physiology of micturition jjjhnhjjhjjjóoóooooooooooóóóó

Uiiiiillo kkkkkkkk

1. MICTURITION

2. MICTURITION Voiding of urine is called Micturition. Micturition is a process by which urine is voided from the urinary Bladder.

3. Urinary Bladder Urinary Bladder is a Triangular Hollow organ located in lower abdomen. It consists of Body, Neck, Internal Urethral sphincter.

4. It consists of three ill defined layer of muscle fibers called “ Detrusor Muscle”. Detrusor Muscle has 3 layers : 1) inner Longitudinal Layer 2) Middle circular Layer 3) outer longitudinal layer. the lower part of Bladder is narrow from neck. It opens into urethra via “Internal urethral sphincter ”

5. URETHRA Male urethra has both urinary functions & reproductive function. It carries urine & semen. Male urethra is 20 cm Long . Male urethra has 3 parts ; 1) Prostatic Urethra =3 cm 2) Membranous urethra = 2 cm 3) spongy urethra or cavernous urethra = 15 cm Female urethra has only urinary functions it carries only urine so male urethra is structurally different from female urethra. Female Urethra is 3.5-4 cm Long

6. 1) Prostatic Urethra =3 cm 2) Membranous urethra = 2 cm 3) spongy urethra or cavernous urethra = 15 cm

7. URETHRAL SPHINCTERS INTERNAL SPHINCTER EXTERNAL SPHINCTER made up of Smooth Muscles Fibers Formed by thickening of Detrusor Muscle. made up of Skeletal Muscles Fibers Innervated by sympathetic &Parasympathetic fibers of ANS Innervated by Somatic nerve Fibers. Function under reflex control Function under voluntary control.

8. MICTURITION REFLEX FIRST PHASE : initially when 300-400 ml of urine is collected in urinary bladder, the stretch receptors in the walls of urinary bladder are stimulated. This leads to contraction of Detrusor Muscles and relaxation of internal sphincter so urine flows into urethra from urinary bladder.

9. II phase In the second phase when urine flows through urethra, the stretch receptors present in urethra are stimulated. This leads to inhibition of Pudendial Nerve , relaxation of external sphincter causing voiding of urine Pudendial Nerve : is responsible for voluntary control of micturition . Pudendial Nerve is always active and keeps the external sphincter constricted, when urine enters the urethra & external sphincter relaxes leading to Micturition.

10. REFLEX ARC (Pathway for any reflex Action) REFLEX : Involuntary response to a Sensory stimuli Reflex arc is the anatomical nervous pathway for a reflex action. A simple reflex arc includes five components. 1) RECEPTORS 2) AFFERENT NERVE/SENSORY NEURONE 3) CENTRE 4)EFFEREMT NERVE/ MOTOR NEURONE 5) EFFECTOR ORGAN.

11. Reflex Arc RECEPTORS Receptors is the end organ, which receive stimulus, when receptor is stimulated impulses are generated in Afferent Nerve. 2) AFFERENT NERVE Afferent or Sensory Nerve Transmit Sensory Impulse from Receptors to Centre. 3) CENTRE Centre receive sensory impulses vis Afferent Nerve Fibres & Turn it into appropriate Motor Impulse. Centre is Located in Brain & Spinal Cord.

12. 4) EFFERENT NERVE Efferent or motor nerve transmit motor impulses from centre to the effector organs. 5) EFFECTOR ORGAN /MUSCLES Is the structure such as Muscles or Gland where the activity occurs in response to stimulus.

13. PATHWAY FOR MICTURITION REFLEX FIRST PHASE : 1) RECEPTORS : are stretch receptors on the wall of the urinary Bladder. 2) AFFERENT NERVE : are the Pelvic Nerve. 3) CENTER : is in Sacral segment of Spinal Cord. 4) EFFERENT NERVE : Efferent fibers are Pelvic Nerve. 5) EFFECTORS: Response is the contraction of Detrusor Muscles & Relaxation of internal Sphincter

14. SECOND PHASE : 1) RECEPTORS : are stretch receptors on the wall of the urethra. 2) AFFERENT NERVE : are the Pelvic Nerve. 3) CENTER : is in Sacral segment of Spinal Cord. 4) EFFERENT NERVE : Inhibition of Pudendal Nerve. 5) EFFECTORS: Response is the relaxation external Sphincter causing Voiding of urine.

15. APPLIED PHYSIOLOGY 1) ATONIC BLADDER The conditions like syphilis, Tabes Dorsalis or injury to sacral segments of spinal cord the tone of detrusor muscles is lost and micturition contraction does not occur so there is overflow dribbling. This condition is called Atonic Bladder.

16. AUTOMATIC BLADDER During the stage of recovery after spinal transection, the voluntary control of urinary bladder is lost. Whenever some amount of urine reaches the bladder, there is automatic emptying of bladder. This is known as automatic bladder .

17. Nocturnal micturition Bedwetting is called nocturnal micturition or Enuresis. It is due to loss of voluntary control of micturition. It is common in children below 3 years due to incomplete myelination of motor nerve fibres of urinary bladder. In adults it occurs in neurological or psychological disorders.