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Medical Dictionary - Dictionary of Medicine and Human Biology


Medical Dictionary


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plasmogen (plaz′mo-jen)
SYN: protoplasm. [plasmo- + G. -gen, producing]

plasmokinin (plaz-mo-ki′nin)
Obsolete term for factor VIII.

plasmolemma (plaz-mo-lem′a)
SYN: cell membrane.

plasmolysis (plaz-mol′i-sis)
Shrinking of plant cells by osmotic loss of cytoplasmic water. SYN: protoplasmolysis. [plasmo- + G. lysis, dissolution]

plasmolytic (plaz-mo-lit′ik)
Relating to plasmolysis.

plasmolyze (plaz′mo-liz)
To subject to plasmolysis.

plasmon (plaz′mon)
The total of the extrachromosomal genetic determinants of the eukaryotic cell cytoplasm. SYN: plasmotype. [cytoplasm + -on]

plasmorrhexis (plaz-mo-rek′sis)
The splitting open of a cell from the pressure of the protoplasm.

plasmoschisis (plaz-mos′ki-sis)
The splitting of protoplasm into fragments. [plasmo- + G. schisis, a cleaving]

plasmosin (plaz′mo-sin)
A highly viscous substance in cytoplasm containing discrete fibers of considerable length; a nucleoprotein regarded as the structural foundation of the cell.

plasmotomy (plaz-mot′o-me)
A form of mitosis in multinuclear protozoan cells in which the cytoplasm divides into two or more masses, later reproducing, in some cases by sporulation. [plasmo- + G. tome, incision]

plasmotropic (plaz-mo-trop′ik)
Pertaining to or manifesting plasmotropism.

plasmotropism (plaz-mot′ro-pizm)
A condition in which the bone marrow, spleen, and liver are sites for the destruction of the erythrocytes, as opposed to destruction in the circulating blood. [plasmo- + G. trope, a turning]

plasmotype (plaz′mo-tip)
SYN: plasmon.

plasmozyme (plaz′mo-zim)
Obsolete term for prothrombin. [plasmo- + G. zyme, leaven]

plastein (plas′te-in)
1. Insoluble polypeptide formed through the random condensation of amino acids or peptides under the catalytic influence of a proteinase-like chymotrypsin; molecular weights as high as 500,000 are reported. 2. A gel that is formed on treating a partial hydrolysate of a protein with an endopeptidase.

plaster
1. A solid preparation that can be spread when heated and that becomes adhesive at the temperature of the body; used to keep the edges of a wound in apposition, to protect raw surfaces, and, when medicated, to redden or blister the skin, as in mustard p., or to apply drugs to the surface to obtain their systemic effects. 2. In dentistry, colloquialism for plas′ter of Paris. [L. emplastrum; G. emplastron, p. or mold] p. of Paris exsiccated calcium sulfate from which the water of crystallization has been expelled by heat, but which, when mixed with water, will form a paste which subsequently sets.

plastic (plas′tik)
1. Capable of being formed or molded. 2. A material that can be shaped by pressure or heat to the form of a cavity or mold. [G. plastikos, relating to molding] Bingham p. a material that, in the idealized case, does not flow until a critical stress (yield stress) is exceeded, and then flows at a rate proportional to the excess of stress over the yield stress; real materials probably only approach this ideal model. modeling p. a thermoplastic material usually composed of gum damar and prepared chalk, used especially for making dental impressions. SYN: impression compound, modeling composition, modeling compound.

plasticity (plas-tis′i-te)
The capability of being formed or molded; the quality of being plastic.

plastid (plas′tid)
1. One of the differentiated structures in cytoplasm of plant cells where photosynthesis or other cellular processes are carried on; plasid contain DNA and are self-replicating. SYN: trophoplast. 2. One of the granules of foreign or differentiated matter, food particles, fat, waste material, chromatophores, trichocysts, etc., in cells. 3. A self-duplicating viruslike particle that multiplies within a host cell, such as κ particles in certain paramecia. [G. plastos, formed, + -id] blood p. any basic, morphologic unit in the biologic composition of blood, e.g., an erythrocyte.

plastochromanol-3, plastochromanol E3 (plas-to-kro′man-ol)
A γ-tocotrienol. See tocotrienol.

