| 单词 | plasma, biological |
| 释义 | plasma, biologicalplasma, biological:see bloodblood,fluid pumped by the heart that circulates throughout the body via the arteries, veins, and capillaries (see circulatory system; heart). An adult male of average size normally has about 6 quarts (5.6 liters) of blood. ..... Click the link for more information. . Seeblood body tissues" href="javascript:eml2('davisTab', 'b17.jpg')">   CharacteristicsBlood has a distinctive, somewhat metallic, odor. Arterial blood is bright red or scarlet and usually pulsates if the artery has been cut. Venous blood is dark red or crimson and flows steadily from a cut vein. CompositionHuman blood is about 52% to 62% plasma and 38% to 48% cells. The plasma is mostly water, ions, proteins, hormones, and lipids. The cellular components are the erythrocytes (red blood cells [RBCs]), leukocytes (white blood cells [WBCs]), and thrombocytes (platelets). The leukocytes comprise neutrophils, eosinophils, basophils, lymphocytes, and monocytes. See: illustration; buffy coat; plasma; serum An adult weighing 70 kg has a blood volume of about 5 L or 70 ml/kg of body weight. Blood constitutes about 7% to 8% of the body weight. The pH of the blood is from 7.35 to 7.45. The specific gravity of blood varies from 1.048 to 1.066, the cells being heavier and plasma lighter than this. Blood is of slightly higher specific gravity in men than in women. Specific gravity is higher after exercise and at night. See: blood count; cell; erythrocyte; leukocyte; plasma; platelet FunctionIn passing through the lungs, the blood gives up carbon dioxide and absorbs oxygen; after leaving the heart, it is carried to the tissues as arterial blood and then returned to the heart in the venous system. It moves in the aorta at an average speed of 30 cm/sec, and it makes the circuit of the vascular system in about 60 seconds. RBCs carry oxygen; WBCs participate in the immune response to infection; platelets are important in blood clotting. The plasma transports nutrients, waste products, hormones, carbon dioxide, and other substances, and contributes to fluid-electrolyte balance and thermal regulation. FormationRBCs are produced in the red bone marrow at the rate of about 2,400,000/sec, and each RBC lives for about 120 days. In healthy individuals, the concentration of RBCs in the blood remains stable over time. Platelets and WBCs are also produced in the red bone marrow, and agranular WBCs are produced in lymphatic tissue. clotting of bloodSee: coagulation, bloodcord blooddefibrinated bloodformed elements of bloodfresh bloodoccult bloodSee: occultoxygenated bloodpredonation of bloodautologous blood transfusion.reconstituted bloodsludged bloodunit of bloodbloodA complex fluid vital to life and circulated by the pumping action of the heart. The average blood volume is 5 litres. It is a transport medium, especially for oxygen, which it carries in the red blood cells linked to the HAEMOGLOBIN with which they are filled. It also transports dissolved sugars, dissolved proteins such as ALBUMIN and GLOBULIN, protein constituents (AMINO ACIDS), fat-protein combinations (LIPOPROTEINS), emulsified fats (TRIGLYCERIDES), vitamins, minerals and hormones. Blood also carries waste products such as carbon dioxide, urea, lactic acid, and innumerable other substances. In addition to the countless red cells the blood carries enormous numbers of uncoloured cells most of which are concerned in the defence of the individual against infection and cancer. It also contains large numbers of small non-nucleated bodies called PLATELETS which are concerned with BLOOD CLOTTING (coagulation). blooda connective tissue with a liquid matrix called BLOOD PLASMA. Suspended in the plasma are three types of cell which form about 45% of total blood volume:
blood(blŭd)See also: arterial blood, venous blood Patient discussion about bloodQ. does serratrol thin your blood? Q. what are Blood thiners what pilles are blood thinners Q. how can i reduce my blood pressure? |
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