Control of Bladder Function 27-Apr-17 Urinary Bldder

Urinary System 27-Apr-17 Urinary Bldder Kidney Ureter Aorta Urinary bladder From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Urinary Bladder 27-Apr-17 Urinary Bldder Urinary bladder Detrusor muscles Orifice of ureter Ureter Trigone of bladder Prostatic urethra From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Urinary Bladder Urinary bladder It is made up of smooth muscles Detrusor muscles Urinary bladder Stores urine Periodically evacuates completely urine It is made up of smooth muscles Detrusor muscle Fibers extend in all directions Spiral, longitudinal, circular Fused to form syncytium Ureter Seminal vesicle Prostate From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Urinary Bladder When contracted can Detrusor muscles When contracted can Increase pressure in bladder by 40 – 60 mm Hg Ureter Seminal vesicle Prostate From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Urinary Bladder On the posterior wall of bladder Small triangular area called Trigone Lower part of trigone opens into posterior urethra The ureters enter the bladder at the upper ends of the trigone Orifice of ureter Trigone of bladder Prostatic urethra From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Innervation Parasympathetic Pelvic nerve from sacral 2,3,4 Contain both sensory and motor fibers Sympathetic fibers T11 – 12 L1,2 Inhibitory to detrusor excitatory to sphincter Internal sphincter Parasympathetic fibers S 2,3,4 Excitatory to detrusor Inhibitory to sphincter External sphincter From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Innervation Sensory fibers For pain Detect the degree of stretch in bladder wall Initiate reflexes for bladder emptying Sympathetic fibers T11 – 12 L1,2 Inhibitory to detrusor excitatory to sphincter Internal sphincter Parasympathetic fibers S 2,3,4 Excitatory to detrusor Inhibitory to sphincter External sphincter From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Innervation The motor fibers Excite the detrusor muscles Inhibit the internal sphincter around the trigone Sympathetic fibers T11 – 12 L1,2 Inhibitory to detrusor excitatory to sphincter Internal sphincter Parasympathetic fibers S 2,3,4 Excitatory to detrusor Inhibitory to sphincter External sphincter From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Innervation The sympathetic nerves Sympathetic activity From lower thoracic and upper lumber segments T11 , 12 & L 1,2,3 Sympathetic activity Inhibit the detrusor Excite the trigone Sphincter vesicae Sympathetic fibers T11 – 12 L1,2 Inhibitory to detrusor excitatory to sphincter Internal sphincter Parasympathetic fibers S 2,3,4 Excitatory to detrusor Inhibitory to sphincter External sphincter From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Sphincter Mechanism In both male and females There are two sphincter elements Internal sphincter Smooth muscle at the bladder neck External sphincter Skeletal muscle Located at the level of membranous urethra 27-Apr-17 Urinary Bldder

Sphincter Mechanism Bladder neck sphincter Detrusor muscle plus Large amount of elastic tissue Muscle in this area is called internal sphincter (sphincter vesicae) Not a true circular sphincter Thickening formed by Interlaced and converged muscle fibres 27-Apr-17 Urinary Bldder

Sphincter Mechanism Receive both In relaxed filling state Parasympathetic nerves Sympathetic In relaxed filling state Bladder neck will remain closed Provide continence mechanism 27-Apr-17 Urinary Bldder

Sphincter Mechanism With contraction Detrusor muscle pull open the bladder neck 27-Apr-17 Urinary Bldder

Sphincter Mechanism Beyond the posterior urethra, The urethra passes through Urogenital diaphragm Contain layers of muscles Form the external sphincter Made up of voluntary muscles 27-Apr-17 Urinary Bldder

Ureters Ducts of Bellini have circular muscles Proximal portionof collection system Ducts of Bellini have circular muscles Proximal portion of collecting system Pacemaker activity Initiate peristalsis Sympathetics T10 T11 T12 S2 S3 S4 Parasympathetics 27-Apr-17 Urinary Bldder

Ureters Urine flowing from collecting ducts into renal calices Ducts of Bellini Proximal portionof collection system Urine flowing from collecting ducts into renal calices Stretches calices  Inherent pacemaker activity Initiates peristaltic contractions Spread to renal pelvis down the ureters Wave of peristalsis Forcing urine into bladder Sympathetics T10 T11 T12 S2 S3 S4 Parasympathetics 27-Apr-17 Urinary Bldder

Ureters Muscle tone and peristalsis  In diuresis Ducts of Bellini Proximal portionof collection system Muscle tone and peristalsis Influenced by rate of urine excretion  In diuresis  Frequency of peristalsis Wave of peristalsis Forcing urine into bladder Sympathetics T10 T11 T12 S2 S3 S4 Parasympathetics 27-Apr-17 Urinary Bldder

Ureters Walls of ureters innervated by ANS Ducts of Bellini Proximal portionof collection system Walls of ureters innervated by ANS Peristaltic contractions in ureters Enhanced by parasympathetic Inhibited by sympathetics Wave of peristalsis Forcing urine into bladder Sympathetics T10 T11 T12 S2 S3 S4 Parasympathetics 27-Apr-17 Urinary Bldder

Ureters Normal tone of detrusor muscles Each peristaltic wave Ducts of Bellini Proximal portionof collection system Normal tone of detrusor muscles Compress the ureters Prevent backward flow of urine into ureters during micturition Each peristaltic wave  Intra-ureteral pressure Force urine to flow into bladder Wave of peristalsis Forcing urine into bladder Sympathetics T10 T11 T12 S2 S3 S4 Parasympathetics 27-Apr-17 Urinary Bldder

