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 […]

Bronchus: A large air tube that begins at the end of the trachea and branches into the lungs. The supporting walls of the bronchus are made up in part of cartilage.

One cavity in a system of four communicating cavities within the brain, which are continuous with the central canal of the spinal cord. The fourth ventricle is the most inferior (lowest) of these. It extends from the aqueduct of the midbrain to the central canal of the upper end of the spinal cord, with which […]

A major source of injury and death from the environment, lightning is one of the top three causes of death from environmental origins. Lightning-related injuries are estimated to account for 3000 admissions to burn units each year in the US. Lightning is neither a direct current nor an alternating current. It is a unidirectional, massive, […]

The lower part of the abdomen that is located between the hip bones in a male. The male pelvis is more robust, narrower, and taller than the female pelvis. The angle of the male pubic arch and the sacrum are narrower as well.

A test in which a small drop of the suspected allergy-provoking substance (allergen) is placed on the skin and the skin is then gently scratched through the drop with a sterile needle. If the skin reddens and, more importantly, if it swells, the test is read as positive, and allergy to that substance is considered […]