blood

blood,

fluid pumped by the heart that circulates throughout the body via the arteries, veins, and capillaries (see circulatory systemcirculatory system,
group of organs that transport blood and the substances it carries to and from all parts of the body. The circulatory system can be considered as composed of two parts: the systemic circulation, which serves the body as a whole except for the lungs, and the
..... Click the link for more information. ; heartheart,
muscular organ that pumps blood to all parts of the body. The rhythmic beating of the heart is a ceaseless activity, lasting from before birth to the end of life. Anatomy and Function

The human heart is a pear-shaped structure about the size of a fist.
..... Click the link for more information. ). An adult male of average size normally has about 6 quarts (5.6 liters) of blood. The blood carries oxygen and nutrients to the body tissues and removes carbon dioxide and other wastes. The colorless fluid of the blood, or plasma, carries the red and white blood cells, platelets, waste products, and various other cells and substances.

Erythrocytes (Red Blood Cells)

The erythrocytes, or red blood cells, make up the largest population of blood cells, numbering from 4.5 million to 6 million per cubic millimeter of blood. They carry out the exchange of oxygen and carbon dioxide between the lungs and the body tissues. To effectively combine with oxygen, the erythrocytes must contain a normal amount of the red protein pigment hemoglobinhemoglobin
, respiratory protein found in the red blood cells (erythrocytes) of all vertebrates and some invertebrates. A hemoglobin molecule is composed of a protein group, known as globin, and four heme groups, each associated with an iron atom.
..... Click the link for more information. , the amount of which in turn depends on the iron level in the body. A deficiency of iron and therefore of hemoglobin leads to anemiaanemia
, condition in which the concentration of hemoglobin in the circulating blood is below normal. Such a condition is caused by a deficient number of erythrocytes (red blood cells), an abnormally low level of hemoglobin in the individual cells, or both these conditions
..... Click the link for more information. and poor oxygenation of the body tissues.

Erythrocytes are constantly developing from stem cells, the undifferentiated, self-regenerating cells that give rise to both erythrocytes and leukocytes in the bone marrowbone marrow,
soft tissue filling the spongy interiors of animal bones. Red marrow is the principal organ that forms blood cells in mammals, including humans (see blood). In children, the bones contain only red marrow.
..... Click the link for more information. . In the fetus, red blood cells are produced in the spleenspleen,
soft, purplish-red organ that lies under the diaphragm on the left side of the abdominal cavity. The spleen acts as a filter against foreign organisms that infect the bloodstream, and also filters out old red blood cells from the bloodstream and decomposes them.
..... Click the link for more information. . As they mature, the erythrocytes lose their nuclei, become disk-shaped, and begin to produce hemoglobin. After circulating for about 120 days, the erythrocytes wear out and undergo destruction by the spleen. Although all red blood cells are essentially similar, certain structures on their surfaces vary from person to person. These serve as the basis for the classification into blood groupsblood groups,
differentiation of blood by type, classified according to immunological (antigenic) properties, which are determined by specific substances on the surface of red blood cells.
..... Click the link for more information. . There are four major blood groups, whose compatibility or incompatibility is an important consideration in successful blood transfusionblood transfusion,
transfer of blood from one person to another, or from one animal to another of the same species. Transfusions are performed to replace a substantial loss of blood and as supportive treatment in certain diseases and blood disorders.
..... Click the link for more information. .

Leukocytes (White Blood Cells)

The leukocytes, or white blood cells, defend the body against infecting organisms and foreign agents, both in the tissues and in the bloodstream itself (see immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
..... Click the link for more information. ). Human blood contains about 5,000 to 10,000 leukocytes per cubic millimeter; the number increases in the presence of infection. An extraordinary and prolonged proliferation of leukocytes is known as leukemialeukemia
, cancerous disorder of the blood-forming tissues (bone marrow, lymphatics, liver, spleen) characterized by excessive production of immature or mature leukocytes (white blood cells; see blood) and consequently a crowding-out of red blood cells and platelets.
..... Click the link for more information. . This overproduction suppresses the production of normal blood cells. Conversely, a sharp decrease in the number of leukocytes (leukopenia) strips the blood of its defense against infection and is an equally serious condition. A dramatic fall in levels of certain white blood cells occurs in persons with AIDSAIDS
or acquired immunodeficiency syndrome,
fatal disease caused by a rapidly mutating retrovirus that attacks the immune system and leaves the victim vulnerable to infections, malignancies, and neurological disorders. It was first recognized as a disease in 1981.
..... Click the link for more information. . Leukocytes as well as erythrocytes are formed from stem cells in the bone marrow. They have nuclei and are classified into two groups: granulocytes and agranulocytes.

Granulocytes

The granulocytes form in the bone marrow and account for about 70% of all white blood cells. Granulocytes include three types of cells: neutrophils, eosinophils, and basophils. Neutrophils constitute the vast majority of granulocytes. They travel about by ameboid movement and can surround and destroy bacteria and other foreign particles. The eosinophils, ordinarily about 2% of the granulocyte count, increase in number in the presence of allergic disorders and parasitic infestations. The basophils account for about 1% of the granulocytes. They release chemicals such as histamine and play a role in the inflammatory response to infection.

Agranulocytes

The agranulocytes include the monocytes and the lymphocytes. Monocytes are derived from the phagocytic cells that line many vascular and lymph channels, called the reticuloendothelial system. Monocytes ordinarily number 4% to 8% of the white cells. They move to areas of infection, where they are transformed into macrophages, large phagocytic cells that trap and destroy organisms left behind by the granulocytes and lymphocytes. In certain diseases of long duration (tuberculosistuberculosis
(TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the intestines, bones and joints, the skin, and the genitourinary, lymphatic, and
..... Click the link for more information. , malariamalaria,
infectious parasitic disease that can be either acute or chronic and is frequently recurrent. Malaria is common in Africa, Central and South America, the Mediterranean countries, Asia, and many of the Pacific islands.
..... Click the link for more information. , and typhoidtyphoid fever
acute, generalized infection caused by Salmonella typhi. The main sources of infection are contaminated water or milk and, especially in urban communities, food handlers who are carriers.
..... Click the link for more information. ) the monocytes act as the main instrument of defense.

Lymphocytes, under normal conditions, make up about 20% to 35% of all white cells, but proliferate rapidly in the face of infection. There are two basic types of lymphocytes: the B lymphocytes and the T lymphocytes. B lymphocytes tend to migrate into the connective tissue, where they develop into plasma cells that produce highly specific antibodies against foreign antigens. Other B lymphocytes act as memory cells, ready for subsequent infection by the same organism. Some T lymphocytes kill invading cells directly; others interact with other immune system cells, regulating the immune response.

Other Constituents of Blood

The blood also contains platelets, or thrombocytes, and at least 15 other factors active in blood clottingblood clotting,
process by which the blood coagulates to form solid masses, or clots. In minor injuries, small oval bodies called platelets, or thrombocytes, tend to collect and form plugs in blood vessel openings.
..... Click the link for more information. . Platelets are tiny plate-shaped cytoplasmic bags of blood-clotting chemicals produced by megakaryocytes; if their production is hindered, as by AIDS or chemotherapy, there is an increased risk of bleeding. Also circulating in the plasma are the hormones that the endocrine glands secrete directly into the bloodstream. In addition, essential salts (such as those of sodium and potassium), essential plasma proteins (albuminalbumin
[Lat.,=white of egg], member of a class of water-soluble, heat-coagulating proteins. Albumins are widely distributed in plant and animal tissues, e.g., ovalbumin of egg, myogen of muscle, serum albumin of blood, lactalbumin of milk, legumelin of peas, and leucosin of
..... Click the link for more information. , globulinsglobulin,
any of a large family of proteins of a spherical or globular shape that are widely distributed throughout the plant and animal kingdoms. Many of them have been prepared in pure crystalline form.
..... Click the link for more information. , and fibrinogen), and metabolic wastes (such as ureaurea
, organic compound that is the principal end product of nitrogen metabolism in most mammals. Urea was the first animal metabolite to be isolated in crystalline form; its crystallization was described in the early 18th cent.
..... Click the link for more information. ) circulate in the plasma.

Serum, a straw-colored liquid, essentially composed of plasma without fibrinogen, makes up the liquid component of blood that separates from the clot. Serum is separated from whole blood by centrifuging and can serve various medical uses. Normal human serum is sometimes used to treat shock and the loss of fluid resulting from severe burns.

Bibliography

See D. Starr, Blood (1998).

Blood

The fluid that circulates in the blood vessels of the body. Blood consists of plasma and cells floating within it. The cells are derived from extravascular sites and then enter the circulatory system. They frequently leave the blood vessels to enter the extravascular spaces, where some of them may be transformed into connective tissue cells. The fluid part of the blood is in equilibrium with the tissue fluids of the body. The circulating blood carries nutrients and oxygen to the body cells, and is thus an important means of maintaining the homeostasis of the body. It carries hormones from their sites of origin throughout the body, and is thus the transmitter of the chemical integrators of the body. Blood plasma also circulates immune bodies and contains several of the components essential for the formation of blood clots. Finally, blood transports waste products to excretory organs for elimination from the body. Because of its basic composition (cells surrounded by a matrix), development, and ability to modify into other forms of connective tissues, blood can be regarded as a special form of connective tissue. See Connective tissue

Formed elements

The cells of the blood include the red blood cells and the white blood cells. In all vertebrates, except nearly all mammals, the red blood cells or corpuscles contain a nucleus and cytoplasm rich in hemoglobin. In nearly all mammals the nucleus has been extruded during the developmental stages.

