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Medical Dictionary


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herniation (her-ne-a′shun)
Protrusion of an anatomic structure ( e.g., intervertebral disk) from its normal anatomic position. caudal transtentorial h. displacement of medial temporal structures through the incisura, with or without rostrocaudal brainstem shift. SYN: uncal h.. cingulate h. displacement of the cingulate gyrus beneath the falx. contained disk h. herniated disk material that remains covered by a thin layer of posterior annulus fibrosus or posterior longitudinal ligament; a disk protrusion is an example of a contained disk h.. disk h. extension of disk material beyond the posterior annulus fibrosus and posterior longitudinal ligament and into the spinal canal. foraminal h. displacement of cerebellar tonsils through the foramen magnum. noncontained disk h. herniated disk material that comes directly in contact with the anterior epidural space through a complete defect in the posterior annulus fibrosus and posterior longitudinal ligament; of two main types: (1) extrusions, herniated material that is in continuity with the disk space, but extends completely into the epidural space and (2) sequestered, material that has lost continuity with the disk space and becomes a free fragment in the epidural space. rostral transtentorial h. displacement of anterior cerebellar structures through the incisura, with or without caudorostral brainstem shift. sphenoidal h. displacement of ventral frontal lobar tissue over the sphenoid ridge. subfalcial h. h. beneath the falx cerebri; usually of the cingulate gyrus. tonsillar h. h. of the cerebellar tonsils through the foramen magnum. transtentorial h. h. into the incisura, either from above (rostral transtentorial h.) or below (caudal transtentorial h.). uncal h. SYN: caudal transtentorial h..

hernio-
A hernia. [L. hernia, rupture]

hernioenterotomy (her′ne-o-en-ter-ot′o-me)
Incision of the intestine following the reduction of a hernia.

herniography (her-ne-og′ra-fe)
Radiographic examination of a hernia following injection of a contrast medium into the hernial sac. [hernia + G. grapho, to write]

hernioid (her′ne-oyd)
Resembling hernia. [hernio- + G. eidos, resemblance]

herniolaparotomy (her′ne-o-lap-a-rot′o-me)
Laparotomy for correction of hernia.

herniopuncture (her′ne-o-punk′choor)
Insertion of a hollow needle into a hernia in order to reduce the size of the tumor by withdrawing gas or liquid.

herniorrhaphy (her′ne-or′a-fe)
Surgical repair of a hernia. [hernio- + G. rhaphe, a seam] Bassini h. an operation for an indirect inguinal hernia repair; after reduction of the hernia, the sac is twisted, ligated, and cut off, then a new inguinal floor is made by uniting the edge of the internal oblique muscle to the inguinal ligament, placing on this the cord, and covering the latter by the external oblique muscle. SYN: Bassini operation.

herniotome (her′ne-o-tom)
SYN: hernia knife. Cooper h. a slender bistoury with short cutting edge for dividing the constricting tissues at the neck of a hernial sac.

herniotomy (her-ne-ot′o-me)
Surgical division of the constriction or strangulation of a hernia, often followed by herniorrhaphy. [hernio- + G. tome, a cutting] Petit h. h. without incision into the sac.

heroic (he-ro′ik)
Denoting an aggressive, daring procedure in a dangerously ill patient which in itself may endanger the patient but which also has a possibility of being successful, whereas lesser action would result in failure. [G. heroikos, pertaining to a hero]

heroin (H) (her′o-in)
An alkaloid, C17H17(OC2H3O)2ON, prepared from morphine by acetylation; rapidly metabolized to morphine in the body; formerly used for the relief of cough. Except for research, its use in the United States is prohibited by federal law because of its potential for abuse. SYN: diacetylmorphine. [trade name (it was marketed as the “heroine” of analgesic drugs)]

Herophilus
Greek physician and anatomist of the Alexandrian school, circa 300 B.C. See torcular herophili.

herpangina (her-pan′ji-na, herp-an-ji′na)
A disease caused by types of Coxsackievirus and marked by vesiculopapular lesions about 1–2 mm in diameter that are present around the fauces and soon break down to form grayish yellow ulcers; accompanied by sudden onset of fever, loss of appetite, dysphagia, sore throat, and sometimes abdominal pain, nausea, and vomiting. [G. herpes, vesicular eruption, + L. angina, quinsy, fr. ango, to strangle]

