Blood is a body fluid in humans and other animals that delivers
necessary substances such as nutrients and oxygen to the cells and
transports metabolic waste products away from those same cells.
In vertebrates, it is composed of blood cells suspended in blood
plasma. Plasma, which constitutes 55% of blood fluid, is mostly water
(92% by volume), and contains dissipated proteins, glucose, mineral
ions, hormones, carbon dioxide (plasma being the main medium for
excretory product transportation), and blood cells themselves. Albumin
is the main protein in plasma, and it functions to regulate the
colloidal osmotic pressure of blood. The blood cells are mainly red
blood cells (also called RBCs or erythrocytes), white blood cells
(also called WBCs or leukocytes) and platelets (also called
thrombocytes). The most abundant cells in vertebrate blood are red
blood cells. These contain hemoglobin, an iron-containing protein,
which facilitates oxygen transport by reversibly binding to this
respiratory gas and greatly increasing its solubility in blood. In
contrast, carbon dioxide is mostly transported extracellularly as
bicarbonate ion transported in plasma.
Vertebrate blood is bright red when its hemoglobin is oxygenated and
dark red when it is deoxygenated. Some animals, such as crustaceans
and mollusks, use hemocyanin to carry oxygen, instead of hemoglobin.
Insects and some mollusks use a fluid called hemolymph instead of
blood, the difference being that hemolymph is not contained in a
closed circulatory system. In most insects, this "blood" does not
contain oxygen-carrying molecules such as hemoglobin because their
bodies are small enough for their tracheal system to suffice for
Jawed vertebrates have an adaptive immune system, based largely on
white blood cells. White blood cells help to resist infections and
parasites. Platelets are important in the clotting of blood.
Arthropods, using hemolymph, have hemocytes as part of their immune
Blood is circulated around the body through blood vessels by the
pumping action of the heart. In animals with lungs, arterial blood
carries oxygen from inhaled air to the tissues of the body, and venous
blood carries carbon dioxide, a waste product of metabolism produced
by cells, from the tissues to the lungs to be exhaled.
Medical terms related to blood often begin with hemo- or hemato- (also
spelled haemo- and haemato-) from the Greek word αἷμα (haima) for
"blood". In terms of anatomy and histology, blood is considered a
specialized form of connective tissue, given its origin in the bones
and the presence of potential molecular fibers in the form of
2.3 pH values
Blood in non-mammalian vertebrates
3.1 Cardiovascular system
3.2 Production and degradation of blood cells
Carbon dioxide transport
3.5 Transport of hydrogen ions
3.6 Lymphatic system
3.8 Rate of blood flow
3.9 Hydraulic functions
5.1 General medical disorders
5.2 Hematological disorders
Carbon monoxide poisoning
6 Medical treatments
7.1 Classical Greek medicine
7.2 Human blood
8 Cultural and religious beliefs
8.1 Indigenous Australians
8.2 European paganism
8.6 Jehovah's Witnesses
8.7 East Asian culture
9.1 In the applied sciences
9.2 In art
9.3 In genealogy and family history
10 See also
12 External links
Hemoglobin, a globular protein
green = haem groups
red & blue = protein subunits
Blood performs many important functions within the body, including:
Supply of oxygen to tissues (bound to hemoglobin, which is carried in
Supply of nutrients such as glucose, amino acids, and fatty acids
(dissolved in the blood or bound to plasma proteins (e.g., blood
Removal of waste such as carbon dioxide, urea, and lactic acid
Immunological functions, including circulation of white blood cells,
and detection of foreign material by antibodies
Coagulation, the response to a broken blood vessel, the conversion of
blood from a liquid to a semisolid gel to stop bleeding
Messenger functions, including the transport of hormones and the
signaling of tissue damage
Regulation of core body temperature
See also: Reference ranges for common blood tests
What's Inside of Blood
Blood accounts for 7% of the human body weight, with an average
density around 1060 kg/m3, very close to pure water's density of
1000 kg/m3. The average adult has a blood volume of roughly 5
litres (11 US pt), which is composed of plasma and
several kinds of cells. These blood cells (which are also called
corpuscles or "formed elements") consist of erythrocytes (red blood
cells, RBCs), leukocytes (white blood cells), and thrombocytes
(platelets). By volume, the red blood cells constitute about 45% of
whole blood, the plasma about 54.3%, and white cells about 0.7%.
Whole blood (plasma and cells) exhibits non-Newtonian fluid dynamics.
If all human hemoglobin were free in the plasma rather than being
contained in RBCs, the circulatory fluid would be too viscous for the
cardiovascular system to function effectively.
