Medical Dictionary banner
Medical Dictionary - Dictionary of Medicine and Human Biology

Medical Dictionary


homology (ho-mol′o-je)
The state of being homologous. h. of chains the degree of similarity between the base sequences of strands of two DNAs. SYN: h. of strands. DNA h. the degree (or percentage) of hybridization capable between the DNA of different microorganisms. h. of strands SYN: h. of chains.

homolysin (ho-mol′i-sin)
A sensitizing hemolytic antibody (hemolysin) formed as the result of stimulation by an antigen derived from an animal of the same species. [homo- + hemolysin]

homolysis (ho-mol′i-sis)
Lysis of red blood cells by a homolysin and complement.

homomorphic (ho-mo-mor′fik)
Denoting two or more structures of similar size and shape. [homo- + G. morphe, shape, appearance]

homonomous (ho-mon′o-mus)
Denoting parts, having similar form and structure, arranged in a series, as the fingers or toes. [G. homonomos, under the same laws, fr. homos, same, + nomos, law]

homonomy (ho-mon′o-me)
The condition of being homonomous.

homonuclear (ho-mo-noo′kle-er)
Denoting a cell line that retains the original chromosome complement.

homonymous (ho-mon′i-mus)
Having the same name or expressed in the same terms, e.g., the corresponding halves (right or left, superior or inferior) of the retinas. [G. h., of the same name, fr. onyma, name]

homophenes (ho′mo-fenz)
Words in which the visible organs of speech behave the same, e.g., tug, tongue, tuck.

homophil (ho′mo-fil)
Denoting an antibody that reacts only with the specific antigen which induced its formation. [homo- + G. philos, fond]

homophobia (ho-mo-fo′be-a)
Irrational fear of homosexual feelings, thoughts, behaviors, or persons. internalized h. h. occurring in a homosexual person, often associated with self-loathing, self-censure, and self-censorship.

homoplastic (ho-mo-plas′tik)
Similar in form and structure, but not in origin. [homo- + G. plastos, formed]

homopolymer (ho-mo-pol′i-mer)
A polymer composed of a series of identical moieties; e.g., polylysine, poly(adenylic acid), polyglucose.

homoproline (ho-mo-pro′len)
SYN: pipecolic acid.

homoprotocatechuic acid (ho′mo-pro′to-kat-e-choo′ik)
(3,4-Dihydroxyphenyl)acetic acid;an isomer of homogentisic acid found in urine; a degradation product of l-tyrosine, l-dopa, and hydroxytyramine.

homorganic (hom-or-gan′ik)
Produced by the same organs, or by homologous organs.

homosalate (ho-mo-sal′at)
An ultraviolet screening agent for topical application to the skin.

homoscedasticity (ho′mo-ske-das-tis′i-te)
Constancy of the variance of a measure over the levels of the factor under study.

homoserine (ho-mo-ser′en)
Amino-4-hydroxybutyric acid;a hydroxyamino acid differing from serine in the possession of an additional CH2 group. An intermediate in the biosynthesis of cystathionine, threonine, and methionine. h. deaminase SYN: cystathionine γ-lyase. h. dehydratase SYN: cystathionine γ-lyase. h. lactone the cyclic ester ( i.e., the δ-lactone) of h.; formed by the reaction of cyanogen bromide on methionyl residues in peptides and proteins.

homosexual (ho-mo-sek′shoo-al)
1. Relating to or characteristic of homosexuality. 2. One whose interests and behavior are characteristic of homosexuality. See gay, lesbian.

homosexuality (ho′mo-sek-shoo-al′i-te)
Erotic attraction or activity, including sexual congress, between individuals of the same sex, especially past puberty. SYN: homoerotism, homoeroticism. ego-dystonic h. a psychological or psychiatric disorder in which an individual experiences persistent distress associated with same-sex preference and a strong need to change the behavior or, at least, to alleviate the distress associated with the h.; no longer a DSM-recognized diagnosis; now included under sexual disorder, not otherwise specified. female h. erotic predisposition, or activity, including sexual congress, between two women past the age of puberty. latent h. an erotic inclination toward members of the same sex not consciously experienced or expressed in overt action, as opposed to overt h. Use of this term is disappearing because of both its potentially iatrogenic effect and the inability to validate the phenomenon by techniques outside of psychoanalytic theory. SYN: unconscious h.. male h. erotic predisposition, or activity, including sexual congress, between two men, past the age of puberty. overt h. homosexual inclinations consciously experienced and expressed in actual homosexual behavior. unconscious h. SYN: latent h..

A steroid that has had at least one of the rings in its structure expanded.

