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Medical Dictionary


synzyme (sin′zim)
A synthetic macromolecule having enzymatic activity. SYN: enzyme analog.

Syphacia (si-fa′she-a)
Genus of oxyurid nematode pinworms of rodents; S. obvelata is the common cecal pinworm of mice, and S. muris, of rats. SEE ALSO: Aspiculuris tetraptera. [fr. L. siphon, tube]

See syphilo-.

syphilemia (sif-i-le′me-a)
A state in which the specific organism, Treponema pallidum, is present in the bloodstream. [syphilis + G. haima, blood]

syphilid (sif′i-lid)
Historic term for any of the several kinds of cutaneous and mucous membrane lesions of secondary and tertiary syphilis. SYN: syphiloderm, syphiloderma. [syphilis + -id (1)]

syphilimetry (sif-i-lim′e-tre)
A test designed to determine intensity of syphilitic infection, e.g., titered serologic test. [syphilis + G. metron, measure]

syphilis (sif′i-lis)
An acute and chronic infectious disease caused by the bacterium Treponema pallidum and transmitted by direct contact, usually through sexual intercourse. After an incubation period of 12–30 days, the first symptom is a chancre, followed by slight fever and other constitutional symptoms (primary s.), followed by a skin eruption of various appearances with mucous patches and generalized lymphadenopathy (secondary s.), and subsequently by the formation of gummas, cellular infiltration, and functional abnormalities usually resulting from cardiovascular and central nervous system lesions (tertiary s.). SYN: lues venerea, malum venereum. [Mod. L. s. (syphilid-), (?) fr. a poem, S. sive Morbus Gallicus, by Fracastorius, Syphilus being a shepherd and principal character] cardiovascular s. involvement of the cardiovascular system seen in late s., usually resulting in aortitis, aneurysm formation, and aortic valvular insufficiency. congenital s. s. acquired by the fetus in utero, thus present at birth. SYN: hereditary s., s. hereditaria. s. d'emblée s. occurring without an initial sore. [Fr. right away] early s. primary, secondary, or early latent s., before any tertiary manifestations have appeared. early latent s. infection with Treponema pallidum, the organism of s., after the primary and secondary phases have subsided, during the first year after infection, before any manifestations of tertiary s. have appeared. endemic s. SYN: nonvenereal s.. s. hereditaria SYN: congenital s.. s. hereditaria tarda s., believed to be congenital, but not manifesting itself until several years after birth. hereditary s. SYN: congenital s.. late s. involvement of the cardiovascular or central nervous system, or the development of a gumma in any organ, due to infection with Treponema pallidum; usually several years to 2–3 decades after the initial infection. SYN: tertiary s.. late benign s. late s., manifested by serologic evidence of infection, but without any clinical manifestations. late latent s. usually infectious in pregnant women only, who may pass the infection on to the fetus. latent s. infection with Treponema pallidum, after the manifestations of primary and secondary s. have subsided (or were never noticed), before any manifestations of tertiary s. have appeared. meningovascular s. a rare manifestation of secondary or tertiary s. characterized by mild, nonsuppurative, chronic inflammation of the leptomeninges and an intracranial or spinal angiitis. nonvenereal s. s. caused by organisms closely related to Treponema pallidum; spread by personal, but not necessarily venereal, contact; usually acquired in childhood, most common in areas of poverty and overcrowding; rare in the United States; includes yaws, pinta and bejel. SYN: endemic s.. primary s. the first stage of s. See s.. quaternary s. SYN: parasyphilis. secondary s. the second stage of s. See s.. tertiary s. SYN: late s..

syphilitic (sif-i-lit′ik)
Relating to, caused by, or suffering from syphilis. SYN: luetic.

syphilo-, syphil-, syphili-
Syphilis. [see syphilis]

syphiloderm, syphiloderma (sif′i-lo-derm, -der′ma)
SYN: syphilid. [syphilo- + G. derma, skin]

syphiloid (sif′i-loyd)
Resembling syphilis. [syphilo- + G. eidos, resemblance]

syphilologist (sif-i-lol′o-jist)
One who specializes in the study, diagnosis, and treatment of syphilis.

syphilology (sif-i-lol′o-je)
The branch of medical science concerned with the origin, prevention, and treatment of syphilis. [syphilo- + G. logos, study]

syphiloma (sif-i-lo′ma)
SYN: gumma. [syphilo- + G. -oma, tumor] s. of Fournier SYN: Fournier disease.

