Porth's Essentials of Pathophysiology, 4e

lthough the kidneys control the formation of urine, its storage and periodic elimination depend on the coordinated activity of the smooth and striated muscle of the two functional units of the lower urinary tract— the urinary bladder, which serves as reservoir for urine storage and the urethra and urethral sphincter, which function as an outlet for urine elimination. Alterations in the storage and expulsion functions of the lower urinary tract can result in urine retention, which has deleteri- ous effects on ureteral and, ultimately, renal function; or incontinence, with its accompanying social and hygienic problems. The discussion in this chapter focuses on the control of urine elimination, disorders of lower urinary tract structures and function, lower urinary tract infec- tions, and bladder cancer. Control of Urine Elimination The urinary bladder is a freely movable organ located retroperitoneally on the pelvic floor, just posterior to the pubic symphysis. It consists of two main components: the body in which urine collects, and the bladder neck, which is a funnel-shaped extension of the body that con- nects with the urethra. 1,2 In the male, the urethra contin- ues anteriorly through the penis, with the prostate gland surrounding the neck of the bladder where it empties into the urethra. In the female, the bladder is located anterior to the vagina and uterus. Urine passes from the kidneys to the bladder through the ureters. The interior of the bladder has openings for both the ureters and the urethra. The smooth triangular area that is bounded by these three openings is called the trigone (Fig. 27-1). There are no valves at the ureteral openings, but as the pressure of the urine in the bladder rises, the ends of the ureters are compressed against the bladder wall to prevent the backflow of urine. Disorders of the Bladder and Lower Urinary Tract 27 C h a p t e r A

Control of Urine Elimination Bladder Structure Neural Control of Bladder Function Spinal Cord Centers Pontine Micturition Center Cortical and Subcortical Centers Neuromediator Control of Bladder Function Evaluation of Bladder Function Disorders of Lower Urinary Tract Structures and Function Lower Urinary Tract Obstruction and Stasis Compensatory and Decompensatory Changes Neurogenic Bladder Disorders Neurogenic Overactive Bladder: Failure to Store Urine Neurogenic Areflexic Bladder: Failure to Empty Urine Nonrelaxing External Sphincter Treatment Urinary Incontinence Types and Causes of Incontinence Diagnosis and Treatment Special Needs of Elderly Persons Urinary Tract Infections Etiologic Factors Clinical Features Diagnosis and Treatment Infections in Special Populations Urinary Tract Infections in Non-Pregnant Women Urinary Tract Infections in Pregnant Women Urinary Tract Infections in Children Urinary Tract Infections in the Elderly Interstitial Cystitis/Painful Bladder Syndrome Cancer of the Bladder Etiology and Pathogenesis Manifestations Diagnosis and Treatment Host–Agent Interactions Obstruction and Reflux Catheter-Induced Infection

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