4-homosulfanilamide (ho′mo-sul-fa-nil′a-mid)
SYN: mafenide.

homothallic (ho-mo-thal′ik)
In fungi, denoting a kind of sexual reproduction in which a nucleus of a thallus is capable of fusing with another nucleus from the same thallus or mating type. Cf.:heterothallic. [homo- + G. thallos, a young shoot]

homothermal (ho-mo-ther′mal)
SYN: homeothermic. [homo- + G. therme, heat]

homotonic (ho-mo-ton′ik)
Of uniform tension or tonus.

homotopic (ho-mo-top′ik)
Pertaining to or occurring at the same place or part of the body. [homo- + G. topos, place]

homotransplantation (ho′mo-tranz-plan-ta′shun)
SYN: allotransplantation.

homotropic (ho-mo-tro-pik)
Referring to the binding of the same ligand to a macromolecule; E.G., the binding of four O2 to hemoglobin is h. cooperativity.

homotype (ho′mo-tip)
Any part or organ of the same structure or function as another, especially as one on the opposite side of the body. [homo- + G. typos, type]

homotypic, homotypical (ho-mo-tip′ik, i-kal)
Of the same type or form; corresponding to the other one of two paired organs or parts.

homovanillic acid (HVA) (ho′mo-va-nil′ik)
4-Hydroxy-3-methoxyphenylacetic acid;a phenol found in human urine; produced through the methylation of homoprotocatechuic acid on the meta-OH group. It is the principal urinary metabolite of dopa and dopamine.

homozoic (ho-mo-zo′ik)
Relating to the same animal or the same species of animal. [homo- + G. zoikos, relating to an animal]

homozygosity, homozygosis (ho′mo-zi-gos′i-te, -zi-go′sis)
The state of being homozygous. [homo- + G. zygon, yoke]

homozygote (ho-mo-zi′got)
A homozygous individual. [homo- + G. zygotos, yoke]

homozygous (ho-mo-zi′gus)
Having identical alleles at one or more loci.

homozygous by descent
Possessing two identical alleles at a given locus that are descended from a single source, as may occur in consanguineous mating.

homunculus (ho-mungk′u-lus)
1. An exceedingly minute body which, according to the views of development held by some medical scientists of the 16th and 17th centuries, was contained in a sex cell. From this preformed but infinitely small structure the human body was thought to be developed. SEE ALSO: preformation theory, animalcule. 2. The figure of a human sometimes superimposed on pictures of the surface of the brain to represent the motor or sensory regions of the body represented there. [L. dim. of homo, man]

Honduras bark (hon-doo′ras)
SYN: cascara amara.

honey (hon′e)
Clarified h., a saccharine substance deposited in the honeycomb by the honeybee, Apis mellifera; used as an excipient, as a flavor in gargles and cough remedies, and as a food. SYN: mel (1) . [A.S. hunig]

honk (hawnk)
1. In medical terms, a sound that can be likened to the call of a goose. 2. Sometimes specifically used to denote a sound of laryngeal origin made by vocal cords vibrating in a forced expiration because of a congenital vascular ring compressing the trachea. [echoic] systolic h. a somewhat musical systolic murmur likened to the honking of a goose; sometimes of innocent but unexplained origin, at other times a sign of mitral insufficiency. SYN: systolic whoop.

hood (hud)
1. The anterior part of the integument of soft ticks (family Argasidae) that extends over the capitulum and forms the roof of the camerostome. 2. An expanded, covering structure that resembles the h. of robe or cloak in shape or function, such as the extensor digital expansions that overly the dorsal aspect of the heads of the metacarpals. [O.E. hod, hat] dorsal h. SYN: extensor digital expansion.

hook (huk)
1. An instrument curved or bent near its tip, used for fixation of a part or traction. 2. hamulus. [A.S. hok] calvarial h. an instrument used in prying off the top of the skull after it has been sawed around, at autopsies and dissections. h. of hamate a hooklike process on the distal and medial part of the palmar surface of the hamate bone. SYN: hamulus ossis hamati [TA] . palate h. an instrument for pulling forward the soft palate in order to facilitate posterior rhinoscopy. sliding h. a movable attachment used on an orthodontic wire for the application of elastic traction or headgear force. h. of spiral lamina SYN: hamulus of spiral lamina. squint h. a surgical instrument used to lift ocular muscles. tracheotomy h. right-angled h. used in holding the trachea steady during tracheotomy.

Robert, British experimental physicist, 1635–1703. See hookean behavior, H. law.

hooklets (huk′letz)
1. Clawlike, retractile chitinous hooks that encircle or line the rostellum of the scolex of certain taenioid tapeworms for attachment to the intestinal mucosa, with the additional aid of suckers; the h. can be withdrawn and the rostellum inverted when the tapeworm moves. Various arrangements and forms of the h. characterize the families of taenioid cestodes. 2. H. of degenerated scoleces of Echinococcus species in the fluids of the hydatid cyst. 3. The h. of the oncosphere, by which it claws out of its membrane sheath after hatching and penetrates the host gut wall; these h. can later be found in the cercomer of the procercoid or cysticercoid.

hookworm (huk′werm)
Common name for bloodsucking nematodes of the family Ancyclostomatidae, chiefly members of the genera Ancylostoma (the Old World h.), Necator, and Uncinaria, and including the species A. caninum (dog h.) and N. americanus (New World h.).

