Medical terms - Letter A (page 25) | MedicalVocabulary.org

Arachnophobia

An abnormal and persistent fear of spiders. Sufferers from arachnophobia experience undue anxiety even though they realize the risk of encountering a spider and being harmed by it is small or nonexistent. They may avoid…
ARB

Angiotensin II receptor blocker
Arbitration agreement

The patient waives the right to sue the doctor and, instead, submit any dispute to arbitration. Arbitration agreements are legal and binding. The arguments in their favor are that, for patients, the case can be settled…
Arborvirus

What's in a name? Although 'arbor' sounds as if it should have something to do with trees, it doesn't. It comes from the first 2 letters of arthropod + the first 3 letters of bor. Arborviruses are transmitted (borne) to…
Arboviral encephalitis

Inflammation of the brain (encephalitis) caused by infection with an arbovirus, a virus transmitted by a mosquito, tick or another arthropod. Infection of vertebrates, including humans, occurs when an infected arthropod…
Arbovirus

A class of viruses transmitted to humans by arthropods such as mosquitoes and ticks. The first two letters of the words arthropod' and borne, make up the 'arbo' that now designates this group of viruses as…
Arc eye

A condition experienced by welders who do not use adequate eye protection. The intense ultraviolet light emitted by the arc causes inflammation of the cornea (keratitis). Arc eye is a form of photokeratitis. See…
Arch, aortic

See: Aortic arch
Arch, vertebral

See: Vertebral arch
Arch, zygomatic

The bone that forms the prominence of the cheek. The zygomatic bone is also known as the zygoma, the zygomatic arch, malar bone, yoke bone. The word 'zygomatic' comes from the Greek 'zygon' meaning a yoke (as for oxen).
Archaea

A unique group of microorganisms classified as bacteria (Archaeobacteria) but genetically and metabolically different from all other known bacteria. They appear to be living fossils, the survivors of an ancient group of…
Archaeogenetics

The study of the past using the techniques of molecular genetics. The application of genetics to archeology. The term 'archaeogenetics' was coined in the 1990s by the archeologist Colin Renfrew from the Greek archaios…
Archaeology

The scientific study of the material remains of past peoples. In archaeology today, a range of biological techniques, including DNA analysis, enter into what has been termed bioarchaeology
Arcuate neuron

A neuron in the arcuate nucleus of the brain. See: Arcuate nucleus
Arcuate nucleus

A collection of neurons (nerve cells) in the hypothalamus of the brain. Some arcuate neurons contain dopamine and act to inhibit the release of the hormone prolactin by the pituitary gland. Other arcuate neurons contain…
Arcus senilis

A cloudy opaque arc or circle around the edge of the eye, often seen in the eye of the elderly.
ARD

Acronym that stands for a disorder known as Adult Respiratory Distress or Acute Respiratory Distress. Also referred to as ARDS (ARD Syndrome). In ARD there is respiratory failure of sudden (acute) onset due to the rapid…
ARDS

ARDS: Acute Respiratory Distress Syndrome. A fulminant lung condition in which trauma to the lungs leads to inflammation of the lungs, accumulation of fluid in the alveolar air sacs, low blood oxygen, and respiratory…
Areflexia

Absence of neurologic reflexes such as the knee jerk reaction
Arenaviridae

See: Arenavirus
Arenavirus

One of a family of viruses called Arenaviridae whose members are generally associated with diseases transmitted by rodents to humans. Each arenavirus is usually associated with a particular rodent host species in which…
Areola

1. The small darkened area around the nipple of the breast. 2. The colored part of the iris around the pupil of the eye. 3. Any small space in a tissue
Arg

Arginine. See also: Amino acid symbols
Argentaffinoma

A tumor which secretes large amounts of the hormone serotonin. Argentaffinoma is also called carcinoid tumor. The tumor usually arises in the gastrointestinal tract, anywhere between the stomach and the rectum (the…
Arginine

An amino acid, one of the 20 amino acids that serve as the building blocks in protein. Arginine is not an 'essential' amino acid. It is not essential to the diet, but can be made by the body from other substances…
Argon laser

A laser with ionized argon as the active medium. Argon lasers are used for photocoagulation in ophthalmology
Argyria

