1. The lower part or bottom; the part of a pyramidal or conical structure opposite the apex; the foundation. SYN: basis [TA], basement (1). 2. In pharmacy, the chief ingredient of a mixture. 3. In chemistry, an electropositive element (cation) that unites with an anion to form a salt; a compound ionizing to yield hydroxyl ion. SYN: alkali (2). SEE ALSO: Brøonsted b., Lewis b.. 4. Nitrogen-containing organic compounds ( e.g., purines, pyrimidines, amines, alkaloids, ptomaines) that act as Brøonsted bases. 5. Cations, or substances forming cations. [L. and G. basis]
- acrylic resin b. a form made of acrylic resin molded to conform to the tissues of the alveolar process and used to support the teeth of a prosthesis.
- anterior cranial b. SYN: anterior cranial fossa.
- b. of arytenoid cartilage [TA] the part of the arytenoid cartilage that articulates with the cricoid cartilage and from which the muscular process extends laterally and the vocal process projects anteriorly. SYN: basis cartilaginis arytenoideae [TA].
- b. of bladder SYN: fundus of bladder.
- b. of brain the inferior surface of the brain, primarily the brainstem, when seen from below; commonly extended to include the inferior surface of the adjacent parts of the cerebral hemisphere. SYN: basis cerebri, inferior cerebral surface.
- Brøonsted b. any molecule or ion that combines with a proton; e.g., OH, CN, NH3; this definition replaces the older and more limited concepts of b. (3).
- cavity preparation b. SYN: cement b..
- cement b. in dentistry, a layer of dental cement, sometimes medicated, that is placed in the deep portion of a cavity preparation to protect the pulp, reduce the bulk of a metallic restoration, or eliminate undercuts. SYN: cavity preparation b..
- b. of cochlea [TA] the enlarged part of the cochlea that is directed posteriorly and medially and lies close to the internal acoustic meatus. SYN: basis cochleae [TA].
- cranial b. [TA] the sloping floor of the cranial cavity. It comprises both the external b. of skull (external view) and the internal b. of skull (internal view). SYN: basis cranii [TA], basicranium, b. of skull.
- denture b. 1. that part of a denture which rests on the oral mucosa and to which teeth are attached; 2. that part of a complete or partial denture which rests upon the basal seat and to which teeth are attached. SYN: saddle (2).
- external b. of skull SYN: external surface of cranial b..
- b. of heart [TA] that part of the heart that lies opposite the apex, formed mainly by the left atrium but to a small extent by the posterior part of the right atrium; it is directed backward and to the right and is separated from the vertebral column by the esophagus and aorta. SYN: basis cordis [TA].
- hexone bases, histone bases the α-amino acid s arginine, histidine, and lysine, which are basic by virtue of the presence in the side chains of a guanidine, imidazole, and amine group, respectively; the term “hexone” is a misnomer since histidine does not have six carbons.
- b. of hyoid bone SYN: body of hyoid bone.
- internal b. of skull SYN: internal surface of cranial b.. SEE ALSO: cranial b..
- Lewis b. a b. that is an electron-pair donor.
- b. of lung [TA] the lower concave part of the lung that rests upon the convexity of the diaphragm. SYN: basis pulmonis [TA].
- b. of mandible [TA] the rounded inferior border of the body of the mandible. SYN: basis mandibulae [TA].
- b. of metacarpal [TA] the expanded proximal extremity of each metacarpal that articulates with one or more of the distal row of carpal bones. SYN: basis ossis metacarpalis [TA].
- metal b. a metallic portion of a denture b. forming a part of the wall of the basal surface of the denture; it serves as a b. for the attachment of the plastic (resin) part of the denture and the teeth.
- b. of metatarsal [TA] the expanded proximal extremity of each metatarsal bone; it articulates with one or more of the distal row of tarsal bones. SYN: basis ossis metatarsalis [TA].
- methamphetamine b. a form of methamphetamine that can be readily volatilized.
- b. of modiolus of cochlea [TA] the part of the modiolus enclosed by the basal turn of the cochlea; it faces the lateral end of the internal acoustic meatus. See cochlear area. SYN: basis modioli cochleae [TA].
- nucleic acid b. a purine or pyrimidine; found in naturally occurring nucleic acid s such as DNA.
- ointment b. the vehicle into which active ingredients may be incorporated. Petrolatum (which may be stiffened with wax) is the most widely used greasy ointment b. and is suitable for the incorporation of oleaginous materials. Lanolin-containing bases will absorb water (and dissolved materials) and form water-in-oil type emulsions. Water soluble (washable) bases are often derived from polymers of ethylene glycol (PEGS); these will absorb water and ingredients dissolved in the water. Ointment bases are usually pharmacologically inert but may entrap water and serve to keep the skin from dying or to provide an emollient protective film.
- b. of patella [TA] the superior border of the patella to which the tendon of the rectus femoris attaches. SYN: basis patellae [TA].
- b. of phalanx the expanded proximal end of each phalanx in the hand or foot that articulates with the head of the next proximal bone in the digit. SYN: basis phalangis.
- b. of phalanx of foot [TA] proximal, concave, articulating end of the bones of the toes. SYN: basis phalangis pedis [TA].
- b. of phalanx of hand [TA] proximal, concave, articulating end of the bones of the fingers. SYN: basis phalangis manus [TA].
- pressor b. 1. one of several products of intestinal putrefaction believed to cause functional hypertension when absorbed; 2. any alkaline substance that raises blood pressure. SYN: pressor amine, pressor substance.
- b. of prostate [TA] the broad upper surface of the prostate contiguous with the bladder wall. SYN: basis prostatae [TA].
- purine b. a purine.
- record b. SYN: baseplate.
- b. of renal pyramid the outer broad part of a renal pyramid that lies next to the cortex. SYN: basis pyramidis renis.
- b. of sacrum [TA] the upper end of the sacrum that articulates with the body of the fifth lumbar vertebra in the midline and the alae on either side. SYN: basis ossis sacri [TA].
- Schiff b. condensation products of aldehydes and ketones with primary amine; the compounds are stable if there is at least one aryl group on the nitrogen or carbon. Cf.:ketimine. SYN: aldimine.
- shellac b. a resinous wafer adapted to maxillary or mandibular casts to form baseplates.
- b. of skull SYN: cranial b.. SEE ALSO: internal surface of cranial b..
- b. of stapes [TA] the flat portion of the stapes that fits in the oval window. SYN: basis stapedis [TA], footplate (1), foot-plate.
- temporary b. SYN: baseplate.
- tinted denture b. a denture b. that simulates the coloring and shading of natural oral tissues.
- b. of tongue SYN: root of tongue.
- tooth-borne b. the denture b. restoring an edentulous area which has abutment teeth at each end for support; the tissue which it covers is not used for support.
- trial b. SYN: baseplate.
- vegetable b. SYN: alkaloid.
- wobble b. the 3′ codon b. that is less strictly specified in the genetic code. SEE ALSO: wobble, wobble hypothesis.
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B27-arthritis-sacroiliitis-extra-articular features [syndrome]