In normal adult men the blood contains about 5,000,000 red blood corpuscles or erythrocytes per cubic millimeter; in normal adult women, about 4,500,000. Human erythrocytes are about 8 micrometers in diameter and about 2 μm at their thickest and have a biconcave shape. They contain hemoglobin, which imparts to them their color, and possess an envelope. When circulating in the blood vessels, the red blood cells are not evenly dispersed. In the capillaries the erythrocytes are often distorted. In certain conditions they may be densely aggregated. This is known as a sludge. The erythrocytes respond to changes in osmotic pressure of the surrounding fluid by swelling in hypotonic fluids and by shrinking irregularly in hypertonic fluids. Shrunken red blood cells are referred to as crenated cells. The average life of the mature red blood cells is surprisingly long, having a span of about 120 days. See Hemoglobin

In humans the white blood cells in the blood are fewer in number. There are about 5000–9000/mm³. In general, there are two varieties, agranular and granular. The agranular cells include the small, medium, and large lymphocytes and the monocytes (see illustration). The small lymphocytes are spherical, about the diameter of erythrocytes or a little larger, and constitute about 20–25% of the white blood cells. The medium and large lymphocytes are relatively scarce. In all lymphocytes the nucleus occupies nearly the whole volume of the cell, and the cytoplasm which surrounds it forms a thin shell. The typical monocyte is commonly as large as a large lymphocyte (12 μm), and constitutes 3–8% of the white blood cells. The nucleus is relatively small, eccentric, and oval or kidney-shaped. The cytoplasm is relatively larger in volume than that in lymphocytes.

The quest for blood is the common trait that all vampires share. Here, a vampire drains an unwilling victim’s blood in the film Vault of Horror.

Blood

(pop culture)

Nothing has so defined the vampire as its relationship to blood. The vampire was essentially a bloodsucker, a creature who lived off of the blood of humans. Quite early in his visit to Castle Dracula, Jonathan Harker was lectured by his host on the general importance of blood. He noted that the Szekelys, “we of the Dracula blood,” helped to throw off the despised Hungarian yoke. He further noted, in a line which soon would take on a double meaning, “Blood is too precious a thing in these days of dishonorable peace …” (chapter 3). As Harker tried to understand his desperate situation, he noted that Dracula had bad breath with “a bitter offensiveness, as one smells in blood.” He discovered the secret when he found Dracula asleep with his mouth redder than ever and “on the lips were gouts of fresh blood, which trickled from the corners of the mouth and ran over the chin and neck…. It seemed as if the whole awful creature were simply gorged with blood; he lay like a filthy leech, exhausted with his repletion.” Harker lamented his role in freeing Dracula on London.

The Significance of Blood: Since ancient times, humans have seen the connection between blood and life. Women made the connection between birth and their menstrual flow. Hunters observed the relationship between the spilling of blood and the subsequent loss of consciousness, the ceasing of breath, and eventual death of the animals they sought. And if an animal died of some cause with no outward wound, when cut, the blood often did not flow. Blood was identified with life, and thinkers through the ages produced endless speculations about that connection. People assigned various sacred and magical qualities to blood and used it in a variety of rituals. People drank it, rubbed it on their bodies, and manipulated it in ceremonies.

Some believed that by drinking the blood of a victim the conqueror absorbed the additional strength of the conquered. By drinking the blood of an animal one took on its qualities. As late as the seventeenth century, the women of the Yorkshire area of England were reported to believe that by drinking the blood of their enemies they could increase their fecundity.

Among blood’s more noticeable qualities was its red color as it flowed out of the body, and as a result redness came to be seen as an essential characteristic of blood, the vehicle of its power. Red objects were often endowed with the same potency as blood. In particular, red wine was identified with blood, and in ancient Greece, for example, red wine was drunk by the devotees of the god Dionysus in a symbolic ritual drinking of his blood.

Blood was (and continues to be) seen as somehow related to the qualities possessed by an individual, and beliefs carried references to admirable people as having “good” blood or evil persons as possessing “bad” blood. The blood of the mother was passed to the child, and with it the virtues and defects of the parents were passed to any offspring. Thus blood, in a somewhat literal sense, carried the essential characteristics of the larger collectives—families, clans, national/ethnic groups, even whole races. Such beliefs underlie the modern myth that permitted the Nazi purge of Jews and other supposed lesser races and the practices in American blood banks until recent decades to separate “Negro” blood from that of “white” people.

To a lesser extent, blood was identified with other body fluids, most notably semen. In the process of creating a baby, men do not supply blood, only their seed. Thus it was through the semen that male characteristics were passed to the child. In the mythology of race, each of the body fluids—semen, the blood that flowed when the hymen was broken, and menstrual blood—were associated together as part of sexual life and ascribed magical properties. This association was quite explicit in the sexual teaching of modern ritual magic.

Blood in the Biblical Tradition: The ancient Jewish leaders made the same identification of blood and life. In the biblical book of Genesis, God tells Noah:

But you must not eat the flesh with the life, which is the blood, still in it. And further, for your life-blood I will demand satisfaction; from every animal will I require it, and from a man also will require satisfaction for the death of his fellow-man.

He that shed the blood of a man, for that man his blood shall be shed; for in the image of God has God made man.

Israel instituted a system of blood sacrifice in which animal blood was shed as an offering to God for the sins of the people. The book of Leviticus included detailed rules for such offerings with special attention given to the proper priestly actions to be taken with the blood. The very first chapter stated the simple rules for offering a bull. It was to be slaughtered before the Tent of the Presence, and the priest was to present the blood and then fling it against the altar. The mysterious sacredness of the blood was emphasized in that God reserved it to himself. The remaining blood was spilled before the altar, and strictures were announced against the people eating the blood. “Every person who eats the blood shall be cut off from his father’s kin” (Lev 7:27).

Special rules were also established for women concerning their menstrual flow and the flow of blood that accompanied childbirth. Both made a woman ritually impure, and purification rituals had to be performed before she could again enter a sanctuary. In like measure, the discharge of semen caused a man to be ritually impure.

The most stringent rules concerning blood were in that section of Leviticus called the Holiness Code, a special set of rules stressing the role of the people, as opposed to the priest, in being holy before God. Very early in the code, the people are told:

If any Israelite or alien settled in Israel eats blood, I will see my face against the eater; and cut him off from his people, because the life of a creature is the blood, and I appoint it to make expiation on the altar for yourselves; for the blood is the life that makes expiation. Therefore I have told the Israelites that neither you, nor any alien settled among you, shall eat blood.

Indeed, “For the blood is the life” has been the most quoted Biblical phrase in the vampire literature.

Christianity took Jewish belief and practice to its extreme and logical conclusion. Following his death and (as Christians believe) his resurrection, Jesus, its founder, was worshiped as an incarnation of God who died at the hands of Roman executioners. Christians depicted his death as a human sacrifice, analogous, yet far more powerful, than the Jewish animal sacrifices. As the accounts of his last days relate Jesus instituted the Lord’s Supper during which he took a cup of wine and told his disciples, “Drink from it, all of you. For this is my blood, the blood of the covenant, shed for many for the forgiveness of sins” (Matthew 26:27). Following his sentencing of Jesus, the Roman governor Pilate washed his hands and told the crowd who had demanded Jesus’s death, “My hands are clean of this man’s blood.” The crowd replied, “His blood be upon us, and on our children” (Matthew 27:24–26). As he hung on the cross, a soldier pierced his side with a lance, and his blood flowed from the wound.

Early Christian thought on the significance of Christ’s death was clearly presented in the Apocalypse (The Book of Revelation) in which John spoke of Jesus as the one who “freed us from our sins with his life’s blood” (Revelation 1:5). He admonished those suffering persecution by picturing their glory in heaven as the martyrs for the faith. They wore a white robe which had been washed in the blood of the Lamb.

In Christian lands, to the common wisdom concerning life and blood, theological reflection added a special importance to blood. The blood of Christ, in the form of the red wine of the Eucharist, became the most sacred of objects. So holy had the wine become that during the Middle Ages a great controversy arose over allowing the laity to have the cup. Because of possible carelessness with the wine, the Roman Catholic Church denied the cup, a practice which added more fuel to the fire of the Protestant Reformation of the sixteenth century.

In the light of the special sacredness of Christ’s blood, the vampire, at least in its European appearances, took on added significance. The vampire drank blood in direct defiance of the biblical command. It defiled the holy and stole that which was reserved for God alone.

The Vampire and Hematology: The vampire myth arose, of course, prior to modern medicine. It has been of some interest that Dracula was written just as modern medicine was emerging, and Bram Stoker mixed traditional lore about blood with the new medicine. Lucy Westenra, even as she anticipated her marriage to Arthur Holmwood, lay hovering near death. Reacting quickly, Abraham Van Helsing gathered Holmwood and Lucy’s two other suitors, Quincey P. Morris and Dr. John Seward, to apply a wholly unique scientific remedy to the vampire’s attack. He had diagnosed a loss of blood, and now Van Helsing ordered a transfusion, at the time a new medical option. He and each of Lucy’s suitors in turn gave her their blood. Following her death, Holmwood, in his grief and disappointment, made the observation that in the giving of blood he had in fact married Lucy and that in the sight of God they were husband and wife. Van Helsing, assuming his scientific role, countered his idea by suggesting that such an observation would make Lucy a polyandrist and the previously married Van Helsing a bigamist.

The idea of using a transfusion to counter the vampire introduced a new concern into the developing myth of the vampire through the twentieth century, especially as the supernatural elements of the myth were being discarded. If vampirism was not a supernatural state, and rather was caused ultimately by a moral or theological flaw of the original vampires, then possibly the blood thirst was the symptom of a diseased condition, caused by a germ or a chemical disorder of the blood, either of which might be passed by the vampire’s bite. In the mid-1960s there was brief, yet serious, medical speculation that vampirism was the result of misdiagnosed porphyria, a disease that causes its victims to be sensitive to sunlight and which could be cured or helped.

Anemia is a disease of the blood that was initially associated with vampirism. Anemia is caused by a reduction of either red blood cells or hemoglobin (the oxygen-carrying pigment of the cells) relative to the other ingredients in the blood. The symptoms include a pale complexion, fatigue, and in its more extreme instances, fainting spells. All are symptoms usually associated with a vampire attack. In Bram Stoker’s novel, Dracula, during the early stages of Lucy Westenra’s illness, Dr. John Seward hypothesized that possibly she was suffering from anemia. He later concluded that she was not suffering from the loss of red blood cells, but from the loss of whole blood. Dr. Abraham Van Helsing agreed with his friend: “I have made careful examination, but there is no functional cause. With you I agree that there has been much blood lost; it has been, but is not. But the conditions of her are in no way anaemic” (chapter 9). While Stoker dismissed any association of anemia and vampirism, over the succeeding decades, attempts to posit anemia as the underlying explanation of vampirism occasionally emerged.

