system (sis´tem)

1. A consistent and complex whole made up of correlated and semi-independent parts. A complex of anatomical structures functionally related. 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, system. 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.systema [NA] ; [G. systema, an organized whole]
absolute s. of unitsa 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 s.'s in common use are the foot-pound-second, centimeter-gram-second, and meter-kilogram-second s.'s.
absorbent s.lymphatic s
alimentary s.digestive s
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.
arch-loop-whorl s. (A.L.W.) See Galton's system 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 system, such as the various areas of the cerebral cortex or the various segments of the spinal cord.
autonomic nervous s.that part of the nervous system which represents the motor innervation of smooth muscle, cardiac muscle, and gland cells. It consists of two physiologically and anatomically distinct, mutually antagonistic components: the sympathetic and parasympathetic parts. In both of these parts the pathway of innervation consists of a synaptic sequence of two motor neurons, one of which lies in the spinal cord or brainstem as the preganglionic neuron, the thin but myelinated axon of which (preganglionic or B fiber) emerges with an outgoing spinal or cranial nerve and synapses with one or more of the postganglionic (or, more strictly, ganglionic) neurons composing the autonomic ganglia; the unmyelinated postganglionic fibers in turn innervate the smooth muscle, cardiac muscle, or gland cells. The preganglionic neurons of the sympathetic part lie in the intermediolateral cell column of the thoracic and upper two lumbar segments of the spinal gray matter; those of the parasympathetic part compose the visceral motor (visceral efferent) nuclei of the brainstem as well as the lateral column of the second to fourth sacral segments of the spinal cord. The ganglia of the sympathetic part are the paravertebral ganglia of the sympathetic trunk and the prevertebral or collateral ganglia; those of the parasympathetic part lie either near the organ to be innervated or as intramural ganglia within the organ itself except in the head, where there are four discrete parasympathetic ganglia (ciliary, otic, pterygopalatine, and submandibular). Impulse transmission from preganglionic to postganglionic neuron is mediated by acetylcholine in both the sympathetic and parasympathetic parts; transmission from the postganglionic fiber to the visceral effector tissues is classically said to be by acetylcholine in the parasympathetic part and by noradrenalin in the sympathetic part; recent evidence suggests the existence of further noncholinergic, nonadrenergic classes of postganglionic autonomica [NA] , systema nervosum autonomicum [NA] , autonomic part, involuntary nervous s., vegetative nervous s., visceral nervous s;
Bethesda s.recent classification for categorizing cervical Papanicolaou smears. [Bethesda, Maryland, site of NIH]
blood group s.'ssee Blood Groups appendix.
blood-vascular s.cardiovascular s
bulbosacral s.parasympathetic part
cardiovascular s.the heart and blood vessels considered as a whole.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 System of Units based on the meter, kilogram, and second.
central nervous s. (CNS) the brain and the spinal centralis [NA] , systema nervosum centrale [NA] ;
cerebrospinal s.the combined central nervous s. and peripheral nervous s.
charge transfer s.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.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 s.'s 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.
conducting s. of heartthe s. of atypical cardiac muscle fibers comprising the sinoatrial node, internodal tracts, atrioventricular node and bundle, the bundle branches, and their terminal ramifications into the Purkinje network; sometimes also called cardionector.
craniosacral s.parasympathetic part
cytochrome s.respiratory chain
dermal s., dermoid s.the skin and its appendages, the nails and hair.
digestive s.the digestive tract from the mouth to the anus with all its associated glands and organs.systema alimentarium, alimentary apparatus, alimentary s., systema digestorium;
ecological s.ecosystem
electron-transport s.respiratory chain
endocrine s.collective designation for those tissues capable of secreting hormones.
endomembrane s.endoplasmic reticulum
esthesiodic s.a s. of neurons and fiber tracts in the spinal cord and brain subserving sensation.
exterofective 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 commonly 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.gamma loop
genital s.the complex s. consisting of the male or female gonads, associated ducts, and external genitalia dedicated to the function of reproducing the species.reproductive s;
genitourinary s.urogenital s
glandular s.all the glands of the body collectively.