Abbreviation of Mod. L. syrupus, syrup.

syrigmus (si-rig′mus)
SYN: tinnitus aurium. [L. fr. G. syrigmos, a hissing]

See syringo-.

syringadenoma (sir′ing-ad-e-no′ma)
A benign sweat gland tumor showing glandular differentiation typical of secretory cells. SYN: syringoadenoma. [syring- + G. aden, gland, + -oma, tumor]

syringadenosus (sir′ing-ad-e-no′sus)
Relating to the sweat glands. [L. fr. syring- + G. aden, gland]

syringe (si-rinj′, sir′inj)
An instrument used for injecting or withdrawing fluids, consisting of a barrel and plunger. [G. syrinx, pipe or tube] air s. SYN: chip s.. chip s. a tapered metal tube through which air is forced from a rubber bulb or pressure tank to blow debris from, or to dry, a cavity in preparing teeth for restoration. SYN: air s.. control s. a type of Luer-Lok s. with thumb and finger rings attached to the proximal end of the barrel and to the tip of the plunger, allowing operation of the s. with one hand. SYN: ring s.. Davidson s. a rubber tube, armed with an appropriate nozzle, intersected with a compressible bulb, with valves so arranged that compression forces the fluid, into which one end of the tube is inserted, forward to the nozzle end. dental s. a breech-loading metal cartridge s. into which fits a hermetically sealed glass cartridge containing the anesthetic solution. fountain s. an apparatus consisting of a reservoir for holding fluid, to the bottom of which is attached a tube with a suitable nozzle; used for vaginal or rectal injections, irrigating wounds, etc., the force of the flow being regulated by the height of the reservoir above the point of discharge. hypodermic s. a small s. with a barrel (which may be calibrated), perfectly matched plunger, and tip; used with a hollow needle for subcutaneous injections and for aspiration. SYN: hypodermic (3) . Luer s. a glass s. with a metal tip and locking device to secure the needle; used for hypodermic and intravenous purposes. SYN: Luer-Lok s.. Luer-Lok s. SYN: Luer s.. Neisser s. a urethral s. used in treatment of gonococcal urethritis. probe s. a s. with an olive-shaped tip, used in treatment of diseases of the lacrimal passages. ring s. SYN: control s.. Roughton-Scholander s. SYN: Roughton-Scholander apparatus. rubber-bulb s. a s. with a hollow rubber bulb and cannula provided with a check valve, used to obtain a jet of air or water.

syringeal (si-rin′je-al)
Relating to a syrinx.

syringectomy (si-rin-jek′to-me)
SYN: fistulectomy. [syring- + G. ektome, excision]

syringitis (si-rin-ji′tis)
Inflammation of the eustachian tube. [syring- + G. -itis, inflammation]

syringo-, syring-
A syrinx; syringeal. [G. syrinx, pipe or tube]

syringoadenoma (si-ring′go-ad-e-no′ma)
SYN: syringadenoma.

syringobulbia (si-ring′go-bul′be-a)
A fluid-filled cavity of the brainstem, analogous to syringomyelia. [syringo- + L. bulbus, bulb (medulla oblongata)]

syringocarcinoma (si-ring′go-kar-si-no′ma)
Obsolete term for a malignant epithelial neoplasm which has undergone cystic change (cystic carcinoma). [syringo- + carcinoma]

syringocele (si-ring′go-sel)
1. SYN: central canal. 2. A meningomyelocele in which there is a cavity in the ectopic spinal cord. [syringo- + G. koilia, a hollow]

syringocystadenoma (si-ring′go-sis-tad-e-no′ma)
A cystic benign sweat gland tumor. [syringo- + cystadenoma] s. papilliferum a s. characterized by numerous fingerlike projections of proliferated neoplastic epithelial cells in two layers on a stromal core of fibrous connective tissue infiltrated by plasma cells occurring singly or as part of a nevus sebaceus.

syringocystoma (si-ring′go-sis-to′ma)
SYN: hidrocystoma. [syringo- + cystoma]

syringoencephalomyelia (si-ring′go-en-sef′a-lo-mi-e′le-a)
A tubular cavity involving both brain and spinal cord and etiologically unrelated to vascular insufficiency. [syringo- + G. enkephalos, brain, + myelos, marrow]

syringoid (si-ring′goyd)
Resembling a tube or fistula. [syringo- + G. eidos, resemblance]

syringoma (si-ring-go′ma)
A benign, often multiple, sometimes eruptive neoplasm of the sweat gland ducts composed of very small round cysts. [syringo- + G. -oma, tumor] chondroid s. a benign tumor of sweat glands with a mucoid stroma showing cartilaginous metaplasia. SYN: mixed tumor of skin.

syringomeningocele (si-ring′go-me-ning′go-sel)
A form of spina bifida in which the dorsal sac consists chiefly of membranes, with very little spinal cord substance, enclosing a cavity that communicates with a syringomyelic cavity. [syringo- + meningocele]

syringomyelia (si-ring′go-mi-e′le-a)
The presence in the spinal cord of longitudinal cavities lined by dense, gliogenous tissue, which are not caused by vascular insufficiency. S. is marked clinically by pain and paresthesia, followed by muscular atrophy of the hands and analgesia with thermoanesthesia of the hands and arms, but with the tactile sense preserved; later marked by painless whitlows, spastic paralysis in the lower extremities, and scoliosis of the lumbar spine. Some cases are associated with low grade astrocytomas or vascular malformations of the spinal cord. SYN: hydrosyringomyelia, Morvan disease, syringomyelus. [syringo- + G. myelos, marrow]

syringomyelocele (si-ring′go-mi′e-lo-sel)
A form of spina bifida, consisting of a protrusion of the membranes and spinal cord through a dorsal defect in the vertebral column, the fluid of the syrinx of the cord being increased and expanding the cord tissue into a thin-walled sac which then expands through the vertebral defect. [syringo- + myelocele]

syringomyelus (si-ring′go-mi′e-lus)
SYN: syringomyelia. [syringo- + G. myelos, marrow]

syringopontia (si-ring′go-pon′she-a)
A condition of cavity formation in the pons, of the same nature as syringomyelia. [syringo- + L. pons, bridge]

syringotome (si-rin′go-tom)
SYN: fistulatome.

