Copy of `Dorland's Medical Dictionary`

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Dorland's Medical Dictionary
Category: Health and Medicine > Medical Dictionary
Date & country: He/al/th a, US
Words: 39130

(ak″ro-mik´re-ә) abnormal smallness of the limbs, including hands and feet, and sometimes the nose and jaws, due to a deficiency in pituitary function after puberty.

(ә-kro″me-o-klә-vik´u-lәr) pertaining to the acromion and clavicle.

acromioclavicular joint
the point at which the clavicle joins with the acromion.

(ә-kro″me-o-hu´mәr-әl) pertaining to the acromion and humerus.

(ә-kro´me-әn) the lateral extension of the spine of the scapula, forming the highest point of the shoulder. adj., acro´mial., adj.

(ә-kro″me-o-nek´tә-me) resection of the acromion.

(ә-kro´me-o-plas″te) surgical removal of the anterior hook of the acromion to relieve mechanical compression of the rotator cuff during movement of the glenohumeral joint; called also anterior acromioplasty.

(ә-kro″me-o-tho-ras´ik) pertaining to the acromion and thorax.

acromiothoracic artery
thoracoacromial artery.

(ә-krom´fә-lәs) bulging of the navel; sometimes a sign of umbilical hernia. the center of the navel.

(ak″ro-mi″o-to´ne-ә) contracture of the hand or foot resulting in spastic deformity.

(ak″ro-ndbobr-ro´sis) any neuropathy of the limbs.

(ak´ro-pak″e) clubbing of the fingers.

(ak″ro-pak″ĭ-dur´mә) thickening of the skin of the limbs, as seen in acromegaly and pachydermoperiostosis.

(ak″ro-pә-ral´ĭ-sis) paralysis of the limbs.

(ak″ro-par″es-the´zhә) an abnormal sensation, such as tingling, numbness, pins and needles, in the hands and fingers.

(ak″ro-pә-thol´ә-je) pathology of diseases of limbs.

(ă-krop´ә-the) any disease of the limbs.

(ak″ro-fo´be-ә) irrational fear of heights.

(ak″ro-pus″tu-lo´sis) pustulosis of the extremities. A congenital form (infantile a.) is characterized by recurring episodes of small pruritic pustules on the hands and feet followed by remission.

(ak″ro-skler″o-dur´mә) acrosclerosis.

(ak″ro-sklә-ro´sis) a combination of Raynaud disease and scleroderma of the distal parts of the limbs, especially the digits, and of the neck and face, particularly the nose.

(ak″ro-so´mәl) pertaining to the acrosome.

(ak´ro-sōm) the caplike, membrane-bound structure covering the anterior portion of the head of a spermatozoon; it contains enzymes involved in penetration of the oocyte.

acrosome reaction
changes in the spermatozoon that result in development of perforations in the acrosome, allowing release of enzymes that facilitate fertilization.

(ak″ro-spi-ro´mә) a benign adnexal tumor of the distal portion of a sweat gland.

(ak´ro-tiz-әm) absence or imperceptibility of the pulse. adj., acrot´ic., adj.

(ә-kril´ә-mīd) a vinyl monomer used in the production of polymers with many industrial uses. The polymers are nontoxic but exposure to acrylamide can cause peripheral neuropathy, polyneuritis, and central nervous system lesions.

(ә-kril´ik) pertaining to or containing polymers of acrylic acid, methacrylic acid, or acrylonitrile, used as acrylic resins in various medical and dental applications.

acrylic acid
a readily polymerizing liquid used as a monomer for acrylic polymers.

acrylic resins
products of the polymerization of acrylic or methacrylic acid or their derivatives, used in a variety of medical and dental applications, including medical prostheses and instruments and dental restorations, prostheses, and appliances. They are also used as adsorbents in chromatography and as ion exchange resins.

(ak″rә-lo-ni´trīl) a colorless halogenated hydrocarbon used in the making of plastics and as a pesticide; its vapors are irritant to the respiratory tract and eyes, can cause systemic poisoning, and are carcinogenic.

acute confusional state; American Cancer Society; American Chemical Society; American College of Surgeons.

adrenocorticotropic hormone; see corticotropin.

ACTH-secreting adenoma
corticotroph adenoma.

(ak´tin) a muscle protein localized in the I band of myofibrils; acting along with myosin particles, it is responsible for the contraction and relaxation of muscle fibers.

actin filament
one of the thin contractile filaments in a myofibril, composed mainly of actin; each actin filament is surrounded by three myosin filaments.

actin-binding proteins
a large and diverse group of proteins that bind to actin and regulate the dynamics and organization of actin filaments.

acting out
(ak´ting out) the habitual use of nonverbal behavior to express unconscious feelings that a person feels unable to directly deal with; she or he is reacting to present situations as if they were the childhood situation that originally caused the feelings and fantasies, and the acting out is a type of transference....