haversian s.osteon
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 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 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. (hI´po-fiz´e-o- por´tal) portal hypophysial circulation
hypophysial portal s.portal hypophysial circulation
hypophysioportal s.portal hypophysial circulation
hypothalamohypophysial portal s.portal hypophysial circulation
hypothalamohypophysial portal s.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 system would warn of impending hypoxia in time for corrective action to be taken.
immune 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 in vitro immunological tests, a combination of reagents used to determine the degree to which immunological 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.the skin, hair, and nails; derived from ectoderm and subjacent mesoderm.
intermediary s.interstitial lamella
International S. of Units See International System 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.autonomic 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.
lateral line s.a series of sense organs that detect pressure or vibrations along the head and side of cyclostomes, fishes, and some amphibians.
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 s.'s; its functions also appear to affect motivational and mood states.visceral brain;
linnaean s. of nomenclaturethe 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).binary nomenclature, binomial nomenclature; [Carl von Linné]
lymphatic consists of lymphatic vessels, nodes, and lymphoid tissue; it empties into the veins at the level of the superior aperture of the thorax.systema lymphaticum [NA] , absorbent s;
s. of macrophagesmononuclear 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 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 system.
meter-kilogram-second absolute s. based on the meter, kilogram, and second; the basis of the International System 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 System of Units (see International System of Units). 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 system. 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 system, as microglia.s. of macrophages;
muscular s.all the muscles of the body collectively.
nervous s.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.systema nervosum [NA] ;
neuromuscular s.the muscles of the body collectively and the nerves supplying them.
nonspecific s.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.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.redox s;
parasympathetic nervous s. See parasympathetic part, autonomic 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's law.
peripheral nervous s.the peripheral part of the nervous system 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 nervous peripherica [NA] , systema nervosum periphericum [NA] , peripheral part;
Pinel's 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 system 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 system 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 system to other portions.
properdin immunological 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 properdin factors A (native C3), B (C3 proactivator), D (C3 proactivator convertase), and perhaps at least one other, E; 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.terminal ramifications in the ventricles of the specialized conducting s. of the heart.
redox s.oxidation-reduction s
renal portal 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.hypothalamohypophysial portal s;
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 cuases the kidney to release renin. This is converted to angiotensin in the circulation. Angiotensin then raises blood pressure directly by arteriolar constriction and stimulates adrenal gland to produce aldosterone which promotes sodium and water retention by kidney, such that blood volume and blood pressure increase.
reproductive s.genital s
respiratory s.all the air passages from the nose to the pulmonary alveoli.apparatus respiratorius [NA] , systema respiratorium [NA] , respiratory apparatus;
reticular activating s. (RAS) a physiological 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.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.the bones and cartilages of the body.systema skeletale [NA] ;
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 receiving, mastication, and deglutition of food. See also masticatory s.masticatory apparatus (2) ;
sympathetic nervous s. 1. originally, the entire autonomic nervous s.; 2. the sympathetic part of the nervous system. See also autonomic nervous sympathica [NA] , sympathetic part;
T s.the transverse tubules that are continuous with the sarcolemma in skeletal and cardiac muscle fibers.
thoracolumbar s. See autonomic nervous s., sympathetic part.
triaxial reference s.the figure resulting from rearranging the lines of derivation of the three standard limb leads of the electrocardiogram (as represented in Einthoven's triangle) so that, instead of forming the sides of an equilateral triangle, they bisect one another.Dieuaide diagram;
urinary s.urogenital s
urogenital s.includes all the organs concerned in reproduction and in the formation and voidance of the urine.apparatus urogenitalis [NA] , systema urogenitale [NA] , genitourinary apparatus, genitourinary s., urinary apparatus, urinary s., urogenital apparatus;
uropoietic s.the kidneys, ureters, bladder, and urethra, considered as a s. for the secretion and excretion of urine.
vascular s.the cardiovascular and lymphatic s.'s collectively.circulatory s;
vegetative nervous s.autonomic 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, the small s. around the vertebral bodies; posterior external vertebral venous plexus, the extensive s. around the vertebral processes; anterior internal vertebral venous plexus, 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.plexus venosus vertebralis [NA] , Batson's plexus, vertebral venous plexus;
visceral nervous s.autonomic nervous s
Zaffaroni s.a chromatographic s. for the separation of steroids.


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