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Medical Dictionary


λ, upper case: Λ
Lambda, the 11th letter of the Greek alphabet
  • Avogadro number
  • wavelength
  • radioactive constant
  • Ostwald solubility coefficient
  • molar conductivity of an electrolyte (Λ)
  • position of a substituent located on the eleventh atom from the carboxyl or other functional group (λ).
  • Abbreviation for left ( e.g., left eye)
  • lumbar vertebrae (L1 to L5).
  • Inductance
  • left
  • levorotatory
  • leucine
  • leucyl.
  • Linking number.
  • light
  • limes
  • liquid
  • liter
  • Lithium.
  • lumbar, used especially with a number from 1 to 5 to indicate a vertebra or segment of the spinal cord in the lumbar region
  • used with a lower case letter, plus sign, subscript letter, or subscript plus sign as a symbol for various doses of toxin.
  • liter
  • liquid
  • length.
  • Levorotatory. Cf.:d-. [L. laevus, on the left-hand side]
  • a chemical compound to be structurally (sterically) related to l-glyceraldehyde. Cf.:d-.
  • having a similar configuration at a selected carbon atom to the configuration of levorotatory glyceraldehyde, e.g., L-fructose, L-tryptophan
l-dehydroascorbic acid (de-hi′dro-as-kor′bik)
The reversibly oxidized form of ascorbic acid; it is antiscorbutic, but is converted in the body to 2,3-diketo-l-gulonic acid, which has no vitamin C activity.

SYN: levodopa.

l-glyceric aciduria
Excretion of l-glyceric acid in the urine; a primary metabolic error due to deficiency of d-glyceric dehydrogenase resulting in excretion of l-glyceric and oxalic acids, leading to the clinical syndrome of oxalosis with frequent formation of oxalate renal calculi.

l-gulonic acid (goo-lon′ik)
Reduction product of glucuronic acid (–CHO → &cbond;CH2OH); oxidation product of l-gulose (–CHO → &cbond;COOH); a precursor (except in certain primates, guinea pigs, certain fishes, and the Indian fruit bat) of ascorbic acid via l-gulonolactone.

l-gulonolactone (goo-lon′o-lak-ton)
The immediate precursor of ascorbic acid in those animals capable of ascorbic acid biosynthesis. SYN: dihydroascorbic acid, l-gulono-γ-lactone. l-gulonolactone oxidase the enzyme catalyzing the conversion of l-gulonolactone and O2 to H2O2 and l-xylo-hexulonolactone, a precursor of ascorbic acid; absent in humans.

SYN: l-gulonolactone.

3-l-hydroxykynurenine (hi-drok′se-ki-noo-re-nen)
An intermediate in the catabolism of l-tryptophan and a precursor of xanthurenate; elevated in cases of a vitamin B6 deficiency.

Symbol for lanthanum.

Peter F., U.S. dentist, *1900. See L. syndrome.

Ernest M., French physician, 1870–1939.

Leon, French surgeon, 1832–1916. See Labbé triangle, Labbé vein.

1. To incorporate into a compound a substance that is readily detected, such as a radionuclide, whereby its metabolism can be followed or its physical distribution detected. 2. The substance so incorporated.

la belle indifférence (lah bel an-dif-er-ahns′)
A naive, inappropriate lack of emotion or concern for the perceptions by others of one's disability, typically seen in persons with conversion hysteria. [Fr.]

labetalol hydrochloride (la-bet′a-lol)
An α-adrenergic and β-adrenergic blocking agent used in the treatment of hypertension.

labia (la′be-a)
Plural of labium.

labial (la′be-al)
1. Relating to the lips or any labium. 2. Toward a lip. 3. One of the letters formed by means of the lips. [L. labium, lip]

labialism (la′be-al-izm)
A form of stammering in which there is confusion in the use of the labial consonants.

labially (la′be-al-e)
Toward the lips.

labile (la′bil, -bil)
Unstable; unsteady, not fixed; denoting: 1. An adaptability to alteration or modification, i.e., relatively easily changed or rearranged. 2. Certain constituents of serum affected by increases in heat. 3. An electrode that is kept moving over the surface during the passage of an electric current. 4. In psychology or psychiatry, denoting free and uncontrolled mood or behavioral expression of the emotions. 5. Easily removable; e.g., a l. hydrogen atom. [L. labilis, liable to slip, fr. labor, pp. lapsus, to slip]

lability (la-bil′i-te)
The state of being labile.