syringotomy (si-rin-got′o-me)
SYN: fistulotomy.

syrinx, pl .syringes (sir′ingks, si-rin′jez)
1. A rarely used synonym for fistula. 2. A pathologic tubular cavity in the brain or spinal cord. [G. a tube, pipe]

syrosingopine (sir-o-sin′go-pen)
Prepared from reserpine by hydrolysis and reesterification; an antihypertensive agent with actions similar to those of reserpine.

syrup (ser′up, sir′up)
1. Refined molasses; the uncrystallizable saccharine solution left after the refining of sugar. 2. Any sweet fluid; a solution of sugar in water in any proportion. 3. A liquid preparation of medicinal or flavoring substances in a concentrated aqueous solution of a sugar, usually sucrose; other polyols, such as glycerin or sorbitol, may be present to retard crystallization of sucrose or to increase the solubility of added ingredients. When the s. contains a medicinal substance, it is termed a medicated s.; although a s. tends (due to its very high [approximately 85%] sucrose content) to resist mold or bacterial contamination, a s. may contain antimicrobial agents to prevent bacterial and mold growth. SYN: sirup, syrupus. [Mod. L. syrupus, fr. Ar. sharab] ipecac s. a sweetened liquid medicinal preparation containing powdered ipecac extract, which contains the alkaloids emetine and cephaline; used as an emetic in certain cases of poisoning and (at lower doses) as an expectorant.

syrupus (syr) (sir′u-pus)
SYN: syrup. [Mod. L.]

syrupy (ser′u-pe, sir′)
Relating to syrup; of the consistency of syrup.

syssarcosic (sis′ar-ko′sik)
SYN: syssarcotic.

syssarcosis (sis′ar-ko′sis)
A muscular articulation; union of bones by muscle; e.g., in man, the muscular connections of the patella. [G. syssarkosis, a being overgrown with flesh, fr. syn, with, + sarx, flesh]

syssarcotic (sis′ar-kot′ik)
Relating to or characterized by syssarcosis. SYN: syssarcosic.

