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 disease characterized by chronic pain, stiffness, and tenderness of muscles, tendons, and joints, without detectable inflammation. Fibromyalgia does not cause body damage or deformity. However, undue fatigue plagues 90 percent of patients with fibromyalgia. Sleep disorder is also common in patients with fibromyalgia. Fibromyalgia can be associated with other rheumatic conditions, and irritable bowel […]

An oily secretion of the sebaceous gland which helps to preserve the flexibility of the hair.

Abnormal rhythm of the heartbeat due to irregularities in transmission of the electrical signals that normally control heart rate and rhythm. Also known as arrhythmias. With an arrhythmia, the heartbeats may be irregular or too slow (bradycardia), too rapid (tachycardia), or occur too early. When a single heartbeat occurs earlier than normal, it is called […]

A fluid secreted by the cells of the alveoli (the tiny air sacs in the lungs) that serves to reduce the surface tension of pulmonary fluids; surfactant contributes to the elastic properties of pulmonary tissue, preventing the alveoli from collapsing.

The outer layer of the pericardium which is a conical sac of fibrous tissue that surrounds the heart and the roots of the great blood vessels. The pericardium has outer and inner coats. The outer coat is tough and thickened, loosely cloaks the heart, and is attached to the central part of the diaphragm and […]