herpes (her′pez)
An inflammatory skin disease caused by h. simplex virus or varicella-zoster virus; an eruption of groups of deep-seated vesicles on erythematous bases. SYN: serpigo (2) . [G. h., a spreading skin eruption, shingles, fr. herpo, to creep] h. catarrhalis SYN: h. simplex. h. corneae SYN: herpetic keratitis. h. digitalis h. simplex infection of the finger. h. facialis SYN: h. simplex. h. febrilis SYN: h. simplex. h. generalisatus generalized h. simplex virus infection. h. genitalis, genital h. h. simplex infection on the genitals, most commonly h. simplex-2 virus. h. gestationis a polymorphous, bullous eruption, more common on the extremities and abdomen than on the upper trunk, with the appearance of pemphigoid or dermatitis herpetiformis; beginning in the second or third trimester, flaring about the time of delivery and subsequently resolving; usually recurrent during subsequent pregnancy. Linear C3 is shown in the epidermal basement membrane by direct immunofluorescence. Not caused by viral infection. h. gladiatorum h. simplex infection associated with trauma to cutaneous tissue. h. labialis SYN: h. simplex. neonatal h. h. simplex virus type 1 or 2 infection transmitted from the mother to the newborn infant, often during passage through an infected birth canal; severity varies from mild to fatal generalized infection, the latter especially with primary maternal genital h.. h. progenitalis genital h. infection caused by h. simplex virus. h. simplex a variety of infections caused by herpesvirus types 1 and 2; type 1 infections are marked most commonly by the eruption of one or more groups of vesicles on the vermilion border of the lips or at the external nares, type 2 by such lesions on the genitalia; both types often are recrudescent and reappear during other febrile illnesses or even physiologic states such as menstruation. The viruses frequently become latent and may not be expressed for years. SYN: h. catarrhalis, h. facialis, h. febrilis, h. labialis, Simplexvirus. traumatic h. h. simplex infection at the site of trauma or of a burn, sometimes accompanied by temperature elevation and malaise. h. whitlow h. simplex inflammation at base of fingernail. h. zoster an infection caused by a herpesvirus (varicella-zoster virus), characterized by an eruption of groups of vesicles on one side of the body following the course of a nerve due to inflammation of ganglia and dorsal nerve roots resulting from activation of the virus, which in many instances has remained latent for years following a primary chickenpox infection; the condition is self-limited but may be accompanied by or followed by severe postherpetic pain. SEE ALSO: varicella. SYN: zona (2) [TA] , shingles, zoster. h. zoster ophthalmicus a herpetic involvement of the ophthalmic branch of the trigeminal nerve, which may lead to corneal ulceration. h. zoster oticus a painful varicella virus infection presenting with a vesicular eruption on the pinna, with or without facial nerve paralysis. SYN: geniculate zoster, Ramsay Hunt syndrome (2) . h. zoster varicellosus h. zoster associated with disseminated varicelliform lesions.

Herpesviridae (her′pes-vir′i-de)
A heterogeneous family of morphologically similar viruses, all of which contain double-stranded DNA and which infect man and a wide variety of other vertebrates. Infections produce type A inclusion bodies; in many instances, infection may remain latent for many years, even in the presence of specific circulating antibodies. Virions are enveloped, ether-sensitive, and vary up to 200 nm in diameter; the nucleocapsids are 100 nm in diameter and of icosahedral symmetry, with 162 capsomeres. The family is subdivided into 3 subfamilies Alphaherpesvirinae, Betaherpesvirinae, and Gammaherpesvirinae, and includes herpes simplex virus, varicella-zoster virus, cytomegalovirus, and EB virus (all of which infect humans), pseudorabies virus of swine, equine rhinopneumonitis virus, infectious bovine rhinotracheitis virus, canine herpesvirus, B virus of Old World monkeys, several viruses of New World monkeys, virus III of rabbits, infectious laryngotracheitis virus of fowl, Marek disease virus of chickens, Lucké tumor virus of frogs, and many others.

