Medical Dictionary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

archin (ar′kin)
SYN: emodin.

archipallium (ar-ki-pal′e-um)
SYN: archicortex. [archi- + L. pallium]

architectonics (ar-ki-tek-ton′iks)
SYN: cytoarchitecture.

archwire (arch′wir)
A device consisting of a wire conforming to the alveolar or dental arch, used as an anchorage in correcting irregularities in the position of the teeth. SYN: arch wire.

arciform (ar′si-form)
SYN: arcuate.

Arcobacter (ar-ko-bak′ter)
A genus of bacteria in the family Campylobacteraceae that are Gram-negative, aerotolerant, and able to grow at 15° C. The type strain is A. butzleri. A. butzleri a bacterial species of A. found in poultry and meat; has been associated with diarrheal and systemic diseases in humans.

arctation (ark-ta′shun)
A narrowing, contraction, stricture, or coarctation. [L. arto (improp. arcto), pp. -atus, to tighten]

arcual (ar′ku-al)
Relating to an arch.

arcuate (ar′ku-at)
Denoting a form that is arched or has the shape of a bow. SYN: arcate, arciform. [L. arcuatus, bowed]

arcuation (ar-ku-a′shun)
A bending or curvature.

arcus (ar′kus) [TA]
SYN: arch. [L. a bow] a. adiposus SYN: a. senilis. a. alveolaris mandibulae [TA] SYN: alveolar arch of mandible. a. alveolaris maxillae [TA] SYN: alveolar arch of maxilla. a. anterior atlantis [TA] SYN: anterior arch of atlas. a. aortae SYN: aortic arch (2) . a. cartilaginis cricoideae [TA] SYN: arch of cricoid cartilage. a. cornealis SYN: a. senilis. a. costalis [TA] SYN: costal margin. a. costarum SYN: costal margin. a. dentalis inferior mandibular dental arcade. a. dentalis mandibularis [TA] SYN: inferior dental arch. a. dentalis maxillaris [TA] SYN: maxillary dental arcade. a. dentalis superior maxillary dental arcade. a. ductus thoracici [TA] SYN: arch of thoracic duct. a. glossopalatinus SYN: palatoglossal arch. a. iliopectineus [TA] SYN: iliopectineal arch. a. inguinalis inguinal ligament. a. juvenilis SYN: a. senilis. a. lipoides SYN: a. senilis. a. lumbocostalis lateralis SYN: lateral arcuate ligament. a. lumbocostalis medialis SYN: medial arcuate ligament. a. marginalis coli marginal artery of colon. a. palatini palatoglossal arch, palatopharyngeal arch. a. palatoglossus [TA] SYN: palatoglossal arch. a. palatopharyngeus [TA] SYN: palatopharyngeal arch. a. palmaris profundus SYN: deep palmar (arterial) arch. a. palmaris superficialis [TA] SYN: superficial palmar (arterial) arch. a. palpebralis inferior [TA] SYN: inferior palpebral (arterial) arch. a. palpebralis superior [TA] SYN: superior palpebral (arterial) arch. a. pedis longitudinalis SYN: longitudinal arch of foot. a. pedis longitudinalis pars lateralis SYN: lateral longitudinal arch of foot. a. pedis longitudinalis pars medialis SYN: medial longitudinal arch of foot. a. pedis transversalis SYN: transverse arch of foot. a. plantaris profundus [TA] SYN: deep plantar (arterial) arch. a. posterior atlantis [TA] SYN: posterior arch of atlas. a. pubis [TA] SYN: pubic arch. a. raninus SYN: ranine anastomosis. a. senilis an opaque, grayish ring at the periphery of the cornea just within the sclerocorneal junction, of frequent occurrence in the aged; it results from a deposit of fatty granules in, or hyaline degeneration of, the lamellae and cells of the cornea. SYN: anterior embryotoxon, a. adiposus, a. cornealis, a. juvenilis, a. lipoides, gerontoxon, linea corneae senilis, lipoidosis corneae. a. superciliaris [TA] SYN: superciliary arch. a. tarseus inferior palpebral (arterial) arch, superior palpebral (arterial) arch. a. tendineus [TA] SYN: tendinous arch. a. tendineus fasciae pelvis [TA] SYN: tendinous arch of pelvic fascia. a. tendineus musculi levatoris ani [TA] SYN: tendinous arch of levator ani muscle. a. tendineus musculi solei [TA] SYN: tendinous arch of soleus muscle. a. tendineus of obturator fascia SYN: tendinous arch of levator ani muscle. a. tendineus of pelvic diaphragm SYN: tendinous arch of levator ani muscle. a. unguium SYN: lunule of nail. a. venosus dorsalis pedis [TA] SYN: dorsal venous arch of foot. a. venosus juguli [TA] SYN: jugular venous arch. a. venosus palmaris profundus [TA] SYN: deep palmar venous arch. a. venosus palmaris superficialis [TA] SYN: superficial palmar venous arch. a. venosus plantaris [TA] SYN: plantar venous arch. a. vertebrae [TA] SYN: vertebral arch. SEE ALSO: hemal arches, under arch. a. volaris profundus SYN: deep palmar (arterial) arch. a. volaris superficialis SYN: superficial palmar (arterial) arch. a. zygomaticus [TA] SYN: zygomatic arch.

