Functional Anatomy and Innervation of the Urinary Tract Ho Siew Hong Consultant Urologist S H Ho Urology & Laparoscopy Centre Gleneagles Hospital With Clinical References

Function of the Micturation System Passive reservoir for temporary storage of urine Active function of eliminating urine from the reservoir at an appropriate time

Passive reservoir for temporary storage of urine

Active function of eliminating urine from the reservoir at an appropriate time

Anatomy of Micturation System Bony pelvis Pelvic viscera – bladder, urethra, prostate Sphincter unit Pelvic floor

Bony pelvis

Pelvic viscera – bladder, urethra, prostate

Sphincter unit

Pelvic floor

Pelvis Female Male

Bony Pelvis - Female Gynaecoid shaped More capacious Ligaments are influenced by female hormones Bony Pelvis - Male Android shaped

Gynaecoid shaped

More capacious

Ligaments are influenced by female hormones

Android shaped

Bladder Storage low pressure capacity 300 – 500 cc Good vascularity, innervated Voiding Strong detrusor contraction Clinical correlation Minimal sensation till filling of 150cc Maximal capacity 300-500cc Rises from pelvis in to abdomen during filling, bladder only palpable when adequately filled

Storage

low pressure

capacity 300 – 500 cc

Good vascularity, innervated

Voiding

Strong detrusor contraction

Clinical correlation

Minimal sensation till filling of 150cc

Maximal capacity 300-500cc

Rises from pelvis in to abdomen during filling, bladder only palpable when adequately filled

Bladder Bladder neck, internal urethral orifice Ureteric orifice Trigone Dome 3 layers – mucosa, muscle, serosa Clinical correlation Bladder muscle hypertrophy in overactive bladder Unwanted / uncoordinated contraction -> urge incontinence Incompetent valves in ureteric orifices results in reflux of urine into kidney

Bladder neck, internal urethral orifice

Ureteric orifice

Trigone

Dome

3 layers – mucosa, muscle, serosa

Clinical correlation

Bladder muscle hypertrophy in overactive bladder

Unwanted / uncoordinated contraction -> urge incontinence

Incompetent valves in ureteric orifices results in reflux of urine into kidney

Bladder Comparison Clinical correlation Shorter urinary tract in females More susceptible to ascending infections

Clinical correlation

Shorter urinary tract in females

More susceptible to ascending infections

Urethra Shorter, 4cm length, 1 cm diameter More exposed to ascending infections Longer, 20 cm length, 1 cm diameter Less likely for ascending infections Challenge to catheterize Clinical correlation Female catheterization is more straight forward, less likely hood of trauma Shorter catheters (e.g. CISC)

Shorter, 4cm length, 1 cm diameter

More exposed to ascending infections

Longer, 20 cm length, 1 cm diameter

Less likely for ascending infections

Challenge to catheterize

Clinical correlation

Female catheterization is more straight forward, less likely hood of trauma

Shorter catheters (e.g. CISC)

Urethra - Male Tightest at fossa navicularis ‘ S’ shape, bend at peno-scrotal junction and bulbar urethra Subjected to compression from and enlarging prostate Clinical correlation Keep penis perpendicular to body during catheterization, overcoming the first bend Care when reaching bulbar urethra – highest likely hood of trauma due to bend and non relaxation of external sphincter

Tightest at fossa navicularis

‘ S’ shape, bend at peno-scrotal junction and bulbar urethra

Subjected to compression from and enlarging prostate

Clinical correlation

Keep penis perpendicular to body during catheterization, overcoming the first bend

Care when reaching bulbar urethra – highest likely hood of trauma due to bend and non relaxation of external sphincter

Prostate Gland ‘ Flush of Youth’ Benign Prostatic Hyperplasia sets in at 55 years Compression of prostatic urethra Clinical correlation Commonest cause of urinary tract obstruction in males – enlarged prostate Enlarged prostate not likely to obstruct catheterization

‘ Flush of Youth’

Benign Prostatic Hyperplasia sets in at 55 years

Compression of prostatic urethra

Clinical correlation

Commonest cause of urinary tract obstruction in males – enlarged prostate

Enlarged prostate not likely to obstruct catheterization

Sphincter Unit - Female Internal sphincter at bladder neck – smooth muscle External sphincter - not well defined structure, slow twitch voluntary muscle Almost entire length of urethra with fibers concentrated at mid urethra

Internal sphincter at bladder neck – smooth muscle

External sphincter - not well defined structure, slow twitch voluntary muscle

Almost entire length of urethra with fibers concentrated at mid urethra

Sphincter Unit - Male Internal sphincter at bladder neck – prevents retrograde ejaculation External sphincter clearly defined at level of membranous urethra – urinary continence Clinical correlation Retrograde ejaculation after TURP surgery – disruption of internal urinary sphincter Risk of urinary incontinence after radical prostatectomy surgery (stress incontinence) but not likely after TURP surgery

Internal sphincter at bladder neck – prevents retrograde ejaculation

External sphincter clearly defined at level of membranous urethra – urinary continence