plastochromenol-8 (plas-to-kro′men-ol)
The chromenol (isomeric) form of plastoquinone-9. SYN: solanochromene.

plastogamy (plas-tog′a-me)
SYN: plasmogamy.

plastoquinone (PQ) (plas-to-kwin′on, -kwi′non)
2,3-Dimethyl-1,4-benzoquinone with a multiprenyl side chain;a trivial name sometimes used for p.-9.

plastoquinone-9 (PQ-9) , plastoquinone E9
2,3-Dimethyl-6-nonaprenyl-1,4-benzoquinone;one of a group of vitamins E and K and coenzymes Q; the isomeric form is plastochromenol-8; a participant in photosynthetic electron transport.

plastron
The sternum with costal cartilages attached. [Fr. a breastplate]

-plasty
Molding, shaping or the result thereof, as of a surgical procedure. [G. plastos, formed, shaped]

-plasty (plas′te)
Surgical procedure for repair of a defect or restoration of form and/or function of a part. [G. plastos, formed]

plate (plat)
1. [TA] In anatomy, a thin, relative flat, structure. SYN: lamina [TA] . 2. A metal bar perforated for screws applied to a fractured bone to maintain the ends in apposition. 3. The agar layer within a Petri dish or similar vessel. 4. To form a very thin layer of a bacterial culture by streaking it on the surface of an agar p. (usually within a Petri dish) to isolate individual organisms from which a colonial clone will develop. 5. Any one of the horizontal perforated plates that comprise the fractionating component of a column in fractional distillation (or, the theoretic equivalent of such a p.). [O.Fr. plat, a flat object, fr. G. platys, flat, broad] alar p. of neural tube SYN: alar lamina of neural tube. amorphous selenium p. SYN: selenium p.. anal p. the anal portion of the cloacal p.. axial p. the primitive streak of an embryo. basal p. of neural tube SYN: basal lamina of neural tube. base p. baseplate. blood p. obsolete term for platelet. bone p. a metal bar with perforations for the insertion of screws; used to immobilize fractured segments. buttress p. a metal p. used to support the internal fixation of a fracture and prevent displacement. cardiogenic p. the thickened layer of splanchnic mesoderm from which the cardiopericardial primordia of very young embryos are derived. cell p. a non-cellulose structure that is the precursor to the cell wall; it forms between daughter nuclei during mitosis. chorionic p. that portion of the chorionic wall in the region of its uterine attachment; it consists of the mesoderm that lines the chorionic vesicle and, on the maternal side, of the trophoblast that lines the intervillous spaces; in the last half of gestation, the mesodermal connective tissue is largely replaced by fibrinoid material, and the amnionic membrane is adherent to the fetal side of the p.. cloacal p. a p., composed of a layer of cloacal endoderm in contact with a layer of proctodeal ectoderm, which subsequently becomes the cloacal membrane and ruptures, forming the anal and urogenital openings of the embryo. compression p. a p. for internal fracture fixation with screw holes so designed that insertion of screws draws bone fragments more firmly together. cribriform p. of ethmoid bone [TA] a horizontal lamina from which are suspended the labyrinth, on either side, and the lamina perpendicularis in the center; it fits into the ethmoidal notch of the frontal bone and supports the olfactory lobes of the cerebrum, being pierced with numerous openings for the passage of the olfactory nerves. SYN: lamina cribrosa ossis ethmoidalis [TA] , cribrum, sieve bone, sieve p.. cutis p. SYN: dermatome (2) . dorsal p. of neural tube SYN: roof p.. dorsolateral p. of neural tube SYN: alar lamina of neural tube. end p. endplate. epiphysial p. [TA] the disc of cartilage between the metaphysis and the epiphysis of an immature long bone permitting growth in length. SYN: lamina epiphysialis [TA] , growth p.. equatorial p. the assembly of chromosomes in mitosis. ethmovomerine p. the central portion of the ethmoid bone, forming a distinct element at birth. flat p. jargon for plain film. floor p. ventral midline thinning of the developing neural tube, a continuity between the basal laminae of either side; opposite of roof p.. SYN: ventral p.. foot p. footplate. frontal p. in the fetus, a cartilage p. between the lateral parts of ethmoid cartilage and the developing sphenoid bone. growth p. SYN: epiphysial p.. horizontal p. of palatine bone [TA] the part of the palatine bone that forms the posterior part (approximately one-third) of the bony palate. SYN: lamina horizontalis ossis palatini [TA] . Kühne p. the endplate of a motor nerve fiber in a muscle spindle. lateral p. a nonsegmented mass of mesoderm on the lateral periphery of the embryonic disk; it forms the somatopleuric (parietal) and splanchnopleuric (visceral) mesoderm. lateral cartilaginous p. SYN: lateral lamina of cartilage of pharyngotympanic (auditory) tube. lateral p. of cartilaginous auditory tube SYN: lateral lamina of cartilage of pharyngotympanic (auditory) tube. lateral pterygoid p. [TA] the larger and more lateral of the two bony plates extending downward from the point of union of the body and greater wing of the sphenoid bone on either side; forms medial wall of infratemporal fossa and gives origin to pterygoi muscles. SYN: lamina lateralis processus pterygoidei [TA] , lateral p. of pterygoid process. lateral p. of pterygoid process SYN: lateral pterygoid p.. lingual p. SYN: linguoplate. medial cartilaginous p. SYN: medial lamina of cartilage of pharyngotympanic (auditory) tube. medial p. of cartilaginous auditory tube SYN: medial lamina of cartilage of pharyngotympanic (auditory) tube. medial pterygoid p. [TA] the smaller and more medial of the two bony plates extending downward from the point of union of the body and greater wing of the sphenoid bone on either side, ending inferiorly in the pterygoid hamulus. SYN: lamina medialis processus pterygoidei [TA] , medial p. of pterygoid process. medial p. of pterygoid process SYN: medial pterygoid p.. medullary p. SYN: neural p.. p. of modiolus SYN: lamina of modiolus of cochlea. motor p. a motor endplate. muscle p. SYN: myotome (2) . nail p. SYN: nail (1) . neural p. the neuroectodermal region of the early embryo's dorsal surface that in later development is transformed into the neural tube and neural crest. SYN: medullary p.. neutralization p. a metal p. used for the internal fixation of a bone fracture to neutralize the forces producing displacement. notochordal p. the sheet of notochordal cells that are intercalated in the endodermal roof of the primitive yolk sac. SEE ALSO: head process. oral p. a circumscribed area of fusion of foregut endoderm and stomodeal ectoderm in the embryo that breaks through early in development to establish the oral opening. SEE ALSO: buccopharyngeal membrane. orbital p. SYN: orbital p. of ethmoid bone. orbital p. of ethmoid bone [TA] a thin p. of ethmoid bone forming part of the medial wall of the orbit and the lateral wall for the ethmoidal labyrinth. SYN: lamina orbitalis ossis ethmoidalis [TA] , lamina papyracea, orbital lamina of ethmoid bone, orbital layer of ethmoid bone, orbital p., paper p., papyraceous p.. palatal p. a partial denture major connector that has an anteroposterior width in excess of two maxillary premolars. palmar plates SYN: palmar ligaments of metacarpophalangeal joints, under ligament. paper p., papyraceous p. SYN: orbital p. of ethmoid bone. parachordal p. the cartilage primordia of the base of the skull situated on either side of the cephalic part of the notochord. parietal p. 1. the outer of the two layers of the lateral p. mesoderm, which becomes associated with the ectoderm; the ectoderm and parietal p. mesoderm together constitute the somatopleure; 2. the lamina of the ethmoid bone that forms part of the nasal septum. perpendicular p. [TA] flat portion of a bone that lies within or closely approximates a vertical plane. See perpendicular p. of ethmoid bone, perpendicular p. of palatine bone. SYN: lamina perpendicularis [TA] , pars perpendicularis, vertical p.. perpendicular p. of ethmoid bone [TA] a thin p. of bone projecting downward from the crista galli of the ethmoid; it forms part of the nasal septum. SYN: lamina perpendicularis ossis ethmoidalis [TA] . perpendicular p. of palatine bone [TA] the part of the palatine bone that extends vertically upward from the horizontal lamina; it forms part of the lateral wall of the nasal cavity. SYN: lamina perpendicularis ossis palatini [TA] . phosphor p. the coated p. used in place of a radiographic film cassette in a computed radiography system. SEE ALSO: selenium p., amorphous silicon. polar plates condensed platelike bodies at the ends of the spindle during mitosis of certain types of cells. prechordal p. SYN: prochordal p.. prochordal p. a small area immediately rostral to the cephalic tip of the notochord where ectoderm and endoderm are in contact; when turned under the growing head, it forms the buceopharyngeal membrane. SEE ALSO: oral p.. SYN: prechordal p.. pterygoid plates lateral pterygoid p., medial pterygoid p.. quadrigeminal p. SYN: lamina of mesencephalic tectum. roof p. the thin layer of the embryonic neural tube connecting the alar plates dorsally. SYN: dorsal p. of neural tube. secondary spiral p. SYN: secondary spiral lamina. segmental p. SYN: segmental zone. selenium p. a radiation-sensitive material used in directed digital radiography. SEE ALSO: digital radiography. SYN: amorphous selenium p.. sieve p. SYN: cribriform p. of ethmoid bone. spiral p. SYN: osseous spiral lamina. stigmal plates area in arthropod larvae where the tracheal system opens to the outside; morphology of this area is used to identify various arthropod larvae. SEE ALSO: spiracle. suction p. in dentistry, a p. held in place by atmospheric pressure. tarsal plates See superior tarsus, inferior tarsus. tectal p. [TA] SYN: lamina of mesencephalic tectum. terminal p. SYN: lamina terminalis of cerebrum. tympanic p. of temporal bone [TA] the bony p. forming the greater part of the anterior wall of the bony part of the external acoustic meatus and the tympanic cavity, and the posterior wall of the mandibular fossa. SYN: pars tympanica ossis temporalis [TA] , tympanic part of temporal bone. urethral p. the endodermal lining of the urethral groove that forms the lining of the penile urethra. ventral p. SYN: floor p.. ventral p. of neural tube SYN: basal lamina of neural tube. vertical p. SYN: perpendicular p.. visceral p. the inner of the two layers of the lateral mesoderm; the splanchnic mesoderm that becomes associated with the endoderm and together with it constitutes the splanchnopleure. wing p. SYN: alar lamina of neural tube.