system (sis′tem)
1. [TA] A consistent and complex whole made up of correlated and semiindependent parts. A complex of functionally related anatomic structures. 2. The entire organism seen as a complex organization of parts. 3. Any complex of structures anatomically related ( e.g., vascular s.) or functionally related ( e.g., digestive s.). 4. A scheme of medical theory. SEE ALSO: apparatus, classification. 5. S. followed by one or more letters denotes specific amino acid transporters; s. N is a sodium-dependent transporter specific for amino acids such as l-glutamine, l-asparagine, and l-histidine; s. y+ is a sodium-independent transporter of cationic amino acids. SYN: systema [TA] . [G. systema, an organized whole] absolute s. of units a s. based on absolute units accepted as being fundamental (length, mass, time) and from which other units (force, energy or work, power) are derived; such systems in common use are the foot-pound-second, centimeter-gram-second, and meter-kilogram-second systems. absorbent s. SYN: lymphoid s.. alimentary s. [TA] the digestive tract from the mouth to the anus with all its associated glands and organs. SYN: systema digestorium [TA] , alimentary apparatus, apparatus digestorius, digestive apparatus, digestive s., systema alimentarium. anterolateral s. a composite bundle of fibers, located in the ventrolateral part of the lateral funiculus, containing spinothalamic, spinohypothalamic, spinoreticular, and spinomesencephalic (spinotectal, spinal to periaqueductal grey, etc.) fibers; occupies the combined areas of the spinal white matter historically divided into anterior and lateral spinothalamic tracts; located in white matter ventral to the denticulate ligament, hence the anatomical basis for the anterolateral cordotomy; concerned with the transmission of nociceptive and thermal information and with crude (nondiscriminative) touch. SEE ALSO: spinothalamic tract. SYN: anterolateral tract, tractus anterolaterales. arch-loop-whorl s. (ALW) Galton s. of classification of fingerprints, under fingerprint. association s. groups or tracts of nerve fibers interconnecting different regions of one and the same major subdivision of the central nervous s., such as the various areas of the cerebral cortex or the various segments of the spinal cord. autonomic nervous s. (ANS) SYN: autonomic division of nervous s.. Bethesda s. a s. for reporting cervical or vaginal cytologic findings and diagnoses. SYN: Bethesda classification. [Bethesda, Maryland, site of NIH] George Papanicolaou divided cytologic findings on stained cervical smears into five classes, ranging from I (normal) to V (carcinoma). Classes II–IV represented increasing degrees of premalignant squamous cellular atypia. Later workers modified the s. by introducing the terms dysplasia (mild, moderate, severe) and cervical intraepithelial neoplasia (CIN) (grades 1–3). Pap smear findings reported according to this nomenclature showed poor reproducibility between observers and even between separate readings by the same observer. In addition, there was little correlation between diagnostic categories and treatment options. In 1988 the National Cancer Institute sponsored a workshop in Bethesda, Maryland, to establish a more useful s.. The Bethesda s. was first used in 1991 and has now become standard throughout the world. This recording s. replaces numerical designations with descriptive diagnoses of cellular changes. The accompanying table compares the Bethesda s. with earlier classifications. The standard format for reporting cervical cytology findings according to the Bethesda s. comprises three elements: 1) a statement of the adequacy of the specimen (satisfactory, unsatisfactory, or satisfactory but limited by, e.g., absence of endocervical cells); 2) general categorization (within normal limits, benign cellular changes, or epithelial cell abnormality); and 3) descriptive diagnosis, elaborating on the general categorization and including mention of all significant abnormalities, as well as of the patient's hormonal status (when vaginal cells are present in the smear). Benign cellular changes include those due to infection (Candida, Trichomonas, herpes simplex), atrophy, radiation therapy, or the presence of an IUD. Epithelial cell abnormalities may involve either squamous or glandular cells. Abnormal squamous cells of undetermined significance (ASCUS) show cellular atypia but not clear evidence of premalignant change. About 20% of women with ASCUS eventually develop squamous intraepithelial lesions or invasive carcinoma. Squamous cell changes formerly called mild dysplasia or CIN 1 (including cellular atypia characteristic of human papillomavirus infection) are now designated low-grade squamous intraepithelial lesion. The category of high-grade squamous intraepithelial lesion encompasses what were formerly called moderate and severe dysplasia or CIN 2 and CIN 3. Abnormalities of glandular cells are similarly categorized. blood group systems see Blood Groups appendix. blood-vascular s. SYN: cardiovascular s.. bulbosacral s. SYN: parasympathetic part of autonomic division of peripheral nervous s.. cardiovascular s. [TA] the heart and blood vessels considered as a whole. SYN: systema cardiovasculare [TA] , blood-vascular s.. caudal neurosecretory s. urohypophysis. centimeter-gram-second s. (CGS, cgs) the scientific s. of expressing the fundamental physical units of length, mass, and time, and those units derived from them, in centimeters, grams, and seconds; currently being replaced by the International S. of Units based on the meter, kilogram, and second. central nervous s. (CNS) [TA] the brain and the spinal cord. SYN: pars centralis systematis nervosi [TA] , systema nervosum centrale&star. cerebrospinal s. the combined central nervous s. and peripheral nervous s.. charge transfer s. SYN: charge transfer complex. chromaffin s. the cells of the body that stain with chromium salts and occur in the medullary portion of the adrenal body, paraganglia, and in relation to certain sympathetic nerves. circulatory s. SYN: vascular s.. closed s. a s. in which there is no exchange of material, energy, or information with the environment. colloid s. a combination of the two phases, internal and external, of a colloid solution; the various systems are: gas + liquid (foam); gas + solid (meerschaum); liquid + gas (fog); solid + gas (smoke); solid + liquid (sol); liquid + solid (gel); liquid + liquid (emulsion); solid + solid (colored glass). complement s. a group of more than 20 serum proteins, some of which can be serially activated and participate in a cascade resulting in cell lysis; the complement s. also functions in chemotaxis, opsonization, and phagocytosis. conducting s. of heart [TA] the s. of atypical modified muscle fibers comprising the sinoatrial node, atrioventricular node and bundle, the right and left bundles, and their terminal subendocardial branches (the Purkinje network). SYN: complexus stimulans cordis [TA] , systema conducens cordis&star. craniosacral nervous s. SYN: parasympathetic part of autonomic division of peripheral nervous s.. cytochrome s. SYN: respiratory chain. cytochrome P-450 s. a heterogeneous group of enzymes that catalyze various oxidative reactions in the human liver, intestine, kidney, lung, and central nervous s.; these enzymes are involved in the metabolism of many endogenous and exogenous substrates, including drugs, toxins, hormones, and natural plant products. Cytochrome P-450 enzymes are classified on the basis of chemical structure (amino acid sequencing). The designation of each enzyme is CYP followed by a numeral for the family to which it has been assigned, a letter for its subfamily, and sometimes a second numeral for the individual enzyme.The steady increase in the number and variety of pharmaceutical agents available for the treatment of infections, degenerative and malignant conditions, mental disorders, and other diseases has led to polypharmacy, with attendant risks of undesirable drug interactions. Disturbances in the function of the cytochrome P-450 s. are increasingly recognized as important causes of such interactions. When a drug increases the formation of a P-450 enzyme, other drugs metabolized by that enzyme are eliminated more rapidly and may fail to produce the desired therapeutic effects. In contrast, a drug that inhibits P-450 enzyme activity can retard the metabolism of substrate drugs, with resultant increases in serum and tissue levels and in drug effects, including side effects. Inhibition usually involves competition between drugs for the same binding site on an enzyme molecule. Reversible inhibition is the most common mechanism of drug interactions involving the P-450 s.. In general, drugs compete for a specific P-450 isoenzyme. Examples of agents that cause interactions through reversible inhibition are fluoroquinolone antibiotics, cimetidine, ketoconazole, and protease inhibitors used in the treatment of AIDS. CYP3A, the most abundant of human cytochrome P-450 enzymes, accounts for 