The Literary Tradition: Increasingly through the century, as knowledge of the minute details concerning the function and makeup of human blood were explored by research specialists, novelists and screenwriters toyed with the idea of vampirism as a disease. During the last years of the pulp fiction era, writers such as Robert Bloch, George Whitley, David H. Keller, and William Tenn suggested the diseased origin of vampirism in a series of short stories. For example, in William Tenn’s 1956 short story “She Only Goes Out at Night,” Tom Judd, the son of a village doctor, falls in love with a strange woman. Tom’s father coincidentally discovers an epidemic in town whose victims are all anemic. The woman, who has just moved to town, is a Romanian by descent and only comes out at night. Putting the sudden wave of anemia together with the behavior patterns of the woman, the wise old doctor suggests she is a vampire. As he explains it, the vampire condition is passed from parent to child, though usually only one child in each generation develops it. His son still wants to marry the woman. He responds with a medical observation, “Vampirism may have been an incurable disease in the fifteenth century, but I am sure it can be handled in the twentieth.” Her symptoms suggests she has an allergy to the sun, for which he prescribes sunglasses and hormone injections. He then deals with her blood thirst by supplying her with dehydrated crystalline blood which she mixes with water and drinks once a day. The vampire and Tom live happily ever after.

Vampirism as disease came powerfully to the fore in the late 1960s television series Dark Shadows. Dr. Julia Hoffman was introduced into the show to treat the problems of Maggie Evans, one of the show’s main characters. A short time after her initial appearance, she meets Barnabas Collins and discovers that he is a vampire. Rather than seek to destroy him, however, she devises a plan to assist him in a cure of his vampiric condition. Collins soon grows impatient and demands that the process be speeded up. His body does not react favorably to the increased dosages of Hoffman’s medicines, and he reverts to his true age—two hundred years old. He is able to revive his youth by biting a young woman, and he then turns on Hoffman. Hoffman is able to thwart his efforts by threatening him with her research book, which contains all the details of her treatments and reveals Collins’s true nature. Before Collins can locate the book, he and the storyline are transported into the past, to 1795.

Shortly after his return to the present (1968), Collins is in a car accident. Hospitalized, he receives a transfusion that temporarily cures him. He is a human and, for the first time in two hundred years, is able to walk in the sunlight. He is, however, returned to his vampiric state by the bite of his former love, Angelique Bouchard, who has died and returned as a vampire.

A character similar to Hoffman also appeared in the recent television series, Forever Knight. Nicolas Knight, the show’s vampire, is a policeman on the Toronto police force. His friend and confidante is Dr. Natalie Lambert, a forensic pathologist. Throughout the series, she seeks a means to transform Knight into a human, but with negative results. In the decades since World War II, novelists have also explored the idea that a diseased condition produced vampirism. Simon Raven’s Doctors Wear Scarlet (1960), for example, described vampirism as a form of “sado-sexual perversion.” The story sent the hero, Richard Fountain, to Greece to escape an oppressive personal situation in England. In Greece he meets a beautiful vampiress who slowly drains his blood. He is rescued before he is killed and returns safe to his British home.

Jan Jennings’s Vampyr (1981) brings a research scientist into a relationship with Valan Anderwalt, a vampiress. The scientist, in love with Valan, tries to find the causes of her state. He traces vampirism to ancient China and finds it to be a contagious physical condition which had been brought to America by the early Dutch colonists. Unfortunately, he is not able to make any progress in curing her.

That same year Whitley Strieber introduced an interesting triangle relationship in The Hunger. Miriam Blaylock is an immortal alien vampire. She is on earth and can transform humans into vampires. Such human vampires, however, are not immortal and begin to age and disintegrate after several centuries pass. Not wishing to lose another companion, Blaylock seeks out the services of an expert in longevity, Sarah Roberts, in the hopes that she will be able to save John, her present male companion. Unfortunately, no solution presents itself before John succumbs to his deteriorating condition. Most recently, Dan Simmons sent his leading character, Kate Neuman, a hematologist, into post-revolutionary Romania in Children of the Night. The book begins with her using her knowledge of rare blood diseases to treat people in Bucharest. While there, she falls in love with a seven-month-old boy, Joshua, presumably an orphan. He is unique in that he requires biweekly transfusions to stay alive. He also has unusual blood which, she comes to believe, holds the clue to cures for AIDS, cancer, and other blood diseases. She arranges his adoption and brings him home with her to Colorado. Soon after, the boy is kidnapped and returned to Romania. In the exciting climax of the story, she is forced to return to Romania and face the boy’s father, Vlad the Impaler, the real Dracula. Because Dracula was dying, his son, Joshua, was to become the leader of the family in his place.

Conclusion: The traditional beliefs that surrounded blood, the medical exploration of its properties, and the analogies it harbored to life itself, facilitated the adaptability of the vampire myth to a seemingly endless number of situations. Such adaptability has provided an understanding of why the vampire myth has stayed alive and has so many devotees to this day. Scientific considerations of the vital function played by blood in the human body have, if anything, given it an even more mystical place in human life and promoted the belief in its sacredness in this post-secular society.

Since the early 1990s, blood and related body fluids have been very much in the news around such subjects as AIDS, the analysis of blood in criminal investigations, and genetic research around DNA. Interestingly, little has been done by vampire writers to exploit these burgeoning fields in the equally expanding field of vampire fiction.

Sources:

Cox, Greg. The Transylvanian Library: A Consumer’s Guide to Vampire Fiction. San Bernadino, CA: Borgo Press, 1993.Scott, Kathryn Leigh, ed. The Dark Shadows Companion: 25th Anniversary Collection. Los Angeles: Pomegranate Press, 1990.Simmons, Dan. Children of the Night. New York: G. P. Putnam’s Sons, 1992.Strieber, Whitley. The Hunger. New York: William Morrow, 1981.Teem, William. “She Only Goes Out at Night.” Fantastic Universe 6, 3 (October 1956). Reprinted in Weird Vampire Tales. Ed. by Robert Weinberg, Stefan R. Dziemianowicz, and Martin H. Greenberg. New York: Gramercy Press, 1992.

Blood Drinking see: Crime, Vampiric

Blood

a fluid tissue that moves through the circulatory system of man and animals, providing for vital activities and the performance of various physiological functions of the body’s cells and tissues.

Overview. One of the principal functions of the blood is the transport of gases (O₂ from the respiratory organs to the tissues and CO₂ from the tissues to the respiratory organs). Blood is also involved in the transfer of glucose, amino acids, fatty acids, salts, and other nutrients from the digestive organs to the tissues. In addition, it carries the end products of metabolism, such as urea, uric acid, and creatinine, to the excretory organs. Blood takes part in the regulation of the body’s water-salt metabolism and acid-base equilibrium and plays an important role in maintaining constant body temperature. A protective function is carried out by the antibodies, antitoxins, and lysines present in the blood and by the white blood cells, or leukocytes, which are capable of absorbing microorganisms and foreign bodies. A very important protective adaptation, one that prevents blood loss from the body, is the arrest of blood flow as a result of coagulation.

Blood contains a number of chemical compounds for which the demand changes with the functional activities of the tissues. However, the blood’s chemical composition, the active reaction of its medium (pH), and other physical and chemical constants maintain relative stability. This is ensured by the mechanisms of homeostasis, which include the blood’s rate of flow (regulating the entry of nutrient substances into the tissues), the capacity of the excretory organs to remove metabolic products, and the maintenance of the water balance (achieved by the exchange of fluid between the blood and the lymph). Homeostasis is also maintained by regulation of the metabolism (matter and energy) of biologically active substances (histamine, serotonin, acetylcholine) and by hormones transported by the blood from site of formation to site of activity.

In unicellular organisms and in many invertebrates (protozoans, sponges, coelenterates), oxygen is supplied by means of diffusion from the external environment through the body surface. In some primitive metazoans there is a system of canals communicating with the external environment (the gastrovascular system) through which hydrolymph circulates. Hydrolymph delivers nutrients to the cells and removes their metabolic products, but it does not, as a rule, bind and transport oxygen. Only in a few invertebrates does the hydrolymph contain protein pigments that are capable of carrying oxygen. In more developed animals (mollusks and arthropods) there is an open system of blood circulation, filled with hemolymph and communicating with the intertissular spaces. In a number of invertebrates, all vertebrates, and man, the circulatory system is closed and the blood is separated from the interstitial fluid and lymph.

Only in a few relatively inactive animals is blood (or hemolymph) able to carry sufficient oxygen in a dissolved state without the participation of respiratory pigments (chromoproteins). With the appearance at a certain stage of animal evolution of respiratory pigments, the ability of the blood to bind oxygen and to release it to the tissues increases sharply. These pigments include hemoglobin, chlorocruorin, and hemerythrin, which contain iron in the nonprotein parts of their molecules, and hemocyanin, which contains copper. The pigments are either dissolved in hemolymph or carried in blood corpuscles. The green pigment chlorocruorin is dissolved in the plasma of polychaetes. Hemerythrin, a violet pigment, is contained in the blood corpuscles of polychaetes, sipunculids, and brachiopods. The blood of many mollusks and coelenterates is blue because of the hemocyanin dissolved in it. Hemoglobin is the most widely distributed. This red pigment is dissolved in the perivisceral fluid or blood of many invertebrates, and it is found in the erythrocytes of all vertebrates, including man.

In invertebrates the ratio of the mass of the fluid that performs the function of blood to the mass of the body is significantly higher than in vertebrates. Whereas hemolymph constitutes 30 percent of the mass of the mollusk Anodonta and 20 percent in many insects, blood constitutes only 2–8 percent of the body mass in vertebrates (in fish, about 3 percent; in amphibians, to 6 percent; in reptiles, 6.5 percent; and in birds and mammals, to 8 percent). Blood averages 6.8 percent of the body weight in man (about 5 liters for a weight of 70 kg). The decrease in the relative volume of the blood in vertebrates may be explained by the development of the closed system of blood circulation and the appearance of respiratory pigments that effectively bind oxygen.

