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.

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 […]

‘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.

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 […]

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 […]

A vertical plane passing through the standing body from front to back. The mid-sagital, or median, plane splits the body into left and right halves. For a more complete listing of terms used in medicine for spatial orientation, please see the entry to “Anatomic Orientation Terms”.

A genetic disease that is characterized by hemangioblastomas (benign blood vessel tumors) in the brain, spinal cord, and retina; kidney cysts, and kidney cancer (renal cell carcinoma); pheochromocytomas (benign tumors of adrenal-like tissue); and endolymphatic sac tumors (benign tumors of the labyrinth in the inner ear). Abbreviated VHL syndrome. The brain hemangioblastomas in VHL syndrome […]

Blackhead: A familiar term for what is medically called an open comedo. A comedo, the primary sign of acne, consists of a widened hair follicle filled with skin debris, bacteria, and oil called sebum. A blackhead has a wide opening to the skin and is capped with a blackened mass of skin debris. In contrast, […]

Hyperthyroidism (the presence of too much thyroid hormone), Ophthalmopathy specifically involving exophthalmos (protrusion of the eyeballs), Dermopathy with skin lesions. Take the Ankylosing Spondylitis Quiz Myths and Facts About Back Pain The ophthalmopathy can cause sensitivity to light and a feeling of “sand in the eyes.” With further protrusion of the eyes, double vision and […]

A surgical treatment for patients with advanced emphysema in which the volume of the emphysematous lung is reduced by wedge excision to allow the remaining tissue to expand more fully and restore some of the patient’s breathing capacity. Also called reduction pneumoplasty or bilateral pneumectomy. When this surgery is successful, there is improvement in lung […]