The lips. SEE ALSO: cheilo-. [L. labium, lip]

labiocervical (la′be-o-ser′vi-kal)
Relating to a lip and a neck; specifically, to the labial or buccal surface of the neck of a tooth. [labio- + L. cervix, neck]

labioclination (la′be-o-kli-na′shun)
Inclination of position more toward the lips than is normal; said of a tooth.

labiodental (la-be-o-den′tal)
Relating to the lips and the teeth; denoting certain letters the sound of which is formed by both lips and teeth. [labio- + L. dens, tooth]

labiogingival (la′be-o-jin′ji-val)
Relating to the point of junction of the labial border and the gingival line on the distal or mesial surface of an incisor tooth.

labioglossolaryngeal (la′be-o-glos′o-la-rin′je-al)
Relating to the lips, tongue, and larynx; describing bulbar paralysis in which these parts are involved. [labio- + G. glossa, tongue, + larynx]

labioglossopharyngeal (la′be-o-glos′o-fa-rin′je-al)
Relating to the lips, tongue, and pharynx; describing bulbar paralysis involving these parts. [labio- + G. glossa, tongue, + pharynx]

labiograph (la′be-o-graf)
An instrument for recording the movements of the lips in speaking. [labio- + G. grapho, to record]

labiomental (la′be-o-men′tal)
Relating to the lower lip and the chin. [labio- + L. mentum, chin]

labionasal (la′be-o-na′sal)
1. Relating to the upper lip and the nose, or to both lips and the nose. 2. Denoting a letter that is both labial and nasal in the production of its sound.

labiopalatine (la′be-o-pal′a-tin)
Relating to the lips and the palate.

labioplacement (la′be-o-plas′ment)
Positioning ( e.g., of a tooth) more toward the lips than normal.

labioplasty (la′be-o-plas-te)
Plastic surgery of a lip. [labio- + G. plastos, formed]

labioversion (la′be-o-ver-zhun)
Malposition of an anterior tooth from the normal line of occlusion toward the lips.

labitome (lab′i-tom)
A forceps with sharp blades. SYN: cutting forceps. [G. labis, pincers, + tome, an incision]

labium, gen. labii, pl .labia (la′be-um, -be-e, -be-a)
  • lip.
  • Any lip-shaped structure.
  • l. anterius ostii uteri: anterior lip of external os of uterus.
  • l. externum cristae iliacae: outer lip of iliac crest.
  • l. inferius oris: lower lip.
  • l. internum cristae iliacae: inner lip of iliac crest.
  • l. laterale lineae asperae: lateral lip of linea aspera.
  • l. limbi tympanicum laminae spiralis ossei: tympanic lip of spiral limbus.
  • l. limbi tympanicum limbi spiralis ossei: tympanic lip of spiral limbus.
  • l. limbi vestibulare laminae spiralis ossei: vestibular lip of spiral limbus.
  • l. limbi vestibulare limbi spiralis ossei: vestibular lip of spiral limbus.
  • l. majus: one of two rounded folds of integument forming the lateral boundaries of the pudendal cleft. The labia majora are the female homolog of the scrotum, aka l. majus pudendi , large pudendal lip.
  • l. majus pudendi, pl .labia majora: l. majus.
  • l. mediale lineae asperae: medial lip of linea aspera.
  • l. minus: one of two narrow longitudinal folds of mucous membrane enclosed in the pudendal cleft within the labia majora; posteriorly, they gradually merge into the labia majora and join to form the frenulum labiorum pudendi (fourchette); anteriorly, each l. divides into two portions that unite with those of the opposite side in front of the glans clitoridis to form the prepuce, aka l. minus pudendi, small pudendal lip.
  • l. minus pudendi, pl .labia minora: l. minus.
  • labia oris: lips of mouth, under lip.
  • l. posterius ostii uteri: posterior lip of external os of uterus.
  • l. superius oris: upper lip.
  • tympanic l. of limbus of spiral lamina: tympanic lip of spiral limbus.
  • l. urethrae: one of the two lateral margins of the external urethral orifice of the female.
  • labia uteri anterior: lip of external os of uterus, posterior lip of external os of uterus.
  • vestibular l. of limbus of spiral lamina: vestibular lip of spiral limbus.
  • l. vocale, pl .labia vocalia: vocal fold.
labor (la′bor)
The process of expulsion of the fetus and the placenta from the uterus. The stages of l. include: first stage, beginning with the onset of uterine contractions through the period of dilation of the os uteri; second stage, the period of expulsive effort, beginning with complete dilation of the cervix and ending with expulsion of the infant; third s. or placental stage, the period beginning at the expulsion of the infant and ending with the completed expulsion of the placenta and membranes. [L. toil, suffering] active l. contractions resulting in progressive effacement and dilation of the cervix. dry l. obsolete term for l. after spontaneous loss of the amniotic fluid. false l. contractions which do not produce cervical dilation or effacement. missed l. brief uterine contractions which do not lead to l. and expulsion of the infant, but which cease, resulting in the indefinite retention of the fetus (usually lifeless) either in utero or in the abdominal cavity. precipitate l. very rapid l. ending in delivery of the fetus. premature l. onset of l. after 20 weeks and before the 37th completed week of pregnancy dated from the last normal menstrual period. trial of l. after cesarean section the attempt to deliver vaginally after a cesarean section; carries some risk of rupture of the uterine scar.

