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Medical Dictionary


placental (pla-sen′tal)
Relating to the placenta.

placental dysmature
Immature development of the placenta so that normal function does not occur.

Placentalia (plas-en-ta′le-a)
See Eutheria. [L. placenta]

placentation (plas-en-ta′shun)
The structural organization and mode of attachment of fetal to maternal tissues in the formation of the placenta. Types of p. are defined under placenta.

placentitis (plas-en-ti′tis)
Inflammation of the placenta.

placentoma (plas-en-to′ma)
SYN: deciduoma.

placentotherapy (pla-sen′to-thar′a-pe)
Therapeutic use of an extract of placental tissue.

Placido da Costa
Antonio, Portuguese ophthalmologist, 1848–1916. See P. disk.

placode (plak′od)
Local thickening in the embryonic ectoderm layer; the cells of the p. ordinarily constitute a primordial group from which a sense organ or ganglion develops. [G. plakodes, fr. plax, anything flat or broad, + eidos, like] auditory placodes SYN: otic placodes. epibranchial placodes ectodermal thickenings associated with the more dorsal parts of the embryonic branchial arches; their cells contribute to formation of the cranial ganglia, including those of nerves V, VII, IX, and X. lens placodes paired ectodermal placodes that become invaginated to form the embryonic lens vesicles. SYN: optic placodes. nasal placodes SYN: olfactory placodes. olfactory placodes paired ectodermal placodes that come to lie in the bottom of the olfactory pits as the pits are deepened by the growth of the surrounding medial and lateral nasal processes. SYN: nasal placodes. optic placodes SYN: lens placodes. otic placodes paired ectodermal placodes that sink below the general level of the superficial ectoderm to form the auditory vesicles. SYN: auditory placodes.

plafond (pla-fon′d)
A ceiling, especially the ceiling of the ankle joint, i.e., the articular surface of the distal end of the tibia. [Fr. ceiling]

Oblique, slanting. [G. plagios]

plagiocephalic (pla′je-o-se-fal′ik)
Relating to or marked by plagiocephaly. SYN: plagiocephalous.

plagiocephalism (pla′je-o-sef′a-lizm)
SYN: plagiocephaly.

plagiocephalous (pla′je-o-sef′a-lus)
SYN: plagiocephalic.

plagiocephaly (pla′je-o-sef′a-le)
An asymmetric craniostenosis due to premature closure of the lambdoid and coronal sutures on one side; characterized by an oblique deformity of the skull. SYN: asynclitism of the skull, plagiocephalism. [G. plagios, oblique, + kephale, head]

plague (plag)
1. Any disease of wide prevalence or of excessive mortality. 2. An acute infectious disease caused by the bacterium Yersinia pestis and marked clinically by high fever, toxemia, prostration, a petechial eruption, lymph node enlargement, and pneumonia, or hemorrhage from the mucous membranes; primarily a disease of rodents, transmitted to humans by fleas that have bitten infected animals. In humans the disease takes one of four clinical forms: bubonic p., septicemic p., pneumonic p., or ambulant p. SYN: pest, pestilence (1) , pestis. [L. plaga, a stroke, injury] ambulant p., ambulatory p. a mild form of bubonic p. characterized by symptoms such as mild fever and lymphadenitis. SYN: larval p., parapestis, pestis ambulans, pestis minor. black p. black death. bubonic p. the usual form of p. of which manifestations include inflammatory enlargement of the lymphatic glands in the groin, axillae, or other parts. SYN: glandular p., pestis bubonica, pestis fulminans, pestis major, polyadenitis maligna. glandular p. SYN: bubonic p.. hemorrhagic p. the hemorrhagic form of bubonic p.. larval p. SYN: ambulant p.. Pahvant Valley p. SYN: tularemia. pneumonic p. a rapidly progressive and frequently fatal form of p. in which there are areas of pulmonary consolidation, with chill, pain in the side, bloody expectoration, high fever, and possible human-to-human transmission. SYN: p. pneumonia, pulmonic p.. pulmonic p. SYN: pneumonic p.. septicemic p. a generally fatal form of p. in which there is an intense bacteremia with symptoms of profound toxemia. SYN: pestis siderans. sylvatic p. bubonic p. in rats and other wild animals.

plakalbumin (plak-al-bu′min)
The product of the action of subtilisin upon egg albumin, removing a hexapeptide.

plakins (pla′kinz)
Bactericidal substances similar to leucins extracted from blood platelets. [G. plax, plakos, anything flat, + -in]

See plano-.

plana (pla′na)
Plural of planum. [L.]

planchet (plan′shet)
A small, flat plate or dish used to support a sample for radioactivity determination; the sample is usually evaporated on (in) the p.. [Fr. planchette, dim. of planche, plank]

Max, German physicist and Nobel laureate, 1858–1947. See P. constant, P. theory.

