Copy of `Dorland's Medical Dictionary`

The wordlist doesn't exist anymore, or, the website doesn't exist anymore. On this page you can find a copy of the original information. The information may have been taken offline because it is outdated.

Dorland's Medical Dictionary Category: Health and Medicine > Medical Dictionary Date & country: 31/12/2010, USA Words: 39128

atomic number
(Z) a number expressive of the number of protons in an atomic nucleus, or the positive charge of the nucleus expressed in terms of the electronic charge.

atomic weight
the sum of the masses of the constituents of an atom, expressed in atomic mass units (or daltons), in SI units (i.e., kilograms), or as a dimensionless ratio derived by comparing the mass to the mass of an atom of carbon-12, which is taken as 12.000. Abbreviated at wt.

atomization
(at″әm-ĭ-za´shәn) nebulization.

atomizer
(at´әm-i″zәr) nebulizer.

atonia
(ә-to´ne-ә) Latin word meaning atony.

atonic bladder
neurogenic bladder in which the bladder is dilated and poorly contracting and the lesion is not in the central nervous system.

atonic neurogenic bladder
neurogenic bladder due to destruction of sensory nerve fibers from the bladder to the spinal cord, marked by absence of control of bladder functions and of desire to urinate, bladder overdistention, and an abnormal amount of residual urine; it is usually associated with tabes dorsalis or pernicious anemia but may be seen ...

atonic seizure
an absence seizure characterized by sudden loss of muscle tone.

atony
(at´ә-ne) lack of normal tone or strength; flaccidity. adj., aton´ic., adj.

atopen
(at´ә-pen) the antigen responsible for atopy.

atopic
(a-top´ik) (ә-top´ik) displaced; ectopic. pertaining to atopy.

atopic allergy
atopy.

atopic asthma
allergic asthma.

atopic cataract
a type seen in persons with longstanding atopic dermatitis, often in the second to third decade of life.

atopic dermatitis
atopic eczema a chronic inflammatory skin disorder seen in persons with a hereditary susceptibility to develop itching (pruritus); it is often accompanied by allergic rhinitis, hay fever, or asthma. The extreme itchiness leads to scratching and rubbing that in turn results in the typical lesions of eczema.

atopic disease
atopy.

atopy
(at´ә-pe) a clinical hypersensitivity state or allergy with a hereditary predisposition; the tendency to develop an allergy is inherited, although the specific clinical form (such as hay fever or asthma) is not. The antibody reagin is involved. Called also atopic, hereditary, or spontaneous allergy

atorvastatin
(ә-tor´vә-stat″in) an agent that inhibits cholesterol synthesis, used as the calcium salt in treatment of primary hypercholesterolemia and hyperlipidemia; administered orally.

atovaquone
(ә-to´vә-kwōn″) an antibiotic used in treatment of mild to moderate pneumocystis pneumonia and the prevention and treatment of falciparum malaria; administered orally.

atoxic
(a-tok´sik) not poisonous; not due to a poison.

ATP
adenosine triphosphate.

ATPase
(a-te-pe´ās) adenosinetriphosphatase. Na+,K+-ATPase an enzyme that spans the plasma membrane and hydrolyzes adenosine triphosphate to provide the energy necessary to drive the cellular sodium pump.

ATPS
ambient temperature and pressure, saturated; denoting a volume of gas saturated with water vapor at ambient temperature and barometric pressure.

atracurium
(at″rә-kūr´e-әm) a neuromuscular blocking agent of intermediate duration; used as the besylate salt for intravenous administration as an adjunct to anesthesia to induce skeletal muscle relaxation during surgery and facilitate mechanical ventilation.

atraumatic
(a″traw-mat´ik) not producing injury or damage.

atraumatic needle
an eyeless surgical needle with the suture attached to a hollow end.

atraumatic suture
a suture fused into the end of a small eyeless needle.

atresia
(ә-tre´zhә) congenital absence or closure of a normal body opening or tubular structure; see also obstruction. adj., atret´ic., adj. atresia ani imperforate anus. atresia folliculi follicular atresia.

atretic ovarian follicle
an involuted ovarian follicle.

atria
(a´tre-ә) plural of atrium.

atrial
(a´tre-әl) pertaining to an atrium.

atrial asynchronous pacemaker
an artificial cardiac pacemaker that stimulates the atrium at a constant rate, without sensing atrial or ventricular activity; now rarely used except to initiate or terminate some tachycardias. Called also AOO pacemaker.

atrial beat
an ectopic beat originating in an atrium.

atrial complex
the P wave of the electrocardiogram, representing electrical activity of the atria. See also ventricular complex.

atrial demand inhibited pacemaker
an artificial cardiac pacemaker that delivers stimuli to the atrium at a fixed rate in the absence of sensed atrial activity; spontaneous cardiac activity causes inhibition of pacemaker output, termination of the current stimulation cycle, and initiation of a new cycle. Called also AAI pacemaker.