ardor (ar′dor)
Old term for a hot or burning sensation. [L. fire, heat]

ARDS
Abbreviation for adult respiratory distress syndrome.

area (a) , pl .areae (ar′e-a, -e)
1. [TA] Any circumscribed surface or space. 2. All of the part supplied by a given artery or nerve. 3. A part of an organ having a special function, as the motor a. of the brain. SEE ALSO: regio, region, space, spatium, zone. [L. a courtyard] acoustic a. the floor of the lateral recess of the fourth ventricle, extending medially to the limiting sulcus and overlying the cochlear and vestibular nuclei of the rhombencephalon. SYN: a. vestibularis [TA] , a. acustica. a. acustica SYN: acoustic a.. amygdaloclaustral a. [TA] that region in the temporal lobe where lateral portions of the amygdaloid nucleus are in close apposition to, or fuse with, ventral aspects of the claustrum. SYN: a. amygdaloclaustralis [TA] . a. amygdaloclaustralis [TA] SYN: amygdaloclaustral a.. a. amygdaloidea anterior [TA] SYN: anterior amygdaloid a.. amygdalopiriform transition a. [TA] the a. where the groups of cells forming the amygdaloid nucleus are closely adjacent to the piriform cortex. SYN: a. transitionis amygdalopiriformis [TA] . anterior amygdaloid a. [TA] the most rostral portion of the amygdaloid complex composed of scattered cells representing a transition into the more distinctly organized divisions of the amygdala. SYN: a. amygdaloidea anterior [TA] . anterior hypothalamic a. the rostral portion of the hypothalamus located generally internal to the region of the optic chiasm; contains the following nuclei: anterior hypothalamic nucleus [TA] (nucleus anterior hypothalami [TA]), anterior periventricular nucleus [TA] (nucleus periventricularis ventralis [TA], interstitial nuclei of anterior hypothalamus [TA] (nuclei interstitiales hypothalami anteriores [TA]), lateral preoptic nucleus [TA] (nucleus preopticus lateralis [TA]), medial preoptic nucleus [TA] (nucleus preopticus medialis [TA]), median preoptic nucleus [TA] (nucleus preopticus medianus [TA]), paraventricular nucleus [TA] (nucleus paraventricularis hypothalami [TA]), periventricular preoptic nucleus [TA] (nucleus preopticus periventricularis [TA]), suprachiasmatic nucleus [TA] (nucleus suprachiasmaticus [TA]) and the supraoptic nucleus [TA] (nucleus supraopticus [TA]). The latter cell group consists of dorsomedial, ventromedial, and dorsolateral parts. SEE ALSO: hypothalamus. SYN: a. hypothalamica rostralis [TA] , anterior hypothalamic region&star. anterior intercondylar a. of tibia [TA] the broad depressed a. between the tibial condyles anteriorly to which attach the anterior ends of the menisci and the anterior cruciate ligament. SYN: a. intercondylaris anterior tibiae [TA] . aortic a. (of auscultation) the region of the chest wall over the second right costal cartilage, where sounds produced at the aortic orifice are often best heard. apical a. the a. about the root end of a tooth. association areas SYN: association cortex. auditory a. SYN: auditory cortex. bare a. of liver [TA] the a. on the posterosuperior (diaphragmatic) surface of the liver, bordered by the coronary ligament but itself devoid of peritoneum, so that the diaphragm and liver lie in direct contact and are adherent to each other. not covered by peritoneum. SYN: a. nuda hepatis [TA] . bare a. of stomach the part of posterior surface of the fundus of the stomach between the two diverging layers of the gastrophrenic ligament, that is not covered by peritoneum. basal seat a. that portion of the oral structures which is available to support a denture. Broca a. SYN: Broca center. Broca parolfactory a. SYN: parolfactory a.. Brodmann areas areas of the cerebral cortex mapped out on the basis of the cortical cytoarchitectural patterns. See cerebral cortex. a. of cardiac dullness a triangular a. determined by percussion of the front of the chest; it corresponds to the part of the heart that is not covered by lung tissue. catchment a. a term relating to community mental health center which delimits the geographic a. surrounding each center, and thus the population of individuals who qualify for mental health services provided by each center. a. centralis SYN: macula of retina. a. cochleae [TA] SYN: cochlear a.. cochlear a. [TA] the a. inferior to the transverse crest of the fundus of the internal acoustic meatus through which the filaments of the cochlear nerve pass to enter the cochlea; forms the base of the conical modiolus about which the cochlear canal spirals. See base of