The document discusses the functional anatomy and innervation of the urinary tract, detailing the micturition system's role in storing and eliminating urine. It covers the anatomical differences in male and female urinary tracts, common clinical correlations, and the complex innervation that governs bladder functions. Additionally, it emphasizes the implications of anatomical knowledge in understanding urinary conditions and catheterization challenges.

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

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

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

4. Pelvis Female Male

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

6. 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

7. 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

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

9. 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)

10. 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

11. 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

12. 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

13. 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

14. Pelvic Floor

15. Pelvic Floor Female Male

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

17. Pelvic Support Bone components Muscular components Ligamentous components

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

19. 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)

20. Innervation of the Urinary Tract and Physiology of Micturition

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

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

23. 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

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

25. 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

26. 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

27. 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

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

29. 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

30. 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

31. Thank you