Human blood fractioned by centrifugation: Plasma (upper, yellow
layer), buffy coat (middle, thin white layer) and erythrocyte layer
(bottom, red layer) can be seen.
Blood circulation: Red = oxygenated, blue = deoxygenated
Illustration depicting formed elements of blood
Two tubes of EDTA-anticoagulated blood.
Left tube: after standing, the RBCs have settled at the bottom of the
Right tube: Freshly drawn blood
Further information: Complete blood count
A scanning electron microscope (SEM) image of a normal red blood cell
(left), a platelet (middle), and a white blood cell (right)
One microliter of blood contains:
4.7 to 6.1 million (male), 4.2 to 5.4 million (female)
erythrocytes: Red blood cells contain the blood's hemoglobin and
distribute oxygen. Mature red blood cells lack a nucleus and
organelles in mammals. The red blood cells (together with endothelial
vessel cells and other cells) are also marked by glycoproteins that
define the different blood types. The proportion of blood occupied by
red blood cells is referred to as the hematocrit, and is normally
about 45%. The combined surface area of all red blood cells of the
human body would be roughly 2,000 times as great as the body's
4,000–11,000 leukocytes: White blood cells are part of the body's
immune system; they destroy and remove old or aberrant cells and
cellular debris, as well as attack infectious agents (pathogens) and
foreign substances. The cancer of leukocytes is called leukemia.
200,000–500,000 thrombocytes: Also called platelets, they take
part in blood clotting (coagulation). Fibrin from the coagulation
cascade creates a mesh over the platelet plug.
Constitution of normal blood
45 ± 7 (38–52%) for males
42 ± 5 (37–47%) for females
−3 to +3
10–13 kPa (80–100 mm Hg)
4.8–5.8 kPa (35–45 mm Hg)
About 55% of blood is blood plasma, a fluid that is the blood's liquid
medium, which by itself is straw-yellow in color. The blood plasma
volume totals of 2.7–3.0 liters (2.8–3.2 quarts) in an average
human. It is essentially an aqueous solution containing 92% water, 8%
blood plasma proteins, and trace amounts of other materials. Plasma
circulates dissolved nutrients, such as glucose, amino acids, and
fatty acids (dissolved in the blood or bound to plasma proteins), and
removes waste products, such as carbon dioxide, urea, and lactic acid.
Other important components include:
Blood-clotting factors (to facilitate coagulation)
Various other proteins
Various electrolytes (mainly sodium and chloride)
The term serum refers to plasma from which the clotting proteins have
been removed. Most of the proteins remaining are albumin and
See also: Acid-base homeostasis
Blood pH is regulated to stay within the narrow range of 7.35 to 7.45,
making it slightly basic.
Blood that has a pH below 7.35 is too
acidic, whereas blood pH above 7.45 is too basic.
Blood pH, partial
pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2),
and bicarbonate (HCO3−) are carefully regulated by a number of
homeostatic mechanisms, which exert their influence principally
through the respiratory system and the urinary system to control the
acid-base balance and respiration. An arterial blood gas test measures
these. Plasma also circulates hormones transmitting their messages to
various tissues. The list of normal reference ranges for various blood
electrolytes is extensive.
Blood in non-mammalian vertebrates
Vertebrate red blood cell types, measurements in micrometers
Frog red blood cells magnified 1000 times
Turtle red blood cells magnified 1000 times
Chicken red blood cells magnified 1000 times
Human red blood cells magnified 1000 times
Human blood is typical of that of mammals, although the precise
details concerning cell numbers, size, protein structure, and so on,
vary somewhat between species. In non-mammalian vertebrates, however,
there are some key differences:
Red blood cells of non-mammalian vertebrates are flattened and ovoid
in form, and retain their cell nuclei.
There is considerable variation in the types and proportions of white
blood cells; for example, acidophils are generally more common than in
Platelets are unique to mammals; in other vertebrates, small
nucleated, spindle cells called thrombocytes are responsible for blood
Circulation of blood through the human heart
Main article: Circulatory system
Blood is circulated around the body through blood vessels by the
pumping action of the heart. In humans, blood is pumped from the
strong left ventricle of the heart through arteries to peripheral
tissues and returns to the right atrium of the heart through veins. It
then enters the right ventricle and is pumped through the pulmonary
artery to the lungs and returns to the left atrium through the
Blood then enters the left ventricle to be circulated
again. Arterial blood carries oxygen from inhaled air to all of the
cells of the body, and venous blood carries carbon dioxide, a waste
product of metabolism by cells, to the lungs to be exhaled. However,
one exception includes pulmonary arteries, which contain the most
deoxygenated blood in the body, while the pulmonary veins contain
Additional return flow may be generated by the movement of skeletal
muscles, which can compress veins and push blood through the valves in
veins toward the right atrium.
