Copy of `Dorland's Medical Dictionary`

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

mental retardation
less than average general intellectual functioning that brings with it some degree of impaired adaptation in learning, social adjustment, or maturation, or in all three areas; it is now classified as a developmental disability.

mental scotoma
in psychiatry, a figurative blind spot in a person's psychological awareness, where the patient has lack of insight and is unable to understand his or her mental problems.

mental tubercle
a prominence on the inner border of either side of the mental protuberance of the mandible.

mentalis muscle
origin, incisive fossa of mandible; insertion, skin of chin; innervation, facial nerve; action, wrinkles skin of chin.

menthol
(men´thol) an alcohol from various mint oils or produced synthetically, used locally to relieve itching and by inhalation for treatment of upper respiratory tract disorders.

mentoanterior position
a position of the fetus in cephalic presentation in labor, with its chin directed toward the right (RMA) or left (LMA) anterior quadrant of the maternal pelvis.

mentolabial furrow
the skin furrow between the lower lip and the chin.

mentoplasty
(men´to-plas″te) plastic surgery of the chin; surgical correction of deformities and defects of the chin.

mentoposterior position
a position of the fetus in cephalic presentation in labor, with its chin directed toward the right (RMP) or left (LMP) posterior quadrant of the maternal pelvis.

mentotransverse position
a position of the fetus in cephalic presentation in labor, with its chin directed toward the right (RMT) or left (LMT) iliac fossa of the maternal pelvis.

mentum
(men´tәm) Latin word meaning chin; a term used in anatomy.

mepenzolate
(me-pen´zo-lāt) an anticholinergic and antimuscarinic used in the form of mepenzolate bromide in the treatment of peptic ulcers and disorders characterized by excessive motility of the colon.

meperidine
(mĕ-per´ĭ-dēn) a synthetic opioid analgesic; the hydrochloride salt is used as an analgesic to relieve moderate to severe pain, including during childbirth, and as an adjunct to anesthesia. Administered orally, intramuscularly, subcutaneously, or intravenously. Abuse of this drug may lead to depende...

mephentermine
(mĕ-fen´ter-mēn) a sympathomimetic administered orally, intramuscularly, or intravenously as the sulfate salt for its vasopressor effects to treat hypotensive conditions, and applied topically to the nasal mucosa as a decongestant.

mephenytoin
(mә-fen´ә-to-in) an anticonvulsant administered orally in treatment of several types of epilepsy when the seizures are refractory to other drugs.

mephitic
(mә-fit´ik) noxious; foul smelling.

mephobarbital
(mef″o-bahr´bĭ-tәl) a long-acting barbiturate used as an anticonvulsant in epilepsy.

mepivacaine
(mĕ-piv´ah-kān) a lidocaine analogue used in the form of the hydrochloride salt as a local anesthetic.

meprednisone
(mә-pred´nĭ-sōn) a glucocorticoid used as an antiinflammatory, antiallergic, and antineoplastic agent; administered orally.

meprobamate
(mә-pro´bә-māt) (mep″ro-bam´āt) an antianxiety agent and skeletal muscle relaxant; administered orally.

mEq
milliequivalent.

meradimate
(mer-ad´ĭ-māt) an absorber of ultraviolet A radiation, used topically as a sunscreen.

meralgia
(mә-ral´jә) pain in the thigh.

meralgia paresthetica
(mә-ral´jә par″әs-thet´ĭ-kә) numbness and tingling on the front and side of the thigh, occasionally with pain; it is due to entrapment of the lateral femoral cutaneous nerve at the inguinal ligaments.

merbromin
(mәr-bro´min) a mercurial antiseptic that has been used topically for the disinfection of skin and wounds.

mercaptan
(mәr-kap´tan) thiol.

mercaptopurine
(mәr-kap″to-pūr´ēn) a purine analogue in which sulfur replaces the oxygen atom of purine; it is used as an antineoplastic agent primarily for treatment of acute lymphoblastic leukemia. It is also used an immunosuppressant in the treatment of Crohn disease and ulcerative colitis. Called also 6-mercaptopur...

Mercedes-Benz sign
shadows shaped like the logo of the Mercedes-Benz automobile, seen on radiographs of the gallbladder; they indicate the presence of gas-filled fissures within gallstones, although the gallstones themselves may not be visible.

mercurial
(mәr-kūr´e-әl) pertaining to mercury. a preparation containing mercury. pertaining to behavior patterns that change rapidly.

mercurialism
(mәr-kūr´e-әl-iz″әm) mercury poisoning.

mercuric
(mәr-kūr´ik) pertaining to mercury as a bivalent element; containing bivalent mercury.