In vertebrates, the blood is a thick, homogeneous, red fluid that consists of a liquid part, or plasma, and formed elements— the erythrocytes, which give blood its red color, the leukocytes, and the thrombocytes, or blood platelets. The volume of formed elements in the lower vertebrates (fish, amphibians, and reptiles) is 15–40 percent. In higher vertebrates (birds and mammals) it is 35–54 percent. Of the formed elements, the erythrocytes are the most numerous. Their number and size differ for different vertebrates. Thus, among the ungulates, 1 cu mm of llama blood contains 15.4 million erythrocytes, and 1 cu mm of goat blood contains 13 million; in the reptiles, the range is from 500,000 to 1.65 million; and among the chondrosteans, from 90,000 to 130,000. The smallest erythrocytes are found in mammals; in the musk deer, the diameter is about 2.5 microns (μm) and in the goat, about 4.0 μm. The largest erythrocytes are found in amphibians (70 μm, in the urodele Amphiumd).

The erythrocytes in all vertebrates except the mammals are elliptical and have a nucleus. In mammals the erythrocytes are nonnucleated and are shaped like biconcave disks (with the exception of the camel, in which the erythrocytes are oval and lentiform). Increasing the number of erythrocytes and decreasing their size improves the oxygen supply to the body. In the lower vertebrates, 100 ml of blood contains 5–10 g of hemoglobin; in fish, 6–11 g; and in the mammals, 10–15 g. In man, 1 cu mm of blood normally contains 4.5–5.5 million erythrocytes (in men, 4.5–5.5 million; in women, 4–4.5 million). The constancy of the number of erythrocytes in the blood is the result of an equilibrium between their formation in the bone marrow (hematopoiesis) and the destruction of old erythrocytes in the cells of the reticuloendothelial system. The average hemoglobin content in men is 13.3–18 g percent; in women, 11.7–15.8 g percent. The diameter of the human erythrocyte is 7.2 μm; the thickness, 2 μm; and the volume, 88 cu μm. The shape of the biconcave disk ensures passage of the erythrocytes through the narrow lumina of the capillaries. According to A. L. Chizhevskii, the flow of blood is a single, structured, dynamic system comprising a huge number of elements. The movement of the erythrocyte through the vascular channel is not chaotic; this is a consequence both of limited space and of electrostatic, hydro-dynamic, and other forces that inhibit approach and contact between erythrocytes.

The principal function of erythrocytes, the transport of O₂ and CO₂, can be accomplished thanks to the large content of hemoglobin (about 265 million molecules of hemoglobin in every erythrocyte), the high activity of the enzyme carboanhydrase, the large concentration of 2,3-diphosphoglyceric acid, and the presence of ATP and ADP (adenosine phosphoric acids). These compounds (mainly 2,3-diphosphoglyceric acid) bond with deoxyhemoglobin and decrease its affinity for O₂, promoting the liberation of oxygen to the tissues. Erythrocytes have an important role in water-salt metabolism, in the regulation of the body’s acid-base equilibrium, and in the regulation (by absorption) of the body’s amino acid and polypeptide content. Erythrocytes are also the carriers of the properties that define blood groups.

The leukocytes are nucleated cells; they are subdivided into granular leukocytes, or granulocytes (comprising the neutrophils, the eosinophils, and the basophils), and agranular leukocytes, or agranulocytes. Neutrophils are characterized by their ability to move and to penetrate from the loci of hematopoiesis to the peripheral blood and tissues. They are capable of capturing (phagocytizing) microbes and other foreign particles that enter the body. Agranulocytes participate in immunological reactions and in the processes of regeneration and inflammation. There are 6,000–8,000 leukocytes per cu mm in the blood of an adult human.

Thrombocytes, or blood platelets, play an important role in stemming blood flow (clotting). There are 200,000–400,000 thrombocytes per cu mm of human blood. Thrombocytes are nonnucleated. Analogous functions in the blood of all other vertebrates are performed by nucleated spindle cells. The relative constancy of the number of formed elements in the blood is regulated by complex nervous (central and peripheral) and humoral-hormonal mechanisms.

Physicochemical properties. The density and viscosity of blood depend mainly on the number of formed elements. Normally they vary within narrow limits. In man, the density of whole blood is 1.05–1.06 g/cm³; of plasma, 1.02–1.03 g/cm³; and of formed elements, 1.09 g/cm³. The difference in densities makes it possible to separate whole blood into plasma and formed elements by centrifugation. The erythrocytes constitute 44 percent, and the leukocytes and thrombocytes, 1 percent, of the total volume of blood. The osmotic pressure of blood, equal to 740 kilonewtons/m² (7.63 atmospheres) at 37°C, is determined predominantly by electrolytes—that is, in the plasma, by Na and Cl ions, and in the erythrocytes, by K and Cl ions. The oncotic pressure is determined by the proteins present in the blood. The hydrogen ion concentration is slightly alkaline (pH 7.26–7.36) and is maintained at a constant level by the blood’s buffering systems—bicarbonate, phosphate, and protein—and by the activity of the respiratory and excretory organs.

Chemical composition. There are 18–24 g of dry residue and 77–82 g of water per 100 ml of blood. The water makes up more than half the mass of the erythrocytes and 90–92 percent of the plasma. The blood plasma contains the intermediate and end products of metabolism, as well as salts, hormones, vitamins, and enzymes. A substantial portion of the blood is composed of proteins. These proteins are represented principally by respiratory pigments, the proteins of the erythrocytic stroma, and the proteins of the other formed elements. Proteins dissolved in the plasma (6.5–8.5 percent of the 9–10 percent dry residue of plasma) are formed predominantly in the cells of the liver and reticuloendothelial system. Plasma proteins do not penetrate capillary walls, so that their content in the plasma is significantly higher than in the interstitial fluid. This leads to the retention of water by the plasma proteins. Despite the fact that oncotic pressure accounts for only a small fraction (about 0.5 percent) of the total osmotic pressure, it is the oncotic pressure that causes the preponderance of the osmotic pressure of blood over that of interstitial fluid. The high hydrodynamic pressure in the circulatory system would otherwise cause water to infiltrate the tissues and produce edema of the various organs and subcutaneous tissue.

Proteins also determine the blood’s viscosity, which is five or six times higher than that of water and plays an important role in maintaining the circulatory system’s hemodynamic relationships. Plasma proteins perform a transport function, participate in the regulation of the blood’s acid-base equilibrium, and serve as a nitrogen reserve. A significant portion of the serum calcium, iron, and magnesium are bound to plasma proteins. Fibrinogen, prothrombin, and other proteins participate in blood coagulation. Other plasma proteins play an important role in immune processes.

Plasma proteins are separated by means of electrophoresis into the albumin fraction, the globulin group (α1, α2, β, and γ), and fibrinogen (which participates in blood coagulation). The protein fractions of plasma are not homogeneous; using modern chemical and physicochemical separation methods, it has been possible to discover about 100 protein components of plasma.

Albumins account for 55–60 percent of the proteins of plasma. Because of their relatively small molecules, their high concentration in the plasma, and their hydrophilic properties, the proteins of the albumin group play an important role in maintaining oncotic pressure. Albumins transport organic compounds, such as cholesterol and bile pigments, and serve as a source of nitrogen for the building of proteins. The free sulfhydryl (—SH) group of albumin binds heavy metals, such as mercury compounds, which are deposited in the kidneys until being eliminated from the body. Albumins are capable of combining with certain medicinal substances, such as penicillin and salicylates, and of binding calcium, magnesium, and manganese.

Globulins are an extremely varied group of proteins, differing in physical and chemical properties and in functional activity. With paper electrophoresis they can be separated into α1, α2, β, and γ-globulins. Most of the proteins of the α- and α-globulin fractions are bound to carbohydrates (glycoproteins) or lipids (lipoproteins). Sugar or amino sugars are usually among the components of the glycoproteins. Blood lipoproteins, which are synthesized in the liver, are separated by their electrophoretic mobility into three principal fractions, differing in lipid composition. The physiological role of lipoproteins consists in delivering water-insoluble lipids, steroid hormones, and fat-soluble vitamins to the tissues.

The α2-globulin fraction comprises several proteins that participate in blood coagulation, including prothrombin, an inactive precursor of the enzyme thrombin that produces the conversion of fibrinogen to fibrin. The fraction also includes haptoglobin, whose content in the blood increases with age. Haptoglobin forms a complex with hemoglobin that is absorbed by the reticuloendothelial system. This prevents the body’s loss of iron, a component of hemoglobin. In addition, the α2-globulins include the glycoprotein ceruloplasmin, which contains 0.34 percent copper (that is, almost all plasma copper). Ceruloplasmin catalyzes the oxidation by oxygen of ascorbic acid and aromatic diamines.

The α2-globulin fraction of the plasma contains the polypep-tides bradykininogen and kallidinogen, which are activated by proteolytic enzymes of the plasma and tissues. Their active forms, bradykinin and kallidin, form the kinin system, which regulates the permeability of the capillary walls and activates the coagulation system of the blood.

The glycoproteins of the β-globulin fraction include transferrin, the carrier of iron in the body. The β1- and β2-globulin fractions contain several of the coagulation factors of the plasma, including antihemophilic globulin.

Fibrinogen migrates between β- and γ-globulins. The plasma proteins that migrate with the γ-globulins include the various antibodies, such as the antibodies to diphtheria, whooping cough, measles, scarlet fever, and poliomyelitis.

The nonprotein nitrogen of the blood is contained mainly in the end or intermediate products of nitrogenous metabolism: urea, ammonia, polypeptides, amino acids, creatine, creatinine, uric acid, and purine bases. The blood that flows away from the intestinal tract carries amino acids through the portal vein to the liver, where the amino acids undergo deamination, reamination, and other transformations (to the formation of urea) and where they are used for the biosynthesis of protein.