modiolus of cochlea. SYN: a. cochleae [TA] . Cohnheim a. a polygonal mosaic-like figure formed by a group of myofibrils, as seen in the cross-section of a skeletal muscle fiber examined under the microscope; a shrinkage artifact of fixation. SYN: Cohnheim field. contact a. that part of the proximal surface of a tooth which touches the adjacent tooth mesially or distally. SYN: contact point, point of proximal contact. cribriform a. of the renal papilla [TA] the apex of a renal papilla pierced by 10–22 openings of the papillary ducts, the foramina papillaria. SYN: a. cribrosa papillae renalis [TA] . a. cribrosa papillae renalis [TA] SYN: cribriform a. of the renal papilla. denture-bearing a. SYN: denture foundation a.. denture foundation a. that portion of the basal seat which supports the complete or partial denture base under occlusal load. SYN: basal seat, denture-bearing a., denture-supporting a., stress-bearing a. (1) , supporting a. (2) , tissue-bearing a.. denture-supporting a. SYN: denture foundation a.. dermatomic a. SYN: dermatome (3) . dorsal hypothalamic a. [TA] a relatively small region of the hypothalamus located ventral to the hypothalamic sulcus; contains the following nuclei: portions of the dorsomedial nucleus [TA] (nucleus dorsomedialis [TA]), endopeduncular nucleus [TA]) (nucleus endopeduncularis [TA]) and portions of the nucleus of the ansa lenticularis (nucleus ansae lenticularis [TA]). SEE ALSO: hypothalamus. SYN: a. hypothalamica dorsalis [TA] , dorsal hypothalamic region&star. embryonal a., embryonic a. the a. of the blastoderm on either side of, and immediately cephalic to, the primitive streak where the component cell layers have become thickened. entorhinal a. brodmann a. 28, a cytoarchitecturally well-defined a. of multilaminate cerebral cortex on the medial aspect of the parahippocampal gyrus, immediately caudal to the olfactory cortex of the uncus; the a. is the origin of the major fiber system afferent to the hippocampus, the so-called perforant pathway. excitable a. SYN: motor cortex. facial nerve a. [TA] the a. of the fundus of the internal acoustic meatus superior to the transverse crest through which the facial nerve passes to enter the facial canal. SYN: a. nervi facialis [TA] . Flechsig areas three divisions (anterior, lateral, posterior) of each lateral half of the medulla as seen on transverse section, marked off by the root fibers of the hypoglossal and vagus nerves. frontal a. SYN: frontal cortex. fronto-orbital a. SYN: orbitofrontal cortex. fusion a. SYN: Panum a.. gastric a. [TA] one of a number of small polygonal areas, 1–6 mm in diameter, separated by linear depressions on the surface of the mucous membrane of the stomach; they contain the gastric pits, with several gastric glands opening into each pit. SYN: a. gastrica [TA] . a. gastrica [TA] SYN: gastric a.. germinal a., a. germinativa the place in the blastoderm where the embryo begins to be formed. SYN: germinal disk. Head areas areas of skin exhibiting reflex hyperesthesia and hyperalgesia due to visceral disease. a. hypothalamica dorsalis [TA] SYN: dorsal hypothalamic a.. a. hypothalamica intermedia SYN: intermediate hypothalamic a.. a. hypothalamica lateralis [TA] SYN: lateral hypothalamic a.. a. hypothalamica posterior [TA] SYN: posterior hypothalamic a.. a. hypothalamica rostralis [TA] SYN: anterior hypothalamic a.. impression a. in dentistry, that surface which is recorded in an impression. inferior vestibular a. [TA] the a. of the fundus of the internal acoustic meatus inferior to the transverse crest through which the inferior portion of the vestibular (saccular) nerve passes. SYN: a. vestibularis inferior [TA] . insular a. SYN: insula (1) . a. intercondylaris anterior tibiae [TA] SYN: anterior intercondylar a. of tibia. a. intercondylaris posterior tibiae [TA] SYN: posterior intercondylar a. of tibia. intermediate hypothalamic a. [TA] the portion of the hypothalamus located generally internal to the region of the infundibulum; contains the following nuclei; dorsal nucleus [TA] (nucleus dorsalis hypothalami [TA]), parts of the dorsomedial nucleus [TA] (nucleus dorsomedialis [TA]), arcuate nucleus [TA] (nucleus arcuatus [TA]), posterior periventricular nucleus [TA] (nucleus periventricularis posterior [TA]), retrochiasmatic a. [TA] (a. retrochiasmatica [TA]), lateral tuberal nuclei [TA] (nuclei tuberales laterales [TA]), and the ventromedial nucleus [TA] (nucleus ventromedialis hypothalami [TA]). SEE ALSO: hypothalamus. SYN: intermediate