| pacchionian bodies | Tufted prolongations of pia-arachnoid, composed of numerous arachnoid villi that penetrate dural venous sinuses and effect transfer of cerebrospinal fluid to the venous system. at advanced age these are more numerous and tend to calcify. Synonym: granulationes arachnoideales, arachnoidal granulations, pacchionian bodies, pacchionian corpuscles, pacchionian glands, pacchionian granulations. (05 Mar 2000) |
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| pacchionian corpuscles | Tufted prolongations of pia-arachnoid, composed of numerous arachnoid villi that penetrate dural venous sinuses and effect transfer of cerebrospinal fluid to the venous system. at advanced age these are more numerous and tend to calcify. Synonym: granulationes arachnoideales, arachnoidal granulations, pacchionian bodies, pacchionian corpuscles, pacchionian glands, pacchionian granulations. (05 Mar 2000) |
| pacchionian depressions | Pits on the inner surface of the skull, along the course of the superior sagittal sinus, in which are lodged the arachnoidal granulations. Synonym: foveolae granulares, pacchionian depressions. (05 Mar 2000) |
| pacchionian glands | Synonym: arachnoid granulations. (05 Mar 2000) |
| pacchionian granulations | Tufted prolongations of pia-arachnoid, composed of numerous arachnoid villi that penetrate dural venous sinuses and effect transfer of cerebrospinal fluid to the venous system. at advanced age these are more numerous and tend to calcify. Synonym: granulationes arachnoideales, arachnoidal granulations, pacchionian bodies, pacchionian corpuscles, pacchionian glands, pacchionian granulations. (05 Mar 2000) |
| pace | 1. A single movement from one foot to the other in walking; a step. 2. The length of a step in walking or marching, reckoned from the heel of one foot to the heel of the other; used as a unit in measuring distances; as, he advanced fifty paces. Ordinarily the pace is estimated at two and one half linear feet; but in measuring distances be stepping, the pace is extended to three feet (one yard) or to three and three tenths feet (one fifth of a rod). The regulation marching pace in the English and United States armies is thirty inches for quick time, and thirty-six inches for double time. The Roman pace (passus) was from the heel of one foot to the heel of the same foot when it next touched the ground, five Roman feet. 3. Manner of stepping or moving; gait; walk; as, the walk, trot, canter, gallop, and amble are paces of the horse; a swaggering pace; a quick pace. "To-morrow, and to-morrow, and to-morrow, Creeps in this petty pace from day to day." (Shak) "In the military schools of riding a variety of paces are taught." (Walsh) 4. A slow gait; a footpace. 5. Specifically, a kind of fast amble; a rack. 6. Any single movement, step, or procedure. "The first pace necessary for his majesty to make is to fall into confidence with Spain." (Sir W. Temple) 7. A broad step or platform; any part of a floor slightly raised above the rest, as around an altar, or at the upper end of a hall. 8. A device in a loom, to maintain tension on the warp in pacing the web. Geometrical pace, the space from heel to heel between the spot where one foot is set down and that where the same foot is again set down, loosely estimated at five feet, or by some at four feet and two fifths. See Roman pace in the Note under def. 2. To keep, or hold, pace with, to keep up with; to go as fast as. "In intellect and attainments he kept pace with his age." Origin: OE. Pas, F. Pas, from L. Passus a step, pace, orig, a stretching out of the feet in walking; cf. Pandere, passum, to spread, stretch; perh. Akin to E. Patent. Cf. Pas, Pass. Source: Websters Dictionary (01 Mar 1998) |
| pacefollower | Any cell in excitable tissue that responds to stimuli from a pacemaker. (05 Mar 2000) |
| pacemaker | 1. <apparatus, physiology> An object or substance that influences the rate at which a certain phenomenon occurs, often used alone to indicate the natural cardiac pacemaker or an artificial cardiac pacemaker. 2. <biochemistry> A substance whose rate of reaction sets the pace for a series of interrelated reactions. (24 Mar 1998) |
| pacemaker failure | Failure of an artificial pacemaker to generate or deliver effective stimuli to the myocardium. (05 Mar 2000) |
| pacemaker output | Electrical energy delivered into a standard load (500 ohms resistance). (05 Mar 2000) |
| pacemaker potential | The voltage inscribed by impulses from an artificial electronic pacemaker. (05 Mar 2000) |
| pacemaker sensitivity | The minimum cardiac activity required to consistently trigger a pulse generator. (05 Mar 2000) |
| pacemaker syndrome | <syndrome> The occurrence of symptoms relating to the loss of atrial-ventricular synchrony in ventricularly paced patients, or symptoms caused by inadequate timing of atrial and ventricular contractions in paced patients. (05 Mar 2000) |
| pacemaker, artificial | A device designed to stimulate, by electric impulses, contraction of the heart muscles. It may be temporary (external) or permanent (internal or internal-external). (12 Dec 1998) |
| pachak | <botany> The fragrant roots of the Saussurea Costus, exported from India to China, and used for burning as incense. It is supposed to be the costus of the ancients. Alternative forms: putchuck. Source: Websters Dictionary (01 Mar 1998) |