Copy of `Dorland's Medical Dictionary`

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Dorland's Medical Dictionary Category: Health and Medicine > Medical Dictionary Date & country: 31/12/2010, USA Words: 39128

pityriasis versicolor
(pit″ĭ-ri´ә-sis vur″sĭ-ko´lor) tinea versicolor.

pityroid
(pit´ĭ-roid) scaly or branny; called also furfuraceous.

Pityrosporon
(pit″ĭ-ros´pә-ron) Malassezia.

pivalate
(piv´ә-lāt) USAN contraction for trimethylacetate.

pivot joint
a synovial joint in which one bone pivots within a bony or osseoligamentous ring, allowing only rotary movement; an example is the joint between the atlas and axis (the first and second cervical vertebrae). Called also rotary or trochoid joint.

pivot shift phenomenon
pivot shift signpivot shift test a sign of anterior cruciate ligament disruption: with the knee held at 20° flexion and in neutral rotation and with the muscles relaxed (which lets the femur drop down if the anterior cruciate ligament is torn), a slight valgus or axial force is applied to the knee; subluxation or reduction...

pixel
(pik´sel) a picture element; a CT scan or PET scan is composed of an array of squares (pixels), each of which is colored a uniform shade of gray or another color. The corresponding region in the tissue slice that is imaged is called a voxel (volume element).

pK
a the negative logarithm of the ionization constant (K) of an acid, the pH of a solution in which half of the acid molecules are ionized.

PKU
phenylketonuria.

PKU1
phenylketonuria.

placebo
(plә-se´bo) a supposedly inert substance such as a sugar pill or injection of sterile water, given under the guise of effective treatment. See also placebo effect. Placebos are sometimes used in controlled clinical trials of new drugs; while some patients selected at random are given the new drug, others are given...

placebo effect
the total of all nonspecific effects, both good and adverse, of treatment; it refers primarily to psychological and psychophysiological effects associated with the caregiver-patient relationship and the patient's expectations and apprehensions concerning the treatment. See also placebo.

placenta
(plә-sen´tә) pl. placentas, placen´tae an organ characteristic of true mammals during pregnancy, joining mother and embryo or fetus. Its major function is to allow diffusion of nutrients from the mother's blood into the fetus's blood and diffusion of waste products from the fetus back to the mother. Anatomica...

placenta accreta
(plә-sen´tә ә-kre´tә) one abnormally adherent to the myometrium, with partial or complete absence of the decidua basalis.

placenta circumvallata
(plә-sen´tә sur″kәm-vә-la´tә) one encircled with a dense, raised, white nodular ring, the attached membranes being doubled back over the edge of the placenta.

placenta fenestrata
(plә-sen´tә fen″ә-stra´tә) one that has spots where placental tissue is lacking.

placenta increta
(plә-sen´tә in-kre´tә) placenta accreta with penetration of the myometrium.

placenta membranacea
(plә-sen´tә mem″brә-na´she-ә) one that is abnormally thin and spread over an unusually large area of the myometrium.

placenta percreta
(plә-sen´tә pәr-kre´tә) placenta accreta with invasion of the myometrium to the peritoneal covering, sometimes causing rupture of the uterus.

placenta previa
(plә-sen´tә pre´ve-ә) low implantation of the placenta so that it partially or completely covers the internal ostium of the uterus; this occurs more often in women who have had multiple pregnancies or are over 35. The exact cause is not known. With the onset of any contractions and cervical dilat...

placenta reflexa
(plә-sen´tә re-flek´sә) one in which the margin is thickened, appearing to turn back on itself.

placenta spuria
(plә-sen´tә spur´e-ә) an accessory portion without blood vessels connecting it with the main placenta.

placenta succenturiata
(plә-sen´tә suk″sәn-tu″re-a´tә) an accessory portion with an artery and a vein connecting it with the main placenta.

placental barrier
the tissue layers of the placenta which regulate the exchange of substances between the fetal and maternal circulation.

placental dysfunction syndrome
postmaturity syndrome.

placental hormones
hormones secreted by the placenta, including chorionic gonadotropin, and other substances having estrogenic, progestational, or adrenocorticoid activity.

placental insufficiency
dysfunction of the placenta, with reduction in the area of exchange of nutrients; it often leads to fetal growth retardation.

placental membrane
the membrane that separates the fetal from the maternal blood in the placenta. Placental membrane separating the blood in the fetal capillaries from the maternal blood in the intervillous space. (A), chorionic villus containing the fetal vessels and surrounded by maternal blood in the intervillo...

placental presentation
placenta praevia.

placental sign
implantation bleeding.

placental transfusion
the transfer of blood from placenta to newborn at the time of birth. Blood flow through the umbilical arteries stops about 45 seconds after birth, but the umbilical vein remains patent longer. Uterine contractions enhance the transfer of blood, and this blood can have significant benefits for the newborn.

placental zone
the area of the uterus to which the placenta is attached.

placentation
(pla″sәn-ta´shәn) the series of events following implantation of the embryo and leading to development of the placenta.