plane (plan) [TA]
1. A two-dimensional flat surface. See planum. 2. An imaginary surface formed by extension of a point through any axis or two definite points, in reference especially to craniometry and to pelvimetry. SYN: planum. [L. planus, flat] Addison clinical planes a series of planes used as landmarks in thoracoabdominal topography; the trunk is divided vertically by a median p. from the upper border of the manubrium of the sternum to the pubic symphysis, by a lateral p. drawn vertically on either side through a point halfway between the anterior superior iliac spine and the median p. at the interspinal p., and by an interspinal p. passing vertically through the anterior superior iliac spine on either side; transversely the trunk is divided by a transthoracic p. passing across the thorax 3.2 cm above the lower border of the body of the sternum, by a transpyloric p. midway between the jugular notch of the sternum and the pubic symphysis, corresponding to the disk between the first and second lumbar vertebrae, and by an intertubercular p. passing through the iliac tubercles and cutting usually the fifth lumbar vertebra; the planes formed on these lines, and also on transverse planes cutting the upper edge of the manubrium and the upper edge of the pubic symphysis, constitute the clinical planes of Addison. Aeby p. in craniometry, a p. perpendicular to the median p. of the cranium, cutting the nasion and the basion. auriculoinfraorbital p. SYN: orbitomeatal p.. axial p. transverse p. at right angles to long axis of body, as in CT scanning. SYN: transaxial p.. axiolabiolingual p. a p. parallel to the long axis of a tooth and extending in a labiolingual direction. axiomesiodistal p. a p. parallel to the long axes of the teeth and extending in a mesiodistal direction. bite p. SYN: occlusal p.. Broca visual p. a p. drawn through the visual axes of each eye. Camper p. a p. running from the tip of the anterior nasal spine (acanthion) to the center of the bony external auditory meatus on the right and left sides. canthomeatal p. p. passing through the two lateral angles of the eye and the center of the external acoustic meatus; this p. lies approximately midway between the Frankfort and the supraorbitomeatal planes. coronal p. SYN: frontal p.. cove p. a classic description of terminal inversion of the electrocardiographic T wave with the initial portion arched above the baseline and the terminal portion below it, the former being rounded and the latter pointed. datum p. an arbitrary p. used as a base from which to make craniometric measurements. Daubenton p. the p. of the foramen magnum. SEE ALSO: Daubenton angle, Daubenton line. equatorial p. in metaphase of mitosis, the p. that touches all of the centromeres and their spindle attachments. eye-ear p. SYN: orbitomeatal p.. facial p. a measurement of the bony profile of the face. SYN: nasion-pogonion measurement. first parallel pelvic p. SYN: pelvic inlet. fourth parallel pelvic p. SYN: pelvic outlet. Frankfort p. SYN: orbitomeatal p.. Frankfort horizontal p. SYN: orbitomeatal p.. frontal p. [TA] a vertical p. at right angles to a sagittal p., dividing the body into anterior and posterior portions, or any p. parallel to the central coronal p.. SYN: plana frontalia [TA] , coronal p., plana coronalia. guide p. a fixed or removable device used to displace a single tooth, an arch segment, or an entire arch toward an improved relationship. horizontal planes [TA] p. parallel and relative to the horizon; in the anatomic position, horizontal planes are transverse planes; in the supine or prone positions, horizontal planes are frontal (coronal planes). SYN: plana horizontalia [TA] . p. of incidence the p. perpendicular to a lens surface that contains the incident light ray. infraorbitomeatal p. SYN: orbitomeatal p.. p. of inlet SYN: pelvic inlet. interspinal p. SYN: interspinous p.. interspinous p. [TA] a transverse p. passing through the anterior superior iliac spines; it marks the boundary between the lateral and umbilical regions superiorly and the inguinal and pubic regions inferiorly. SYN: planum interspinale [TA] , interspinal p., Lanz line. intertubercular p. [TA] a transverse p. passing through the iliac tubercles. SYN: planum intertuberculare [TA] . labiolingual p. a p. parallel to the labial and lingual surfaces of the teeth. p. of least pelvic dimensions SYN: pelvic p. of least dimensions. mean foundation p. the mean of the various irregularities in form and inclination of the basal seat; the ideal condition for denture stability exists when the mean foundation p. is most nearly at right angles to the direction of force. Meckel p. a craniometric p. cutting the alveolar and the auricular points. median p. [TA] a p. vertical in the anatomic position, through the midline of the body that divides the body into right and left halves. SEE ALSO: Addison clinical planes. SYN: planum medianum [TA] . p. of midpelvis SYN: pelvic p. of least dimensions. midsagittal p. obsolete term for median p.. Morton p. a p. passing through the summits of the parietal and occipital protuberances. nasion-postcondylar p. a p. passing through the nasion anteriorly and to a point immediately behind each condylar