Mercurochrome
(mәr-ku´rә-krōm) trademark for preparations of merbromin, a topical antibacterial.

mercurous
(mur´kūr-әs) pertaining to mercury as a monovalent element; containing monovalent mercury.

mercury
(Hg) (mur´kūr-e) a chemical element, atomic number 80, atomic weight 200.59. Mercury forms two sets or classes of compounds: mercurous, in which a single atom of mercury combines with a monovalent radical, and mercuric, in which a single atom of mercury combines with a bivalent radical. Mercury and...

mercury arc lamp
mercury vapor lamp a lamp in which the arc is struck in mercury and is enclosed in a quartz burner; used in photodynamic therapy. The two most common types are the low pressure or cold quartz type and the high pressure or hot quartz type.

mercury poisoning
acute or chronic disease caused by exposure to mercury or its salts; an important aspect is its toxic effect on the brain, causing impaired judgment, memory loss, sleeplessness, and nervousness. The acute form, due to ingestion, is marked in the beginning by severe abdominal pain, metallic taste in the mouth, vomiting, and decr...

mercury test
see specific tests, including Magpie test, Reinsch test, and Vogel and Lee test.

meridian
(mә-rid´e-әn) an imaginary line on the surface of a globe or sphere, connecting the opposite ends of its axis. adj., merid´ional., adj. Meridians of eyeball. in acupuncture, a system of 20 lines (12 principal and 8 collateral) connecting acupoints and r...

Merkel cell
a specialized cell at or near the dermal-epidermal junction, believed to act as a tactile receptor.

Merkel cell carcinoma
Merkel cell tumor a rapidly growing malignant dermal or subcutaneous tumor occurring on sun-exposed areas in middled-aged or older adults and containing irregular anastomosing trabeculae and small dense granules typical of Merkel cells.

Merkel disk
small cup-shaped tactile receptors in the skin that are particularly sensitive to continuous pressure.

Merkel tactile cell
Merkel cell.

Merkel-Ranvier cell
a type of clear cell found in the basal layer of the epidermis; it contains catecholamine granules and resembles a melanocyte.

meroblastic
(mer″o-blas´tik) partially dividing; undergoing cleavage in which only part of the zygote participates.

merocrine
(mer´o-krin) partly secreting: denoting that type of glandular secretion in which the secreting cell remains intact throughout the process of formation and discharge of the secretory products, as in the salivary and pancreatic glands. See also apocrine and holocrine.

merocrine gland
one whose discharged secretion contains no part of the secreting cells.

merogenesis
(mer″o-jen´ә-sis) cleavage of a zygote.

merogony
(mә-rog´ә-ne) the development of only a portion of an egg. schizogony resulting in the production of merozoites. adj., merogon´ic., adj.

meromelia
(mer″o-me´le-ә) congenital absence of a part, but not all, of a limb.

meromicrosomia
(mer″o-mi″kro-so´me-ә) unusual smallness of some part of the body.

meromyosin
(mer″o-mi´o-sin) a fragment of the myosin molecule isolated by treatment with proteolytic enzyme; there are two types, heavy (H-meromyosin) and light (L-meromyosin).

meropenem
(mer″o-pen´әm) a broad-spectrumβ-lactam antibiotic effective against a wide variety of gram-positive and gram-negative organisms; used in treatment of intra-abdominal infections and bacterial meningitis.

meropia
(mә-ro´pe-ә) partial blindness.

merorachischisis
(me″ro-rә-kis´kĭ-sis) fissure of part of the spinal cord.

merosmia
(mә-ros´me-ә) inability to perceive certain odors.

merozoite
(mer″o-zo´īt) one of the organisms formed by multiple fission (schizogony) of a sporozoite within the body of the host.

MERRF syndrome
myoclonus with epilepsy and ragged red fibers; a familial type of mitochondrial encephalopathy, of maternal (mitochondrial) inheritance.

Merthiolate
(mәr-thi´o-lāt) trademark for preparations of thimerosal, a topical antibacterial.

Merzbacher-Pelizaeus disease
(merts´bah-ker pa″le-tsa´oos) Pelizaeus-Merzbacher disease.

mesalamine
(mә-sal´ә-mēn) an active metabolite of sulfasalazine, used in prophylaxis and treatment of inflammatory bowel disease; administered orally or rectally. Called also 5-aminosalicylic acid.

mesalazine
(mә-sal´ә-zēn) mesalamine.

mesangial cells
phagocytic cells found in the mesangium of the glomerular capsule of the kidney, thought to aid in cleaning the filtration apparatus. Called also intercapillary cells.

mesangiocapillary
(mes-an″je-o-kap´ĭ-lar″e) pertaining to or affecting the mesangium and the associated capillaries.

mesangium
(mes-an´je-әm) the thin membrane supporting the capillary loops in renal glomeruli. adj., mesan´gial., adj.

