| alveolocapillary block | The presence of material that impairs the diffusion of gases between the air in the alveolar spaces and the blood in alveolar capillaries; block can be caused by oedema, cellular infiltration, fibrosis, or tumour, and results in undersaturation of peripheral arterial blood with oxygen. (05 Mar 2000) |
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| anterograde block | Conduction block of an impulse traveling anywhere in its ordinary direction, for example, from the sinoatrial node toward the ventricular myocardium. (05 Mar 2000) |
| arborization block | Intraventricular block supposedly due to widespread blockage in the Purkinje ramifications and manifested in the electrocardiogram by a pattern similar to bundle-branch block but with complexes of low amplitude. (05 Mar 2000) |
| atrioventricular block | <cardiology> A conduction disturbance that results in the inappropriate delay (or complete inability) of a electrical impulse, generated in the atria, to reach the ventricles (via the atrioventricular node). Clinical types are divided into first (nonserious), second and third degree (most serious). Some drugs may precipitate atrioventricular block (for example clonidine, methyldopa, verapamil). A permanent pacemaker may be required for a third degree (complete) heart block. (02 Jan 1998) |
| autonomic nerve block | Interruption of sympathetic pathways, by local injection of an anaesthetic agent, at any of four levels: peripheral nerve block, sympathetic ganglion block, extradural block, and subarachnoid block. (12 Dec 1998) |
| A-V block | <cardiology> A conduction disturbance that results in the inappropriate delay (or complete inability) of a electrical impulse, generated in the atria, to reach the ventricles (via the atrioventricular node). Clinical types are divided into first (nonserious), second and third degree (most serious). Some drugs may precipitate atrioventricular block (for example clonidine, methyldopa, verapamil). A permanent pacemaker may be required for a third degree (complete) heart block. (02 Jan 1998) |
| block | An obstruction or stoppage. (18 Nov 1997) |
| block anaesthesia | Regional anaesthesia in which local anaesthetic solution is injected about nerves to inhibit nerve transmission; includes spinal, epidural, nerve block, and field block anaesthesia, but not local or topical anaesthesia. Synonym: block anaesthesia. (05 Mar 2000) |
| block book | A book printed from engraved wooden blocks instead of movable types. Source: Websters Dictionary (01 Mar 1998) |
| block design test | A performance test using coloured blocks which the individual must use to match pictured designs; one of the subtests of the Wechsler intelligence scales. (05 Mar 2000) |
| block-out | Elimination of undercuts by filling such areas with a medium such as wax or wet pumice. (05 Mar 2000) |
| block vertebra | <radiology> Congenital vertebral fusion, location: lumbar or cervical, height of the fused vertebral bodies equals the sum of heights of the involved bodies and intervertebral disc, waist at level of disc space see: cervical spine fusion (12 Dec 1998) |
| block vertebrae | Congenitally fused and hypoplastic vertebral bodies which, on radiographs, give the appearance of a more or less solid bony mass. See: Klippel-Feil syndrome. (05 Mar 2000) |
| bone block | A surgical procedure in which the bone adjacent to the joint is modified to limit the motion of the joint mechanically; e.g., at the ankle joint to correct foot-drop by preventing extension below 90 |
| bundle-branch block | <cardiology, physiology> Abnormal conduction through one of the conductive branches which normally supply the right and left ventricles. Usually results in delayed conduction though either the right or left bundle branches where one ventricle is excited before the other because of absence of conduction in one of the branches of the bundle of His. Intraventricular block due to interruption of conduction in one of the two main branches of the bundle of His and manifested in the electrocardiogram by marked prolongation of the QRS complex; block of each branch has distinctive QRS morphology. (05 Mar 2000) |