placentitis
(pla″sәn-ti´tis) inflammation of the placenta.

placentography
(pla″sәn-tog´rә-fe) radiologic visualization of the placenta after injection of a contrast medium.

placentoid
(plә-sen´toid) resembling the placenta.

placing reflex
flexion followed by extension of the leg when the infant is held erect and the dorsum of the foot is drawn along the under edge of a table top; it is obtainable in the normal infant up to the age of six weeks.

placode
(plak´ōd) a platelike structure, especially a thickening of the ectoderm marking the site of future development in the early embryo of an organ of special sense; for example the otic placode is for the ear, the lens placode is for the eye, and the nasal placode is for the nose.

placoid
(plak´oid) platelike or plaquelike.

plagiocephaly
(pla″je-o-sef´ә-le) an asymmetric condition of the head, resulting from irregular closure of the cranial sutures.

plague
(plāg) an acute febrile, infectious, highly fatal disease caused by the bacillus Yersinia pestis. It is primarily a disease of rats and other rodents and is usually spread to human beings by fleas. The most common form is bubonic plague, and a second type is pneumonic plague. It is a devastating disease; three epidemics ...

plague pneumonia
pneumonic plague.

plague vaccine
a preparation of killed Yersinia pestis bacilli, administered intramuscularly as an active immunizing agent against plague.

planar xanthoma
plane xanthoma a benign skin tumor consisting of soft macules or plaques of a variety of colors; there are both localized and generalized types. Sometimes the condition is associated with other types of xanthomas, certain types of hyperlipoproteinemia, lymphoma, or multiple myeloma.

plane
(plān) a flat surface determined by the position of three points in space. an imaginary flat surface that divides the body into sections. adj., pla´nar., adj. a specified level, as the plane of anesthesia. to rub away or abrade; see also planing. a superfic...

plane joint
gliding joint.

plane of occlusion
occlusal plane.

planigraphy
(plә-nig´rә-fe) a method of body section radiography that shows in detail structures lying in a predetermined plane of the body while blurring structures in other planes, produced by movement of the film and x-ray tube in certain specified directions. adj., planigraph´ic., adj.

planing
(plān´ing) abrasion of disfigured skin to promote epithelialization with minimal scarring; done by mechanical means (dermabrasion) or chemical means (chemabrasion). root planing. root planing smoothing of the root surface of a tooth after subgingival scaling or débridem...

Planned Parenthood
an organization that provides reproductive health care services, including the promotion of accessible means of voluntary fertility control, operation of clinics, conduction of educational programs, conduction of research, and dissemination of information.

planning
(plan´ing) consciously setting forth a scheme to achieve a desired end or goal. family planning the practice of birth control measures, including any of numerous methods; see contraception. natural family planning methods of avoiding conception without the ...

planocellular carcinoma
squamous cell carcinoma.

planoconcave
(pla″no-kon´kāv) flat on one side and concave on the other.

planoconcave lens
a lens with one plane and one concave side.

planoconvex
(pla″no-kon´veks) flat on one side and convex on the other.

planoconvex lens
a lens with one plane and one convex side.

plant
(plant) any multicellular eukaryotic organism that performs photosynthesis to obtain its nutrition; plants comprise one of the five kingdoms in the most widely used classification of living organisms.

planta
(plan´tә) the bottom of the foot; called also sole. adj., plan´tar., adj.

Plantago
(plan-ta´go) a genus of herbs, including P. in´dica, P. psyl´lium (Spanish psyllium), and P. ova´ta (blond psyllium); see also psyllium hydrophilic mucilloid, plantago seed, and psyllium husk.

plantalgia
(plan-tal´jә) pain in the sole of the foot.

plantar
(plan´tәr) pertaining to the sole of the foot.

plantar digital veins
veins from the plantar surfaces of the toes which unite at the clefts to form the plantar metatarsal veins of the foot.

plantar fibromatosis
fibromatosis involving the plantar fascia manifested as single or multiple nodular swellings, sometimes accompanied by pain but usually unassociated with contractures.

plantar interossei muscles
plantar interosseous muscles (3): origin, medial surfaces of third, fourth, and fifth metatarsal bones; insertion, medial side of base of proximal phalanges of third, fourth, and fifth toes and their extensor expansions; innervation, lateral plantar nerve; action, adduct, flex toes.

plantar ischemia test
(for circulatory disturbances in legs and feet) the elevated leg is alternately flexed and extended and the plantar surface of the patient's foot is checked for blanching.

plantar metatarsal arteries
origin, plantar arch; branches, perforating branches, common and proper plantar digital arteries; distribution, toes.

plantar metatarsal veins
deep veins of the foot that arise from the plantar digital veins at the clefts of the toes and pass back to open into the plantar venous arch.

plantar reflex
plantar flexion of the foot when the ankle is grasped firmly and the lateral border of the sole is stroked or scratched from the heel toward the toes.

plantar ulcer
a deep ulcer of the sole of the foot, resulting from repeated injury because of lack of sensation in the part; seen with diseases that cause neuropathy, such as diabetes mellitus and leprosy.

