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Medical Dictionary


impairment (im-par′ment)
A physical or mental defect at the level of a body system or organ. The official WHO definition is: any loss or abnormality of psychologic, physiologic, or anatomic structure or function. mental i. a disorder characterized by the display of an intellectual defect, as manifested by diminished cognitive, interpersonal, social, and vocational effectiveness and quantitatively evaluated by psychological examination and assessment.

IMP-aspartate ligase
SYN: adenylosuccinate synthase.

impatent (im-pat′ent, im-pa′tent)
Not patent; closed.

impedance (im-pe′dans)
1. Total opposition to flow. In electricity, when flow is steady, i. is simply the resistance, e.g., the driving pressure per unit flow; when flow is changing, i. also includes the factors that oppose changes in flow. Thus, deviations of i., from simple ohmic resistance because of the effects of capacitance and inductance, become more important in alternating current as the frequency of oscillations increases. In fluid analogies ( e.g., pulsatile flow of blood, to-and-fro flow of respiratory gas), i. depends not only on viscous resistance but also on compressibility, compliance, inertance, and the frequency of imposed oscillations. 2. Resistance of an acoustic system to being set in motion. acoustic i. the resistance that a material offers to the passage of a sound wave (colloquial); a property of a medium computed as the product of density and sound propagation speed (characteristic acoustic i.). Discontinuities in acoustic i. are responsible for the echoes on which ultrasound imaging is based. Unit: the rayl.

imperception (im-per-sep′shun)
Inability to form a mental image of an object by combining the sensory data obtained therefrom. [L. in-, not, + per-cipio, pp. -ceptus, to perceive]

imperforate (im-per′for-at)
SYN: atretic.

imperforation (im-per-for-a′shun)
Condition of being atretic, occluded, or closed; indicated in compound words by the prefix atreto- or the suffix -atresia. [L. im- neg. + per-foro, pp. -atus, to bore through]

impermeable (im-per′me-a-bl)
Not permeable; not permitting the passage of substances ( e.g., liquids, gases) or heat through a membrane or other structure. SYN: impervious. [L. im- permeabilis, not to be passed through]

impermeant (im-per′me-ant)
Unable to pass through a particular semipermeable membrane. [L. im-, neg., + permano, to penetrate]

impersistence (im-per-sis′tens)
A transitory existence or occurrence, lasting only a short time. [L. im-, neg. + persisto, to persist] motor i. inability to sustain a movement.

impervious (im-per′ve-us)
SYN: impermeable.

impetiginization (im′pe-tij′i-ni-za′shun)
The occurrence of impetigo by infection of an area of preexisting dermatosis.

impetiginous (im-pe-tij′i-nus)
Relating to impetigo.

impetigo (im-pe-ti′go)
A contagious superficial pyoderma, caused by Staphylococcus aureus and/or group A streptococci, that begins with a superficial flaccid vesicle that ruptures and forms a thick yellowish crust, most commonly occurring in children. SYN: i. contagiosa, i. vulgaris. [L. a scabby eruption, fr. im-peto (inp-), to rush upon, attack] Bockhart i. SYN: follicular i.. i. bullosa i. with lesions of large size, forming bullae. bullous i. of newborn usually, widely disseminated bullous lesions appearing soon after birth, caused by infection with Staphylococcus aureus. SYN: i. neonatorum (2) , pemphigus gangrenosus (2) . i. circinata a ringlike configuration of bullous lesions of i. formed by confluence of several bullae or by the rupture of a single lesion with crusting of the periphery. i. contagiosa SYN: i.. i. contagiosa bullosa discrete purulent skin lesions occasionally seen with streptococcal pyoderma. follicular i. a superficial follicular pustular eruption involving the scalp or other hairy area. SYN: Bockhart i.. i. herpetiformis a rare pyoderma, which may be related to pustular psoriasis, occurring most commonly in pregnant women in the third trimester as an eruption of small, closely aggregated pustules developing upon an inflammatory base and accompanied by severe constitutional symptoms and fetal death; recurs with subsequent pregnancy. i. neonatorum 1. SYN: dermatitis exfoliativa infantum. 2. SYN: bullous i. of newborn. i. vulgaris SYN: i..

impetus (im′pe-tus)
In psychoanalysis, the motor element of an instinct; the amount of force of the individual's energy which the instinctive impulse demands. [L. an onset, fr. im-peto, to attack]