atrial demand triggered pacemaker
an artificial cardiac pacemaker that delivers stimuli to the atrium at a fixed rate in the absence of sensed atrial activity; spontaneous cardiac activity triggers pacemaker output, which falls ineffectively in the myocardial refractory period and initiates a new pacemaker stimulation cycle. Called also AAT pacemaker.

atrial extrasystole
one in which the stimulus is thought to arise in the atrium elsewhere than at the sinoatrial node.

atrial flutter
a cardiac arrhythmia in which the atrial contractions are rapid (230–380 per minute), but regular. Two types, I and II, are distinguished according to rate; Type I is also more amenable to cardioversion. In Type I the atrial rate is usually 290 to 310 per minute but can range from 230 to 350. In Type II the atrial rate is...

atrial gallop
S4 gallop.

atrial pacing stress test
a stress test in which temporary immediately reversible atrial pacing is used to stress coronary reserve; used for patients incapable of exercise or in whom an exercise stress test is contraindicated.

atrial pressure waves
the three elevations commonly seen on the graphic representation of the cardiac cycle, known as the a wave, c wave, and v wave.

atrial reentry
reentry in which the entire reentrant circuit lies within one or both atria, excluding the sinus node.

atrial septal defect
a congenital heart defect in which the ostium primum or ostium secundum (openings in the septum primum of the embryonic heart) fails to close completely after birth. When an opening remains between the atria, some of the oxygen-rich blood from the left atrium passes into the right atrium and travels back to the lungs with...

atrial septum
interatrial septum.

atrial tachycardia
tachycardia originating from an atrial locus, usually having between 160 and 190 beats per minute, with no participation by the atrioventricular node or the sinoatrial node. It is recognizable on the electrocardiogram because the P wave precedes the QRS complex, as opposed to being merged with it or following it. This con...

atrial venous pulse
a venous pulse in the neck that has an accentuated a wave during atrial systole, because of increased force of contraction of the right atrium; this is characteristic of tricuspid stenosis.

atriomegaly
(a″tre-o-meg´ә-le) abnormal enlargement of an atrium of the heart.

atriopeptin
(a″tre-o-pep´tin) a peptide hormone that promotes the loss of fluid and electrolytes and the reduction of vascular tone.

atriopressor reflex
rise in arterial blood pressure (vasoconstriction) attributed to a change of pressure in the right atrium and great veins.

atrioseptopexy
(a″tre-o-sep´to-pek″se) surgical correction of a defect in the interatrial septum.

atrioseptoplasty
(a″tre-o-sep´to-plas″te) repair of the interatrial septum.

atriovenous pulse
atrial venous pulse.

atrioventricular
(a″tre-o-ven-trik´u-lәr) pertaining to or connecting an atrium and ventricle of the heart.

atrioventricular (AV) nodal reentry
an arrhythmia-causing mechanism in which two opposing pathways are established within the atrioventricular node (longitudinal dissociation); the anterograde pathway, which is usually slower, activates the ventricles and the retrograde pathway, which is usually faster, activaties the atria. This mechanism is responsible fo...

atrioventricular block
any interruption of the conduction of electrical impulses from the atria to the ventricles; it can occur at the level of the atria, the atrioventricular node, the bundle of His, or the Purkinje system. See also heart block. a type of heart block in which the blocking is at the atrioventricular junction. It is call...

atrioventricular bundle
bundle of His.

atrioventricular canal
the common canal connecting the primordial atrium and ventricle; it sometimes persists as a congenital anomaly.

atrioventricular conduction
AV conduction the normal conduction of atrial impulses in the heart, passing through the atrioventricular node and the His-Purkinje system to the ventricles.

atrioventricular extrasystole
an ectopic beat arising prematurely in the atrioventricular junction and traveling toward both the atria and ventricles. If unimpeded, it causes the P wave to be premature and abnormal or absent and the QRS complex to be premature. Called also junctional extrasystole.

atrioventricular furrow
the transverse groove marking off the atria of the heart from the ventricles.

atrioventricular interval
AV interval P–R interval. in dual chamber pacing, the length of time between the sensed or paced atrial event and the next sensed or paced ventricular event, measured in milliseconds; called also atrioventricular or AV delay.

atrioventricular junction
in the conduction system of the heart, the junction between the atrioventricular node and the nonbranching portion of the bundle of His.

atrioventricular junctional rhythm
a junctional rhythm originating in the bundle of His, with a heart rate of 40 to 60 beats per minute; called also nodal rhythm.

atrioventricular nodal artery
a branch of the right coronary artery usually arising opposite the origin of the posterior interventricular artery and inserting into the atrioventricular node.

atrioventricular node
AV node a collection of cardiac fibers at the base of the interatrial septum that transmits the cardiac impulse initiated by the sinoatrial node.

atrioventricular septum
the part of the membranous portion of the interventricular septum between the left ventricle and the right atrium.