laboratorian (lab′o-ra-tor′e-an)
One who works in a laboratory; in the medical and allied health professions, one who examines or performs tests (or supervises such procedures) with various types of chemical and biologic materials, chiefly as an aid in the diagnosis, treatment, and control of disease, or as a basis for health and sanitation practices.

laboratory (lab′o-ra-to-re, lab′ra-)
A place equipped for the performance of tests, experiments, and investigative procedures and for the preparation of reagents, therapeutic chemical materials, and so on. [Mediev. L. laboratorium, a workplace, fr. L. laboro, pp. -atus, to labor] personal growth l. a sensitivity training setting in which the primary emphasis is on each participant's potentialities for creativity, empathy, and leadership. SEE ALSO: sensitivity training group.

labra (la′bra)
Plural of labrum. [L.]

labrale inferius (la-bra′le in-fe′re-us)
A point where the boundary of the vermilion border of the lower lip and the skin is intersected by the median plane.

labrale superius (la-bra′le soo-pe′re-us)
The point on the upper lip lying in the median sagittal plane on a line drawn across the boundary of the vermilion border and skin.

labrocyte (lab′ro-sit)
SYN: mast cell.

labrum, pl .labra (la′brum, la′bra)
  • A lip. 2. A lip-shaped structure. 3. A fibrocartilaginous lip around the margin of the concave portion of some joints. SYN: articular l., articular lip, l. articulare. [L.] acetabular l. [TA] a fibrocartilaginous rim attached to the margin of the acetabulum of the hip bone. SYN: l. acetabulare [TA] , acetabular lip, circumferential cartilage (1) , cotyloid ligament, ligamentum cotyloideum. l. acetabulare [TA] SYN: acetabular l.. articular l. SYN: l. (3) . l. articulare SYN: l. (3) . l. glenoidale scapulae [TA] SYN: glenoid l. of scapula. glenoid l. of scapula [TA] a ring of fibrocartilage attached to the margin of the glenoid cavity of the scapula to increase its depth. SYN: l. glenoidale scapulae [TA] , articular margin, circumferential cartilage (2) , glenoid ligament (1) , glenoidal lip, ligamentum glenoidale.

    labyrinth (lab′i-rinth)
    • Any of several anatomic structures with numerous intercommunicating cells or canals.
    • The internal or inner ear, composed of the semicircular ducts, vestibule, and cochlea.
    • Any group of communicating cavities, as in each lateral mass of the ethmoid bone.
    • A group of upright test tubes terminating below in a base of communicating, alternately ∪-shaped and ∩-shaped tubes, used for isolating motile from nonmotile organisms in culture, or a motile from a less motile organism (as the typhoid from the colon bacillus), the former traveling faster and farther through the tubes than the latter.
    • bony l.: a series of cavities (cochlea, vestibule, and semicircular canals) contained within the otic capsule of the petrous portion of the temporal bone; the bony l. is filled with perilymph, in which the delicate, endolymph-filled membranous l. is suspended, aka labyrinthus osseus , osseous l..
    • cochlear l.: the portion of the membranous l. concerned with the sense of hearing (vs. the vestibular l., which is concerned with the sense of equilibration) and innervated by the cochlear nerve; it is located within the cochlea of the bony l., and consists of the cochlear duct, which contains the spiral organ, aka labyrinthus cochlearis , organ of hearing.
    • ethmoidal l.: a mass of air cells with thin bony walls forming part of the lateral wall of the nasal cavity; the cells are arranged in three groups, anterior, middle, and posterior, and are closed laterally by the orbital plate which forms part of the wall of the orbit, aka labyrinthus ethmoidalis , ectethmoid, ectoethmoid, lateral mass of ethmoid bone.
    • Ludwig l.: convoluted part of kidney lobule.
    • membranous l.: a complex arrangement of communicating membranous canaliculi and sacs, filled with endolymph and surrounded by perilymph, suspended within the cavity of the bony l.; its chief divisions are the cochlear duct and the vestibular l., aka labyrinthus membranaceus .
    • osseous l.: bony l..
    • renal l.: convoluted part of kidney lobule.
    • Santorini l.: prostatic venous plexus.
    • vestibular l.: the portion of the membranous l. concerned with the sense of equilibration (vs. the cochlear l., which is concerned with the sense of hearing) and innervated by the vestibular nerve; it is located within the semicircular canals and vestibule of the bony l., and consists of the utricle, saccule, and the semicircular, utriculosaccular, and endolymphatic ducts, aka labyrinthus vestibularis, vestibular organ.
    labyrinthectomy (lab-i-rin-thek′to-me)
    Excision of the labyrinth; a destructive operation to destroy labyrinthine function. [labyrinth + G. ektome, excision]