(ak-tin´ik) producing chemical action; see actinic rays.

actinic dermatitis
photodamage with dermatitis from exposure to actinic rays, such as that from the sun, ultraviolet rays, x-rays, or gamma rays. See also chronic actinic dermatitis and phototoxic dermatitis.

actinic elastosis
photoaging of the skin, especially in light-skinned persons, characterized by inelasticity, thinning or sometimes thickening, wrinkling, dryness with fine scaling, and sometimes hyperpigmentation, cherry angiomas, telangiectasis, senile lentigines, ecchymosis, milia, and senile keratosis. Called also senile or solar elast...

actinic granuloma
an annular lesion seen on skin chronically exposed to the sun, with a raised border and a center that appears normal but is actually elastotic.

actinic keratitis
a form due to the action of ultraviolet light; called also ultraviolet keratitis.

actinic keratosis
a sharply outlined wartlike or keratotic growth that sometimes develops into a cutaneous horn or becomes malignant; it usually occurs in the middle-aged or elderly and is due to excessive exposure to the sun. Called also solar keratosis.

actinic rays
light rays that produce chemical action, especially those beyond the violet end of the spectrum.

actinic reticuloid syndrome
chronic actinic dermatitis.

(Ac) (ak-tin´e-әm) a highly radioactive chemical element, atomic number 89, atomic weight 227. It is used in radiotherapy.

(ak″tĭ-no-bas″ĭ-lo´sis) a disease of domestic animals and occasionally humans, resembling actinomycosis but caused by Actinobacillus ligniere´sii; the bacilli form radiating structures in the tissues.

(ak″tĭ-no-bә-sil´us) a genus of gram-negative, nonmotile bacteria that are part of the normal microflora of mammals but sometimes cause actinobacillosis. A. ligniere´sii is the causative agent of human infection.

(ak″tĭ-no-dur″mә-ti´tis) cutaneous inflammation due to excessive exposure to sunlight or to exposure to x-rays.

(ak″tĭ-no-mә-dldbomacr´ә) a genus of actinomycetes including A. madu´rae, the cause of maduromycosis in which the granules in the discharged pus are white, and A. pelletier´ii, the cause of maduromycosis in which the granules are red.

(ak″tĭ-no-mi´sēz) a genus of gram-negative, non–acid fast, nonmotile bacteria that form branched filaments. It includes A. israe´lii and A. naeslun´dii, both of which cause human actinomycosis and periodontal disease.

(ak″tĭ-no-mi´sēz) an organism of the genus Actinomyces. adj., actinomycet´ic., adj.

(ak″tĭ-no-mi´sēt) a moldlike bacterium (order Actinomycetales) occurring as elongated, frequently filamentous cells, with a branching tendency. adj., actinomycet´ic., adj.

(ak″tĭ-no-mi´sin) a family of antibiotics from various species of Streptomyces, which are active against bacteria and fungi; it includes the antineoplastic agentdactinomycin (actinomycin D).

(ak″tĭ-no-mi-ko´sis) an infection involving the deeper tissues of the skin and mucous membranes, usually on the head or neck, caused by bacteria of the genus Actinomyces. The lesions begin as painless tumorlike masses that later break down and begin to discharge pus through a network of sinuses in the skin. Sometim...

(ak″tĭ-no-ther´ә-pe) phototherapy.

action potential
the electrical activity developed in an excitable cell when stimulated; it may be elicited by electrical, chemical, or mechanical stimulation, by temperature change, or in certain other situations. On an electrocardiogram, action potential is seen as the cardiac cycle of a single cell, produced by a rapid sequence of changes at...

action tremor
abnormal rhythmic back-and-forth movements of the outstretched upper limb when a person tries to move it voluntarily, such as in writing or lifting a cup; this can also affect the voice or another part of the body. Called also intention or volitional tremor.

(ak″tĭ-va´shәn) the act or process of rendering active. the transformation of a proenzyme into an active enzyme by the action of a kinase or another enzyme. the process by which the central nervous system is stimulated into activity through the mediation of the reticular activating...

activation-induced cell death
(AICD) recognition and deletion of T lymphocytes that have been activated and so induced to proliferate. T lymphocytes are activated when a foreign agent is perceived, and AICD thereby prevents them from overgrowth. It is particularly important for regulation of lymphocytes that recognize self antigens.

(ak´tĭ-va″tәr) a substance that makes another substance active or reactive, induces a chemical reaction, or combines with an enzyme to increase its catalytic activity. plasminogen activator any of a group of substances that activate plasminogen and convert it into p...