1. (im-plant′)To graft or insert. 2. Material inserted into nonliving tissues. SEE ALSO: graft, transplant. 3. (im′plant)In genitourinary surgery a device inserted to restore continence or potency. Also an injectable material to create a valvular competence of the ureterovesical junction or bladder outlet. SEE ALSO: prosthesis. [L. im-, in, + planto, pp. -atus, to plant, fr. planta, a sprout, shoot] carcinomatous implants transference of carcinoma cells from a primary tumor to adjacent tissues where growth continues. cochlear i. an electronic device consisting of a microphone, speech processor, and electrodes that are implanted in the inner ear to stimulate the remaining nerve fibers of the auditory division of the eighth cranial nerve in adults and children with profound hearing impairment and deafness. Many recipients of cochlear implants achieve high, open-set word recognition and can understand speech even over the telephone. SEE ALSO: auditory prosthesis. SYN: cochlear prosthesis. dental implants crowns, bridges, or dentures attached permanently to the jaw by means of metal anchors, most frequently titanium posts. endometrial implants fragments of endometrial mucosa implanted on pelvic structure following retrograde transference through the oviducts. SYN: endometriosis. endo-osseous i. an i. into alveolar bone inserted through the prepared root canal of a tooth in order to increase effective root length. endosseous i. SYN: endosteal i.. endosteal i. an i. that is inserted into the alveolar and/or basal bone and protrudes through the mucoperiosteum. SYN: endosseous i.. inflatable i. an empty silicone rubber bag with an inlet tube and a valve inserted into or behind the breast, then inflated with a liquid to the desired size; used in augmentation mammaplasty, and breast reconstruction. intracorneal implants inserts placed within corneal pockets to alter the refractive power of the eye. intraocular i. a plastic lens placed in the anterior or posterior chamber of the eye to substitute for the lens removed in cataract extraction. magnetic i. a tissue-tolerated, magnetized metal placed within the bone to aid in denture retention; a similar magnet is placed in the overlying denture to complete the field. orbital i. the glass, plastic, or metal device placed in the muscle cone after enucleation of an eye. penile i. a rigid, flexible, or inflatable device surgically placed in the corpora cavernosa to produce an erection. pin i. a type of dental i. usually rod-shaped, used in the area of the maxillary sinuses. post i. that portion of a dental i. substructure that protrudes through the mucosa to connect with the restoration. root-form i. an i. shaped like the root of a tooth. silicone i. i. composed of silicone; common form of breast i. for augmentation. submucosal i. a dental i. resting beneath the mucosa. SEE ALSO: i. denture. subperiosteal i. an artificial dental metal appliance made to conform to the shape of a bone and placed on its surface beneath the periosteum. See i. denture substructure. supraperiosteal i. an alloplastic graft inserted superficial to the periosteum to change the contour of an area. testicular i. a device placed surgically in the scrotum in males with absence or severe hypoplasia of the testis. SYN: testicular prosthesis. threaded i. an i. with screwlike threads that is either screwed into bone previously threaded by a tap, or by self-tapping, the i. cutting threads in the bone as it is inserted into a predrilled hole. triplant i. a combination of three pin implants to form a single abutment to support or retain a dental prosthesis.

implantation (im-plan-ta′shun)
1. Attachment of the fertilized ovum (blastocyst) to the endometrium, and its subsequent embedding in the compact layer, occurring 6 or 7 days after fertilization of the ovum in humans. 2. The process of placing a device or substance within the body, e.g., placement of a saline-filled device beneath the breast mound. 3. Insertion of a natural tooth into an artificially constructed alveolus. 4. Tissue grafting. SEE ALSO: transplantation. central i. i. in which the blastocyst remains in the uterine cavity, as in carnivores, rhesus monkeys, and rabbits. SYN: circumferential i., superficial i.. circumferential i. SYN: central i.. collagen i. SYN: collagen injection. cortical i. i. of blastocyst in the ovarian cortex, causing an ovarian pregnancy. See ectopic pregnancy. eccentric i. i. in which the blastocyst lies in a uterine crypt, as in the mouse, rat, and hamster. interstitial i. i. in which the blastocyst lies within the substance of the endometrium, as in humans and guinea pigs. nerve i. planting one nerve into the sheath of another nerve. pellet i. intramuscular or subcutaneous insertion of an active therapeutic agent in pellet form to provide protracted absorption at a rate slower than subcutaneous or intramuscular injection and as a means of providing a sustained therapeutic effect without repeated administration. periosteal i. insertion of a normal tendon into a periosteum as part of a tendon transplantation operation. subcutaneous i. insertion of material under the skin. superficial i. SYN: central i..