Blood carbohydrates are represented mainly by glucose and the intermediate products of its conversions. The glucose content of the blood varies in man from 80 to 100 mg percent. The blood also contains small amounts of glycogen and fructose and a significant amount of glucosamine. The products of the digestion of carbohydrates and proteins—glucose, fructose, other monosaccharides, amino acids, and low-molecular-weight peptides, as well as salts and water—are absorbed directly into the blood flowing through the capillaries of the intestine and delivered to the liver. Some of the glucose is transported to the organs and tissues, where it breaks down, releasing energy. The rest is converted to glycogen in the liver. When the intake of carbohydrates with the food is insufficient, this glycogen breaks down to form glucose. These processes are regulated by the enzymes of carbohydrate metabolism, by the central nervous system, and by the endocrine glands.

The blood contains a complex mixture of lipids that consist of neutral fats and free fatty acids and the products of their decomposition, free and bound cholesterol, steroid hormones, and other substances. Neutral fats, glycerin, and fatty acids are absorbed from the mucosa of the intestine partially into the blood but mainly into the lymph. The amount of lipids in the blood is not constant and depends on the composition of the diet and the stage of digestion. The blood transports lipids in the form of various complexes; a large proportion of both the plasma lipids and the cholesterol in the blood is found in the form of lipo-proteins, bound with α- and β-globulins. Free fatty acids are transported in the form of complexes with albumins, which are soluble in water. Triglycerides form compounds with phosphatides and proteins. The blood transports a fatty emulsion to the depots of adipose tissue, where it is deposited in the form of reserve fat and can, when needed, again be transferred to the blood plasma (fats and the products of their decomposition are used for the energy requirements of the body). The principal organic components of the blood are shown in Table 1.

Mineral substances maintain the blood’s active reaction (pH) and the constancy of the blood’s osmotic pressure and influence the state of blood colloids and intracellular metabolism. Sodium (Na) and chlorine (Cl) are the principal plasma minerals, and potassium (K) is found predominantly in the erythrocytes. Sodium participates in water metabolism, holding water in the tissues by swelling colloidal matter. Chlorine, which penetrates readily from the plasma into the erythrocytes, participates in the maintenance of the blood’s acid-base equilibrium. Calcium (Ca), which is necessary for clotting, is found in the plasma, mostly as ions or bound to proteins. HCO₃^- ions and dissolved carbonic acid form the bicarbonate buffer system. HPO₄^- and H₂PO₄^- ions form the phosphate buffer system. A number of other anions and cations, including those of microelements, are found in the blood.

In addition to the compounds that are transported by the blood to the various organs and tissues to be used for biosynthesis, energy, and other body needs, metabolic products are continuously entering the blood and being excreted by the kidneys with the urine (mainly urea and uric acid). The products of hemoglobin decomposition (mainly bilirubin) are excreted with the bile.

REFERENCES

Chizhevskii, A. L. Strukturnyi analiz dvizhushcheisia krovi Moscow, 1959.
Korzhuev, P. A. Gemoglobin. Moscow, 1964.
Haurowitz, F. Khimiia i funktsiia belkov. Moscow, 1965. (Translated from English.)

Table 1. Most important organic components of human whole blood, plasma, and erythrocytes
Components	Whole blood	Plasma	Erythrocytes
	100%	54-59%	41-46%
Water (%). . . . . . . . . .	75-85	90-91	57-68
Dry residue (%). . . . . . . . . .	15-25	9-10	32-43
Hemoglobin (%). . . . . . . . . .	13-16	—	30-41
Total protein (%). . . . . . . . . .	—	6.5-8.5	—
Fibrinogen (%). . . . . . . . . .	—	0.2-0.4	—
Globulins (%). . . . . . . . . .	—	2.0-3.0	—
Albumins (%). . . . . . . . . .	—	4.0-5.0	—
Residual nitrogen (nitrogen of nonprotein compounds; mg % ). . . . . . . . . .	25-35	20-30	30-40
Glutathione (mg %). . . . . . . . . .	35-45	traces	75-120
Urea (mg %). . . . . . . . . .	20-30	20-30	20-30
Uric acid (mg %). . . . . . . . . .	3-4	4-5	2-3
Creatinine (mg %). . . . . . . . . .	1-2	1-2	1-2
Creatine (mg %). . . . . . . . . .	3-5	1-1.5	6-10
Amino-acid nitrogen (mg %). . . . . . . . . .	6-8	4-6	8
Glucose (mg %). . . . . . . . . .	80-100	80-120	—
Glucosamine (mg %). . . . . . . . . .	—	70-90	—
Total lipids (mg %). . . . . . . . . .	400-720	385-675	410-780
Neutral fats (mg %). . . . . . . . . .	85-235	100-250	11-150
Total cholesterol (mg %). . . . . . . . . .	150-200	150-250	175
Indican (mg %). . . . . . . . . .	—	0.03-0.1	—
Kinins (mg %). . . . . . . . . .	—	1-20	—
Guanidine (mg %). . . . . . . . . .	—	0.3-0.5	—
Phospholipids (mg %). . . . . . . . . .	—	220-400	—
Lecithin (mg %). . . . . . . . . .	about 200	100-200	350
Ketone bodies (mg %). . . . . . . . . .	—	0.8-3.0	—
Acetoacetic acid (mg %). . . . . . . . . .	—	0.5-2.0	—
Acetone (mg %). . . . . . . . . .	—	0.2-0.3	—
Lactic acid (mg %). . . . . . . . . .	—	10-20	—
Pyruvic acid (mg %). . . . . . . . . .	—	0.8-1.2	—
Citric acid (mg %). . . . . . . . . .	—	2.0-3.0	—
Ketoglutaric acid (mg %). . . . . . . . . .	—	0.8	—
Succinic acid (mg %). . . . . . . . . .	—	0.5	—
Bilirubin (mg %). . . . . . . . . .	—	0.25-1.5	—
Choline (mg %). . . . . . . . . .	—	18-30	—

Rapoport, S. M. Meditsinskaia khimiia. Moscow, 1966. (Translated from German.)
Prosser, L., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. (Translated from English.)
Vvedenie v klinicheskuiu biokhimiiu. Edited by I. I. Ivanov. Leningrad, 1969.
Kassirskii, I. A., and G. A. Alekseev. Klinicheskaia gematologiia, 4th ed. Moscow, 1970.
Semenov, N. V. Biokhimicheskie komponenty i konstanty zhidkikh sred i tkanei cheloveka. Moscow, 1971.
Biochimie médicale, 6th ed., fasc. 3. Paris, 1961.
The Encyclopedia of Biochemistry. Edited by R. J. Williams and E. M. Lansford. New York, 1967.
Brewer, G. J., and J. W. Eaton. “Erythrocyte Metabolism.” Science, 1971, vol. 171, p. 1205.
The Red Cell: Metabolism and Function. Edited by G. J. Brewer. New York-London, 1970.N. B. CHERNIAKPathology. The blood reflects, to a degree, shifts in the functioning of certain organs and systems and pathological processes. With metabolic disturbances and diseases of the endocrine glands, kidneys, liver, and certain other organs, there are observable chemical changes in the blood’s composition, such as increased protein content (hyperproteinemia), decreased protein content (hypoproteinemia), increased nonprotein nitrogen (azotemia or, more correctly, hyperazotemia), increased plasma lecithin (hyperlecithinemia), and increased plasma sugar (hyperglycemia). One of the most characteristic indexes of pathology is the blood’s hemoglobin content, which may fall with anemias and a number of other diseases. A change in the color index of the blood (the degree of coloration of the erythrocytes, which depends on their hemoglobin content) toward increased color (hyperchromatism) or decreased color (hypochromatism) is a symptom of some anemias. An increase in the hemoglobin content of the blood (polyglobulia) is observed with an increase in the number of erythrocytes (polycythemias). In congenital anomalies and diseases of the hematopoietic apparatus (hemoglobinoses, or hemoglobinopathies), anomalous hemoglobins, which differ from normal hemoglobins in structure and physico-chemical properties (solubility, resistance to denaturation), appear in the blood. Physiological increase in the number of erythrocytes (erythrocytosis) may occur as a compensatory phenomenon in hypoxia, or oxygen starvation of the tissues (for example, during ascents to high altitudes). Decrease in the number of erythrocytes (oligocythemia, erythropenia) is found with blood loss, anemias, and chronic wasting diseases.
When erythrocytes regenerate after blood loss or in the presence of intensive erythrocytic decomposition (hemolysis), altered erythrocytes and reticulocytes (erythrocytes with a granuloreticulate substance) appear in the peripheral blood. A sharp intensification of new growth of erythrocytes leads to the appearance of young forms: normoblasts, erythroblasts, and, in severe cases, megaloblasts.
The number of white cells in the blood (leukocytes) may also change. Cases of increased leukocytes, called leukocytoses, appear with certain physiological conditions and in various pathological states. Decreased leukocyte content is called leukopenia. It is seen mainly with a suppression of hematopoiesis in the bone marrow. Change in the amount of various types of leukocytes in the blood plays an important role in the diagnosis and prognosis of disease.
The thrombocyte content of the blood increases (thrombocytosis) after bleeding, in certain diseases of the blood system, such as myeloleukosis, polycythemia, and hemorrhagic thrombocythemia, and with certain tumor diseases. A decrease in the number of thrombocytes (thrombocytopenia) occurs under the influence of radiation and chemical factors, with immunoaggressive diseases, and in certain diseases of the blood system. A low thrombocyte count is manifested in the form of thrombocytopenic purpura, or Werlhof’s disease. The normal course of blood coagulation, in which the thrombocytes participate (along with other factors), depends on the balance between the clotting and anticlotting systems of the blood. Disruption of this balance may produce increased susceptibility to bleeding, which is observed in hemophilia, hemorrhagic diatheses, disturbances of vitaminK absorption (obstructive jaundices), and thromboembolic disease (increased thrombogenesis).
In a number of pathological states there is a change in blood volume. An increase in blood volume (hypervolemia) may occur without change in the proportion between the volumes of plasma and erythrocytes, or it may occur chiefly through an increase in the cell mass (true plethora, or polycythemic hypervolemia). A decrease in blood volume (hypovolemia) occurs as a result of loss of plasma (with intractable vomiting, diarrhea, or overheating) or loss of erythrocytic mass (as a result of hemorrhage).
Blood changes may be reactive—that is, they may arise as a responsive physiological reaction to stresses: blood loss, infection (bacterial, viral, or parasitic), or the entry into the body of toxic substances or allergens of external or internal origin. Pathological (nonreactive) changes in the blood arise in connection with diseases of the blood system or of the hematopoietic system. The etiologies of a number of these diseases (in particular, of leukemias) remain unelucidated.G. A. ALEKSEEVIn anthropology. The investigation of many of the hereditary features of the blood has great significance for anthropology. These features reveal genetic polymorphism (hereditary diversity) in the majority of peoples of the world and clearly expressed ethnic variations in the frequency of the genes determining them. The most thoroughly studied hereditary aspects of the blood are the variations of the erythrocytic blood groups of various systems (ABO, MNS5, Rh, or rhesus factor), anomalous hemoglobins (hemoglobinopathies), serum proteins (haptoglobins, transferrins, immunoglobulins), and certain blood enzymes.
Complex analysis of these blood factors makes it possible to distinguish several large population groups that do not coincide entirely with the large races but are found to be in definite correlation with them. Serological differences are being traced between the Caucasoid, Negroid, Australoid, and Mongoloid (including American Indian) populations.
Various serological complexes that are characteristic of certain populations arise and change in the course of time as a result of mutations, prolonged isolation, and racial mixing. However, the blood is qualitatively equivalent in all peoples and races, and no blood group has advantages over any other.
Many serological features are also being studied from the point of view of physiological anthropology, including such widely varying indexes as the levels in the blood of proteins, lipids (particularly cholesterol), carbohydrates, and enzymes. The quantitative content of these components, unlike blood groups, is closely associated with living conditions.
Fossil bone material is also being investigated in order to elucidate group serological characteristics and the connections between different groups of prehistoric and modern man and animals. The blood groups of monkeys are being studied for this purpose. In addition, the genetically determined blood factors in primates are being compared in terms of evolution. These investigations have made substantial contributions to primate taxonomy.

