ETYM Old Eng. blod, blood, AS. blôd; akin to Dutch bloed, Old High Germ. bluot, German blut, Goth. blôth, Icel. blôth, Swed. and Dan. blod; prob. from the same root as Eng. blow to bloom. Related to Blow to bloom.
Fluid circulating in the arteries, veins, and capillaries of vertebrate animals; the term also refers to the corresponding fluid in those invertebrates that possess a closed circulatory system. Blood carries nutrients and oxygen to each body cell and removes waste products, such as carbon dioxide. It is also important in the immune response and, in many animals, in the distribution of heat throughout the body.
In humans blood makes up 5% of the body weight, occupying a volume of 5.5 l/10 pt in the average adult. It is composed of a colorless, transparent liquid called plasma, in which are suspended microscopic cells of three main varieties.
Red cells (erythrocytes) form nearly half the volume of the blood, with about six million red cells in every milliliter of an adult’s blood. Their red color is caused by hemoglobin.
White cells (leukocytes) are of various kinds. Some (phagocytes) ingest invading bacteria and so protect the body from disease; these also help to repair injured tissues. Others (lymphocytes) produce antibodies, which help provide immunity.
Blood platelets (thrombocytes) assist in the clotting of blood.
Blood cells constantly wear out and die and are replaced from the bone marrow. Red blood cells die at the rate of 200 billion per day but the body produces new cells at an average rate of 9 billion per hour.
Arterial blood, which is rich in oxygen, is bright red in color; venous blood, containing little oxygen, is dark red. Blood is slightly heavier than water (specific gravity 1.06) and has an alkaline reaction. It has a circulatory movement, being pumped through the arteries and veins by the heart.
1. People viewed as members of a group.
2. Temperament or disposition.
3. The fluid (red in vertebrates) that is pumped by the heart. + prikaži više