(ak´tiv) characterized by action; not passive; not expectant.

active assistive exercise
voluntary contraction of muscles controlling a part, assisted by a therapist or by some other means.

active electrode
therapeutic electrode.

active exercise
motion imparted to a part by voluntary contraction and relaxation of its controlling muscles.

active immunity
a type of acquired immunity that develops in response to antigenic stimulus. See also passive immunity.

active movement
movement produced by the person's own muscles.

active site
the three-dimensional region of an enzyme or other catalyst at which the reaction occurs, binding the substrate and facilitating its conversion to a reaction product. See also binding site and catalytic site.

active sleep
REM sleep.

active zone
a site in a presynaptic membrane that is especially adapted for the release of synaptic vesicles.

(ak´tĭ-vin) any of several proteins that stimulate the secretion of follicle-stimulating hormone, play roles in regulation of the neuroendocrine system, help regulate production of other hormones, and affect the functioning of the gonads.

activities of daily living
(ADL) activities that are necessary for daily care of oneself, such as using the toilet, grooming, dressing, and feeding oneself.

(ak-tiv´ĭ-te) the quality or process of exerting energy or of accomplishing an effect. a thermodynamic quantity that represents the effective concentration of a solute in a non-ideal solution. Symbol a. the number of disintegrations per unit of a radioactive material. Symbol A. t...

(ak″to-mi´o-sin) the complex of actin and myosin constituting muscle fibers and responsible for the contraction and relaxation of muscle.

(ә-ku´ĭ-te) clearness of the visual perception of an image. visual acuity the ability to discriminate visually between forms.

(ә-ku´mĭ-nāt) sharp-pointed.

(ak´u-point) any of the specific sites for needle insertion in acupuncture; stimulation of acupoints also forms the basis of other therapies, including acupressure and moxibustion. There are 361 basic, named acupoints along the 12 principal and two of the collateral meridians, and a large number of other points derived from c...

(ak´u-presh″әr) the use of pressure applied, usually with the hands, at acupoints in order to release muscular tension for therapeutic purposes. According to traditional theory, the release of tension allows qi (vital energy) to flow through the meridians and restore balance to the body's systems; biological...

(ak´u-punk″chәr) a technique from traditional chinese medicine in which fine needles are inserted into acupoints for preventive and therapeutic purposes, for relief of discomfort associated with painful disorders, and sometimes for anesthesia. (Its use as a form of anesthesia is only a minor use in traditional Chi...

acupuncture point

(a´kәs) a needle or needle-like process.

(ә-kūt´) sharp. having severe symptoms and a short course. Some serious illnesses that were formerly considered acute (such as myocardial infarction) are now recognized to be acute episodes of chronic conditions.

acute anterior poliomyelitis
the major illness of poliomyelitis; see poliomyelitis.

acute arthritis
arthritis marked by pain, heat, redness, and swelling.

acute ascending spinal paralysis
acute idiopathic polyneuritis.

acute bacterial otitis externa
acute otitis externa caused by a bacterial infection, usually with a species of Pseudomonas and less often with Staphylococcus and formation of a furuncle. See also circumscribed o. externa.

acute benign pericarditis
idiopathic pericarditis.

acute brain syndrome

acute care
the level of care in a health care system that consists of emergency treatment and intensive care. Called also secondary care.

acute chest syndrome
a complex of symptoms seen in patients with sickle cell disease, often due to a bacterial infection or to infarction of lung tissue; characteristics include severe chest pain, dyspnea, tachypnea, fever, excessive leukocytosis, pulmonary edema, and sometimes petechiae on the chest or conjunctivae as well as fat emboli. Dea...

acute cholecystitis
a form usually due to obstruction of the gallbladder outlet, with signs ranging from mild edema and congestion to severe infection with gangrene and perforation.

acute compression triad
Beck triad.

acute contagious conjunctivitis
a contagious inflammation of the conjunctiva caused by Haemophilus aegypticus; secretions must be handled with extreme care to prevent its spread. Popularly known as pinkeye.

acute coronary syndrome
a classification encompassing clinical presentations ranging from unstable angina through myocardial infarctions not characterized by alterations in Q waves; the classification sometimes also includes myocardial infarctions characterized by altered Q waves.

acute disseminated encephalitis
acute disseminated encephalomyelitis an acute or subacute encephalomyelitis or myelitis occurring most commonly following an acute viral infection, especially measles, but sometimes occurring without a recognizable antecedent. Clinical manifestations include fever, headache, vomiting, and drowsiness progressing to lethargy...

acute eosinophilic pneumonia
a condition resembling chronic eosinophilic pneumonia but with a more rapid onset and more limited duration, accompanied by acute respiratory failure and diffuse pulmonary infiltrates.

acute fungal otitis externa

acute gastritis
sudden, severe gastritis, often with enteritis. Symptoms are generally pain and a distended feeling in the abdomen with loss of appetite and nausea; there may be a slight fever and vomiting. The most common causes are intake of aspirin or other nonsteroidal antiinflammatory drugs, food poisoning, overeating, excessive drinking ...