atrioventricular sequential time
a fixed nonprogrammable interval that extends from the atrial stimulus to the ventricular stimulus.

atrioventricular valves
cardiac valves that connect an atrium and a ventricle. The right atrioventricular valve is the tricuspid valve and the left atrioventricular valve is the mitral valve.

atrioventricularis communis
(a″tre-o-ven-trik″u-la´ris kә-mu´nis) a congenital cardiac anomaly in which the endocardial cushions fail to fuse, the ostium primum persists, the atrioventricular canal is undivided, a single atrioventricular valve has anterior and posterior cusps, and there is a defect of the membranous interve...

atrium
(a´tre-әm) pl. a´tria a chamber affording entrance, especially one of the upper chambers on either side of the heart, which receive blood from the body and transmit it to the ventricles. Atria of the heart. left atrium the upper chamber of...

Atromid-S
(at´ro-mid) trademark for a preparation of clofibrate, used in treatment of hyperlipoproteinemia.

atrophia
(ә-tro´fe-ә) Latin word meaning atrophy.

atrophic acne
acne vulgaris in which, after the small papular lesions disappear, tiny atrophic pits and scars remain.

atrophic candidiasis
oral candidiasis marked by erythematous, pebbled patches on the hard or soft palate, buccal mucosa, and dorsal surface of the tongue, a complication of numerous different conditions such as vitamin deficiency, diabetes mellitus, or poorly fitting dentures. There are acute forms and a chronic form called denture stomatitis...

atrophic cirrhosis
a type in which the liver is decreased in size; it may be seen in the alcoholic, but is more common in posthepatic or postnecrotic cirrhosis.

atrophic emphysema
senile emphysema.

atrophic fracture
a spontaneous fracture resulting from atrophy of the bone.

atrophic gastritis
chronic gastritis with atrophy of the mucous membranes and glands.

atrophic pharyngitis
a type of chronic pharyngitis involving wasting of the submucous tissue, dryness, and thick secretions. Called also pharyngitis sicca.

atrophic rhinitis
a chronic form of nonallergic noninfectious rhinitis marked by wasting of the mucous membrane and the glands. It is sometimes the result of trauma, vascular damage by radiation therapy, and environmental irritants, and disease has also been implicated.

atrophic striae
striae distensae.

atrophic thyroiditis
a type of autoimmune thyroiditis with atrophy of the follicles and without goiter.

atrophic vaginitis
vaginitis occurring in postmenopausal women, associated with estrogen deficiency. The two most common types are senile vulvovaginitis and adhesive vaginitis.

atrophoderma
(at″ro-fo-dur´mә) atrophy of the skin.

atrophy
(at´rә-fe) decrease in size of a normally developed organ or tissue; see also wasting. to undergo or cause such a decrease. adj., atroph´ic., adj.

atrophy of aging
senile atrophy.

atrophy of disuse
disuse atrophy.

atropine
(at´ro-pēn) an anticholinergic alkaloid found in belladonna; it acts as a competitive antagonist of acetylcholine at muscarinic receptors, blocking stimulation of muscles and glands by parasympathetic and cholinergic sympathetic nerves; used as the sulfate salt as a smooth muscle relaxant, as an antiarrhythmic, as ...

atropine poisoning
severe toxic reaction due to overdosage of atropine. Symptoms include dryness of mouth, thirst, difficulty in swallowing, dilated pupils, tachycardia, fever, delirium, stupor, and a rash on the face, neck, and upper trunk.

atropinic
(at″ro-pin´ik) having actions similar to those of atropine; that is, antagonizing the muscarinic effects of acetylcholine.

ATS
American Thoracic Society.

ATSDR
Agency for Toxic Substances and Disease Registry, an agency of the United States Department of Health and Human Services.

attachment
(ә-tach´mәnt) the initial stage of infection of a cell by a virus, in which the viral envelope finds a suitable receptor on the cell surface, enabling the virus to enter. Called also adsorption.

attachment plaques
small regions of increased density along the sarcolemma of skeletal muscles to which myofilaments seem to attach; cf. dense bodies, under body.

attack
(ә-tak´) an episode or onset of illness. anxiety attack panic attack. heart attack popular term for myocardial infarction. any of various types of acute episodes of ischemic heart disease. panic attack ...

attack rate
in analysis of acute outbreaks of disease, the proportion of persons exposed to the disease during the outbreak who do become ill.

attapulgite
(at″ә-pul´jīt) a clay mineral that contains aluminum silicate and is the main ingredient of fuller's earth; activated attapulgite is a heat-treated form that is administered orally in the treatment of diarrhea.

attending
(ә-ten´ding) attending physician. being or pertaining to such a physician.

attention reflex of pupil
alteration of size in the pupil when the attention is suddenly fixed; called also Piltz reflex.

attenuated vaccine
a vaccine prepared from live microorganisms or viruses cultured under adverse conditions, leading to loss of their virulence but retention of their ability to induce protective immunity.