The blood circulation was famously described by
William Harvey in
Production and degradation of blood cells
In vertebrates, the various cells of blood are made in the bone marrow
in a process called hematopoiesis, which includes erythropoiesis, the
production of red blood cells; and myelopoiesis, the production of
white blood cells and platelets. During childhood, almost every human
bone produces red blood cells; as adults, red blood cell production is
limited to the larger bones: the bodies of the vertebrae, the
breastbone (sternum), the ribcage, the pelvic bones, and the bones of
the upper arms and legs. In addition, during childhood, the thymus
gland, found in the mediastinum, is an important source of T
lymphocytes. There are recent reports that the lungs may also be
the site of hematopoiesis. The proteinaceous component of blood
(including clotting proteins) is produced predominantly by the liver,
while hormones are produced by the endocrine glands and the watery
fraction is regulated by the hypothalamus and maintained by the
Healthy erythrocytes have a plasma life of about 120 days before they
are degraded by the spleen, and the Kupffer cells in the liver. The
liver also clears some proteins, lipids, and amino acids. The kidney
actively secretes waste products into the urine.
Basic hemoglobin saturation curve. It is moved to the right in higher
acidity (more dissolved carbon dioxide) and to the left in lower
acidity (less dissolved carbon dioxide)
About 98.5%  of the oxygen in a sample of
arterial blood in a healthy human breathing air at sea-level pressure
is chemically combined with the hemoglobin. About 1.5% is physically
dissolved in the other blood liquids and not connected to hemoglobin.
The hemoglobin molecule is the primary transporter of oxygen in
mammals and many other species (for exceptions, see below). Hemoglobin
has an oxygen binding capacity between 1.36 and 1.40 ml O2 per gram
hemoglobin, which increases the total blood oxygen capacity
seventyfold, compared to if oxygen solely were carried by its
solubility of 0.03 ml O2 per liter blood per mm Hg partial
pressure of oxygen (about 100 mm Hg in arteries).
With the exception of pulmonary and umbilical arteries and their
corresponding veins, arteries carry oxygenated blood away from the
heart and deliver it to the body via arterioles and capillaries, where
the oxygen is consumed; afterwards, venules and veins carry
deoxygenated blood back to the heart.
Under normal conditions in adult humans at rest, hemoglobin in blood
leaving the lungs is about 98–99% saturated with oxygen, achieving
an oxygen delivery between 950 and 1150 ml/min to the body. In a
healthy adult at rest, oxygen consumption is approximately 200–250
ml/min, and deoxygenated blood returning to the lungs is still
roughly 75% (70 to 78%) saturated. Increased oxygen
consumption during sustained exercise reduces the oxygen saturation of
venous blood, which can reach less than 15% in a trained athlete;
although breathing rate and blood flow increase to compensate, oxygen
saturation in arterial blood can drop to 95% or less under these
Oxygen saturation this low is considered dangerous in
an individual at rest (for instance, during surgery under anesthesia).
Sustained hypoxia (oxygenation less than 90%), is dangerous to health,
and severe hypoxia (saturations less than 30%) may be rapidly
A fetus, receiving oxygen via the placenta, is exposed to much lower
oxygen pressures (about 21% of the level found in an adult's lungs),
so fetuses produce another form of hemoglobin with a much higher
affinity for oxygen (hemoglobin F) to function under these
Carbon dioxide transport
CO2 is carried in blood in three different ways. (The exact
percentages vary depending whether it is arterial or venous blood).
Most of it (about 70%) is converted to bicarbonate ions HCO−
3 by the enzyme carbonic anhydrase in the red blood cells by the
reaction CO2 + H2O → H2CO3 → H+ + HCO−
3; about 7% is dissolved in the plasma; and about 23% is bound to
hemoglobin as carbamino compounds. Hemoglobin, the main
oxygen-carrying molecule in red blood cells, carries both oxygen and
carbon dioxide. However, the CO2 bound to hemoglobin does not bind to
the same site as oxygen. Instead, it combines with the N-terminal
groups on the four globin chains. However, because of allosteric
effects on the hemoglobin molecule, the binding of CO2 decreases the
amount of oxygen that is bound for a given partial pressure of oxygen.
The decreased binding to carbon dioxide in the blood due to increased
oxygen levels is known as the Haldane effect, and is important in the
transport of carbon dioxide from the tissues to the lungs. A rise in
the partial pressure of CO2 or a lower pH will cause offloading of
oxygen from hemoglobin, which is known as the Bohr effect.
