| conducting system of heart | The system of atypical cardiac muscle fibres 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. (05 Mar 2000) |
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| multienzyme system | A group of related enzymes that operate in a particular metabolic pathway. (09 Oct 1997) |
| multiple system atrophy | A name grouping together the four cerebral degenerative diseases of olivopontocerebellar atrophy, shy-drager syndrome, striatonigral degeneration, and one form of parkinson disease, considering them different forms of the same disease process. (12 Dec 1998) |
| muscular system | All the muscles of the body collectively. (05 Mar 2000) |
| musculoskeletal system | All the muscles, bones, and cartilages of the body collectively. (12 Dec 1998) |
| point system test types | A near-vision test chart in which the various test types are multiples of a point (1/72 inch), lower-case letters being one-half the designated point size; reading 4-point at 16 inches is normal, and is designated N-4. (05 Mar 2000) |
| craniosacral system | parasympathetic part |
| portal system | A system of vessels in which blood, after passing through one capillary bed, is conveyed through a second set of capillaries before it returns to the systemic circulation. It pertains especially to the hepatic portal system. (12 Dec 1998) |
| haematopoietic system | 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. (05 Mar 2000) |
| haemolytic system | <haematology> A haemolytic system is composed of red blood cells covered with antibodies which are genetically identical to the surface proteins (antigens) of the red blood cells. It is used to measure how much complement is left after a round of complement fixation. (09 Oct 1997) |
| cytochrome system | The mitochondrial electron transport chain. (18 Nov 1997) |
| pressoreceptor system | The pressoreceptive areas which with their afferent fibres 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: baroreceptor. (05 Mar 2000) |
| haversian system | <anatomy> The basic unit of structure of compact bone, comprising a haversian canal and its concentrically arranged lamellae, of which there may be 4 to 20, each 3 to 7 microns thick, in a single haversian system. A haversian canal is a freely anastomosing channel in compact bone containing blood vessels and running longitudinally in the centre of haversian systems of compact osseous tissue. It was originally described by Clopton Havers, an english physician, in 1691. (12 Dec 1998) |
| heart conduction system | An impulse-conducting system composed of modified cardiac muscle and having the power of spontaneous rhythmicity and conduction more highly developed than the rest of the heart. (12 Dec 1998) |
| projection system | The system of axons carrying stimuli from one portion of the nervous system to other portions. (05 Mar 2000) |