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(plă″sĕn-tī′tĭs) [″ + Gr. itis, inflammation] Inflammation of the placenta.


(pla′kōd″) [Gr. plax, stem plak-, plate + -ode] In embryology, a platelike thickening of epithelium, usually the ectoderm, that serves as the precursor of an organ or structure.

lens p. A placode developing in the ectoderm directly overlying the optic vesicle. It forms the lens vesicle, which becomes enclosed in the optic cup and eventually becomes the lens of the eye.

olfactory p. A placode that first gives rise to the olfactory pit and later to the major portion of the nasal cavity.


(plak′oyd″) [Gr. plax, plate + -oid] Shaped like a plate.


[Gr. plagios, slanting, sideways] Prefix meaning slanting, oblique.


(plā″jē-ō-sef′ă-lē) [plagio + -cephaly] Flattening of one side of the skull producing an asymmetrically shaped head.

deformational p. Plagiocephaly on one side of the skull of an infant, usually after repeatedly sleeping in a single position, e.g., on the infant's back, to prevent SIDS.

 It can usually be treated nonoperatively by repositioning the developing infant frequently, or by having the child wear a protective, adjustable helmet while resting. SYN: positional p.

positional p. Deformational p.


(plāg) [L., plaga, blow, injury] 1. Any widespread contagious disease associated with a high death rate. 2. An often fatal disease caused by Yersinia pestis. The natural hosts are ground squirrels, wild rodents, and rats; the vector is the rat flea. In the U.S., hunters, trappers, and campers may encounter infected mammals. Outbreaks are also associated with crowded living conditions and poor sanitation. Although plague was responsible for millions of deaths during the Middle Ages, improvements in sanitation, medical care, and the availability of antibiotics now prevent widespread epidemics. Plague is characterized by high fever, restlessness, confusion, prostration, delirium, shock, and coma. Streptomycin (the antibiotic of choice), gentamicin, tetracyclines, doxycycline, fluoroquinolones, and chloramphenicol are effective in treating plague. In the U.S., about 15 cases of plague are reported annually , primarily in western and southwestern regions. If treated promptly, plague is rarely fatal; however, in the U.S. about 1 in 7 people infected dies, usually because of delayed diagnosis or treatment.

ambulatory p. A mild form of bubonic plague.

black p. Plague.

bubonic p. Plague.

hemorrhagic p. A severe form of bubonic plague in which there is hemorrhage into the skin.

murine p. A plague infecting rats.

pneumonic p. A highly virulent ...

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