* * *

base 'bās n, pl bas·es 'bā-səz
1) that portion of a bodily organ or part by which it is attached to another more central structure of the organism <the \base of the thumb>
2 a) the usu. inactive ingredient of a preparation serving as the vehicle for the active medicinal preparation <the fatty \base of an ointment>
b) the chief active ingredient of a preparation called also basis
3 a) any of various typically water-soluble and bitter tasting compounds that in solution have a pH greater than 7, are capable of reacting with an acid to form a salt, and are molecules or ions able to take up a proton from an acid or are substances able to give up an unshared pair of electrons to an acid compare ALKALI
b) any of the five purine or pyrimidine bases of DNA and RNA that include cytosine, guanine, adenine, thymine, and uracil
4) freebase
based 'bāst adj

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(bās) [L., Gr., basis] 1. the lowest part or foundation of anything; see also basis. 2. the main ingredient of a compound. 3. in chemistry, the nonacid part of a salt; a substance that combines with acids to form salts; a substance that dissociates to give hydroxide ions in aqueous solutions; a substance whose molecule or ion can combine with a proton (hydrogen ion); a substance capable of donating a pair of electrons (to an acid) for the formation of a coordinate covalent bond. 4. a unit of a removable prosthesis that supports the supplied tooth and any intermediary material and in turn receives support from the tissue of the basal seat. 5. in genetics, a nucleotide, particularly one in a nucleic acid sequence. See also base pair, under pair.

Medical dictionary. 2011.

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