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

ultracentrifuge
(ul″trә-sen´trĭ-fūj) the centrifuge used in ultracentrifugation.

ultradian
(ul″trә-de´әn) pertaining to a period of less than 24 hours; applied to the rhythmic repetition of certain phenomena in living organisms occurring in cycles of less than a day. See also ultradian rhythm.

ultradian rhythm
the regular recurrence in cycles of less than 24 hours, as certain biological activities which occur at such intervals, regardless of conditions of illumination or other environmental conditions.

ultrafilter
(ul″trә-fil´tәr) the filter used in ultrafiltration.

ultrafiltration
(ul″trә-fil-tra´shәn) filtration through filters with minute pores, thus allowing the separation of extremely minute particles. It occurs naturally, as in the filtration of plasma at the capillary membrane, and is also performed clinically and in the laboratory, such as in hemodialysis, where it ...

Ultralente insulin
extended insulin zinc suspension.

ultramicroscopic
(ul″trә-mi″kro-skop´ik) too small to be seen with the ordinary light microscope.

ultrashort wave
an electromagnetic wave of wavelength of less than 10 meters; called also microwave.

ultrasonic
(ul″trә-son´ik) beyond the audible range; relating to sound waves having a frequency of more than 20,000 Hz.

ultrasonic lithotripsy
lithotripsy in which a rigid probe is inserted to the site and high frequency sound waves disintegrate the calculus; it may be either through the skin (percutaneous ultrasonic lithotripsy) or through an endoscope.

ultrasonic tomography
the ultrasonographic visualization of a cross-section of a predetermined plane of the body; see B-mode ultrasonography.

ultrasonic waves
waves similar to sonic waves but of such high frequency (20,000 hertz or higher) that the human ear does not perceive them as sound; see ultrasonics.

ultrasonics
(ul″trә-son´iks) that part of the science of acoustics dealing with the frequency range beyond the upper limit of perception by the human ear (20,000 hertz), but usually restricted to frequencies above 50,000 hertz. Ultrasonic radiation is harmful to tissues because it heats up matter that absorbs it; ...

ultrasonogram
(ul″trә-son´o-gram) the record obtained by ultrasonography.

ultrasonography
(ul″trә-sә-nog´rә-fe) a radiologic technique in which deep structures of the body are visualized by recording the reflections (echoes) of ultrasonic waves directed into the tissues. Frequencies in the range of one to ten million hertz are used. The lower frequencies provide a greater depth of pen...

ultrasound
(ul´trә-sound) sound waves with a frequency greater than 20,000 Hz; used in medicine in the technique of ultrasonography. ultrasonography. a mechanical and thermal physical modality that uses sound waves of a frequency of approximately 1 million Hz for the treatment of soft tissue injury. It ...

ultrastructure
(ul´trә-struk″chәr) the structure visible only under the ultramicroscope and electron microscope.

ultraviolet
(ul″trә-vi´ә-lәt) denoting electromagnetic radiation of wavelength shorter than that of the violet end of the spectrum, having wavelengths of 4–400 nanometers. ultraviolet A(UVA) ultraviolet radiation with wavelengths between 320 and 4...

ultraviolet keratitis
actinic keratitis.

ultraviolet lamp
sun lamp.

ultraviolet light
see ultraviolet rays.

ultraviolet radiation
the portion of the spectrum of electromagnetic radiation of wavelengths between 0.39 and 0.18 μm; see also ultraviolet rays.

ultraviolet rays
electromagnetic radiation beyond the violet end of the visible spectrum. These rays are produced by the sun but are mostly absorbed by particles of dust and smoke in the earth's atmosphere; they can also be produced by so-called sun lamps. They are not visible to humans, and can produce sunburn or affect skin pigmentation to ca...

ultraviolet therapy
the use of ultraviolet radiation in treatment of diseases, particularly those affecting the skin. Among the diseases that respond to this form of therapy are acne vulgaris, psoriasis, and external ulcers. See also PUVA therapy and photochemotherapy.

