Dictionary

hernia, Velpeau A protrusion of tissue in front of the femoral blood vessels in the groin. Treatment is via surgery.

herniated disk A disk, situated between two vertebrae, that protrudes and tends to press on a nerve root, causing radiating pain. A herniated disk may cause sciatica (pain in the lower back, leg, and behind the knee). Treatment options include use of anti-inflammatory medications, local injection of steroids, and surgical procedures. Also known as herniated…

herniation Abnormal protrusion of tissue through an opening.

heroin A semisynthetic drug derived from, but more potent than, morphine. Heroin is now better known as a drug of abuse than for its medical uses. Heroin may be injected into a vein, injected under the skin, snorted, or smoked. It is highly addictive, and overdose is an ever-present possibility due to the varying purity…

herpes 1 Infection with one of the human herpes viruses, particularly herpes simplex 1 or 2. 2 The family of herpesviruses.

herpes, genital See genital herpes.

herpes simplex virus type 2 A herpes virus that causes genital herpes, which is characterized by sores in the genital area. Abbreviated HSV-2. HSV-2 may also be a cause of fever blisters around the mouth. In rare cases, as when a patient’s immune system is severely compromised, this virus can cause widespread infection of the…

herpes zoster The herpes virus that causes chickenpox (varicella). Herpes zoster and chickenpox are usually contracted in childhood, at which time the virus infects nerves (namely, the dorsal root ganglia). It remains latent for years but can later be reactivated to cause shingles (blisters over the distribution of the affected nerve). Shingles is often accompanied…

herpesvirus One of a family of viruses that contain DNA and that cause infections in humans (human herpesviruses) or animals. Herpesviruses are common and often live in the host’s tissue for years or even decades without causing symptoms.

herpetiform virus A virus with the characteristic shape and behavior of a virus in the herpes family. Not all members of the herpes virus family have been identified. Some herpetiform viruses may eventually be called herpesviruses, and others are merely similar to herpesviruses. See also herpesvirus.

hetero- Prefix meaning different, as in heteromorphism (something that is different in form) and heterozygous (possessing two different forms of a particular gene). The opposite of hetero- is homo-.

heterochromatin A genetically inactive part of the genome. Heterochromatin was so named because its chromosomal material (chromatin) stains more darkly throughout the cell cycle than most chromosomal material (euchromatin). There are two types of heterochromatin: constituitive heterochromatin and facultative heterochromatin.