implosion (im-plo′shun)
1. A sudden collapse, as of an evacuated vessel, in which there is a bursting inward rather than outward as in an explosion. 2. A type of behavior therapy, similar to flooding, during which the patient is given massive exposure to extreme anxiety-arousing stimuli by being asked to describe, and thus relive in imagination, those life events or situations typically producing these overwhelming emotional reactions. As the patient does so, the therapist attempts to extinguish the future influence of such unconscious material over the patient's behavior and feelings, and previous avoidance responses to the stimuli are replaced by more appropriate responses.

impotence, impotency (im′po-tens, -ten-se)
1. Weakness; lack of power. 2. Specifically, inability of the male to achieve and/or maintain penile erection and thus engage in copulation; a manifestation of neurologic, vascular, or psychological dysfunction. [L. impotentia, inability, fr. in- neg. + potentia, power] psychic i. that caused by psychologic factors. vasculogenic i. i. due to alterations in the flow of blood to and from the penis.

impregnate (im-preg′nat)
1. To fecundate; to cause to conceive. 2. To diffuse or permeate with another substance. SEE ALSO: saturate. [L. im-, in, + praegnans, with child]

impregnation (im-preg-na′shun)
1. The act of making pregnant. 2. The process of diffusing or permeating with another substance, as in metallic i. of tissue components with silver nitrate or ammoniacal silver. SEE ALSO: saturation.

impressio, pl .impressiones (im-pres′e-o, im-pres-e-o′nez) [TA]
SYN: impression. [L.] i. aortica pulmonis sinistri SYN: aortic impression of left lung. i. cardiaca faciei diaphragmaticae hepatis [TA] SYN: cardiac impression of diaphragmatic surface of liver. i. cardiaca pulmonis SYN: cardiac impression on lung. i. colica hepatis [TA] SYN: colic impression on liver. impressiones digitatae impressions of cerebral gyri. i. duodenalis hepatis [TA] SYN: duodenal impression on liver. i. esophagea hepatis [TA] SYN: esophageal impression on liver. i. gastrica hepatis [TA] SYN: gastric impression on liver. impressiones gyrorum [TA] SYN: impressions of cerebral gyri. i. ligamenti costoclavicularis [TA] SYN: impression for costoclavicular ligament. i. petrosa pallii SYN: petrosal impression of the pallium. i. renalis hepatis [TA] SYN: renal impression on liver. i. suprarenalis hepatis [TA] SYN: suprarenal impression on liver. i. trigeminalis [TA] SYN: trigeminal impression.