30% of those found in the liver. Its substrates include many psychoactive medicines, ketoconazole, erythromycin, and protease inhibitors. This enzyme is inhibited by some antidepressants, azole antifungals, cimetidine, erythromycin, and other drugs. Increased formation of CYP3A is induced by carbamazepine, phenobarbital, phenytoin, and rifampin. Ethnic differences in the expression of CYP2D6 explain why whites are more likely than blacks and Asians to experience toxicity from accumulation and excessive serum levels of drugs metabolized by this enzyme, such as tricyclic antidepressants, SSRIs, antipsychotics, and beta-blockers. digestive s. SYN: alimentary s.. ecological s. SYN: ecosystem. electron-transport s. SYN: respiratory chain. endocrine s. SYN: endocrine glands, under gland. endomembrane s. SYN: endoplasmic reticulum. esthesiodic s. a s. of neurons and fiber tracts in the spinal cord and brain subserving sensation. exterofective s. name applied by Cannon to the somatic nervous s. as opposed to the interofective or autonomic s.. extrapyramidal motor s. literally: all of the brain structures affecting bodily (somatic) movement, excluding the motor neurons, the motor cortex, and the pyramidal (corticobulbar and corticospinal) tract. Despite its very wide literal connotation, the term is more often used to denote in particular the striate body (basal ganglia), its associated structures (substantia nigra, subthalamic nucleus), and its descending connections with the midbrain. feedback s. 1. a complex of neuronal circuits whereby a part of the efferent path returns to the input to modulate its activity, thus acting as a governor on the s.; 2. See feedback. foot-pound-second s. (FPS, fps) a s. of absolute units based on the foot, pound, and second. gamma motor s. SYN: gamma loop. genital s. [TA] the complex s. consisting of the male or female gonads, associated ducts, and external genitalia dedicated to the function of reproducing the species. SYN: systema genitalia [TA] , reproductive s.. genitourinary s. SYN: urogenital s.. geographic information s. a computer-based s. that combines cartographic capabilities with electronic data processing to rapidly produce customized maps for use in epidemiologic studies. glandular s. all the glands of the body collectively. haversian s. SYN: osteon. health information s. combination of vital and health statistical data from multiple sources, used to derive information about the health needs, health resources, use of health services, and outcomes of use by the people in a defined region or jurisdiction. hematopoietic s. the blood-making organs; in the embryo at different ages these are the yolk sac, liver, thymus, spleen, lymph nodes, and bone marrow; after birth they are principally the bone marrow, spleen, thymus, and lymph nodes. hepatic portal s. a venous portal s. in which the portal vein receives blood via its tributaries from the capillaries of most of the abdominal viscera and drains it into the hepatic sinusoids. heterogeneous s. in chemistry, a s. that contains various distinct and mechanically separable parts or phases; e.g., a suspension or an emulsion. hexaxial reference s. the figure resulting if the lines of derivation of the unipolar limb leads of the electrocardiogram are added to the triaxial reference s.. His-Tawara s. the complex s. of interlacing Purkinje fibers within the ventricular myocardium. SEE ALSO: conducting s. of heart. homogeneous s. in chemistry, a s. whose parts cannot be mechanically separated and is therefore uniform throughout and possesses in every part identically physical properties; e.g., a solution of sodium chloride in water. hypophyseoportal s. SYN: portal hypophysial circulation. hypophysial portal s. SYN: portal hypophysial circulation. hypophysioportal s. SYN: portal hypophysial circulation. hypothalamohypophysial portal s. 1. SYN: portal hypophysial circulation. 2. SYN: renal portal s.. hypoxia warning s. a device designed to produce an audio or visual signal at a predetermined level of oxygen partial pressure; ideally, the s. would warn of impending hypoxia in time for corrective action to be taken. immune s. an intricate complex of interrelated cellular, molecular, and genetic components which provides a defense (immune response) against foreign organisms or substances and aberrant native cells. indicator s. in in vitro immunological tests, a combination of reagents used to determine the degree to which immunologic reagents have combined ( e.g., sensitized erythrocytes in complement-fixation tests; enzyme and substrate in enzyme-linked immunosorbent assays). information s. combination of vital and health statistical data from multiple sources, used to derive information and make decisions about the health needs, health resources, costs, use, and outcome of health care. integumentary s. SYN: integument. intermediary s. SYN: interstitial lamella. International S. of Units International S. of Units. interofective s. term applied by W. Cannon to the autonomic nervous s. as opposed to the somatic nervous s. or exterofective s.. involuntary nervous s. SYN: autonomic division of nervous s.. kallikrein s. a blood serum s., the activity of which is initiated by factor XII (Hageman factor) leading to the production of prekallikrein activator and then to kallikrein which, after activation by plasmin, splits bradykinin from kininogen. kinetic s. 1. a term proposed by G.W. Crile to denote the chain of organs through which latent energy is transformed into motion and heat: it includes the brain, the thyroid, the adrenals, the liver, the pancreas, and the muscles; 2. that part of the neuromuscular s. whereby active movements are effected; distinguished from the static s.. limbic s. collective term denoting a heterogeneous array of brain structures at or near the edge (limbus) of the medial wall of the cerebral hemisphere, in particular the hippocampus, amygdala, and fornicate gyrus; the term is often used so as to include also the interconnections of these structures, as well as their connections with the septal area, the hypothalamus, and a medial zone of mesencephalic tegmentum. By way of the latter connections, the limbic s. exerts an important influence upon the endocrine and autonomic motor systems; its functions also appear to affect motivational and mood states. SYN: visceral brain. linnaean s. of nomenclature the s. of nomenclature in which the names of species are composed of two parts, a generic name and a specific epithet (species name, in botany). SYN: binary nomenclature, binomial nomenclature. [Carl von Linné] lymphatic s. SYN: lymphoid s.. lymphoid s. [TA] it consists of lymphatic vessels, nodes, and lymphoid tissue; it empties into the veins at the level of the superior aperture of the thorax. SYN: systema lymphoideum [TA] , absorbent s., lymphatic s., systema lymphaticum. s. of macrophages SYN: mononuclear phagocyte s.. masticatory s. the organs and structures primarily functioning in mastication: the jaws, teeth with their supporting structures, temporomandibular joint, muscles of mastication, tongue, lips, cheeks, and oral mucosa. SYN: dental apparatus, masticatory apparatus (1) . metameric nervous s. that part of the nervous s. which innervates body structures developed in ontogeny from the segmentally arranged somites or, in the head region, branchial arches. The term implies reference to the neural mechanisms intrinsic to the spinal cord and brainstem (represented by the sensory nuclei, motoneuronal cell groups, and their associated interneurons in the reticular formation); by strict definition it should exclude the autonomic nervous s.. meter-kilogram-second s. an absolute s. based on the meter, kilogram, and second; the basis of the International S. of Units. metric s. a s. of weights and measures, universal for scientific use, based upon the meter, which was originally intended to be one ten-millionth of a quadrant of the earth's meridian and now is based on the length that light travels in a vacuum in a given period of time (see meter). Prefixes of the meter (and other standards) reflect either fractions or multiples of the meter and are identical to the International S. of Units (q.v.). The unit of weight is the gram, which is the weight of one cubic centimeter of water, equivalent to 15.432358 grains. The unit of volume is the liter or one cubic decimeter, equal to 1.056688 U.S. liquid quarts; a cubic centimeter is about 16.23073 U.S. minims. mononuclear phagocyte s. (MPS) a widely distributed collection of both free and fixed macrophages derived from bone marrow precursor cells by way of monocytes; their substantial phagocytic activity is mediated by immunoglobulin and the serum complement s.. In both connective and lymphoid tissue, they may occur as free and fixed macrophages; in the sinusoids of the liver, as Kupffer cells; in the lung, as alveolar macrophages; and in the nervous s., as microglia. SYN: s. of macrophages. muscular s. all the muscles of the body collectively. nervous s. [TA] the entire nerve