. 1) When the volume of urine in the bladder reaches nearly 400ml, intra-
vesical pressure increases.
2) Bladder wall stretches.
3) Stretch receptors on the bladder wall are activated. (M1,M2,M3 receptors)
4) Sensory signal is given to spinal centers through sensory fibres of
parasympathetic (pelvic) nerve.
5) Reflex arc is produced in spinal cord.
6) Motor signal is given to urinary bladder through motor fibres of
parasympathetic nerve ( pelvic nerve).
PATHWAY OF MICTURITION

17. 7) As a result of parasympathetic activity, DETRUSOR muscle contracts and
INTERNAL SPHINCTER relaxes.
8) Urine passes down into proximal urethra.
9) Again afferent impulse is given to spinal cord.
10)Afferent impulse reaches the higher centers in brain. ( pathway of afferent
impulse inside CNS is through spinothalamic tracts).
PATHWAY OF MICTURITION

18. 11)If the signal from brain stem is TO MICTURATE , impulse
created from spinal center to BLOCK PUDENDAL
NERVE.
12)At the same time, sympathetic efferents are inhibited.
13)So, External sphincter relaxes and micturition occurs…
PATHWAY OF MICTURITION

19. 14) If the signal from brain stem is NOT TO MICTURATE,
sympathetic efferents are stimulated.
15) As a result, DETRUSOR EXPANDS and INTERNAL
SPHINCTER constricts.
16) External sphincter remain constricted.
17) So, Urine continues to accumulate in bladder.
PATHWAY OF MICTURITION