base (bas)

1. The lower part or bottom; the part of a pyramidal or cone-shaped structure opposite the apex; the foundation.basis [NA], 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.alkali (2); See also Broonsted b., Lewis b. 4. Nitrogen-containing organic compounds (e.g., purines, pyrimidines, amines, alkaloids, ptomaines) that act as Broonsted b.'s. 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.
aldehyde base obsolete term for an imide.
anterior cranial b. anterior cranial fossa
b. of arytenoid cartilage 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.basis cartilaginis arytenoideae [NA];
b. of bladder fundus of urinary bladder
b. of brain the inferior surface of the brain visible when seen from below.facies inferior cerebri [NA], basis cerebri, inferior cerebral surface;
Broonsted 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 base (3).
cavity preparation b. 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.cavity preparation b;
b. of cochlea the enlarged part of the cochlea that is directed posteriorly and medially and lies close to the internal acoustic meatus.basis cochleae [NA];
cranial b. 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.saddle (2);
external b. of skull external aspect of the b. of skullnorma basilaris [NA], basis cranii externa [NA], norma inferior, norma ventralis;
b. of heart 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.basis cordis [NA];
hexone b.'s , histone b.'s the a-amino acids 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 body of hyoid bone
internal b. of skull the interior aspect of the skull b. on which the brain rests; the floor of the cranial cavity. See also b. of skull.basis cranii interna [NA];
Lewis b. a b. that is an electron-pair donor.
b. of lung the lower concave part of the lung that rests upon the convexity of the diaphragm.basis pulmonis [NA];
b. of mandible the rounded inferior border of the body of the mandible.basis mandibulae [NA];
b. of metacarpal bone the expanded proximal extremity of each metacarpal that articulates with one or more of the distal row of carpal bones.basis ossis metacarpalis [NA];
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 bone the expanded proximal extremity of each metatarsal bone; it articulates with one or more of the distal row of tarsal bones.basis ossis metatarsalis [NA];
methamphetamine b. a form of methamphetamine that can be readily volatilized.
b. of modiolus 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.basis modioli [NA];
nucleic acid b. a purine or pyrimidine; found in naturally occurring nucleic acids such as DNA.
nucleinic b. obsolete term for purine.
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. lin-containing b.'s will absorb water (and dissolved materials) and form water-in-oil type emulsions. Water soluble (washable) b.'s are often derived from polymers of ethylene glycol (PEGS); these will absorb water and ingredients dissolved in the water. Ointment b.'s 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 the superior border of the patella to which the tendon of the rectus femoris attaches.basis patellae [NA];
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.basis phalangis [NA];
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.pressor amine, pressor substance;
b. of prostate the broad upper surface of the prostate contiguous with the bladder wall.basis prostatae [NA];
purine b. a purine.
pyrimidine b. a pyrimidine.
record b. baseplate
b. of renal pyramid the outer broad part of a renal pyramid that lies next to the cortex.basis pyramidis renis [NA];
b. of sacrum 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.basis ossis sacri [NA];
Schiff b. R-CH=N-R´;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. aldimine;
shellac b. a resinous wafer adapted to maxillary or mandibular casts to form baseplates.
b. of skull 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). See also internal b. of skull.basis cranii, cranial b;
b. of stapes the flat portion of the stapes that fits in the oval window.basis stapedis [NA], footplate (1), foot-plate;
temporary b. baseplate
tinted denture b. a denture b. that simulates the coloring and shading of natural oral tissues.
b. of tongue 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. baseplate
vegetable b. 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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