apparatus, composed of a central part, the brain and spinal cord, and a peripheral part, the cranial and spinal nerves, autonomic ganglia, and plexuses. SYN: systema nervosum [TA] . neuromuscular s. the muscles of the body collectively and the nerves supplying them. nonspecific s. SYN: reticular activating s.. occlusal s. the form or design and arrangement of the occlusal and incisal units of a dentition or the teeth on a denture. SYN: occlusal scheme. oculomotor s. that part of the central nervous s. having to do with eye movements; it is composed of pathways connecting various regions of the cerebrum, brainstem, and ocular nuclei, utilizing multisynaptic articulations. open s. a s. in which there is a continual exchange of material, energy, and information with the environment. O-R s. abbreviation for oxidation-reduction s.. oxidation-reduction s. (O-R s.) an enzyme s. in the tissues by which oxidation and reduction proceed simultaneously through the transference of hydrogen or of one or more electrons from one metabolite to another. SEE ALSO: oxidation-reduction. SYN: redox s.. parasympathetic nervous s. parasympathetic part of autonomic division of peripheral nervous s., autonomic division of nervous s.. pedal s. efferent fibers connecting the forebrain with more caudal structures. periodic s. the arrangement of the chemical elements in a definite order as indicated by their respective atomic numbers in such a way that groups of elements with similar chemical properties (similar valence shell electron number) are grouped together. See Mendeléeff law. peripheral nervous s. [TA] the peripheral part of the nervous s. external to the brain and spinal cord from their roots to their peripheral terminations. This includes the ganglia, both sensory and autonomic, and any plexuses through which the nerve fibers run. SEE ALSO: autonomic division of nervous s.. SYN: pars peripherica systematis nervosi [TA] , systema nervosum periphericum&star, peripheral part of nervous s.. Pinel s. the abolition of forcible restraint in the treatment of the mental hospital patient. portal s. a s. of vessels in which blood, after passing through one capillary bed, is conveyed through a second capillary network, as in the hepatic portal s. in which blood from the intestines passes through the liver sinusoids. pressoreceptor s. the pressoreceptive areas which with their afferent fibers and connections with the autonomic s. react to a rise in arterial blood pressure and serve to buffer it by inhibiting the heart rate and vascular tone. SEE ALSO: baroreceptor. projection s. the s. of axons carrying stimuli from one portion of the nervous s. to other portions. properdin s. an immunologic s. that is the alternative pathway for complement, composed of several distinct proteins that react in a serial manner and activate C3 (third component of complement), seemingly without utilizing components C1, C4, and C2; in addition to properdin, the s. includes Factors B, D, H, and I. The s. can be activated, in the absence of specific antibody, by bacterial endotoxins, by a variety of polysaccharides and lipopolysaccharides, and by a component of cobra venom. Purkinje s. SYN: subendocardial conducting s. of heart. redox s. SYN: oxidation-reduction s.. renal portal s. an arterial portal s., in which efferent glomerular arterioles receive blood from the capillaries of the renal glomeruli and carry it to the peritubular capillary plexus surrounding the proximal and distal convoluted tubules. SYN: hypothalamohypophysial portal s. (2) . renin-angiotensin s. a selective regulator of the aldosterone biosynthetic pathway that acts by increasing aldosterone production and sodium retention as a result of volume depletion, with resulting increased renin production in the kidney and conversion of angiotensin I in the plasma to angiotensin II. renin-angiotensin-aldosterone s. the hormones, renin, angiotensin, and aldosterone work together to regulate blood pressure. A sustained fall in blood pressure causes the kidney to release renin. This is converted to angiotensin in the circulation. Angiotensin then raises blood pressure directly by arteriolar constriction and stimulates the adrenal gland to produce aldosterone which promotes sodium and water retention by the kidney, such that blood volume and blood pressure increase. reproductive s. SYN: genital s.. respiratory s. [TA] all the air passages from the nose to the pulmonary alveoli. SYN: systema respiratorium [TA] , apparatus respiratorius, respiratory apparatus. reticular activating s. (RAS) a physiologic term denoting that part of the brainstem reticular formation that plays a central role in the organism's bodily and behavorial alertness; it extends as a diffusely organized neural apparatus through the central region of the brainstem into the subthalamus and the intralaminar nuclei of the thalamus; by its ascending connections it affects the function of the cerebral cortex in the sense of behavioral responsiveness; its descending (reticulospinal) connections transmit its activating influence upon bodily posture and reflex mechanisms ( e.g., muscle tonus), in part by way of the gamma motor neurons. SEE ALSO: reticular formation. SYN: nonspecific s.. reticuloendothelial s. (RES) a collection of putative macrophages, first described by Aschoff, which included most of the true macrophages (now classified under the mononuclear phagocytic s.) as well as cells lining the sinusoids of the spleen, lymph nodes, and bone marrow, and the fibroblastic reticular cells of hematopoietic tissues; all of these latter cells are only weakly phagocytic and are not true macrophages. The term persists in the literature and is often equated with the mononuclear phagocytic s.. second signaling s. pavlovian term for speech in which words are considered to be the “second signals” capable of producing conditioned responses. skeletal s. [TA] the bones and cartilages of the body. SYN: systema skeletale [TA] . somesthetic s. sensory data derived from skin, muscles, and body organs in contrast to that derived from the five special senses. static s. that part of the neuromuscular s. whereby the animal organism is maintained in posture and equilibrium and counteracts the forces of gravity and atmospheric pressure; distinguished from the kinetic s. (2). stomatognathic s. all of the structures involved in speech and in the reception, mastication, and deglutition of food. SEE ALSO: masticatory s.. SYN: masticatory apparatus (2) . subendocardial conducting s. of heart terminal ramifications in the ventricles of the specialized conducting s. of the heart. SYN: Purkinje s.. sympathetic nervous s. SYN: sympathetic part of autonomic division of peripheral nervous s.. T s. the transverse tubules that are continuous with the sarcolemma in skeletal and cardiac muscle fibers. thoracolumbar s. See autonomic division of nervous s., sympathetic part of autonomic division of peripheral nervous s.. thoracolumbar nervous s. SYN: sympathetic part of autonomic division of peripheral nervous s.. triaxial reference s. the figure resulting from rearranging the lines of derivation of the three standard limb leads of the electrocardiogram (as represented in the Einthoven triangle) so that, instead of forming the sides of an equilateral triangle, they bisect one another. SYN: Dieuaide diagram. urinary s. [TA] all organs concerned with the formation, storage, and voidance of urine including kidneys, ureters, bladder, and urethra. SYN: systema urinarium [TA] , urinary apparatus, uropoietic s.. urogenital s. includes all the organs concerned in reproduction and in the formation and voidance of urine. SYN: apparatus urogenitalis, genitourinary apparatus, genitourinary s., systema urogenitale, urogenital apparatus. uropoietic s. SYN: urinary s.. vascular s. the cardiovascular and lymphatic systems collectively. SYN: circulatory s.. vegetative nervous s. SYN: autonomic division of nervous s.. vertebral-basilar s. the arterial complex comprising the two vertebral arteries joining to form the basilar artery, and their immediate branches. vertebral venous s. any of four interconnected venous networks surrounding the vertebral column; anterior external vertebral venous plexus [TA] (plexus vertebralis externus anterior [TA]), the small s. around the vertebral bodies; posterior external vertebral venous plexus [TA] (plexus vertebralis internus anterior [TA]), the extensive s. around the vertebral processes; anterior internal vertebral venous plexus [TA] (plexus vertebralis internus posterior [TA]), the s. running the length of the vertebral canal anterior to the dura; posterior internal vertebral venous plexus, the s. running the length of the vertebral canal posterior to the dura; the latter two constitute the epidural venous plexus. SYN: Batson plexus, plexus venosus vertebralis, vertebral venous plexus. visceral motor s. SYN: autonomic division of nervous s.. visceral nervous s. SYN: autonomic division of nervous s.. Zaffaroni s. a chromatographic s. for the separation of steroids.