REFERENCES

Cheboksarov, N. N., and I. A. Cheboksarova. Narody, rosy, kul’tury. Moscow, 1971.
Biologiia cheloveka. Moscow, 1968. (Translated from English.)

V. A. SPITSYN

What does it mean when you dream about blood?

Blood has a rich and complex symbology and can represent any number of different kinds of human experiences. Because of certain familiar experiences and metaphors, many of these do not require explanation (e.g., menstrual blood may symbolize fertility; one can be “bled dry”; one may have “blood on one’s hands”). Blood often represents vitality and the life force. Images of confused, bloody violence often occur in the dreams of people undergoing some sort of emotional upheaval.

blood

[bləd] (histology) A fluid connective tissue consisting of the plasma and cells that circulate in the blood vessels.

blood

humor effecting temperament of sanguineness. [Medieval Physiology: Hall, 130]See: Cheerfulness

blood

1. a reddish fluid in vertebrates that is pumped by the heart through the arteries and veins, supplies tissues with nutrients, oxygen, etc., and removes waste products. It consists of a fluid (see blood plasma) containing cells (erythrocytes, leucocytes, and platelets) 2. a similar fluid in such invertebrates as annelids and arthropods 3. Obsolete one of the four bodily humours

Blood

(dreams)It is the life-giving, vital part of our physiology and it may symbolize our strengths and weaknesses and our physical and mental health. If you are currently experiencing a very difficult time in your life, you may have dreams with bloody and frightening images. Don’t worry: you may be venting your fears! Some believe that when you see blood in your dream, the distressing situation in your life, which is at the root of the dream, has come to an end, and the worst is over. Consider the details and the relationships between all of the symbols in your dream before making an interpretation.

blood

[blud] the fluid that circulates through the heart, arteries, capillaries, and veins and is the chief means of transport within the body. It transports oxygen from the lungs to the body tissues, and carbon dioxide from the tissues to the lungs. It transports nutritive substances and metabolites to the tissues and removes waste products to the kidneys and other organs of excretion. It has an essential role in the maintenance of fluid balance.
In an emergency, blood cells and antibodies carried in the blood are brought to a point of infection, or blood-clotting substances are carried to a break in a blood vessel. The blood distributes hormones from the endocrine glands to the organs they influence. It also helps regulate body temperature by carrying excess heat from the interior of the body to the surface layers of the skin, where the heat is dissipated to the surrounding air.
Blood varies in color from a bright red in the arteries to a duller red in the veins. The total quantity of blood within an individual depends upon body weight; a person weighing 70 kg (154 lb) has about 4.5 liters of blood in the body.
Blood is composed of two parts: the fluid portion is called plasma" >plasma, and the solid portion or formed elements (suspended in the fluid) consists of the blood cells (erythrocytes and leukocytes) and the platelets. Plasma accounts for about 55 per cent of the volume and the formed elements account for about 45 per cent. ( and table.)
Chemical analyses of various substances in the blood are invaluable aids in (1) the prevention of disease by alerting the patient and health care provider to potentially dangerous levels of blood constituents that could lead to more serious conditions, (2) diagnosis of pathologic conditions already present, (3) assessment of the patient's progress when a disturbance in blood chemistry exists, and (4) assessment of the patient's status by establishing baseline or “normal” levels for each individual patient.
In recent years, with the increasing attention to preventive health care and rapid progress in technology and automation, the use of a battery of screening tests performed by automated instruments has become quite common. These instruments are capable of performing simultaneously a variety of blood chemistry tests. Some of the more common screening tests performed on samples of blood include evaluation of electrolyte, albumin, and bilirubin levels, blood urea nitrogen" >blood urea nitrogen (BUN), cholesterol, total protein, and such enzymes as lactate dehydrogenase and aspartate transaminase. Other tests include electrophoresis for serum proteins, blood gas analysis, glucose tolerance tests, and measurement of iron levels.

