1. Micturition

2. Micturition
Micturition is the process by which the urinary bladder empties when it becomes filled.

3. Micturition
First, the bladder fills progressively until the tension in its walls rises above a threshold level
This elicits the second step, which is a nervous reflex called the micturition reflex that empties the bladder
If this fails, at least causes a conscious desire to urinate.

4. Urinary bladder Detrusor muscle
body, passing inferiorly and anteriorly into the urogenital triangle and connecting with the urethra
40 to 60 mm

5. Micturition Filling Regular peristaltic contractions
Renal pelvis to the bladder
Oblique passage
No significant changes in the composition of urine (urothelium)
Emptying
Detrusor muscle
Internal urethral sphincter (Smooth Muscle)
External urethral sphincter (Skeletal Muscle)
occurring one to five times per minute
Urine flowing from the collecting ducts into the renal calyces stretches the calyces and increases their inherent pacemaker activity, which
Urothelium complete barrier

6. Innervation of the Bladder
Sympathetic
Parasympathetic
main function in males is believed to be the prevention of reflux of semen into the bladder during ejaculation.
Carry pain sensation
Somatic

7. Filling of the Bladder
Bladder muscle has the property of plasticity; when it is stretched, the tension initially produced is not maintained.
This relation between intravesical pressure and volume can be studied by a procedure called cystometry.

8. CYSTOMETROGRAM Insert a catheter and emptying the bladder
Then record the pressure while the bladder is filled with 50-mL increments of water or air (cystometry).
A plot of intravesical pressure against the volume of fluid in the bladder is called a CYSTOMETROGRAM

9. Law of Laplace States that
“The pressure in a spherical viscus is equal to twice the wall tension divided by the radius”
P =2T/R
P =2T/R
In the case of the bladder, the tension increases as the organ fills, but also the radius increases.

10. CYSTOMETROGRAM
10 cm water
10 cm H20

11. CYSTOMETROGRAM II
Stretch receptor stimulation Ib Ia

12. Micturition Reflex
Micturition reflex is an autonomic spinal cord reflex
But it can also be inhibited or facilitated by centers in the cerebral cortex or brain stem.
Stretch reflex
300 to 400 mL
stretch receptors in the bladder wall, especially by the receptors in the posterior urethra when

13. Micturition Reflex Higher control
Facilitatory area : Pontine region and posterior hypothalamus
Inhibitory area : Midbrain.

14. Micturition Reflex Receptor : Stretch receptor
Afferent : Pelvic nerve S2,3,4
Centre : Sacral portion of the spinal cord
Sensory area of cerebral cortex (desire)
Efferent : Parasympathetic nerve
Pudendal nerve inhibition

15. Micturition Reflex
The perineal muscles and external urethral sphincter are relaxed
The detrusor muscle contracts
Abdominal muscle contracts
Breathing held with glottis clossed
Urine passes out through the urethra.
Female urethra empties by gravity
Male urethra is emptied by several contractions of the bulbocavernosus muscle.

16. Micturition Reflex Voluntary urination Children Emotional stress
Cystitis , stones

17. Abnormalities of micturition
Deafferentation
Tabes dorsalis
All reflex contractions of the bladder are abolished.
The bladder becomes distended, thin-walled, and hypotonic
But some contractions occur because of the intrinsic response of the smooth muscle to stretch.
Voluntary voiding still possible

18. Abnormalities of micturition
Denervation
Afferent and Efferent nerves are both destroyed
Tumors of the cauda equina or filum terminale
The bladder is flaccid and distended for a while.
Gradually, however, the muscle of the "decentralized bladder" becomes active, with many contraction waves that expel dribbles of urine out of the urethra.
The bladder becomes shrunken and the bladder wall hypertrophied.

19. Abnormalities of micturition
Spinal Cord Transection
During spinal shock, the bladder is flaccid and unresponsive.
It becomes overfilled, and urine dribbles through the sphincters (overflow incontinence).
After spinal shock has passed, the voiding reflex returns
no voluntary control
no inhibition or facilitation from higher centers

20. Abnormalities of micturition
Spinal Cord Transection
Some paraplegic patients train themselves to initiate voiding by pinching or stroking their thighs, provoking a mild mass reflex
In some instances, the voiding reflex becomes hyperactive, bladder capacity is reduced, and the wall becomes hypertrophied.
This type of bladder is sometimes called the spastic neurogenic bladder.
The reflex hyperactivity is made worse by, and may be caused by, infection in the bladder wall.

21. Kidney Diseases Edema Uremia Acidosis Anemia Osteomalacia
Acute renal failure
Chronic renal failure
Glomerulonephritis
Nephrotic Syndrome
Nephrogenic Diabetes Insipidus
Hypertension and Kidney Disease

22. Treatment of Renal Failure
Dialysis
Renal transplant