Ultzmann test
(for bile pigments) to 10 mL of the urine to be tested add 3 or 4 mL of a 1:3 solution of potassium hydroxide, and an excess of hydrochloric acid; bile pigments will cause an emerald-green coloration.

umbau zones
Looser transformation zones.

umbilical
(әm-bil´ĭ-kәl) pertaining to the umbilicus.

umbilical artery
origin, internal iliac artery; branches, artery of ductus deferens and superior vesical arteries; distribution, ductus deferens, seminal vesicles, testes, urinary bladder, ureter.

umbilical cord
the structure that connects the fetus and placenta; it is the lifeline of the fetus in the uterus throughout pregnancy. About two weeks after conception, the umbilical cord and the placenta are sufficiently developed to begin their functions. Through two arteries and a vein in the cord, nourishment and oxygen pass from th...

umbilical fistula
an abnormal passage communicating with the intestine or urachus at the umbilicus.

umbilical hernia
a type of abdominal hernia in which abdominal contents protrude through the abdominal wall at the umbilicus; the abdominal wall defect and the protruding intestine are covered with skin and subcutaneous tissue. This usually is a congenital condition, but it can also occur as a complication of pregnancy or a surgical incision. C...

umbilical region
the abdominal region that is most central in location, surrounding the umbilicus; it is bounded laterally by the two lateral regions, superiorly by the epigastric region, and inferiorly by the hypogastric region.

umbilical ring
the orifice in the abdominal wall of the fetus for transmission of the umbilical vein and arteries.

umbilical veins
the two veins (left umbilical vein and right umbilical vein) that carry blood from the placenta to the sinus venosus of the heart in the early embryo; the right later degenerates, leaving the left as a single umbilical vein which carries the blood from the placenta to the ductus venosus.

umbilical vesicle
the pear-shaped expansion of the mammalian yolk sac growing out into the cavity of the chorion, joined to the midgut by the yolk stalk.

umbilicated
(әm-bil´ĭ-kāt″әd) marked by depressed spots resembling the umbilicus.

umbilication
(әm-bil″ĭ-ka´shәn) a depression resembling the umbilicus.

umbilicus
(әm-bil´ĭ-kәs) the (usually) depressed scar marking the site where the umbilical cord entered the fetus; called also navel.

umbo
(um´bo) Latin word meaning rounded elevation; a term used in anatomy. specifically, the slight projection at the center of the outer surface of the tympanic membrane.

umbra
(um´brә) the part of a shadow in which there is no light from any light source. a sharp appearance to the edges of a structure on a radiograph.

unarmed tapeworm
Taenia saginata.

uncal artery
a branch of the internal carotid, or rarely the middle cerebral, artery; it supplies the uncus.

uncal herniation
transtentorial herniation.

unciform
(un´sĭ-form) uncinate (def. 1).

unciform bone
hamate bone.

uncinarial dermatitis
ground itch.

uncinate
(un´sĭ-nāt) shaped like a hook; see also hamate. Called also unciform. relating to or affecting the uncinate gyrus.

uncinate bone
hamate bone.

uncinate gyrus
uncus.

uncinate process
any hooklike process, as of vertebrae, the lacrimal bone, or the pancreas.

uncombable hair syndrome
an abnormality of the hair inherited as an autosomal dominant trait, in which the individual hairs are triangular in cross section, with a longitudinal groove; the hair has a spun-glass appearance and is arranged in bundles that stand out in different directions. Called also pili canaliculi, pili trianguli et canaliculi, ...

unconditioned reflex
unconditioned response an unlearned reflex or response; one that occurs naturally, in contrast to a conditioned response.

unconditioned stimulus
any stimulus that naturally evokes a specific response; see also conditioning.

unconjugated hyperbilirubinemia
that due to excessive bilirubin production (hemolysis), to defective clearance of bilirubin from the blood by the liver, or to defective conjugation by the liver; it includes hemolytic states, Crigler-Najjar syndrome, Gilbert syndrome, and neonatal hyperbilirubinemia.

unconscious
(әn-kon´shәs) insensible; incapable of responding to sensory stimuli and of having subjective experiences. the part of the mind that is not readily accessible to conscious awareness by ordinary means but whose existence may be manifested in symptom formation, in dreams, or under the influence o...

unconsciousness
(un-kon´shus-nes) an abnormal state of lack of response to sensory stimuli, resulting from injury, illness, shock, or some other bodily disorder. A brief loss of consciousness from which the person recovers spontaneously or with slight help is called syncope or faint. Deep, prolonged unconsciousness is known as coma. See also...

uncoupling protein
a protein that occurs in the inner membrane of the mitochondria of brown adipose tissue, important in nonshivering thermogenesis; it dissipates the proton gradient created by the respiratory chain, thus uncoupling oxidation from phosphorylation so that production of heat occurs instead of phosphorylation of ADP to ATP. Ca...

uncovertebral
(ung″ko-vur´tә-brәl) pertaining to the uncinate processes of a vertebra.

unction
(ungk´shәn) ointment. inunction.

unctuous
(ungk´choo-әs) greasy or oily.

uncus
(ung´kәs) hook. the medially curved anterior part of the parahippocampal gyrus. adj., un´cal., adj.

undecylenic acid
(un″des-әl-en´ik) an unsaturated fatty acid, used topically, in ointment or powder form, as an antifungal agent.

undercutting
(un´der-kut″ing) the effect of scatter on a radiographic image, caused when an unattenuated x-ray beam strikes the film screen detector.

undermining burrowing ulcer
progressive synergistic gangrene. Meleney ulcer (def. 1).