hypothalamic region&star, a. hypothalamica intermedia. Kiesselbach a. an a. on the anterior portion of the nasal septum rich in capillaries (Kiesselbach plexus) and often the seat of epistaxis. SYN: Little a.. a. of Laimer a triangular (or V-shaped) a. on the posterior aspect of the proximal esophagus, with its apex directed inferiorly in the midline and the cricopharyngeus muscle forming its base, which is an a. of weakness due to a near absence of longitudinal muscle; potential site of herniation of pharyngeal or esophageal mucosa. SYN: Laimer-Haeckerman a., V-shaped a. of esophagus. Laimer-Haeckerman a. SYN: a. of Laimer. lateral hypothalamic a. [TA] the portion of the hypothalamus located generally lateral to a rosterocaudal line drawn through the column of the fornix and the mammillothalamic tract; contains fibers collectively comprising the medial forebrain bundle [TA] and the following nuclei: portions of the preoptic a. [TA] (a. preoptica [TA]), portions of the lateral tuberal nuclei [TA] (nuclei tuberales laterales [TA]), the perifornical nucleus [TA] (nucleus perifornicalis [TA]), and the tuberomammillary nucleus [TA] (nucleus tuberomammillaris [TA]). SEE ALSO: hypothalamus. SYN: a. hypothalamica lateralis [TA] . lateral inferior hepatic a. [TA] SYN: (left anterior) lateral hepatic segment [III]. lateral superior hepatic a. [TA] SYN: (left posterior) lateral hepatic segment III. Little a. SYN: Kiesselbach a.. macular a. SYN: macula of retina. Martegiani a. SYN: Martegiani funnel. mitral a. the region of the chest over the apex of the heart, where the sounds, normal or pathologic, produced at the mitral valves are usually heard most distinctly. motor a. SYN: motor cortex. a. nervi facialis [TA] SYN: facial nerve a.. a. nuda hepatis [TA] SYN: bare a. of liver. olfactory a. SYN: anterior perforated substance. oval a. of Flechsig semilunar fasciculus. Panum a. a. in space surrounding the empirical horopter where single binocular vision is observed despite stimulation of noncorresponding retinal points. SYN: fusion a.. parastriate a. visual cortex. a. parolfactoria [TA] SYN: parolfactory a.. parolfactory a. [TA] a small region of cerebral cortex on the medial surface of the frontal lobe, formed by the junction of the straight gyrus with the cingulate gyrus, demarcated from the subcallosal gyrus by the posterior parolfactory sulcus. SYN: a. parolfactoria [TA] , Broca parolfactory a.. pear-shaped a. SYN: retromolar pad. peristriate a. visual cortex. piriform a. SYN: piriform cortex. Pitres a. prefrontal cortex of the cerebral hemisphere. See frontal cortex. postcentral a. the cortex of the postcentral gyrus. post dam a. SYN: posterior palatal seal a.. posterior hypothalamic a. [TA] the portion of the hypothalamus located generally inside the region of the mammillary bodies; contains the following nuclei: dorsal premammillary nucleus [TA] (nucleus premammillaris dorsalis [TA]), lateral nucleuus of mammillary body [TA] (nucleus mammillaris medialis [TA]), supramammillary nucleus [TA] (nucleus supramammillaris [TA]_, and the ventral premammillary nucleus [TA] (nucleus premammillaris ventralis [TA]). The posterior nucleus of hypothalamus [TA] is located at the interface of intermediate and posterior hypothalamic areas and is sometimes considered a part of the latter. SEE ALSO: hypothalamus, posterior hypothalamic region. SYN: a. hypothalamica posterior [TA] . posterior intercondylar a. of tibia [TA] the deep notch between the tibial condyles posteriorly to which attaches the posterior cruciate ligament. SYN: a. intercondylaris posterior tibiae [TA] . posterior palatal seal a. the soft tissues along the junction of the hard and soft palates on which pressure within the physiologic limits of the tissues can be applied by a denture to aid in the retention of the denture. SYN: post dam a., postpalatal seal a.. postpalatal seal a. SYN: posterior palatal seal a.. a. postrema (AP) [TA] a small, elevated a. in the lateral wall of the inferior recess of the fourth ventricle; one of the few loci in the brain where the blood-brain barrier is lacking; a chemoreceptor a. associated with vomiting. precentral a. the cortex of the precentral gyrus. precommissural septal a. SYN: subcallosal gyrus. prefrontal a. frontal cortex. premotor a. SYN: premotor cortex. preoptic a. [TA] SYN: preoptic region. a. preoptica [TA] SYN: preoptic region. prestriate a. visual cortex. pretectal a. [TA] a narrow, transversely oriented rostral zone of the mesencephalic tectum, bounded