systema (sis′te′ma) [TA]
SYN: system. SEE ALSO: system, apparatus. [L. fr. G. s.] s. alimentarium SYN: alimentary system. s. cardiovasculare [TA] SYN: cardiovascular system. s. conducens cordis conducting system of heart. s. digestorium [TA] SYN: alimentary system. s. genitalia [TA] SYN: genital system. s. lymphaticum SYN: lymphoid system. s. lymphoideum [TA] SYN: lymphoid system. s. nervosum [TA] SYN: nervous system. s. nervosum autonomicum SYN: autonomic division of nervous system. s. nervosum centrale central nervous system, central nervous system. s. nervosum periphericum peripheral nervous system. s. respiratorium [TA] SYN: respiratory system. s. skeletale [TA] SYN: skeletal system. s. urinarium [TA] SYN: urinary system. s. urogenitale SYN: urogenital system.

systematic (sis′te-mat′ik)
Relating to a system in any sense; arranged according to a system.

systematic name
As applied to chemical substances, a s. is composed of specially coined or selected words or syllables, each of which has a precisely defined chemical structural meaning, so that the structure may be derived from the name. Water (trivial name) is hydrogen oxide (systematic). The s. of histamine (a semisystematic name) is imidazolethylamine, which indicates that a radical of imidazole replaces one hydrogen atom of ethylamine, which in turn is an ethyl group attached to an amine group. Dimethyl sulfoxide states that two methyl radicals are attached to a sulfur atom that holds an oxygen atom. Carbolic acid (trivial name) or phenol (semisystematic name) are, systematically, phenyl hydroxide or hydroxybenzene. SEE ALSO: semisystematic name.