Uretero-renal Reflex Well supplied by pain fibers When ureters become obstructed (renal stones) Intense reflex constriction occurs accompanied by severe pain Ureteric colic 27-Apr-17 Urinary Bldder

Uretero-renal Reflex The pain causes reflex Uretero-renal reflex Constriction of renal arterioles  Urine output from the kidney Uretero-renal reflex Prevent excess flow of urine When ureters are blocked 27-Apr-17 Urinary Bldder

Filling of Bladder During the collecting phase Sympathetics Emptying is prevented or made difficult By neural activity Sympathetics Inhibit detrusor muscles Excite internal sphincter Pudendal fibers  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Filling of Bladder Pudendal fibers Excite external sphincter  Intra-urethral pressure Maintain continence Pudendal fibers  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Urinary Bladder Bladder fills at a rate of 50 ml/hr Plasticity of smooth muscle Stretch (stress) relaxation Ensure that pressure inside the bladder Increases only slightly 27-Apr-17 Urinary Bldder

Urinary Bladder When bladder collects 150 –250 ml urine 1st signs of brief urge to urinate appears 250 –500 ml of urine Evacuation phase begins 27-Apr-17 Urinary Bldder

Cystometry Cystometry Relationship between P = (2T)/R Intravesicle pressure & volume Governed by Laplace’s law P = (2T)/R 80 60 Intravesicle pressure (cm H2O) 40 20 500 100 200 300 400 Intravesicle volume (ml) 27-Apr-17 Urinary Bldder

Cystometry As urine collect in the bladder Bladder distend Both T & R increase so Pressure does not increase appreciably in the initial phases Until critical volume is attained 80 60 Intravesicle pressure (cm H2O) 40 20 500 100 200 300 400 Intravesicle volume (ml) 27-Apr-17 Urinary Bldder

Micturition Reflex As bladder fill with urine Cortex As bladder fill with urine Stretch receptors are stimulated Sensory signal relayed to spinal cord (sacral segment) Cause reflex contraction of detrusor muscle Micturition reflex Micturition contraction Impulses to spinal cord Brain stem Stretch of muscle during filling  Bladder pressure  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Micturition Reflex When the bladder is partially full Cortex When the bladder is partially full Reflex can relax spontaneously As blood continues to fill Reflex becomes more frequent  Strength of contraction of detrusor muscle  Intra-vesicle pressure More stimulation of stretch receptors Impulses to spinal cord Brain stem Stretch of muscle during filling  Bladder pressure  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Micturition Reflex But once the reflex Cortex But once the reflex Has not succeeded in emptying the bladder It is inhibited Can remain inhibited for several hours Impulses to spinal cord Brain stem Stretch of muscle during filling  Bladder pressure  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Micturition Reflex But as the bladder becomes more filled with urine Cortex But as the bladder becomes more filled with urine Reflex becomes more powerful Initiate reflex inhibition of External sphincter via pudendal nerves Causing urination to occur Impulses to spinal cord Brain stem Stretch of muscle during filling  Bladder pressure  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Evacuation of Urinary Bladder During evacuation Perineal muscle relax Voluntary sphincter around urethra relax Trigone contract Leads to occlusion of ureteral-vesicle junction Prevent reflux of urine into ureters 27-Apr-17 Urinary Bldder

Evacuation of Urinary Bladder Contraction of trigone also Pulls open the posterior portion of bladder neck Become funnel shaped Detrusor muscle contract Intra-vesicle pressure begins to rise This pressure is directed downwards towards urethra 27-Apr-17 Urinary Bldder

Evacuation of Urinary Bladder Voiding begins Detrusor maintain contraction until bladder is empty When bladder is empty Detrusor relax Bladder neck is allowed to close Urethra and perineal muscles tone return to normal Trigone resumes its normal tone 27-Apr-17 Urinary Bldder

Paracentral lobule Fibers from paracentral lobule descend to the micturition center to the pelvic and pudendal nerve Signals reaching the brain, initiate desire to hold As the Detrusor muscle contracts abdominal wall muscle and diaphragm contract,  abdominal pressure. Stretch receptors stimulated Detrusor muscles An initial relaxation of perineal muscles is followed by contraction of detrusor muscle. Bladder neck closed when detrusor muscle relaxes assisted by elastic recoil External vesical sphincter relaxes. Bladder neck opens. Voiding occurs with at pressure of 50 to 150 cm water. 27-Apr-17 Urinary Bldder

Facilitation & Inhibition Cortex Micturition reflex Spinal cord phenomenon Can be inhibited or facilitated by brain centers Brain stem, pons Several centers located in cerebral cortex Impulses to spinal cord Brain stem Stretch of muscle during filling  Bladder pressure  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Facilitation & Inhibition Cortex When micturition is desired Higher centers Keep micturition reflex partially inhibited Higher centers can prevent micturition Even if reflex does occur Tonic contration of external sphincter Impulses to spinal cord Brain stem Stretch of muscle during filling  Bladder pressure  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder

Facilitation & Inhibition Cortex When it is time to urinate Higher centers can facilitate sacral micturition centers Initiate micturition reflex At the same time inhibit external sphincter Urination can occur Impulses to spinal cord Brain stem Stretch of muscle during filling  Bladder pressure  Urethral pressure From Hansen T. Sherrief; Texbook of Physiology CD 27-Apr-17 Urinary Bldder