Mesantoin
(mә-san´toin) trademark for a preparation of mephenytoin, an anticonvulsant.

mesarteritis
(mes″ahr-tәr-i´tis) inflammation of the tunica media of an artery.

mesatipellic
(mә-sat″ĭ-pel´ik) having a round pelvis.

mescaline
(mes´kә-lēn) a poisonous alkaloid derived from the flowering heads (mescal buttons) of a Mexican cactus; it is a hallucinogen, producing hallucinations of sound and color.

mescalism
(mes´kә-liz″әm) intoxication due to mescal buttons or mescaline.

mesencephalic arteries
origin,basilar artery; branches, none; distribution, cerebral peduncle.

mesencephalic flexure
cephalic flexure.

mesencephalitis
(mez″en-sef″ә-li´tis) inflammation of the mesencephalon, or midbrain.

mesencephalon
(mez″en-sef´ә-lon) the short part of the brainstem just above the pons; it contains the nerve pathways between the cerebral hemispheres and the medulla oblongata, as well as nuclei (relay stations or centers) of the third and fourth cranial nerves. The center for visual reflexes, such as moving the head and ...

mesencephalotomy
(mez″en-sef″ә-lot´ә-me) surgical production of lesions in the midbrain for the relief of intractable pain.

mesenchyma
(mez-eng´kĭ-mә) the meshwork of embryonic connective tissue in the mesoderm; from it are formed the connective tissues of the body as well as blood vessels and lymph vessels. adj., mesen´chymal., adj.

mesenchymal cells
the pluripotent cells constituting the mesenchyme.

mesenchymal tissue
embryonic connective tissue composed of stellate cells and a ground substance of coagulable fluid.

mesenchyme
(mez´әng-kīm″) mesenchyma.

mesenchymoma
(mez″әn-ki-mo´mә) a tumor of mixed mesenchymal tissue with two or more cellular elements that are not commonly associated, not including fibrous tissue.

mesenterectomy
(mez″әn-tә-rek´tә-me) resection of the mesentery.

mesenteric adenitis
mesenteric lymphadenitis.

mesenteric hernia
herniation of intestine through an opening in the mesentery.

mesenteric infarction
coagulation necrosis of the intestines due to a decrease in blood flow in the mesenteric vessels.

mesenteric lymphadenitis
inflammation of the mesenteric lymph nodes, causing pain and swelling resembling that of acute appendicitis.

mesentericoparietal hernia
paraduodenal hernia.

mesenteriopexy
(mez″әn-ter´e-o-pek″se) fixation or suspension of a torn mesentery.

mesenteriorrhaphy
(mez″әn-ter″e-or´ә-fe) suture of the mesentery.

mesenteriplication
(mez″әn-ter″ĭ-plĭ-ka´shәn) the operation of taking a tuck in the mesentery to shorten it.

mesenteritis
(mez″en-tә-ri´tis) inflammation of the mesentery.

mesenterium
(mez″әn-ter´e-әm) mesentery (def. 2).

mesenteron
(mez-en´tәr-on) the midgut.

mesentery
(mez´әn-ter″e) a membranous fold attaching an organ to the body wall. the peritoneal fold attaching the small intestine to the dorsal body wall; called also mesenterium. adj., mesenter´ic., adj. Mesentery in a median sagittal section.

mesh graft
a type of split-thickness graft in which many tiny slits have been made in the skin to allow it to be stretched to cover a larger area.

meshwork
(mesh´wәrk) a network or reticulum. trabecular meshwork a trabecula of loose fibers found at the iridocorneal angle between the anterior chamber of the eye and the venous sinus of the sclera; the aqueous humor filters through the spaces between the fibers into the sinus and passes i...

mesiad
(me´ze-ad) toward the middle or center.

mesial
(me´ze-әl) situated in the middle; median; nearer the middle line of the body or nearer the center of the dental arch.

mesial angles
the tooth angles formed between the mesial surface and other surfaces of a tooth; the cavity angles between the mesial wall of a tooth cavity and other walls.

mesial surface
the surface of a tooth that is closest to the midline of the dental arch, opposite to its distal surface.

mesially
(me´ze-al″e) toward the median line.

mesio-occlusal
(me″ze-o-ŏ-kloo´zәl) pertaining to or formed by the mesial and occlusal surfaces of a tooth, or the mesial and occlusal walls of a tooth cavity.