systematization (sis-te-mat′i-za′shun, sis-tem′a-ti-)
The arrangement of ideas into orderly sequence.

Système International d'Unités
See International System of Units.

systemic (sis-tem′ik)
Relating to a system; specifically somatic, relating to the entire organism as distinguished from any of its individual parts.

systemoid (sis′te-moyd)
Resembling a system; denoting a tumor of complex structure resembling an organ.

systole (sis′to-le)
Contraction of the heart, especially of the ventricles, by which the blood is driven through the aorta and pulmonary artery to traverse the systemic and pulmonary circulations, respectively; its occurrence is indicated physically by the first sound of the heart heard on auscultation, by the palpable apex beat, and by the arterial pulse. [G. s., a contracting] aborted s. a loss of the systolic beat in the radial pulse through weakness of the ventricular contraction. atrial s. contraction of the atria. SYN: auricular s.. auricular s. SYN: atrial s.. electrical s. the duration of the QRST complex ( i.e., from the earliest Q wave to the end of the latest T wave on the ECG). electromechanical s. the period from the beginning of the QRS complex to the first (aortic) vibration of the second heart sound. SYN: QS2 interval. extra-s. extrasystole. late s. SYN: prediastole. premature s. SYN: extrasystole. ventricular s. contraction of the ventricles.

systolic (sis-tol′ik)
Relating to, or occurring during cardiac systole.

systolometer (sis′to-lom′e-ter)
1. An apparatus for determining the force of the cardiac contraction. 2. An instrument for analyzing the sounds of the heart. [systole + G. metron, measure]

systremma (sis-trem′a)
A muscular cramp in the calf of the leg, the contracted muscles forming a hard ball. [G. anything twisted]

syzygial (si-zij′e-al)
Relating to syzygy.

syzygiology (si-zij′e-ol′o-je)
The study of interrelationships, or interdependencies, especially of the whole, as opposed to the study of separate parts or isolated functions. [G. syzygios, yoked (see syzygy), + logos, study]

syzygium (si-zij′e-um)
SYN: syzygy.

syzygy (siz′i-je)
1. The association of gregarine protozoans end-to-end or in lateral pairing (without sexual fusion). 2. Pairing of chromosomes in meiosis. SYN: syzygium. [G. syzygios, yoked, bound together, fr. syn, together, + zygon, a yoke]


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