Charles F., U.S. physician, 1865–1927. See H. signs, under sign.

Sir Frederick G., English biochemist and Nobel laureate, 1861–1947. See Benedict-H.-Cole reagent.

H. H., 20th century Br. optical physicist. See H. rod-lens telescope.

Hoplopsyllus anomalus (hop-lo-sil′us a-nom′a-lus)
A species of flea parasitic on ground squirrels of the western U.S., and a vector of plague. [G. hoplo, tool, weapon, + psyll, flea]

Carl M., German rhinologist, 1849–1925. See H. papilloma, H. polyp.

SYN: humulus.

hor. decub.
Abbreviation for L. hora decubitus, at bedtime.

hordenine (hor′den-en)
A biogenic amine first isolated from barley; increases blood pressure. [L. hordeum, barley, + -in]

hordeolum (hor-de′o-lum)
A suppurative inflammation of a gland of the eyelid. [Mod. L., hordeolus, a sty in the eye, dim. of hordeum, barley] h. externum inflammation of the sebaceous gland of an eyelash. SYN: sty, stye. h. internum an acute purulent infection of a meibomian (tarsal) gland. SYN: acute chalazion, h. meibomianum, meibomian sty. h. meibomianum SYN: h. internum.

Bernard L., U.S. biochemist, *1914. See Warburg-Dickens-H. shunt.

horehound, hoarhound (hor-hound)
Marrubium vulgare (family Labitae); bitter principle is marrubium, a volatile oil. A compound alleged to have expectorant properties and often found in cough drops and other patent medicines. [O.E. har, hoary, + hune, herb]

horizontalis (hor-i-zon-ta′lis)
Horizontal, referring to the plane of the body, perpendicular to the vertical plane, at right angles both to the median and coronal planes, that separates the body into upper and lower parts. [L.]

hormesis (hor-me′sis)
The stimulating effect of subinhibitory concentrations of any toxic substance on any organism. [Gr. h., rapid motion]

hormion (hor′me-on)
A craniometric point at the junction of the posterior border of the vomer with the sphenoid bone. [G. hormos, cord, chain, necklace]

hormogonal (hor-mo′go-nal)
Referring to a class of Cyanobacteria in which the cells grow in filaments.

hormonal (hor-mon′al)
Pertaining to hormones.