caudally by the superior colliculus, rostrally by the habenular trigone, and laterally by the pulvinar thalami; the pretectal a. contains several nuclei that receive fibers from the optic tract; it has bilateral efferent connections with the Edinger-Westphal nucleus of the oculomotor nuclear complex by way of which it mediates the pupillary light reflex. SYN: pretectal region, pretectum. primary visual a. visual cortex. pulmonary a. the region of the chest at the second left intercostal space, where sounds produced at the pulmonary valve of the right ventricle are heard most distinctly. relief a. in dentistry, the portion of the denture-bearing a. over which the denture base is altered to reduce functional pressure. rest a. the portion of a tooth structure or of a restoration in a tooth that is prepared to receive the positive seating of the metallic occlusal, incisal, lingual, or cingulum rest of a removable prosthesis. SYN: rest seat. retention a. an a. of a tooth provided during its preparation for restoration that will aid in holding the restoration in place. SEE ALSO: retention groove, retention point. retrochiasmatic a. [TA] See intermediate hypothalamic a.. SYN: a. retrochiasmatica [TA] . a. retrochiasmatica [TA] SYN: retrochiasmatic a.. See intermediate hypothalamic a.. Rolando a. SYN: motor cortex. secondary aortic a. region of the chest at the mid-left sternal bases where aortic diastolic murmurs are often best heard. secondary visual a. visual cortex. sensorial areas, sensory areas cerebral cortex. sensorimotor a. the precentral gyrus [TA] and postcentral gyrus [TA] of the cerebral cortex. septal a. [TA] the region of the cerebral hemisphere that stretches as a thin sheet of brain tissue between the fornix bundle and the ventral surface of the corpus callosum, forming the medial wall of the lateral ventricle's frontal horn; it extends ventrally through the narrow interval between the anterior commissure and the rostrum of corpus collosum as the precommissural septum or subcallosal gyrus, which is continuous caudally with the preoptic a. and hypothalamus, as well as more laterally with the innominate substance; its major functional connections are with the hippocampus and hypothalamus. It is composed of a dorsal septal nucleus [TA], lateral septal nucleus [TA], medial septal nucleus [TA], septofimbrial nucleus [TA], and triangular nucleus of septum [TA]. The subformical organ [TA] is also found in this a.. silent a. any a. of the cerebrum or cerebellum in which lesions cause no definite sensory or motor symptoms. skip areas subsidiary segments of diseased intestine or colon in regional enteritis or Crohn colitis, separated from the region of major involvement. somesthetic a. SYN: somatic sensory cortex. stress-bearing a. 1. SYN: denture foundation a.. 2. surfaces of oral structures that resist forces, strains, or pressures brought upon them during function. striate a. visual cortex. a. subcallosa [TA] SYN: subcallosal gyrus. subcallosal a. [TA] SYN: subcallosal gyrus. superior vestibular a. [TA] the a. in the fundus of the internal acoustic meatus superior to the transverse crest through which the superior part of the vestibular (utriculoampullary) nerve passes to reach the macula utriculus and the ampullae of the anterior and lateral semicircular ducts. SYN: a. vestibularis superior [TA] . supporting a. 1. those areas of the maxillary and mandibular edentulous ridges which are considered best suited to carry the forces of mastication when the dentures are in function; 2. SYN: denture foundation a.. tissue-bearing a. SYN: denture foundation a.. a. transitionis amygdalopiriformis [TA] SYN: amygdalopiriform transition a.. tricuspid a. the region of the chest wall over the lower part of the body of the sternum, where the sounds produced at the tricuspid valve are heard most distinctly. trigger a. SYN: trigger point. vagus a. a portion of the floor of the fourth ventricle overlying the vagoglossopharyngeal nuclei. vestibular a. [TA] the a. in the floor of the fourth ventricle lateral to the sulcus limitans [TA] and medial to the restiform body [TA] that overlies the vestibular nuclei and portions of the cochlear nuclei. SEE ALSO: inferior vestibular a., superior vestibular a.. a. vestibularis [TA] SYN: acoustic a.. a. vestibularis inferior [TA] SYN: inferior vestibular a.. a. vestibularis superior [TA] SYN: superior vestibular a.. visual a. SYN: visual cortex. V-shaped a. of esophagus SYN: a. of Laimer. Wernicke a. SYN: Wernicke center.

