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 […]

Baldness. There are many types of alopecia, each with a different cause. Alopecia may be localized to the front and top of the head as in common male pattern baldness. It may be patchy as in a condition called alopecia areata. A variant of alopecia involves the entire head and is called alopecia capitis totalis. […]

A common minor anomaly, this is a rudimentary tag of ear tissue. It often contains a core of cartilage. The tag is typically located just in front of the ear (auricle) and is therefore called a preauricular tag.

A cyst of the little glands in the eyelids that make a lubricant which they discharge through tiny openings in the edges of the lids. The lubricant is a fatty substance called sebum characteristic of sebaceous glands. These glands are called the meibomian glands. Inflammation of them is termed meibomianitis or, alternatively, meibomitis. Chronic inflammation […]

Angina trachealis: This has nothing whatsoever to do with the usual type of angina (angina pectoris) which is chest pain of cardiac origin. Angina trachealis is more commonly known as croup. This is an infection of the larynx, trachea, and the bronchial tubes, that occurs mainly in children. It is usually caused by viruses, less […]

Disease, Forestier: A form of degenerative arthritis characteristically associated with flowing calcification along the sides of the vertebrae of the spine and commonly with inflammation (tendinitis) and calcification of the tendons at their attachments points to bone. Because areas of the spine and tendons can become inflamed, nonsteroidal antiinflammatory drugs (NSAIDs) such as ibuprofen can […]