process of the mandible, posteriorly. nodal p. the p. corresponding to the optical center of a simple lens. See nodal point. nuchal p. the external surface of the squamous part of the occipital bone below the superior nuchal line, giving attachment to the muscles of the back of the neck. occipital p. [TA] the external surface of the occipital bone above the superior nuchal line. SYN: planum occipitale [TA] . occlusal p., p. of occlusion an imaginary surface that is related anatomically to the cranium and that theoretically touches the incisal edges of the incisors and the tips of the occluding surfaces of the posterior teeth; it is not a p. in the true sense of the word but represents the mean of the curvature of the surface. SEE ALSO: curve of occlusion. SYN: bite p.. orbital p. the orbital surface of the maxilla, lying perpendicular to the orbitomeatal p. at the orbitale. SYN: planum orbitale. orbitomeatal p. 1. a line approximating the base of the skull, passing from the infraorbital ridge to the midline of the occiput, intersecting the superior margin of the external auditory meatus; the skull is in the anatomical position when the base line lies in the horizontal p. and right and left sides are level. 2. a standard craniometric reference p. passing through the right and left porion and the left orbitale; drawn on the profile radiograph or photograph from the superior margin of the acoustic meatus to the orbitale. SYN: auriculoinfraorbital p., eye-ear p., Frankfort horizontal p., Frankfort p., infraorbitomeatal p.. p. of outlet SYN: pelvic outlet. parasagittal p. obsolete term for sagittal p.. p. of pelvic canal SYN: axis of pelvis. pelvic p. of greatest dimensions the p. extending from the middle of the posterior surface of the pubic symphysis to the junction of the second and third sacral vertebrae, and laterally passing through the ischial bones over the middle of the acetabulum. SYN: second parallel pelvic p., wide p.. pelvic p. of inlet SYN: pelvic inlet. pelvic p. of least dimensions the p. that extends from the end of the sacrum to the inferior border of the pubic symphysis; it is bounded posteriorly by the end of the sacrum, laterally by the ischial spines, and anteriorly by the inferior border of the pubic symphysis. SYN: midplane, p. of least pelvic dimensions, p. of midpelvis, third parallel pelvic p.. pelvic p. of outlet SYN: pelvic outlet. popliteal p. of femur SYN: popliteal surface of femur. principal p. the theoretic p. of a compound lens system. See principal point. planes of reference planes that act as a guide to the location of other planes. p. of regard an imaginary p. through which the point of regard moves as the eyes are turned from side to side. sagittal p. [TA] p. parallel to the median p.; sagittal planes are vertical planes in the anatomic position. SYN: plana sagittalia [TA] . second parallel pelvic p. SYN: pelvic p. of greatest dimensions. spectacle p. the p. at which spectacles are worn. sternal p. a p. indicated by the front surface of the sternum. SYN: planum sternale. subcostal p. [TA] a transverse p. passing through the inferior limits of the costal margin, i.e., the tenth costal cartilages; it marks the boundary between the hypochondriac and epigastric regions superiorly and the lateral and umbilical regions inferiorly. SYN: planum subcostale [TA] , infracostal line. supracrestal p. SYN: supracristal p.. supracristal p. [TA] a transverse p. passing through the summits of the iliac crests; it usually passes through the fourth lumbar spinous process. SYN: planum supracristale [TA] , supracrestal p.. supraorbitomeatal p. a p. passing the superior orbital margins and the superior margin of the external acoustic meatuses; it makes an angle of approximately 25°–30° with the Frankfort p.; routine CT scans of the brain are made parallel to this p. to limit exposure of eyeball to ionizing radiation. suprasternal p. a transverse p. passing through the body at the level of the superior margin of the manubrium of the sternum. temporal p. [TA] a slightly depressed area on the side of the cranium, below the inferior temporal line, formed by the temporal and parietal bones, the greater wing of the sphenoid, and a part of the frontal bone. SYN: planum temporale [TA] . third parallel pelvic p. SYN: pelvic p. of least dimensions. tooth p. any one of the imaginary planes of section of a tooth, such as the axial, horizontal, or vertical. transaxial p. SYN: axial p.. transpyloric p. [TA] a transverse p. midway between the superior margins of the manubrium sterni and the symphysis pubis; the pylorus may be located on this p. in the supine or prone positions, but in the erect (anatomic) position it descends to a lower level. SYN: planum transpyloricum [TA] . transverse p. [TA] a p. across the body at right angles to the coronal and sagittal planes; transverse planes are perpendicular to the long axis of the body or limbs, regardless of the position of the body or limb; in the anatomic position, transverse planes are horizontal planes; otherwise the two terms are not synonymous. SYN: plana transversalia [TA] . wide p. SYN: pelvic p. of greatest dimensions.


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