Plateau
Joseph Antoine Ferdinand, Belgian physicist, 1801–1883. See P.-Talbot law.

plateau (pla-to)
A flat elevated segment of a graphic record. [Fr.] ventricular p. a level diastolic portion of the intraventricular blood pressure curve, representing graphically an equilibrium or final state of filling.

platelet (plat′let)
An irregularly shaped disklike cytoplasmic fragment of a megakaryocyte that is shed in the marrow sinus and subsequently found in the peripheral blood, where it functions in clotting. A p. contains granules in the central part (granulomere) and, peripherally, clear protoplasm (hyalomere), but no definite nucleus; is about one-third to one-half the size of an erythrocyte; and contains no hemoglobin. SYN: Bizzozero corpuscle, blood disk, elementary bodies (2) , elementary particle (1) , third corpuscle, thrombocyte, thromboplastid (1) , Zimmermann corpuscle. [see plate]

plateletpheresis (plat′let-fe-re′sis)
Removal of blood from a donor with replacement of all blood components except platelets. [platelet + G. aphairesis, a withdrawal]

plating (plat′ing)
1. Sowing of bacteria on a solid medium in a Petri dish or similar container; the making of a plate culture. 2. Application of a metal bar to keep the ends of a fractured bone in apposition. 3. Electrolytic deposition of a metal. compression p. a technique for internal fixation using a compression plate. replica p. a procedure for producing an accurate copy of bacterial colonies from one agar plate to another.

platinic (pla-tin′ik)
Relating to platinum; denoting a compound containing platinum in its higher valency.

platinous (plat′i-nus)
Relating to platinum; denoting a compound containing platinum in its lower valency.

platinum (Pt) (plat′i-num)
A metallic element, atomic no. 78, atomic wt. 195.08, used for making small parts for chemical apparatus because of its resistance to acids; in powdered form (p. black), it is an important catalyst in hydrogenation. Some of its salts have been used in the treatment of syphilis. A derivative, cisplatin, is used as an antineoplastic agent. [Mod. L., originally platina, fr. Sp. plata, silver]

platinum foil
Pure platinum rolled into extremely thin sheets; its high fusing point makes it suitable as a matrix for various soldering procedures in dentistry and also suitable for providing internal form to porcelain restorations during their fabrication.

platinum group
A group of six amphoteric elements: iridium, osmium, palladium, platinum, rhodium, and ruthenium.

