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Anatomy & Physiology of the Urinary System Gillian Nottidge Continence Nurse Specialist

Skills for Health CCO1 Urine production Normal micturition The nervous system including autonomic dysreflexia The bowel and it’s links to voiding problems The endocrine system The pelvic floor The prostate gland, the urethra and sphincters Voiding dysfunction Reflexes

Definition of Urinary Incontinence The complaint of any involuntary leakage of urine Abrams 2002

Physical Requirements for Continence A bladder A sphincter mechanism A pelvic floor A nervous system

Urine production

Glomerulus receives blood via afferent arteriole Fluids and waste material forced out and collected in Bowman’s capsule Blood leaves glomerulus via efferent arteriole Urine drained into bladder via ureters – peristalsis 1-2 mls per minute (Guyton et al 2006)

Effect of endocrine system Vasopressin released by hypothalamus– concentrates urine Diabetes Mellitus – polyuria may be presenting symptom Diabetes Insipidus – loss of production of vasopressin Renin-angiotensin system

What does the Bladder do? The normal bladder has two phases:  A storage phase  An emptying phase Average bladder capacity:  Approximately 500mls  First desire to void at 300mls

The Bladder Is a hollow muscular sac made up of 4 layers  An outer layer (Visceral peritoneum) covers bladder and other abdominal organs  A muscular layer (Detrusor muscle) 3 layers of muscle  A submucous layer (With nerve & blood supply)  An inner layer (Epithelium)

Anatomy of the bladder (female)  Under voluntary control  Divided into 2 segments  The base – Trigone  The body - Detrusor Ureter Internal sphincter Urethra External Sphincter (Pelvic floor muscle) Trigone Detrusor Muscle

Female Urethra 3-5cm long Consists of smooth muscle Lining of squamous epithelium– easily damaged External sphincter striated muscle - control Credit to Alexander Tsiaras - Science photo library Endoscope image of the human urethra

Anatomy of the urinary tract - man Cross section of male anatomy Including:  Bladder  Prostate  Urethra

Male urethra cm long Inside has spiral groove – wider urinary stream Prostatic Bulbourethra Membranous Spongy Sexual function

Effect of bowel on the bladder

Pelvic floor muscles Supports the pelvic organs Contraction causes urethral compression – helps maintain continence during abdominal pressure Collectively called “Levator Ani” Striated muscle slow and fast muscle fibres (under Voluntary control)

Normal micturition 1. Filling and Storage Stage Detrusor relaxed Bladder neck closed External sphincter contracted 2. Voiding Phase Bladder neck opens External sphincter & pelvic floor relaxed Urine expelled Detrusor Contracts Detrusor relaxes

Emptying the bladder Micturition centre co-ordinates the change from storage to voiding Sensory impulses initiate the desire to void Co-ordinated relaxation of the urethral sphincter and detrusor contraction allows the bladder to empty This action can be suppressed

Neuronal control of the bladder

Cerebral Function So, what might go wrong and why? Who might be at risk? How might they feel about it?

Autonomic Dysreflexia It develops after spinal cord injury/ lesion at or above T6 Exaggerated response of nervous system to localised trigger below level of spinal cord injury This causes an sudden extreme rise in blood pressure It can occur without warning and is a medical emergency

Autonomic Dysreflexia Normally a harmful stimulus causes the autonomic nervous system to respond resulting in a rise in blood pressure. If T6 lesion or above present, stimulus below the injury causes BP to rise, but autonomic nervous system does not act to lower it below the lesion. Therefore BP continues to rise until stimulus is removed Autonomic nervous system attempts to lower BP above lesion: this causes the symptoms that aid the diagnosis of AD

Signs and symptoms Stuffy nose / nasal obstruction Severe pounding headache, usually frontal Raised BP (by 20mm/hg) / bradycardia Cutis anserina (goose bumps) above and possibly below level of SCI and shivering Flushing above level of lesion due to vasodilation Reduced urine output Blurring vision – spots before eyes Increased spasms

Voiding Dysfunction Voiding dysfunction and urinary incontinence are conditions in which the bladder is not able to store urine properly (incontinence) or conditions in which the bladder is not able to empty properly (voiding dysfunction). (US Department of Urology 2009)

Reflex Voiding Dysfunction Detrusor areflexiaDetrusor areflexia Detrusor-sphincter dyssynergia Detrusor failure / hyporeflexia Detrusor hyperreflexiaDetrusor hyperreflexia Neurogenic bladder Spinal cord injuries/MS

Risk Factors Age Gender Obesity Smoking Exercises Previous surgery Childbirth

Skills for Health CCO1 Urine production Normal micturition The nervous system including autonomic dysreflexia The bowel and it’s links to voiding problems The endocrine system The pelvic floor The prostate gland, the urethra and sphincters Voiding dysfunction Reflexes

Thank You for listening. Any Questions?