• Z chromosome

    A sex chromosome in certain animals, such as chickens, turkeys, and moths. In humans, males are XY and females XX, but in animals with a Z chromosome, males are ZZ and females are WZ.

  • ZAP-70

    Zeta-chain-associated protein kinase 70. A member of the protein tyrosine kinase family, ZAP-70 is normally expressed in T cells and natural killer cells and has a critical role in the initiation of T-cell signaling. ZAP-70 is expressed in T cells and tumors of T-cell lineage. A high level of ZAP-70 expression appears restricted to T-cell […]

  • Zebra

    ‘When you hear hoof beats, think of horses, not zebras.’ For example, when someone develops a mild transient cough, a virus infection is the most logical and likely cause, and tuberculosis is a zebra.

  • Zygotic lethal gene

    A gene that is lethal (fatal) for the zygote, the cell formed by the union of a sperm (male sex cell) and an ovum (female sex cell). The zygote would normally develop into an embryo, as instructed by the genetic material within the unified cell. However, a zygotic lethal gene scotches prenatal development at its […]

  • Zygote intrafallopian transfer (ZIFT)

    A technique in which a woman’s egg is fertilized outside the body, then implanted in one of her fallopian tubes. This technique is one of the methods used to overcome infertility, the inability of couples to produce offspring on their own. First, the egg and the male sperm needed to fertilize it are harvested. Then […]

  • Ulcer, stasis

    A skin ulcer that develops in an area in which the circulation is sluggish and the return of venous blood toward the heart is poor. A common location for stasis ulcers is on the ankles. Stasis refers to a stoppage or slowdown in the flow of blood (or other body fluid, such as lymph).

  • Angiosarcoma

    Angiosarcoma: A form of tissue cancer (sarcoma) that arises in the lining of blood vessels. Angiosarcomas tend to be aggressive, recur locally, and spread widely. Predisposing factors include lymphedema (as from a radical mastectomy), radiotherapy, foreign materials (such as steel and plastic) in the body, and environmental agents (such as arsenic solutions used to spray […]

  • Bleb

    Bleb: A bladder-like structure more than 5 mm in diameter with thin walls that may be full of fluid. Also called a bulla.

  • Heat syncope

    Sudden dizziness, feeling faint and sometimes fainting experienced after exercising in the heat. The skin appears pale and sweaty but is generally moist and cool. The pulse may be weakened, and the heart rate is usually rapid. Body temperature is normal.

  • Nit

    Nits are lice eggs. They are hard to see and are often confused with dandruff or hair spray droplets. Nits are found firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about a week to hatch. All nits must be removed to prevent reinfestation with lice. They can […]