| blood-borne pathogens | Infectious organisms in the blood, of which the predominant medical interest is their contamination of blood-soiled linens, towels, gowns, bandages, other items from individuals in risk categories, needles and other sharp objects, and medical and dental waste, all of which health workers are exposed to. This concept is differentiated from the clinical conditions of bacteraemia, viraemia, and fungaemia where the organism is present in the blood of a patient as the result of a natural infectious process. (12 Dec 1998) |
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| blood-brain barrier | <pharmacology, physiology> A protective barrier formed by the blood vessels and glia of the brain. It prevents some substances in the blood from entering brain tissue. The blood vessels of the brain (and the retina) are much more impermeable to large molecules (like antibodies) than blood vessels elsewhere in the body. This has important implications for the ability of the organism to mount an immune response in these tissues, although the basis for the difference in endothelial permeability is not well understood. (16 Dec 1997) |
| blood calculus | An angiolith or concretion of coagulated blood. Synonym: hemic calculus. (05 Mar 2000) |
| blood capillary | A vessel whose wall consists of endothelium and its basement membrane; its diameter, when the capillary is open, is about 8 um; with the electron microscope, fenestrated capillary's and continuous capillary's are distinguished. (05 Mar 2000) |
| blood cast | A cast usually formed in renal tubules, but may occur in bronchioles; consists of inspissated material that includes various elements of blood (i.e., erythrocytes, leukocytes, fibrin, and so on), resulting from bleeding into the glomerulus or tubule, or into the alveolus or bronchiole. (05 Mar 2000) |
| blood catecholamine | <investigation> The measurement of noradrenaline and adrenaline in the blood. Often these same catecholamines can be measured in the urine. Elevations may be seen in pheochromocytoma or neuroblastoma. Normal blood levels of adrenaline should be: 20 ng/ml and normal blood levels of noradrenaline should be 60 ng/ml. (05 Jan 1998) |
| blood cell | <haematology> There are three main types of cell in the blood stream. The red cell, which carries oxygen, the white cell, which fights infections and the platelet, which helps prevent bleeding. The correct balance between each cell type must be maintained for the body to remain healthy. (13 Nov 1997) |
| blood cell count | A count of the number of leukocytes and erythrocytes per unit volume in a sample of venous blood. A complete blood count (cbc) also includes measurement of the haemoglobin, haematocrit, and erythrocyte indices. (12 Dec 1998) |
| blood-cerebrospinal fluid barrier | A barrier located at the tight junctions which surround and connect the cuboidal epithelial cells on the surface of the choroid plexus; capillaries and connective tissue stroma of the choroid do not represent a barrier to protein tracers or dyes. (05 Mar 2000) |
| blood circulation | The course of the blood from the heart through the arteries, capillaries, and veins back again to the heart. (05 Mar 2000) |
| blood circulation time | Determination of the shortest time interval between the injection of a substance in the vein and its arrival at some distant site in sufficient concentration to produce a recognizable end result. It represents approximately the inverse of the average velocity of blood flow between two points. (12 Dec 1998) |
| blood clot | <haematology> The conversion of blood from a liquid form to solid through the process of coagulation. A thrombus is a clot which forms inside of a blood vessel. If that clot moves inside the vessel it is referred to as an embolus (embolism). The presence of atherosclerotic plaque lining blood vessel walls is a significant stimulus for clot formation. (27 Sep 1997) |
| blood clotting factor | <haematology> Any of a number of different protein factors which, when acting together, can form a blood clot shortly after platelets have broken at the site of the wound. The factors have Roman numeral names, like VII, VIII, IX, X, XI, and XIII. Defects in the genes which code for any of these factors result in genetic diseases like haemophilia, which results from a defect in the gene for factor VIII or IX. (09 Oct 1997) |
| blood coagulation | The sequential process by which the multiple coagulation factors of the blood interact, ultimately resulting in the formation of an insoluble fibrin clot; it may be divided into three stages: stage 1, the formation of intrinsic and extrinsic prothrombin converting principle; stage 2, the formation of thrombin; stage 3, the formation of stable fibrin polymers. (12 Dec 1998) |
| blood coagulation factor inhibitors | Substances, usually endogenous, that act as inhibitors of blood coagulation. They may affect one or multiple enzymes throughout the process. As a group, they also inhibit enzymes involved in processes other than blood coagulation, such as those from the complement system, fibrinolytic enzyme system, blood cells, and bacteria. (12 Dec 1998) |