Clinical correlation

Retrograde ejaculation after TURP surgery – disruption of internal urinary sphincter

Risk of urinary incontinence after radical prostatectomy surgery (stress incontinence) but not likely after TURP surgery

Pelvic Floor

Pelvic Floor Female Male

Function of the Pelvic Floor Support pelvic visera Allow passage of nerves, waste products, ie. Urine and faeces

Support pelvic visera

Allow passage of nerves, waste products, ie. Urine and faeces

Pelvic Support Bone components Muscular components Ligamentous components

Bone components

Muscular components

Ligamentous components

Pelvic Floor – continence in females ‘ Buttress effect’ ‘ Hammock effect’

Pelvic Floor - Female Both slow and fast twitch fibres Clinical correlation Pelvic floor exercise – fast and slow contractions Different set of exercises for bladder (continence), uterus + rectum (prolapse)

Clinical correlation

Pelvic floor exercise – fast and slow contractions

Different set of exercises for bladder (continence), uterus + rectum (prolapse)

Innervation of the Urinary Tract and Physiology of Micturition

Filling Phase Bladder distends without rise in intra-vesicle pressure sphincter unit contracts and closes urethra Bladder

Bladder distends without rise in intra-vesicle pressure

sphincter unit contracts and closes urethra

Voiding Phase Bladder contracts and expels urine Sphincter unit relaxes and urethra opens Bladder

Bladder contracts and expels urine

Sphincter unit relaxes and urethra opens

Innervation of Micturation System Parasympathetic (S2-S4) – pelvic plexus, supplying bladder and sphincter Sympathetic (T10-L2) – supplying bladder base, internal sphincter, proximal urethra Somatic (S2-S3) – pudendal nerve, supplying external sphincter Somatic afferent in pudendal nerve Visceral afferent in autonomic system

Parasympathetic (S2-S4) – pelvic plexus, supplying bladder and sphincter

Sympathetic (T10-L2) – supplying bladder base, internal sphincter, proximal urethra

Somatic (S2-S3) – pudendal nerve, supplying external sphincter

Somatic afferent in pudendal nerve

Visceral afferent in autonomic system

Control Of Micturation - filling phase Autonomic Nervous System Spinal cord Bladder, relaxed Sphincter, closed sensory pons cortex

Control Of Micturation - micturation phase Clinical correlation - UTI bladder and urethra irritation Uninhibited contraction of detrusor muscles due to facilitation of micturition reflex Resulting in urinary frequency, leakage Micturition Reflex Sphincter, activated, open sensory cortex pons Spinal cord, S 2,3,4 Bladder, activated, contracts motor

Clinical correlation - UTI

bladder and urethra irritation

Uninhibited contraction of detrusor muscles due to facilitation of micturition reflex

Resulting in urinary frequency, leakage

Control of Micturation - input from higher centres Sphincter, activated, open Bladder, activated, contracts cortex pons Spinal cord Other muscle groups Clinical correlation - Spinal cord injury Uninhibited contraction of detrusor muscles and non relaxation of sphincter due to lack of inhibition of higher centre ‘ Neurogenic bladder’- high pressure bladder

Clinical correlation - Spinal cord injury

Uninhibited contraction of detrusor muscles and non relaxation of sphincter due to lack of inhibition of higher centre

‘ Neurogenic bladder’- high pressure bladder

Control of Micturation - input from higher centres Sphincter, activated, open Bladder, activated, contracts cortex pons Spinal cord Other muscle groups Clinical correlation - Pelvic nerve injury in pelvic surgery Loss of detrusor muscle contraction Large, non contracting bladder – Acontractile bladder Urinary retention with overflow incontinence

Clinical correlation - Pelvic nerve injury in pelvic surgery

Loss of detrusor muscle contraction

Large, non contracting bladder – Acontractile bladder

Urinary retention with overflow incontinence

Higher Center Modifications Voiding can be initiated or inhibited by higher center control of the external sphincter

Voiding can be initiated or inhibited by higher center control of the external sphincter

Control of Micturation - input from higher centres Sphincter, activated, open Bladder, activated, contracts cortex pons Spinal cord Other muscle groups Clinical correlation - Cerebral vascular accident (CVA) / Stroke Loss of ‘fine’ tuning from higher centers Micturition reflex intact Mixed presentation of incontinence and retention

Clinical correlation - Cerebral vascular accident (CVA) / Stroke

Loss of ‘fine’ tuning from higher centers

Micturition reflex intact

Mixed presentation of incontinence and retention

Conclusion Lower urinary tract functions to store urine and expel urine Innervation of lower urinary tract is complex but can be simplified as a micturition reflex with modification from higher center Good understanding of anatomy and innervation can assist our understanding of many clinical conditions

Lower urinary tract functions to store urine and expel urine

Innervation of lower urinary tract is complex but can be simplified as a micturition reflex with modification from higher center

Good understanding of anatomy and innervation can assist our understanding of many clinical conditions

Thank you