impression (im-presh′un)
1. A mark seemingly made by pressure of one structure or organ on another, seen especially in cadaveric dissections. See also groove for the various impressions of the lungs, e.g., descending aorta, subclavian artery, and vena cavae. 2. An effect produced upon the mind by some external object acting through the organs of sense. SYN: mental i.. 3. An imprint or negative likeness; especially, the negative form of the teeth and/or other tissues of the oral cavity, made in a plastic material that becomes relatively hard or set while in contact with these tissues, made in order to reproduce a positive form or cast of the recorded tissues; classified, according to the materials of that they are made, as reversible and irreversible hydrocolloid i., modeling plastic i., plaster i., and wax i.. SYN: impressio [TA] . [L. impressio, fr. im- primo, pp. -pressus, to press upon] aortic i. of left lung a broad deep groove on the medial aspect of the left lung above and behind the hilum receiving the arch of the aorta and the thoracic aorta. SYN: aortic sulcus, impressio aortica pulmonis sinistri, sulcus aorticus. basilar i. an invagination of the base of the skull into the posterior fossa with compression of the brainstem and cerebellar structures into the foramen magnum. Cf.:platybasia. cardiac i. of diaphragmatic surface of liver [TA] a depression on the superior area of the diaphragmatic surface of the liver corresponding to the position of the heart. SYN: impressio cardiaca faciei diaphragmaticae hepatis [TA] . cardiac i. on lung [TA] the depression on the medial surface of each lung produced by the presence of the heart. It is more pronounced on the left lung. SYN: impressio cardiaca pulmonis. impressions of cerebral gyri [TA] the depressions on the inner surface of the skull which correspond to the convolutions of the brain. SYN: impressiones gyrorum [TA] , impressiones digitatae&star, juga cerebralia&star, digitate impressions. colic i. on liver [TA] a hollow on the visceral surface of the right lobe of the liver anteriorly, corresponding to the situation of the right flexure and beginning of the transverse colon. SYN: impressio colica hepatis [TA] . colic i. of spleen [TA] the part of the visceral surface of the spleen in contact with the colon. SYN: facies colica splenis [TA] , colic surface of spleen. complete denture i. 1. an i. of an edentulous arch made for the purpose of constructing a complete denture; 2. a negative registration of the entire denture-bearing, stabilizing area of either the maxillae or mandible; 3. a negative registration of the entire denture foundation and border seal areas present in the edentulous mouth. i. for costoclavicular ligament [TA] an irregular pitted area on the inferior surface of the clavicle at its sternal end, giving attachment to the costoclavicular ligament. SYN: impressio ligamenti costoclavicularis [TA] , costal tuberosity, rhomboid i., tuberositas costalis. deltoid i. SYN: deltoid tuberosity (of humerus). digitate impressions SYN: impressions of cerebral gyri. direct bone i. an i. of denuded bone, used in the construction of subperiosteal denture implants. duodenal i. on liver [TA] a hollow on the visceral surface of the right lobe of the liver alongside the gallbladder, marking the situation of the duodenum. SYN: impressio duodenalis hepatis [TA] . esophageal i. on liver [TA] the marking of the esophagus on the back of the left lobe of the liver. SYN: impressio esophagea hepatis [TA] . impressions of esophagus SYN: esophageal constrictions, under constriction. final i. in dentistry, the i. that is used to make the master cast. gastric i. on liver [TA] a hollow on the visceral surface of the left lobe of the liver corresponding to the location of the stomach. SYN: impressio gastrica hepatis [TA] . gastric i. on spleen [TA] the surface of the spleen in contact with the stomach. SYN: facies gastrica splenis [TA] , gastric surface of spleen. mental i. SYN: i. (2) . partial denture i. an i. or negative copy of all or a part of the partially edentulous dental arch or area, made for the purpose of designing or constructing a partial denture. petrosal i. of the pallium a shallow i. on the inferior surface of the cerebral hemisphere made by the superior margin of the petrous part of the temporal bone. SYN: impressio petrosa pallii. preliminary i. in dentistry, one made for the purpose of diagnosis or the construction of a tray. SYN: primary i.. renal i. on liver [TA] a hollow on the visceral surface of the right lobe of the liver, in which lies the right kidney. SYN: impressio renalis hepatis [TA] . renal i. of spleen [TA] the portion of the visceral surface of the spleen that contacts the left kidney. SYN: facies renalis splenis [TA] , facies renalis lienis&star, renal surface of spleen. rhomboid i. SYN: i. for costoclavicular ligament. sectional i. an i. that is made in sections. suprarenal i. on liver [TA] a hollow on the visceral surface of the right lobe of the liver, adjoining the groove for inferior venae cava, in which lies the right suprarenal gland. SYN: impressio suprarenalis hepatis [TA] . trigeminal i. [TA] a depression on the anterior surface of the petrous portion of the temporal bone, near the apex, formed in relationship to the trigeminal ganglion. SYN: impressio trigeminalis [TA] .

A particular kind of learning characterized by its occurrence in the first few hours of life, and which determines species-recognition behavior. genomic i. epigenetic process that leads to inactivation of paternal or maternal allele of certain genes susceptible to epigenetic regulation; accounts, among others, for the Angelman and Prader-Willi syndromes.

impromidine (im′pro-mi-den)
An agent which is an agonist at H2-type histamine receptors. Causes gastric acid secretion and tachycardia. Actions can be blocked by agents such as cimetidine and ranitidine.

impulse (im′puls)
1. A sudden pushing or driving force. 2. A sudden, often unreasoning, determination to perform some act. 3. The action potential of a nerve fiber. [L. im-pello, pp. -pulsus, to push against, impel (inp-)] apex i. conventionally the lowermost, leftmost area of cardiac pulsation that is usually palpable. cardiac i. movement of the chest wall produced by cardiac contraction. ectopic i. an electrical i. from an area of the heart other than the sinus node. escape i. one or more impulses (atrial, junctional, or ventricular) arising as a result of delay in the formation or arrival of impulses from the prevailing pacemaker. irresistible i. a compulsion to act such that one feels or claims it cannot be resisted. morbid i. an i. that drives one to commit some act, usually of a deviant or forbidden nature, notwithstanding efforts to restrain oneself. right parasternal impulses cardiac activity as palpable or recordable just to the right of the sternum.

impulsion (im-pul′shun)
An abnormal urge to perform a certain activity.

impulsive (im-pul′siv)
Relating to or actuated by an impulse, rather than controlled by reason or careful deliberation.

imus (i′mus)
Lowest; the most inferior or caudal of several similar structures. [L.]

Abbreviation for intermittent mandatory ventilation.

Acronym for indole production, methyl red, Voges-Proskauer reaction, and ability to use citrate as a sole source of carbon (i inserted for euphony); used primarily to differentiate Escherichia coli from Enterobacter aerogenes and related organisms.

