X

X chromosome - one of the two sex chromosomes; determines female sex characteristics

Xerophthalmia - Abnormal dryness and thickening of the mucous membrane lining of the eyelids and white part of the eye and cornea. Caused by vitamin-A deficiency or certain eye diseases.

Xerostomia - a dry mouth condition; can be caused by a number of things, including rheumatoid arthritis, diabetes, kidney failure, infection with HIV (the virus that causes AIDS), drugs used to treat depression, and radiation treatment for mouth or throat cancer.

Y

Y chromosome - one of the two sex chromosomes; determines male sex characteristics

yeast infection - a term usually referring to a candidiasis infection; characterized by itching, burning, or redness of the vaginal area.

yellow fever - a life-threatening viral infection transmitted by mosquitoes that causes jaundice, fever, headache, and vomiting.

Z

Zenker's diverticulum - pouches in the esophagus from increased pressure in and around the esophagus.

Zollinger-Ellison syndrome - Group of symptoms that occur when a tumor called a gastrinoma forms in the pancreas. The tumor releases large amounts of the hormone gastrin, which causes too much acid in the duodenum, resulting in ulcers, bleeding, and perforation.

zygote intrafallopian transfer (ZIFT) - method of treating infertility by removing eggs from a woman's ovaries, fertilizing them in the laboratory with sperm from her partner or a donor, and inserting one or more of the fertilized eggs into one of her fallopian tubes.