Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells.
In vertebrates, it is composed of blood cells suspended in a liquid called blood plasma. Plasma, which constitutes 55% of blood fluid, is mostly water (92% by volume), and contains dissipated proteins, glucose, mineral ions, hormones, carbon dioxide (plasma being the main medium for excretory product transportation), and blood cells themselves. Albumin is the main protein in plasma, and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are mainly red blood cells (also called RBCs or erythrocytes) and white blood cells, including leukocytes and platelets. The most abundant cells in vertebrate blood are red blood cells. These contain hemoglobin, an iron-containing protein, which facilitates transportation of oxygen by reversibly binding to this respiratory gas and greatly increasing its solubility in blood. In contrast, carbon dioxide is almost entirely transported extracellularly dissolved in plasma as bicarbonate ion.
Vertebrate blood is bright red when its hemoglobin is oxygenated. Some animals, such as crustaceans and mollusks, use hemocyanin to carry oxygen, instead of hemoglobin. Insects and some mollusks use a fluid called hemolymph instead of blood, the difference being that hemolymph is not contained in a closed circulatory system. In most insects, this "blood" does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their tracheal system to suffice for supplying oxygen.
Jawed vertebrates have an adaptive immune system, based largely on white blood cells. White blood cells help to resist infections and parasites. Platelets are important in the clotting of blood. Arthropods, using hemolymph, have hemocytes as part of their immune system.
Blood is circulated around the body through blood vessels by the pumping action of the heart. In animals with lungs, arterial blood carries oxygen from inhaled air to the tissues of the body, and venous blood carries carbon dioxide, a waste product of metabolism produced by cells, from the tissues to the lungs to be exhaled.
Medical terms related to blood often begin with hemo- or hemato- (also spelled haemo- and haemato-) from the Greek word αἷμα (haima) for "blood". In terms of anatomy and histology, blood is considered a specialized form of connective tissue, given its origin in the bones and the presence of potential molecular fibers in the form of fibrinogen.
Other articles related to "blood":
... murder is supposed to be handled, which often in the past and sometimes still now lead to blood feuds that last until all the men of the two involved families are killed ... feuding families and try to get them to "pardon the blood" (Albanian Falja e Gjakut), but often the only resort is for men of age to stay in their homes, which are ... The Albanian name for blood feud is Gjakmarrja ...
... by Marc Quinn, a frozen cast of the artist's head made entirely of his own blood The Home-Coming of Navel Strings, an installation by Noritoshi Hirakawa for the 2004 London Frieze Art Fair, which consisted of a ... However, there have been rarer uses of blood (and perhaps feces) for quite some time ... Pete Doherty has painted with blood, while Marcel Duchamp used semen in his Paysage fautif ("Faulty Landscape") of 1946 ...
... Blood tests and microscopy can be used to aid in the diagnosis of trichinosis ... Blood tests include a complete blood count for eosinophilia, creatine phosphokinase activity, and various immunoassays such as ELISA for larval antigens ...
... dioxide levels in the lungs and then in the blood ... This leads to shifts in blood pH (respiratory alkalosis or hypocapnia), which in turn can lead to many other symptoms, such as tingling or numbness ... panic attack causes vasoconstriction resulting in slightly less blood flow to the head which causes dizziness and lightheadedness ...
... The term blood is used in genealogical circles to refer to one's ancestry, origins, and ethnic background as in the word bloodline ... Other terms where blood is used in a family history sense are blue-blood, royal blood, mixed-blood and blood relative ...
Famous quotes containing the word blood:
“The blood weeps from my heart when I do shape,
In forms imaginary, th unguided days
And rotten times that you shall look upon
When I am sleeping with my ancestors.”
—William Shakespeare (15641616)
“I was born upon thy bank, river,
My blood flows in thy stream,
And thou meanderest forever
At the bottom of my dream.”
—Henry David Thoreau (18171862)
“The principle of majority rule is the mildest form in which the force of numbers can be exercised. It is a pacific substitute for civil war in which the opposing armies are counted and the victory is awarded to the larger before any blood is shed. Except in the sacred tests of democracy and in the incantations of the orators, we hardly take the trouble to pretend that the rule of the majority is not at bottom a rule of force.”
—Walter Lippmann (18891974)