Underwood disease
(un´dәr-wood) sclerema.

undescended testis
a testis in the normal pathway of descent but failing to descend into the scrotum; see also cryptorchidism. Called also cryptorchid or retained testis. cryptorchidism.

undifferentiated
(әn-dif″әr-en´she-āt-әd) anaplastic. not distinguished on the basis of differences.

undifferentiated cell leukemia
acute undifferentiated leukemia.

undifferentiated lymphoma
a type of malignant lymphoma composed of undifferentiated cells (cells not showing morphologic evidence of maturation toward lymphocytes or macrophages), which vary in size and may include bizarre giant forms.

undifferentiated schizophrenia
a type characterized by prominent psychotic symptoms such as delusions, hallucinations, incoherence, or grossly disorganized behavior, but that cannot be classified as one of other types.

undifferentiation
(un″dif-әr-en″she-a´shәn) anaplasia.

undoing
(un-doo´ing) a defense mechanism aimed at negating or atoning for some disapproved act or impulse by doing something that is somehow opposite to that feared; this is most often seen in the rituals done by someone with obsessive-compulsive disorder.

undulant fever
brucellosis.

undulation
(un´jә-) (un″dyә-la´shәn) a wavelike motion in any medium; a vibration.

unequal twins
conjoined twins of which one is incompletely developed.

unerupted tooth
one that has failed to erupt; in some persons this happens with several permanent teeth. See also embedded tooth and impacted tooth.

ungual
(ung´gwәl) pertaining to the nails.

unguent
(ung´gwәnt) ointment.

unguiculate
(әng-gwik´u-lāt) having claws. clawlike.

unguis
(ung´gwis) pl. un´gues Latin word meaning nail (def. 2).

unheated serum reagin test
a modification of the VDRL test using unheated serum, used primarily for screening. Called also USR test.

uniaxial
(u″ne-ak´se-әl) having only one axis. developed in an axial direction only.

unicameral
(u″nĭ-kam´әr-әl) having only one cavity or compartment.

unicameral bone cyst
simple bone cyst.

unicellular
(u″nĭ-sel´u-lәr) made up of a single cell, as the bacteria.

unicellular gland
a single cell that functions as a gland, such as a goblet cell.

unicornuate uterus
one with a single horn, or cornu.

unifascicular block
impairment of conduction in the right bundle branch or in either the anterior or posterior limb of the left bundle branch. See also fascicular block.

uniform donor card
a document carried by an individual giving permission for the donation of organs in case of death.

uniglandular
(u″nĭ-glan´du-lәr) affecting only one gland.

unigravida
(u″nĭ-grav´ĭ-dә) primigravida.

unilateral
(u″nĭ-lat´әr-әl) affecting only one side.

unilateral emphysema
pulmonary emphysema affecting only one lung; it may be either congenital, such as from defects in circulation, or acquired, such as in Swyer-James syndrome.

unilateral hermaphroditism
presence of gonadal tissue typical of both sexes on one side and of only an ovary or a testis on the other.

unilocular
(u″nĭ-lok´u-lәr) having only one loculus or compartment; monolocular.

unilocular hydatid disease
infection with the larval forms (hydatid cysts) of Echinococcus granulosus, characterized by the formation of unilocular single or multiple expanding cysts; as the cysts expand they may give rise to symptoms of space-occupying lesions in the tissues or organs affected.

uninephrectomy
(u″nĭ-nә-frek´tә-me) surgical removal of a single kidney.

uninhibited neurogenic bladder
neurogenic bladder due to a lesion in the upper motoneurons with subtotal interruption of corticospinal pathways, marked by urgency, frequent involuntary urination, and a small volume threshold of activity. It is associated with stroke syndrome and multiple sclerosis.

uninterrupted suture
continuous suture.

uninucleated
(u″nĭ-noo´kle-āt″әd) mononuclear.