herpesvirus (her′pez-vi′rus)
Any virus belonging to the family Herpesviridae. cercopithecrine h. an h., in the family Herpesviridae, affecting Old World monkeys, that is very similar morphologically to herpes simplex virus; fatal infection may occur in humans following the bite of an infected monkey, although other modes of transmission have also been documented. SYN: B virus. human h. 1 herpes simplex virus, type 1. See herpes simplex. human h. 2 herpes simplex virus, type 2. See herpes simplex. human h. 3 SYN: varicella-zoster virus. human h. 4 SYN: Epstein-Barr virus. human h. 5 a highly species-specific h. (Cytomegalovirus) with particular affinity for the salivary gland tissue. SYN: salivary gland virus, salivary virus. human h. 6 a human h. that was found in certain lymphoproliferative disorders, replicates in a number of different types of leukocytes, and is associated with the childhood disease roseola (exanthema subitum). human h. 7 virus found in association with human T lymphocytes and is shed in the saliva of most adults; however, a causal relationship to any known disease has not been determined. human h. 8 a linear double-stranded DNA virus that induces Kaposi sarcoma (KS) in immunodeficient persons. DNA sequences unique to this virus are regularly found in KS specimens from HIV-negative persons as well. The virus is also associated with several uncommon lymphoproliferative syndromes in AIDS patients, including multicentric Castleman disease and primary effusion lymphoma (body cavity–based lymphoma).Among persons with AIDS, Kaposi sarcoma occurs in 15–25% of male homosexuals but only in 1–3% of persons who acquire AIDS by nonsexual routes ( e.g., hemophiliacs and other transfusion recipients). These facts support the hypothesis that the virus is sexually transmitted. KS is characterized histologically by abnormal vascularization and the presence of proliferating endothelial cells, fibroblasts, infiltrating leukocytes, and spindle-shaped tumor cells. Replication of HHV8 occurs only in a small subset of spindle cells, but the majority of such cells are latently infected. Spindle cell proliferation is apparently triggered by growth factors released from HIV-infected cells. Spindle cells, in turn, produce factors that promote angiogenesis. HHV8 DNA can also be found in circulating CD19 B lymphocytes in 40–50% of AIDS patients with KS. Serologic assays are available for anti-HHV8 antibodies, most of them using viral antigen from cell lines derived from body cavity–based lymphomas. Viral replication is insensitive to acyclovir, but is inhibited by ganciclovir, foscarnet, cidofovir, and interferon alpha. H. saimiri an ubiquitous infection of squirrel monkeys that is highly oncogenic when injected into other monkey species. suid h. the causative agent of pseudorabies.

herpetic (her-pet′ik)
1. Relating to or characterized by herpes. 2. Relating to or caused by a herpesvirus.

herpetiform (her-pet′i-form)
Resembling herpes.

herpetologist (her-pet-ol′o-jist)
One who specializes in herpetology.

herpetology (her-pet-ol′o-je)
The branch of zoology concerned with the study of reptiles and amphibians.

Herpetomonas (her-pe-tom′o-nas)
A genus of asexual monogenetic flagellates (family Trypanosomatidae) that are strictly insect parasites, with a variety of body forms including promastigote (leptomad), epimastigote (crithidial), amastigote (leishmanial), and trypomastigote (trypanosome-like); infective forms are passed in the host feces. H. muscae domesticae, the type species, is found in the common housefly. [G. herpeton, a reptile (fr. herpo, to creep), + monas, unit (one of the Monadidae)]

Herpetoviridae
Obsolete term for Herpesviridae.

herpetovirus (her′pe-to-vi′rus)
Obsolete name for a virus belonging to the family Herpesviridae. SEE ALSO: herpesvirus.

Herring
Percy T., English physiologist, 1872–1967. See H. bodies, under body.

Herrmann
C., Jr., 20th century. See H. syndrome.

Hers
G., French biochemist. See H. disease.

hersage (ar-sahzh′)
Separating the individual fibers of a nerve trunk. [Fr. (from L. hirpex, a large rake), a harrowing]

Hertwig
Wilhelm A.O., German embryologist, 1849–1922. See H. sheath.

Hertwig
Richard, German zoologist, 1850–1937. See Magendie-H. sign, Magendie-H. syndrome.

Hertz
Heinrich R., German physicist, 1857–1894. See h., hertzian experiments, under experiment.

hertz (Hz) (herts)
A unit of frequency equivalent to 1 cycle/sec; this term should not be used for radial (circular) frequency or for angular velocity, in which cases the term sec−1 should be used. [H.R. H.]

hertzian (hert′ze-an)
Attributed to or described by Heinrich R. Hertz.

Herxheimer
Karl, German dermatologist, 1861–1944. See H. reaction, Jarisch-H. reaction.

herzstoss (harz′stos)
Cardiac systole producing a diffuse precordial heave with or without any definite point of maximal impulse. [Ger. heart thrust]

Heschl
Richard L., Austrian pathologist, 1824–1881. See H. gyri, under gyrus.

hesitancy (hez′i-tan-se)
An involuntary delay or inability in starting the urinary stream.

hesitant (hez′i-tant)
Term used to descibe the state of RNA polymerase when it is susceptible to pause, arrest or termination signals. SEE ALSO: overdrive, antitermination.

hesperidin (hes-per′i-din)
A flavone diglycoside obtained from unripe citrus fruit, which reputedly possesses vitamin P activity. SYN: cirantin.