Composition of the blood, which constitutes 8% of total body weight. From Applegate, 2000.blood bank 1. a place of storage for blood.2. an organization that collects, processes, stores, and transfuses blood. In most health agencies the blood bank is located in the pathology laboratory. It is operated by medical technologists under the direction of a pathologist.blood bank technologist a clinical laboratory scientist/medical technologist who has postgraduate education in blood banking and is certified by the Board of Registry of the American Society of Clinical Pathologists; designated as MT(ASCP)SBB. Specialists in blood bank technology perform both routine and specialized tests in blood bank immunohematology and perform transfusion services. The address of the American Association of Blood Banks is 8101 Glenbrook Road, Bethesda, MD 20814 (telephone 301-907-6582). The address of the Board of Registry of the American Society of Clinical Pathologists is P.O. Box 12270, Chicago, IL 60612. Their telephone number is 312-738-1336 and their web site is http://www.aabb.org.blood-brain barrier BBB; the barrier separating the blood from the brain parenchyma everywhere except in the hypothalamus. It is permeable to water, oxygen, carbon dioxide, and nonionic solutes, such as glucose, alcohol, and general anesthetics, and is only slightly permeable to electrolytes and other ionic substances. Some small molecules, e.g., amino acids, are taken up across the barrier by specific transport mechanisms.citrated blood blood treated with sodium citrate or citric acid to prevent its coagulation.cord blood the blood contained in the umbilical vessels at the time of delivery of the infant. It is rich in stem cells that could be used in place of bone marrow for a transplant; thus, it is sometimes collected and stored for future use.blood count determination of the number of blood cells in a given sample of blood, usually expressed as the number in a cubic millimeter; it may be either a count" >complete blood count or a count of just one of the elements such as an count" >erythrocyte count, count" >leukocyte count or a count" >platelet count. Methods include manual counts using a hemacytometer" >hemacytometer and automated counts using a flow cytometer, a Coulter counter, or other means. The blood count is useful in the diagnosis of various blood dyscrasias, infections, or other abnormal conditions and is one of the most common tests done on the blood. Called also blood cell count. (See accompanying table.)defibrinated blood whole blood from which fibrin has been separated during the clotting process.blood gas analysis laboratory studies of arterial and venous blood for the purpose of measuring oxygen and carbon dioxide levels and pressure or tension, and hydrogen ion concentration (pH). (See accompanying table.) Analyses of blood gases provide the following information:
Pa_O_₂—partial pressure (P) of oxygen (O₂) in the arterial blood (a)
Sa_O_₂—percentage of available hemoglobin that is saturated (Sa) with oxygen (O₂)
Pa_CO_₂—partial pressure (P) of carbon dioxide (CO₂) in the arterial blood (a)
pH—an expression of the extent to which the blood is alkaline or acidic
HCO₃⁻—the level of plasma bicarbonate; an indicator of the metabolic acid-base status
These parameters are important tools for assessment of a patient's acid-base balance. They reflect the ability of the lungs to exchange oxygen and carbon dioxide, the ability of the kidneys to control the retention or elimination of bicarbonate, and the effectiveness of the heart as a pump. Because the lungs and kidneys act as important regulators of the respiratory and metabolic acid-base balance, assessment of the status of a patient with any disorder of respiration and metabolism includes periodic blood gas measurements.
The partial pressure of a particular gas in a mixture of gases, as of oxygen in air, is the pressure exerted by that gas alone. It is proportional to the relative number of molecules of the gas, for example, the fraction of all the molecules in the air that are oxygen molecules. The partial pressure of a gas in a liquid is the partial pressure of a real or imaginary gas that is in equilibrium with the liquid.
Pa_O_₂ measures the oxygen content of the arterial blood, most of which is bound to hemoglobin, forming oxyhemoglobin. The Sa_O_₂ measures the oxygen in oxyhemoglobin as a percentage of the total hemoglobin oxygen-carrying capacity.
A Pa_O_₂ of 60 mm Hg represents an Sa_O_₂ of 90 per cent, which is sufficient to meet the needs of the body's cells. However, as the Pa_O_₂ falls, the Sa_O_₂ decreases rapidly. A Pa_O_₂ below 55 indicates a state of hypoxemia that requires correction. Normal Pa_O_₂ values at sea level are 80 mm Hg for elderly adults and 100 mm Hg for young adults.
However, some patients with chronic obstructive pulmonary disease can tolerate a Pa_O_₂ as low as 70 mm Hg without becoming hypoxic. In caring for patients with this condition, it is important to know that attempts to elevate the Pa_O_₂ level to the normal level can be dangerous and even fatal. It is best to establish a baseline for each individual patient before supplementary oxygen is given, and then to assess his condition and the effectiveness of his therapy according to this baseline.
The Pa_CO_₂ gives information about the cellular production of carbon dioxide through metabolic processes, and the removal of it from the body via the lungs. The normal range is 32 to 45 mm Hg. Values outside this range indicate a primary respiratory problem associated with pulmonary function, or a metabolic problem for which there is respiratory compensation.
In the newborn the normal Pa_O_₂ is 50 to 80 mm Hg. At 40 to 50 mm Hg cyanosis may become apparent. Respiratory distress in an infant who is unable to ventilate the lungs adequately will produce a drop in Pa_O_₂ level. However, there is no marked increase in Pa_CO_₂ level in some infants as in adults with respiratory distress because many infants can still eliminate carbon dioxide from the lungs even though weakness prevents inhaling an adequate oxygen supply. All infants being ventilated and receiving oxygen therapy require frequent blood gas analyses and also pH, base excess, and oxygen saturation levels to avoid oxygen toxicity and acid-base imbalance.
Blood pH gives information about the patient's metabolic state. A pH of 7.4 is considered normal; a value lower than 7.4 indicates acidemia and one higher than 7.4 alkalemia.
Because the amount of CO₂ in the blood affects its pH, abnormal Pa_CO_₂ values are interpreted in relation to the pH. If the Pa_CO_₂ value is elevated, and the pH is below normal, respiratory acidosis from either acute or chronic hyperventilation is suspected. Conversely, a Pa_CO_₂ below normal and a pH above normal indicates respiratory alkalosis. When both the Pa_CO_₂ and the pH are elevated, there is respiratory retention of CO₂ to compensate for metabolic acidosis. If both values are below normal, there is respiratory elimination of CO₂ (hyperventilation) to compensate for metabolic acidosis.
Abnormal levels of bicarbonate (HCO₃⁻) in the plasma are also interpreted in relation to the pH in the diagnosis of disturbances in the metabolic component of the acid-base balance. The normal range for HCO₃⁻ is 22 to 26 mEq per liter. Abnormally low levels of both HCO₃⁻ and pH indicate acidosis of metabolic origin. Conversely, elevations of both of these values indicate metabolic alkalosis. The kidneys maintain bicarbonate levels by filtering bicarbonate and returning it to the blood; they also produce new bicarbonate to replace that which is used in buffering. Therefore, a decreased HCO₃⁻ and an increased pH level indicate either retention of hydrogen ions by the kidneys or the elimination of HCO₃⁻ in an effort to compensate for respiratory alkalosis. Conversely, if the HCO₃⁻ level is increased and the pH is decreased, the kidneys have compensated for respiratory acidosis by retaining HCO₃⁻ or by eliminating hydrogen ions.blood gas analysis, mixed venous blood gas analysis performed on a blood sample obtained from the pulmonary artery.blood gas analysis, transcutaneous the determination of PO₂ and PCO₂ by placement of a heated electrode over the skin to get an inference of Pa_O_₂ and Pa_CO_₂.blood group the phenotype of erythrocytes defined by one or more cellular antigenic structural groupings under the control of allelic genes. In clinical practice there are four main blood groups or blood types: A, B, O, and AB (see table). In addition to this major grouping there is an Rh-hR system that is important in the prevention of erythroblastosis fetalis resulting from incompatibility of blood groups in mother and fetus.
The ABO blood group system was first introduced in 1900 by Karl Landsteiner; in 1920 group AB was discovered by van Descatello and Sturli. Identification of these four major blood groups represented a major step toward resolving the problem of blood transfusion reactions resulting from donor-recipient incompatibility. In 1938 Landsteiner and Weiner discovered another blood factor related to maternal-fetal incompatibility. The factor was named Rh because the researchers were using rhesus monkeys in their studies. Further research has uncovered additional factors in the Rh group.
Although more than 90 factors have been identified, many of these are not highly antigenic and are not, therefore, a cause for concern in the typing of blood for clinical purposes.
The term factor, in reference to blood groups, is synonymous with antigen, and the reaction occurring between incompatible blood types is an antigen-antibody reaction. In cases of incompatibility, the antigen, located on the red blood cells, is an agglutinogen and the specific antibody, located in the serum, is an agglutinin. These are so named because whenever red blood cells with a certain factor come in contact with the agglutinin specific for it, there is agglutination or clumping of the erythrocytes.
In determining blood group, a sample of blood is taken and mixed with specially prepared sera. One serum, anti-A agglutinin, causes blood of group A to agglutinate; another serum, anti-B agglutinin, causes blood of group B to agglutinate. Thus, if anti-A serum alone causes clumping, the blood is group A; if anti-B serum alone causes clumping, it is group B. If both cause clumping, the blood group is AB, and if it is not clumped by either, it is identified as group O.occult blood that present in such small amounts as to be detectable only by chemical tests or by spectroscopic or microscopic examination.peripheral blood that obtained from acral areas, or from the circulation remote from the heart; the blood in the systemic circulation.blood poisoning popular term for septicemia" >septicemia.blood pressure 1. the pressure of the blood against the walls of any blood vessel.2. the term usually refers to the pressure of the blood within the arteries, or pressure" >arterial blood pressure. This pressure is determined by several interrelated factors, including the pumping action of the heart, the resistance to the flow of blood in the arterioles, the elasticity of the walls of the main arteries, the blood volume and extracellular fluid volume, and the blood's viscosity, or thickness.
The pumping action of the heart refers to how hard the heart pumps the blood (force of heartbeat), how much blood it pumps (the cardiac output), and how efficiently it does the job. Contraction of the heart, which forces blood through the arteries, is the phase known as systole. Relaxation of the heart between contractions is called diastole.
The main arteries leading from the heart have walls with strong elastic fibers capable of expanding and absorbing the pulsations generated by the heart. At each pulsation the arteries expand and absorb the momentary increase in blood pressure. As the heart relaxes in preparation for another beat, the aortic valves close to prevent blood from flowing back to the heart chambers, and the artery walls spring back, forcing the blood through the body between contractions. In this way the arteries act as dampers on the pulsations and thus provide a steady flow of blood through the blood vessels. Because of this, there are actually two blood pressures within the blood vessels during one complete beat of the heart: a higher blood pressure during systole (the contraction phase) and a lower blood pressure during diastole (the relaxation phase). These two blood pressures are known as the systolic pressure and the diastolic pressure, respectively.
It is generally agreed that a reading of 120 mm Hg systolic and 80 mm Hg diastolic are the norms for a blood pressure reading; that is, it represents the average blood pressure obtained from a large sampling of healthy adults. In general, a blood pressure of 95 mm Hg systolic and 60 mm Hg diastolic indicates hypotension. However, a reading equal to or below this level must be interpreted in the light of each patient's “normal” reading as determined by baseline data.
On the basis of validated research on the long-term effects of an elevated blood pressure, it is generally agreed that some degree of risk for major cardiovascular disease exists when the systolic pressure is greater than or equal to 140 mm Hg, and the diastolic pressure is greater than or equal to 90 mm Hg. Life expectancy is reduced at all ages and in both males and females when the diastolic pressure is above 90 mm Hg. (See accompanying table.)Measurement of the Blood Pressure. The blood pressure is usually measured in the artery of the upper arm, with a sphygmomanometer.