Symbol for indium; inulin.

Symbol for indium-111.

1. Not, akin to G. a-, an-, or Eng. un-. 2. In, within, inside. 3. Very; appears as im- before b, p, or m. [L.]

A suffix widely used to form names of biochemical substances, including proteins (e.g., globulin), lipids (lecithin), hormones (insulin), botanical principles (digoxin), antibiotics (streptomycin), synthetic drugs (aspirin), dyes (eosin), and others; initially a variant of -ine; in a few terms (e.g., dentin, thyroxin, spellings with and without final e are both found. [G. -inos,, L. -inus, adj. suffixes]

inaction (in-ak′shun)
Inactivity, rest, or lack of response to a stimulus.

inactivate (in-ak′ti-vat)
To destroy the biologic activity or the effects of an agent or substance, as the activity of complement is destroyed when serum is heated.

inactivation (in-ak-ti-va′shun)
The process of destroying or removing the activity or the effects of an agent or substance; e.g., the complementary effect of a serum may be destroyed by means of i. at 56°C for 30 min. insertional i. a technique of recombinant DNA technology used to select bacteria that carry recombinant plasmids; a fragment of foreign DNA is inserted into a restriction site within a gene for antibiotic resistance, thus causing that gene to become nonfunctional. X i. lyonization.

inanimate (in-an′i-mat)
Not alive. [L. in- neg. + anima, breath, soul]

inanition (in′a-nish′un)
Severe weakness and wasting as occurs from lack of food, defect in assimilation, or neoplastic disease. [L. inanis, empty]

inapparent (in′a-par′ent)
Not apparent; beneath the threshold of clinical recognition, as an i. infection.

inappetence (in-ap′e-tens)
Lack of desire or of craving. [L. in- neg. + ap-peto, pp. -petitus, to strive after, long for (adp-)]

inarticulate (in-ar-tik′u-lit)
1. Not articulate in intelligible speech. 2. Unable to express oneself satisfactorily in words.

inassimilable (in-a-sim′il-a-bl)
Not assimilable; not capable of undergoing assimilation. See assimilation.

inattention (in-a-ten′shun)
Lack of attention; negligence. selective i. an aspect of attentiveness in which a person attempts to ignore or avoid perceiving that which generates anxiety. sensory i. the inability to feel a tactile stimulus when a similar stimulus, presented simultaneously in a homologous area of the body, is perceived. visual i. the inability to perceive a photic stimulus in a visual field when a similar but perceived stimulus is presented simultaneously in the homologous field.

inborn (in′born)
Initiated during development in utero. In the specific context of i. error of metabolism, it connotes a genetic disruption of an enzyme. See i. errors of metabolism, under error. SYN: innate.

Denoting populations (groups, genetic lines, etc.) descended over several generations almost exclusively from a small set of ancestors, and hence having a high rate of consanguinity, often occult.

inbreeding (in′bred-ing)
1. Mating between organisms that are genetically more closely related than organisms selected at random from the population. 2. A practice of mating animals that are closely related. The term is clearly relative to how the population is defined; the higher the i. in the population, the less it will lie in the individual mating.

incarcerated (in-kar′ser-a-ted)
Confined; imprisoned; trapped. [L. in, in, + carcero, pp. -atus, to imprison, fr. carcer, prison]

incarnant (in-kar′nant)
Promoting or accelerating the granulation of a wound. SYN: incarnative. [L. incarno, fr. in + caro (carn-), flesh]

incarnative (in-kar′na-tiv)
SYN: incarnant.

incendiarism (in-sen′di-a-rizm)
SYN: pyromania. [L. incendiarius, causing a conflagration]

incentive (in-sen′tiv)
In experimental psychology, an object or goal of motivated behavior. [LL. incentivus, provocative]

incertae sedis (in-ser′te se′dis)
Of uncertain or doubtful affiliation or doubtful position, said of organisms in taxonomic classifications. [L.]

incest (in′sest)
1. Sexual relations between persons closely related by blood, especially between parents and children, brother and sister. 2. The crime of sexual relations between persons related by blood, where such cohabitation is prohibited by law. [L. incestus, unchaste, fr. in-, not, + castus, chaste]

incestuous (in-ses′choo-us)
1. Pertaining to incest. 2. Guilty of incest.

incidence (in′si-dens)
1. The number of specified new events, e.g., persons falling ill with a specified disease, during a specified period in a specified population. 2. In optics, intersection of a ray of light with a surface. [L. incido, to fall into or upon, to happen]

incident (in′si-dent)
Going toward; impinging upon, as i. rays. [L. incido, pp. -casus, to fall into, to meet with]


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