hormone (hor′mon)
A chemical substance, formed in one organ or part of the body and carried in the blood to another organ or part; depending on the specificity of their effects, hormones can alter the functional activity, and sometimes the structure, of just one organ or tissue or various numbers of them. A number of hormones are formed by ductless glands, but secretin, cholecystokinin, and pancreozymin, formed in the gastrointestinal tract, by definition are also hormones. For hormones not listed below, see specific names. [G. hormon, pres. part. of hormao, to rouse or set in motion] adipokinetic h. SYN: adipokinin. adrenal androgen-stimulating h. (AASH) a putative pituitary h. that may be responsible for increased secretion of adrenal androgens at the time of puberty. adrenocortical hormones hormones secreted by the human adrenal cortex; e.g., cortisol, aldosterone, corticosterone. adrenocorticotropic h. (ACTH) the h. of the anterior lobe of the hypophysis that governs the nutrition and growth of the adrenal cortex, stimulates it to functional activity, and also possesses extraadrenal adipokinetic activity; it is a polypeptide containing 39 amino acids, but exact structure varies from one species to another; sometimes prefixed by α to distinguish it from β-corticotropin. The first 13 amino acids at the N-terminal region are identical to α-melanotropin. SYN: adrenocorticotropin, adrenotropic h., adrenotropin, corticotropic h., corticotropin (1) . adrenomedullary hormones hormones produced by the adrenal medulla, particularly the catecholamines epinephrine and norepinephrine. adrenotropic h. SYN: adrenocorticotropic h.. androgenic h. any h. that produces a masculinizing effect; of the naturally occurring androgenic hormones, testosterone is the most potent. antidiuretic h. (ADH) SYN: vasopressin. anti-müllerian h. SYN: müllerian inhibiting substance. cardiac h. SYN: herz h.. chorionic gonadotropic h., chorionic gonadotrophic h. SYN: chorionic gonadotropin. chorionic “growth h.-prolactin” (CGP) SYN: human placental lactogen. cortical hormones steroid hormones produced by the adrenal cortex. corticotropic h. SYN: adrenocorticotropic h.. corticotropin-releasing h. (CRH) a factor secreted by the hypothalamus that stimulates the pituitary to release adrenocorticotropic h.. SYN: corticotropin-releasing factor. ectopic h. a h. formed by tissue outside the normal endocrine site of production; e.g., adrenocorticotropic h. produced by a bronchogenic carcinoma. SYN: inappropriate h.. endocrine hormones hormones produced by the endocrine system. Cf.:tissue hormones. erythropoietic h. 1. generally, any h. that promotes the formation of red blood cells, e.g., testosterone; 2. SYN: erythropoietin. estrogenic h. SYN: estradiol. follicle-stimulating h. (FSH) SYN: follitropin. follicular h. SYN: estrone. galactopoietic h. SYN: prolactin. gametokinetic h. SYN: follitropin. gastrointestinal h. any secretion of the gastrointestinal mucosa affecting the timing and quantity of various digestive secretions ( e.g., secretin) or causing enhanced motility of the target organ ( e.g., cholecystokinin). gonadal hormones SYN: sex hormones. gonadotropic h. SYN: gonadotropin. gonadotropin-releasing h. (GnRH, GRH) SYN: gonadoliberin (1) . growth h. (GH) SYN: somatotropin. growth h.-inhibiting h. (GIH) SYN: somatostatin. growth h.-releasing h. (GHRH, GH-RH) SYN: somatoliberin. heart h. SYN: herz h.. herz h. a substance present in extracts of cardiac tissue that augments cardiac contraction; possibly adenosine, a catecholamine, or some nonspecific stimulant present generally in tissues. SYN: cardiac h., heart h.. human chorionic somatomammotropic h. (HCS) SYN: human placental lactogen. hypophysiotropic h. a h. that stimulates the rate of secretion of hypophysial hormones; e.g., a releasing factor; hypothalamic (regulatory) factor. inappropriate h. SYN: ectopic h.. interstitial cell-stimulating h. (ICSH) SYN: lutropin. lactation h. SYN: prolactin. lactogenic h. SYN: prolactin. lipid-mobilizing h. SYN: lipotropin. lipotropic h. (LPH) , lipotropic pituitary h. SYN: lipotropin. local h. a metabolic product secreted by one set of cells that affects the function of nearby cells; an autacoid; e.g., prostaglandins and neurotransmitters. luteinizing h. (LH) SYN: lutropin. luteinizing h.-releasing h. (LH-RH, LRH) SYN: luliberin. mammotropic h. SYN: prolactin. melanocyte-stimulating h. (MSH) SYN: melanotropin. melanotropin release-inhibiting h. (MIH) SYN: melanostatin. melanotropin-releasing h. (MRH) SYN: melanoliberin. neurohypophysial hormones hormones produced in the hypothalamus; E.G., oxytocin, vasopressin. ovarian h. SYN: relaxin. pancreatic hyperglycemic h. SYN: glucagon. parathyroid h. (PTH) a peptide h. formed by the parathyroid glands; it raises the serum calcium levels when administered parenterally by causing bone resorption, reducing renal clearance of calcium and increasing efficiency of calcium absorption in the intestine. It acts in conjunction with calcitonin and other hormones. SYN: parathormone, parathyrin. pituitary gonadotropic h. SYN: anterior pituitary gonadotropin. pituitary growth h. SYN: somatotropin. placental growth h. SYN: human placental lactogen. pregnancy h. SYN: progesterone. progestational h. SYN: progesterone. proparathyroid h. the immediate precursor of parathyroid h.; proparathyroid differs from parathyroid h. by an N-terminal hexapeptide extension. releasing h. (RH) SYN: releasing factors. salivary gland h. SYN: parotin. sex hormones a general term covering those steroid hormones that are formed by testicular, ovarian, and adrenocortical tissues, and that are androgens or estrogens. SYN: gonadal hormones. somatotropic h. (STH) SYN: somatotropin. somatotropin release-inhibiting h. (SIH) SYN: somatostatin. somatotropin-releasing h. (SRH) SYN: somatoliberin. steroid hormones those hormones possessing the steroid ring system; e.g., androgens, estrogens, adrenocortical hormones. sympathetic h. SYN: sympathin. thyroid-stimulating h. (TSH) SYN: thyrotropin. thyrotropic h. SYN: thyrotropin. thyrotropin-releasing h. (TRH) SYN: thyroliberin. tissue hormones hormones synthesized by cells other than those in the endocrine system. Cf.:endocrine hormones. tropic hormones, trophic hormones those hormones of the anterior lobe of the pituitary that affect the growth, nutrition, or function of other endocrine glands ( e.g., TRH, ACTH). vertebrate hormones hormones synthesized in vertebrates.

hormonogenesis (hor′mo-no-jen′e-sis)
The formation of hormones. SYN: hormonopoiesis.


. . . Feedback