Measurement of blood pressure. From Applegate, 2000. This consists of a rubber cuff and a gauge or column of mercury for measuring pressure. The rubber cuff is wrapped about the patient's arm, and then air is pumped into the cuff by means of a rubber bulb. As the pressure inside the rubber cuff increases, the flow of blood through the artery is momentarily checked.
A stethoscope is placed over the artery at the elbow and the air pressure within the cuff is slowly released. As soon as blood begins to flow through the artery again, Korotkoff sounds are heard. The first sounds heard are tapping sounds that gradually increase in intensity. The initial tapping sound that is heard for at least two consecutive beats is recorded as the systolic blood pressure.
The first phase of the sounds may be followed by a momentary disappearance of sounds that can last from 30 to 40 mm Hg as the gauge needle (or mercury column) descends. It is important that this gap" >auscultatory gap not be missed; otherwise, either an erroneously low systolic pressure or high diastolic pressure will be obtained.
During the second phase following the temporary absence of sound there are murmuring or swishing sounds. As deflation of the cuff continues, the sounds become sharper and louder. These sounds represent phase three. During phase four the sounds become muffled rather abruptly and then are followed by silence, which represents phase five.
Although there is disagreement as to which of the latter phases should represent the diastolic pressure, it is usually recommended that phase five, the point at which sounds disappear, be used as the diastolic pressure for adults, and phase four be used for children. The reason for this is that children, having a high cardiac output, often will continue to produce sounds when the gauge is at a very low reading or even at zero. In some adult patients whose arterioles have lost their elasticity, the fifth phase is also extremely low or nonexistent. In these cases, it is recommended that three readings be recorded: phase one and phases four and five. For example, the blood pressure would be written as 140/96/0. On most occasions, however, the blood pressure is written as a fraction. The systolic pressure is written as the top number, a line is drawn, and the diastolic pressure is written as the bottom number.
Errors in blood pressure measurement can result from failure of the cuff to reach and compress the artery. The cuff diameter should be 20 per cent greater than the diameter of the limb, the bladder of the cuff must be centered over the artery, and the cuff must be wrapped smoothly and snugly to ensure proper inflation. When a mercury gauge is used, the meniscus should be at eye level to avoid a false reading. Direct Measurement of Blood Pressure. Critically ill patients who require continuous monitoring of the blood pressure may have a catheter inserted into an artery and attached to a catheter-monitor-transducer system. The blood pressure is displayed on an oscilloscope at the bedside so that the patient's pressure can be determined at a glance. This intra-arterial technique of blood pressure monitoring provides accurate, objective, and continuous data on the patient's status.blood pressure, mean arterial MAP; the average pressure within an artery over a complete cycle of one heartbeat; in the brachial artery, calculated to be the diastolic pressure plus 1/3 of the difference between the systolic and diastolic pressures.blood stream bloodstream.blood urea nitrogen see urea nitrogen.blood volume 1. the total quantity of blood in the body; the volume" >plasma volume added to the volume." >red cell volume.2. a laboratory test performed to determine this. The indicators used to determine these measurements are ¹²⁵I-labeled human serum albumin for plasma volume and ⁵¹Cr-labeled erythrocytes for red cell volume. The regulation of blood volume in the circulatory system is affected by the intrinsic mechanism for fluid exchange at the capillary membranes and by hormonal influences and nervous reflexes that affect the excretion of fluids by the kidneys. A rapid decrease in the blood volume, as in hemorrhage, greatly reduces the cardiac output and creates a condition called shock or circulatory shock. Conversely, an increase in blood volume, as when there is retention of water and salt in the body because of renal failure, results in an increase in cardiac output. The eventual outcome of this situation is increased arterial blood pressure.
The blood volume in the pulmonary circulation is approximately 12 per cent of the total blood volume. Such conditions as left-sided heart failure and mitral stenosis can greatly increase the pulmonary blood volume while decreasing the systemic volume. As would be expected, right-sided heart failure has the opposite effect. The latter condition has less serious effects because the volume of the systemic circulation is about seven times that of the pulmonary circulation and it is therefore better able to accommodate a change in fluid volume. Tests. Clinical assessment of blood volume can be accomplished in a number of ways, for example, by measuring the patient's blood pressure while he is lying down, sitting, and standing. The quality and volume of peripheral pulses will give information about blood volume, as does determining the ease and speed with which a compressed vein will refill after pressure is released. Neck veins that are engorged indicate hypervolemia; the collapse of these veins indicates hypovolemia. A more accurate assessment can be done through the use of intravascular catheters such as the central venous pressure catheter, which measures pressure in the right atrium, and the swan-ganz catheter, which measures pressure on both sides of the heart.
Measurement of blood volume is accomplished by using substances that combine with red blood cells, for example, iron, chromium, and phosphate, or substances that combine with plasma proteins. In either case the measurement of the blood volume is based on the “dilution” principle. That is, the volume of any fluid compartment can be measured if a given amount of a substance is dispersed evenly in the fluid within the compartment, and then the extent of dilution of the substance is measured.
For example, a small amount of radioactive chromium (⁵¹Cr), which is widely used to determine blood volume, is mixed with a sample of blood drawn from the patient. After about 30 minutes the ⁵¹Cr will have entered the red blood cells. The sample with the tagged red blood cells is then returned by injection into the patient's bloodstream. About 10 minutes later a sample is removed from the patient's circulating blood and the radioactivity level of this sample is measured. The total blood volume is calculated according to this formula:When volume is used to arrive at the total blood volume, a dye (usually T-1824, also known as Evans blue) is injected into the circulating blood. The dye immediately combines with the blood proteins and within 10 minutes is dispersed throughout the circulatory system. A sample of blood is then drawn and the exact quantity of dye is measured. Using the information about plasma volume obtained by applying the above formula, the total blood volume can be calculated, provided the hematocrit is also known. The formula for this calculation is:whole blood that from which none of the elements has been removed, sometimes specifically that drawn from a selected donor under aseptic conditions, containing citrate ion or heparin, and used as a blood replenisher.

blood

(blŭd), The "circulating tissue" of the body; the fluid and its suspended formed elements that are circulated through the heart, arteries, capillaries, and veins; blood is the means by which 1) oxygen and nutritive materials are transported to the tissues, and 2) carbon dioxide and various metabolic products are removed for excretion. Blood consists of a pale yellow or gray-yellow fluid, plasma, in which are suspended red blood cells (erythrocytes), white blood cells (leukocytes), and platelets.
See also: arterial blood, venous blood. Synonym(s): haema [TA] [A.S. blōd]

blood

hemophobia.

blood

(blŭd)n.1. a. The fluid consisting of plasma, blood cells, and platelets that is circulated by the heart through the vertebrate vascular system, carrying oxygen and nutrients to and waste materials away from all body tissues.b. A similar fluid in animals other than vertebrates.c. The juice or sap of certain plants.2. A vital or animating force; lifeblood.3. One of the four humors of ancient and medieval physiology, identified with the blood found in blood vessels, and thought to cause cheerfulness.4. Temperament or disposition: a person of hot blood and fiery temper.5. a. Descent from a common ancestor; parental lineage.b. Family relationship; kinship.c. Descent from noble or royal lineage: a princess of the blood.d. Recorded descent from purebred stock.e. National or racial ancestry.

blood

Hematology A circulating tissue composed of a fluid portion–plasma, suspended formed elements–RBCs, WBCs, platelets, and other components, including CO₂, O₂, proteins, glucose, cholesterol and other fats, which circulates in a closed system–the heart, arteries, capillaries and veins, and is charged with transporting O₂ and nutrients to cells, and removing CO₂ and waste products to the appropriate sites. See Artificial blood, Bad blood, Deoxygenated blood, Euroblood, Fecal occult blood, Frozen blood, Leukocyte-poor blood, Occult blood, Safe blood, Strawberry cream blood, Umbilical cord blood, Whole blood, Yellow blood. Cf Snake blood.

blood

(blŭd) The fluid and its suspended formedelements that are circulated through the heart, arteries, capillaries, and veins; the means by which oxygen and nutritive materials are transported to the tissues, and carbon dioxide and various metabolic products are removed for excretion. The blood consists of a pale yellow or gray-yellow fluid, plasma, in which red blood cells (erythrocytes), white blood cells (leukocytes), and platelets are suspended.
See also: arterial blood, venous blood[A.S. blōd]

blood

(blud)

BLOOD COMPOSITION: Components of blood and relationship to other body tissues

BLOOD COMPOSITION: Cell types found in smears of peripheral blood from normal individuals.The cell-containing fluid that circulates through the heart, arteries, veins, and capillaries, carrying nourishment, electrolytes, hormones, vitamins, antibodies, heat, and oxygen to the tissues and taking away waste matter and carbon dioxide. See: erythropoietin

Characteristics

Blood 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.

Composition

Human 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

Function

In 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.

Formation

RBCs 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 blood

See: coagulation, blood

cord blood

The blood present in the umbilical vessels connecting the placenta to the fetus. Because cord blood is immunologically immature, it is esp. useful in transfusion therapy and hematological transplantation.

defibrinated blood

Whole blood from which fibrin has been removed. It does not clot.

formed elements of blood

Blood cells, as opposed to blood proteins or other chemical constituents of blood.

fresh blood

Blood that has been collected less than 48 hours prior to its use in a transfusion.

occult blood

See: occult

oxygenated blood

Blood that has been exposed to oxygen in the lung; sometimes referred to as arteriolized blood.

predonation of blood

autologous blood transfusion.

reconstituted blood

A blood product used in transfusion therapy composed of components of blood (packed red blood cells plus plasma), which have been recombined after their separation and storage.

sludged blood

Hemagglutinated blood.

unit of blood

Approx. 1 pint (473 ml) of blood, the usual amount used in adult transfusion.illustration

blood

A 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).

Fig. 71 Blood . The constituents of blood.

blood

a 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:

red blood cells or ERYTHROCYTES,
white blood cells or LEUCOCYTES and
cell fragments or PLATELETS.

blood

(blŭd) The "circulating tissue" of the body; the fluid and its suspended formed elements that are circulated through the heart, arteries, capillaries, and veins; blood is the means by which: 1) oxygen and nutritive materials are transported to the tissues, and 2) carbon dioxide and various metabolic products are removed for excretion. Blood consists of a pale yellow or gray-yellow fluid, plasma, in which are suspended red blood cells (erythrocytes), white blood cells (leukocytes), and platelets.
See also: arterial blood, venous blood[A.S. blōd]

Patient discussion about blood

Q. does serratrol thin your blood? A. i don't know about blood thinning but i do know that when i looked for information about it (i looked for an alternative medicine for my mother) i found out this review about it:
http://www.medicine.ox.ac.uk/bandolier/booth/alternat/serrapep.html
according to this after reviewing 34 researches done on serratrol - they found no evidence supporting the claim it helps.

Q. what are Blood thiners what pilles are blood thinnersA. anticoagulants, given in order to avoid blood clots in your systems. some heard conditions (for example) like damaged valves can cause blood to clot on them and then there's a big risk that it'll detach itself and move around your body until it'll get stuck and block the blood vessel. can be blood vessels to the leg, hand,lungs or even brain. the most well known anticoagulants are Warfarin and Low Molecular Heparin (which is given in a shot not per os like WArfarin).
hope i helped :)

Q. how can i reduce my blood pressure? A. The main steps in lowering high blood pressure is to take some very important changes in lifestyle- consuming much less salt in food, losing weight and exercising regulary. If this doesn't help (and usually it doesn't help mainly when people don't try hard enought and make an effort), medications can be added to control the blood pressure.

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Erythrocytes (Red Blood Cells)

Leukocytes (White Blood Cells)

Granulocytes

Agranulocytes

Other Constituents of Blood

Bibliography

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Formed elements

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REFERENCES

REFERENCES

What does it mean when you dream about blood?

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Characteristics

Composition

Function

Formation

clotting of blood

cord blood

defibrinated blood

formed elements of blood

fresh blood

occult blood

oxygenated blood

predonation of blood

reconstituted blood

sludged blood

unit of blood

blood

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Patient discussion about blood

Blood

BLOOD

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Synonyms for blood

noun lifeblood

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noun family

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phrase bad blood

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phrase in cold blood

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Synonyms for blood

noun the fluid circulated by the heart through the vascular system

Synonyms

noun the crime of murdering someone