areatus, areata (a-re-a′tus, -ta)
Occurring in patches or circumscribed areas. [L.]

Areca (ar′e-ka)
A genus of palms of India and the Malay Archipelago. A species, A. catechu, furnishes a. nuts, or betel nuts, which contain arecoline and 15% red tannin, are chewed in the East Indies, and have an anthelmintic and stimulant action. SEE ALSO: betel nut. [Malay]

arecaidine (a-rek′a-den)
A crystalline alkaloid resembling betaine, derived from the betel nut. SYN: arecaine.

arecaine (ar′e-kan)
SYN: arecaidine.

arecoline (a-rek′o-len)
A colorless oily alkaloid from the betel nut.

areflexia (a-re-flek′se-a)
Absence of reflexes. detrusor a. a failure of the detrusor muscle to have a reflex contraction even though the bladder has reached or exceeded its capacity.

arenaceous (ar-e-na′shus)
Sandy; of sandlike consistency. [L. arena, sand]

Arenaviridae (a-re-na-vir′i-de)
A family of over 15 RNA viruses, many of which are natural parasites of rodents, that includes lymphocytic choriomeningitis virus, Lassa virus, and the Tacaribe virus complex. The virions are 50–300 nm (average 100 nm) in diameter, enveloped, ether-sensitive, and contain 2 single-stranded RNA molecules (molecular weight 3–5 × 106); they also contain electron-dense, RNA-containing granules (20 to 30 nm in diameter) that resemble ribosomes, with an electron-microscopic appearance of sandiness. [L. arena (harena), sand]

Arenavirus (a-re′na-vi′rus)
A genus in the family Arenaviridae that is associated with lymphocytic choriomeningitis and a number of hemorrhagic fevers.

areola, pl .areolae (a-re′o-la, -le)
1. [NA] Any small area. 2. One of the spaces or interstices in areolar tissue. 3. SYN: a. of breast. 4. A pigmented, depigmented, or erythematous zone surrounding a papule, pustule, wheal, or cutaneous neoplasm. SYN: halo (3) . [L. dim. of area] a. of breast [TA] a circular pigmented area surrounding the nipple (papilla mammae); its surface is dotted with little projections due to the presence of areolar glands beneath. SYN: a. mammae [TA] , a. of nipple, a. papillaris, a. (3) . a. mammae [TA] SYN: a. of breast. a. of nipple SYN: a. of breast. a. papillaris SYN: a. of breast. a. umbilicus a pigmented ring around the umbilicus in the pregnant woman.

areolar (a-re′o-lar)
Relating to an areola.

areometer (ar-e-om′e-ter)
SYN: hydrometer. [G. araios, thin, + G. metron, measure]

Arg
Symbol for arginine or its mono- or diradical.

