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ulcer: A break in the skin or other surface that often occurs along with inflammation, infection, or cancerous growth.

ultrasound: A painless, noninvasive imaging method that uses high-frequency sound waves.

unopposed estrogen: Estrogen taken without an accompanying progestogen.

unresolved losses: Personal losses that are not acknowledged and mourned. Many mental health experts believe that reactions to these losses crop up later, often skewing a person's response to an entirely different loss.

unsaturated fat: Healthy dietary fats from plant sources such as vegetable oils, nuts, and whole grains, as well as from fatty fish. Includes monounsaturated fat and polyunsaturated fat.

unstable angina: Chest pain that occurs or worsens in frequency, severity, or duration when a person is at rest or engaging in mild activity.

upper airway resistance syndrome: Inhalation that requires undue extra exertion; this extra work may cause insomnia and daytime sleepiness.

upper esophageal sphincter: Muscular valve located at the upper portion of the esophagus that opens to allow food or liquid to enter the digestive system.

urea: A waste product of protein digestion and metabolism.

ureter: The tube that connects each kidney to the bladder.

urethra: The tube leading from the bladder through which urine is carried from the body.

urethral hypermobility: Movement of the urethra out of place when abdominal pressure increases, leading to stress incontinence.

urethritis: Inflammation of the urethra.

urgency: The sudden and uncontrollable need to urinate or defecate.

urinary frequency: Routinely needing to urinate more than eight times during the day or more than twice at night.

urinary incontinence: Inability to control urine flow, resulting in involuntary discharge or leakage.

urinary tract: Part of the body that produces and excretes urine. It consists of the kidneys, ureters, bladder, and urethra.

urologist: A specialist who deals with the urinary tract and male reproductive system.

urticaria: An itchy rash of usually short duration. Also known as hives.

uveitis: Inflammation of the pigmented part of the eye (the iris); may seriously affect vision.

uvula: A small, fleshy flap of tissue that hangs from the back of the throat over the root of the tongue.

uvulopalatopharyngoplasty: A surgical treatment for obstructive sleep apnea that involves removing the uvula, the tonsils, and a rim of loose tissue at the back of the soft palate.