plantar wart
a viral epidermal tumor on the sole of the foot, usually transmitted by human papillomavirus. These are sometimes the result of going barefoot; unlike other warts, they are usually sensitive to pressure and may be painful during walking. Called also verruca plantaris.

plantaris
(plan-ta´ris) Latin word meaning plantar; a term used in anatomy.

plantaris muscle
plantar muscle: origin, oblique popliteal ligament, lateral supracondylar line of femur; insertion, posterior part of calcaneus; innervation, tibial nerve; action, plantar flexes foot; flexes knee.

plantigrade
(plan´tĭ-grād) walking or running flat on the full sole of the foot; characteristic of humans and of such quadrupeds as the bear.

planula
(plan´u-lә) a larval coelenterate.

planum
(pla´nәm) Latin word meaning plane; a term used in anatomy.

plaque
(plak) any patch or flat area. a superficial, solid, elevated skin lesion with a diameter equal to or greater than 1.0 cm (0.5 cm according to some authorities); see also papule. dental plaque.

plaque morphea
plaque type morphea the most common type of morphea, with lesions arranged in plaques.

plaque psoriasis
the most common type of psoriasis, in which lesions are in round plaques with distinct borders.

Plaquenil
(pla´kwә-nil) trademark for a preparation of hydroxychloroquine, an antiinflammatory and antiprotozoal agent used for treatment of malaria, lupus erythematosus, rheumatoid arthritis, and giardiasis.

plasm
(plaz´әm) plasma. a formative substance; used as a word element in terms such as cytoplasm and hyaloplasm.

plasma
(plaz´mә) the fluid portion of the lymph. the fluid portion of the blood, in which the formed elements (blood cells) are suspended. Plasma is to be distinguished from serum, which is plasma from which the fibrinogen has been separated in the process of clotting. Of the total volume of blood, 55 per cent is...

plasma cell
a round cell with an off-center nucleus containing coarsely clumped chromatin and deep blue cytoplasm with a clear zone adjacent to the nucleus; these cells are involved in synthesis, storage, and release of immunoglobulins. Pathological plasma cells are seen in multiple myeloma and Waldenström macroglobulinemia. Called also pl...

plasma cell leukemia
a rare type in which the predominating cell in the peripheral blood is the plasma cell; it is often seen in association with multiple myeloma .

plasma cell mastitis
a condition of the breast characterized by infiltration of the breast stroma with plasma cells and proliferation of the cells lining the ducts, possibly related to mammary duct ectasia.

plasma cell pneumonia
pneumocystis pneumonia.

plasma cell tumor
plasma cell dyscrasias. solitary myeloma.

plasma membrane
the membrane that encloses a cell, composed of phospholipids, glycolipids, cholesterol, and proteins. The primary structure is a lipid bilayer. Phospholipid molecules have an electrically charged “head” that attracts water and a hydrocarbon “tail” that repels water. These molecules line up side by side in two ...

plasma protein fraction
a sterile preparation of serum albumin and globulin obtained by fractionating material (source blood, plasma, or serum) from healthy human donors; used as a blood volume supporter.

plasma proteins
the hundreds of different proteins present in blood plasma, including transport proteins such as albumin, transferrin, and haptoglobin; fibrinogen and other coagulation factors; complement components; immunoglobulins; enzyme inhibitors; precursors of substances such as angiotensin and bradykinin; and many others.

plasma refilling rate
in hemodialysis, the rate at which plasma that has been withdrawn and dialyzed flows back into the patient's circulatory system.

plasma therapy
the therapeutic use of blood plasma.

plasma volume
the total volume of blood plasma, which is the extracellular fluid volume of the vascular space; see also blood volume.

plasmablast
(plaz´mә-blast) the immature precursor of a plasmacyte, or plasma cell.

plasmablastic lymphoma
an uncommon, aggressive B-cell lymphoma, occurring mainly in the jaws and oral cavity and chiefly affecting HIV-positive persons, characterized by cells that morphologically resemble those of immunoblastic large B-cell lymphoma but whose immunophenotype shows them to be of plasma cell differentiation.

plasmacyte
(plaz´mә-sīt) plasma cell. adj., plasmacyt´ic., adj.

plasmacyte series
plasmacytic series a series of morphologically distinguishable cells that are stages in plasma cell development: in order of maturity, the plasmablast (an activated B cell usually referred to as a large lymphocyte or lymphoblast), proplasmacyte, and plasmacyte.

plasmacytic lymphoma
plasmacytoid lymphoma lymphoplasmacytic lymphoma.

plasmacytoid lymphocytic lymphoma
a rare type of small lymphocytic lymphoma in which the predominant cell type is the plasma cell; it may be the manifestation in lymphoid tissue of Waldenström macroglobulinemia in the blood.

plasmacytoma
(plaz″mә-si-to´mә) plasma cell dyscrasias. solitary myeloma.

plasmacytosis
(plaz″mә-si-to´sis) an excess of plasma cells in the blood.