Platt
Sir Harry, British surgeon, *1886. See Putti-P. operation, Putti-P. procedure.

platy-
Width; flatness. [G. platys, flat, broad]

platybasia (plat-i-ba′se-a)
A developmental anomaly of the skull or an acquired softening of the skull bones so that the floor of the posterior cranial fossa bulges upward in the region about the foramen magnum. SYN: basilar invagination. [platy- + G. basis, ground]

platycephaly (plat′i-sef′a-le)
Flatness of the skull, a condition in which the vertical cranial index is below 70. SYN: platycrania. [platy- + G. kephale, head]

platycnemia (plat′ik-ne′me-a)
A condition in which the tibia is abnormally broad and flat. SYN: platycnemism. [platy- + G. kneme, leg]

platycnemic (plat′ik-ne′mik)
Relating to or marked by platycnemia.

platycnemism (plat′ik-ne′mizm)
SYN: platycnemia.

platycrania (plat′i-kra′ne-a)
SYN: platycephaly. [platy- + G. kranion, skull]

platycyte (plat′i-sit)
Obsolete term for a relatively small giant cell sometimes formed in tubercles. [platy- + G. kytos, cell]

platyglossal (plat′i-glos′al)
Having a broad, flattened tongue. [platy- + G. glossa, tongue]

platyhelminth (plat-i-hel′minth)
Common name for any flatworm of the phylum Platyhelminthes; any cestode (tapeworm) or trematode (fluke). [platy- + G. helmins, worm]

Platyhelminthes (plat′i-hel-min′thez)
A phylum of flatworms that are bilaterally symmetric, flattened, and acelomate. There is no digestive tract in some platyhelminths (Cestoda), or the gut may be incomplete (without an anus), as in the Trematoda; most of the forms are hermaphroditic. There are three major classes, but the parasitic species of medical and veterinary importance are in the subclass Cestoda (the true tapeworms) of the class Cestoidea, and in the subclass Digenea (the digenetic flukes) of the class Trematoda.

platyhieric (plat-i-hi-er′ik)
Having a broad sacrum. [platy- + G. heiron, sacrum]

platymeric (plat-i-me′rik, -mer′ik)
Having a broad femur. [platy- + G. meros, thigh]

platymorphia (plat′i-mor′fe-a)
Having a flat shape; term denoting an eye with a short anteroposterior axis. [platy- + G. morphe, shape]

platyopia (plat′i-o′pe-a)
Broadness of the face; denoting a condition in which the orbitonasal index is less than 107.5. [platy- + G. ops, eye, face]

platyopic (plat′i-op′ik, -o′pik)
Relating to or characterized by platyopia.

platypellic (plat-i-pel′ik)
Having a broad pelvis, with an index below 90°. See p. pelvis. SYN: platypelloid. [platy- + G. pellis, bowl (pelvis)]

platypelloid (plat-e-pel′oyd)
SYN: platypellic.

platypnea (pla-tip′ne-a)
Difficulty in breathing when erect, relieved by recumbency. Cf.:orthopnea. [platy- + G. pnoe, a breathing]

platyrrhine (plat′i-rin)
1. Characterized by a nose of large width in proportion to its length. 2. Denoting a skull with a nasal index between 53 and 58. [platy- + G. rhis, nose]

platyrrhiny (plat′i-ri-ne)
A condition in which the nose is wide in proportion to its length.

platysma, pl .platysmasplatysmata (pla-tiz′ma, -tiz′ma-ta) [TA]
SYN: p. (muscle). [G. p., a flatplate]

platyspondylia, platyspondylisis (plat-i-spon-dil′e-a, plat′i-spon-dil′i-sis)
Flatness of the bodies of the vertebrae. [platy- + G. spondylos, vertebra]

platystencephaly (pla-tis′ten-sef′a-le)
Extreme width of the skull in the occipital region, with narrowing anteriorly and prognathism. [G. platystos, widest, superl. of platys, wide, + enkephale, brain]




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