Hess
Carl von, German ophthalmologist, 1860–1923. See H. screen.

Hess
Walter R., Swiss physiologist and Nobel laureate, 1881–1973. See trophotropic zone of H..

Hesselbach
Franz K., German anatomist and surgeon, 1759–1816. See H. fascia, H. hernia, H. ligament, H. triangle.

hetastarch (het′a-starch)
A carbohydrate starch derivative used as a cryoprotective agent for erythrocytes. Also used as an extender of blood plasma volume.

heter-
See hetero-.

heteradelphus (het-er-a-del′fus)
Unequal conjoined twins in which the smaller incomplete parasite is attached to the larger, more nearly normal autosite. See conjoined twins, under twin. [heter- + G. adelphos, brother]

heteralius (het-er-a′le-us)
Unequal conjoined twins in which the parasite appears as little more than an excrescence on the autosite. See conjoined twins, under twin. [heter- + G. halios, useless]

heteraxial (het-er-ak′se-al)
Having mutually perpendicular axes of unequal length.

heterecious (het-er-e′shus)
Having more than one host; said of a parasite passing different stages of its life cycle in different animals. SYN: metoxenous. [heter- + G. oikion, home]

heterecism (het′er-e-sizm)
The occurrence, in a parasite, of two cycles of development passed in two different hosts. SYN: metoxeny (1) . [heter- + G. oikion, home]

heteresthesia (het-er-es-the′ze-a)
A change occurring in the degree (either plus or minus) of the sensory response to a cutaneous stimulus as the latter crosses a certain line on the surface. [heter- + G. aisthesis, sensation]

hetero-, heter-
The other, different; opposite of homo- [G. heteros, other]

heteroagglutinin (het′er-o-a-gloo′ti-nin)
A form of hemagglutinin, one that agglutinates the red blood cells of species other than that in which the h. occurs. SEE ALSO: hemagglutinin.

heteroalleles (het′er-o-a-lelz′)
Genes that have undergone mutation at different nucleotide positions and therefore result from different mutational events. Cf.:eualleles.

heteroantibody (het′er-o-an′ti-bod-e)
Antibody that is heterologous with respect to antigen, in contradistinction to isoantibody.

heteroantiserum (het′er-o-an′ti-se-rum)
Antiserum developed in one animal species against antigens or cells of another species.

heteroatom (het′er-o-at′om)
An atom, other than carbon, located in the ring structure of an organic compound, as the N in pyridines or pyrimidines (heterocyclic compounds).

heteroblastic (het-er-o-blas′tik)
Developing from more than a single type of tissue. [hetero- + G. blastos, germ]

heterocellular (het′er-o-sel′u-lar)
Formed of cells of different kinds.

heterocentric (het′er-o-sen′trik)
1. Having different centers; said of rays that do not meet at a common focus. Cf.:homocentric. 2. SYN: allocentric. [hetero- + G. kentron, center]

heterocephalus (het-er-o-sef′a-lus)
Conjoined twins with heads of unequal size. See conjoined twins, under twin. [hetero- + G. kephale, head]

heterocheiral, heterochiral (het-er-o-ki′ral)
Relating to or referred to the other hand. [hetero- + G. cheir, hand]

heterochromatic (het′er-o-kro-mat′ik)
Characteristic of heterochromatin.

heterochromatin (het′er-o-kro′ma-tin)
The part of the chromonema that remains tightly coiled and condensed during interphase and thus stains readily. SYN: heteropyknotic chromatin. constitutive h. repetitive h. that lies in secondary constrictions in the nucleolar organizers. facultative h. nonrepetitive h. that comprises translatable sequences of DNA. satellite-rich h. h. that codes for 18 S and 28 S components of ribosomal RNA and is located close to the centromeres of certain chromosomes.

heterochromia (het′er-o-kro′me-a)
A difference in coloration in two structures which are normally alike in color. [hetero- + G. chroma, color] atrophic h. h. iridis after trauma or inflammation, or in old age. binocular h. an increase or decrease in pigmentation of one eye, with or without extraocular pigmentary defects. h. iridis, h. of iris a difference in coloration of the irides. See binocular h.. monocular h. SYN: iris bicolor. simple h. h. iridis appearing as a developmental defect, without any innervation defect. sympathetic h. h. iridis occurring after lesions of the cervical sympathetic nerves.

heterochromous (het′er-o-kro′mus)
Having an abnormal difference in coloration.




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