    labyrinthine (lab-i-rin′thin)
    Relating to any labyrinth.

    labyrinthitis (lab′i-rin-thi′tis)
    Inflammation of the labyrinth (the internal ear), sometimes accompanied by vertigo and deafness. SYN: otitis interna.

    labyrinthotomy (lab-i-rin-thot′o-me)
    Incision into the labyrinth. [labyrinth + G. tome, incision]

    labyrinthus (lab-i-rin′thus)
    SYN: convoluted part of kidney lobule. [L. fr. G. labyrinthos, labyrinth] l. cochlearis: cochlear labyrinth. l. ethmoidalis: ethmoidal labyrinth. l. membranaceus: membranous labyrinth. l. osseus: bony labyrinth. l. vestibularis: vestibular labyrinth.

    lac, gen. lactis (lak, lak′tis)
    1. SYN: milk (1) . 2. Any whitish, milklike liquid. [L. milk] l. sulfuris SYN: precipitated sulfur. l. vaccinum cow's milk.

    lacca (lak′a)
    SYN: shellac.

    laccase (lak′as)
    An enzyme oxidizing benzenediols to semiquinones with O2. SYN: monophenol monooxygenase (2) , phenol oxidase, phenolase, polyphenol oxidase, urushiol oxidase.

    lacerable (las′er-a-bl)
    Capable of being, or liable to be, torn. [L. lacero, to tear to pieces, fr. lacer, mangled]

    lacerated (las′er-a-ted)
    Torn; rent; having a ragged edge. [L. lacero, pp. -atus, to tear to pieces]

    laceration (las-er-a′shun)
    1. A torn or jagged wound, or an accidental cut wound. 2. The process or act of tearing the tissues. [L. lacero, pp. -atus, to tear to pieces] brain l. gross tearing of neural tissue. scalp l. a tear of the dermis or underlying tissues and galea aponeurotica of the scalp. through-and-through l. a l. that penetrates two surfaces of a structure, generally restricted to skin or mucosal surfaces, such as the cheek, lip, ala nasi, pinna, etc. vaginal l. tearing of the vaginal wall, aka colporrhexis.

    lacertus (la-ser′tus)
    1. [TA] A fibrous band, bundle, or slip related to a muscle. 2. Originally the muscular part of the upper limb from shoulder to elbow. [L.] l. cordis one of the trabeculae carneae. l. fibrosus bicipital aponeurosis. l. of lateral rectus muscle the part of the tendon of origin of the lateral rectus muscle attaching to the greater wing of the sphenoid bone, lateral to the common tendinous ring; often incorrectly equated to the lateral check ligament of the eyeball. SYN: l. musculi recti lateralis. l. medius SYN: anterior longitudinal ligament. l. musculi recti lateralis SYN: l. of lateral rectus muscle.

    lachrymal (lak′ri-mal)
    SYN: lacrimal.

    Abbreviation for lipoprotein-associated coagulation inhibitor.

    laciniae tubae (la-sin′e-e too′be)
    SYN: fimbriae of uterine tube, under fimbria. [L. lacinia, fringe]

    lacrimal (lak′ri-mal)
    Relating to the tears, their secretion, the secretory glands, and the drainage apparatus. SYN: lachrymal. [L. lacrima, a tear]

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