Silver poisoning resulting in ashen gray discolored skin (and other tissues of the body). Due to long-term use of silver salts. For example, a medical report related the case of a woman, now in her 50s, with discolored…
Arhythmia

We do not usually give a misspelling but this is a frequent misspelling of arrhythmia (with two r's), meaning an abnormal heart rhythm. In an arrhythmia the heartbeats may be too slow, too rapid, too irregular, or too…
Arimidex

Brand name for anastrozole, an oral antiestrogen. Arimidex inhibits the enzyme aromatase in the adrenal glands that produces the estrogens (estradiol and estrone) and thereby lowers their levels. See also: Aromatase…
Aristolochia fangchi

A Chinese herb that is injurious to the kidney and is also associated with an increased risk of cancer of the urinary system. Aristolochia can cause kidney failure requiring renal dialysis or a kidney transplant. The…
Aristolochic acid

A chemical found in nature in the plant Aristolochia fangchi. Aristolochic acid is contained in a number of botanical products sold as 'traditional medicines' or as dietary supplements or weight-loss remedies. The use…
Aristotle

Aristotle of Stagira (384-322 B.C.), Greek philosopher and scientist. The son of a physician, Aristotle was a student of Plato but developed methods of inquiry different from those of his teacher. Unlike Plato…
ARM

Abbreviation of age-related maculopathy, any pathologic condition of the macula, the small spot in the retina where vision is keenest. The late stages of ARM are also referred to as age-related macular degeneration…
Arm

1. In popular usage, the appendage that extends from the shoulder to the hand. However, the medical definition refers to the upper extremity extending from the shoulder only to the elbow, excluding the forearm, which…
ARMD

Age-related macular degeneration (which may also be abbreviated as AMD)
Armed Forces Institute of Pathology

An agency of the US Department of Defense specializing in pathology consultation, education and research. The Armed Forces Institute of Pathology (AFIP) consults on many cases, including difficult, unusual, or rare…
Armed tapeworm

Taenia solium
Arms

An appendage in anatomy and in clinical trials. See: Arm
Aromasin

Brand name of exemestane, an oral antiestrogen. Aromasin inhibits the enzyme aromatase in the adrenal glands that produces the estrogens (estradiol and estrone) and thereby lowers their levels. See also: Aromatase…
Aromatase

An enzyme involved in the production of estrogen that acts by catalyzing the conversion of testosterone (an androgen) to estradiol (an estrogen). Aromatase is located in estrogen-producing cells in the adrenal glands…
Aromatase inhibitor

A drug that inhibits the enzyme aromatase and by that means lowers the level of the estrogen estradiol. Aromatase inhibitors represent a class of antiestrogens. Aromatase catalyzes the conversion of testosterone (an…
Aromatherapy

A form of alternative and complimentary medicine based on the use of very concentrated 'essential' oils from the flowers, leaves, bark, branches, rind or roots of plants with purported healing properties. In…
Arrayed library

In genetics, an arrayed library consists of (in technical terms) individual primary recombinant clones which are hosted in phage, cosmid, YAC, or another vector that have been placed in two- dimensional arrays in…
Arrector pili

A microscopic band of muscle tissue which connects a hair follicle to the dermis. When stimulated, the arrector pili will contract and cause the hair to become more perpendicular to the skin surface (stand on end)
Arrectores pilorum

Tiny muscles that act as the hair erector muscles. The arrectores pilorum play a key role in goose bumps, a temporary local change in the skin The chain of events leading to this skin change starts with a stimulus such…
Arrhythmia

An abnormal heart rhythm. In an arrhythmia the heartbeats may be too slow, too rapid, too irregular, or too early. Rapid arrhythmias (greater than 100 beats per minute) are called tachycardias. Slow arrhythmias (slower…
Arrhythmia, sinus

The normal increase in heart rate that occurs during inspiration (when you breathe in). This is a natural response and is more accentuated in children than adults. The 'sinus' refers to the natural pacemaker of the…
Arrhythmias, atrial

Abnormal heart rhythm due to electrical disturbances in the atria (the upper chambers of the heart) or the AV node 'relay station', leading to fast heart beats. Examples of atrial arrhythmias includes atrial…
Arrhythmias, rapid

Abnormally rapid heart rhythms, medically termed tachycardia
Arrhythmias, slow

Abnormally slow heart rhythms, medically termed bradycardia