Argas
A genus of soft ticks of the family Argasidae, some species of which usually infest birds but may attack humans. A. reflexus the pigeon tick, a species that may cause a cutaneous inflammatory lesion in humans.

argasid (ar-gas′id)
Common name for members of the family Argasidae.

Argasidae (ar-gas′i-de)
Family of ticks (superfamily Ixodoidea, order Acarina), the soft ticks, so called because of their wrinkled, leathery, tuberculated appearance that fills out when the tick is engorged with blood. A. contains 4 genera: Argas, Ornithodoros, Otobius, and Antricola; argasid ticks, chiefly species of Ornithodoros, harbor and transmit spirochetes of the genus Borrelia that cause relapsing fever in birds and mammals.

argentaffin, argentaffine (ar-jen′ta-fin, -fen)
Pertaining to cells or tissue elements that reduce silver ions in solution, thereby becoming stained brown or black. [L. argentum, silver, + affinitas, affinity]

argentation (ar-jen-ta′shun)
Impregnation with a silver salt. SEE ALSO: argyria. [L. argentum, silver]

argentic (ar-jen′tik)
1. Relating to silver. SYN: argyric (1) . 2. Denoting a chemical compound containing silver as the rare dication (Ag2+).

argentine (ar′jen-ten)
Relating to, resembling, or containing silver.

argentophil, argentophile (ar-jen′to-fil, -fil)
SYN: argyrophil.

argentous (ar-jen′tus)
Denoting a chemical compound containing silver as a singly charged (Ag+) ion. The vast majority of silver compounds contain the a. ion; where the ionic state of silver is not specifically stated, as in silver nitrate, the a. state is assumed.

argentum, gen. argenti (ar-jen′tum, -jen′ti)
SYN: silver. [L.]

arginase (ar′ji-nas)
An enzyme of the liver that catalyzes the hydrolysis of l-arginine to l-ornithine and urea; a key enzyme of the urea cycle. A deficiency of a. leads to arginemia. SYN: canavanase.

arginine (Arg) (ar′ji-nen)
2-Amino-5-guanidinopentanoic acid;one of the amino acids occurring among the hydrolysis products of proteins, particularly abundant in the basic proteins such as histones and protamines. A dibasic amino acid. a. deiminase an enzyme catalyzing the hydrolytic deamination of l-a. to l-citrulline and ammonia. Cf.:nitric oxide synthase. a. glutamate a compound composed of a. and glutamic acid, given intravenously to detoxify ammonia; used in the treatment of ammoniemia resulting from liver dysfunction. a. hydrochloride a form of a. used for intravenous administration as an adjunct in the treatment of encephalopathies associated with liver diseases and ammoniacal azotemia. a. phosphate SYN: phosphoarginine.

argininosuccinase (ar′ji-ni-no-suk′si-nas)
SYN: argininosuccinate lyase.

argininosuccinate lyase (ar′ji-ni-no-suk′si-nat)
An enzyme cleaving l-argininosuccinate nonhydrolytically to l-arginine and fumarate; a deficiency of this enzyme leads to argininosuccinoaciduria; a key step in the urea cycle. SYN: argininosuccinase.

argininosuccinic acid (ar′ji-ni-no-suk-sin′ik)
Formed as an intermediate in the conversion of l-citrulline to l-arginine in the urea cycle.

argininosuccinicaciduria (ar-ji-nin′o-suk-sin′ik-as-i-doo′re-a) [MIM*207900]
A disorder of urea cycle due to a deficiency of argininosuccinate lyase; characterized by physical and mental retardation, epilepsy, ataxia, liver disease, friable, tufted hair, and excessive urinary excretion of argininosuccinic acid. Autosomal recessive inheritance, caused by mutation in argininosuccinate lyase gene (ASL) on chromosome 7q.

arginyl (ar′jin-il)
The aminoacyl radical of arginine. SYN: arabinosyladenine.

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