Transport of hydrogen ions
Some oxyhemoglobin loses oxygen and becomes deoxyhemoglobin.
Deoxyhemoglobin binds most of the hydrogen ions as it has a much
greater affinity for more hydrogen than does oxyhemoglobin.
Main article: Lymphatic system
In mammals, blood is in equilibrium with lymph, which is continuously
formed in tissues from blood by capillary ultrafiltration.
collected by a system of small lymphatic vessels and directed to the
thoracic duct, which drains into the left subclavian vein where lymph
rejoins the systemic blood circulation.
Blood circulation transports heat throughout the body, and adjustments
to this flow are an important part of thermoregulation. Increasing
blood flow to the surface (e.g., during warm weather or strenuous
exercise) causes warmer skin, resulting in faster heat loss. In
contrast, when the external temperature is low, blood flow to the
extremities and surface of the skin is reduced and to prevent heat
loss and is circulated to the important organs of the body,
Rate of blood flow
Rate of blood flow varies greatly between different organs.
the most abundant blood supply with an approximate flow of 1350
Kidney and brain are the second and the third most supplied
organs, with 1100 ml/min and ~700 ml/min, respectively.
Relative rates of blood flow per 100 g of tissue are different, with
kidney, adrenal gland and thyroid being the first, second and third
most supplied tissues, respectively.
The restriction of blood flow can also be used in specialized tissues
to cause engorgement, resulting in an erection of that tissue;
examples are the erectile tissue in the penis and clitoris.
Another example of a hydraulic function is the jumping spider, in
which blood forced into the legs under pressure causes them to
straighten for a powerful jump, without the need for bulky muscular
In insects, the blood (more properly called hemolymph) is not involved
in the transport of oxygen. (Openings called tracheae allow oxygen
from the air to diffuse directly to the tissues.) Insect blood moves
nutrients to the tissues and removes waste products in an open system.
Other invertebrates use respiratory proteins to increase the
Hemoglobin is the most common respiratory
protein found in nature.
Hemocyanin (blue) contains copper and is
found in crustaceans and mollusks. It is thought that tunicates (sea
squirts) might use vanabins (proteins containing vanadium) for
respiratory pigment (bright-green, blue, or orange).
In many invertebrates, these oxygen-carrying proteins are freely
soluble in the blood; in vertebrates they are contained in specialized
red blood cells, allowing for a higher concentration of respiratory
pigments without increasing viscosity or damaging blood filtering
organs like the kidneys.
Giant tube worms have unusual hemoglobins that allow them to live in
extraordinary environments. These hemoglobins also carry sulfides
normally fatal in other animals.
The coloring matter of blood (hemochrome) is largely due to the
protein in the blood responsible for oxygen transport. Different
groups of organisms use different proteins.
Main article: Hemoglobin
Capillary blood from a bleeding finger
Hemoglobin is the principal determinant of the color of blood in
vertebrates. Each molecule has four heme groups, and their interaction
with various molecules alters the exact color. In vertebrates and
other hemoglobin-using creatures, arterial blood and capillary blood
are bright red, as oxygen imparts a strong red color to the heme
group. Deoxygenated blood is a darker shade of red; this is present in
veins, and can be seen during blood donation and when venous blood
samples are taken. This is because the spectrum of light absorbed by
hemoglobin differs between the oxygenated and deoxygenated states.
Blood in carbon monoxide poisoning is bright red, because carbon
monoxide causes the formation of carboxyhemoglobin. In cyanide
poisoning, the body cannot utilize oxygen, so the venous blood remains
oxygenated, increasing the redness. There are some conditions
affecting the heme groups present in hemoglobin that can make the skin
appear blue—a symptom called cyanosis. If the heme is oxidized,
methemoglobin, which is more brownish and cannot transport oxygen, is
formed. In the rare condition sulfhemoglobinemia, arterial hemoglobin
is partially oxygenated, and appears dark red with a bluish hue.
Veins close to the surface of the skin appear blue for a variety of
reasons. However, the factors that contribute to this alteration of
color perception are related to the light-scattering properties of the
skin and the processing of visual input by the visual cortex, rather
than the actual color of the venous blood.
Skinks in the genus
Prasinohaema have green blood due to a buildup of
the waste product biliverdin.
Main article: Hemocyanin
The blood of most mollusks – including cephalopods and gastropods
– as well as some arthropods, such as horseshoe crabs, is blue, as
it contains the copper-containing protein hemocyanin at concentrations
of about 50 grams per liter.
Hemocyanin is colorless when
deoxygenated and dark blue when oxygenated. The blood in the
circulation of these creatures, which generally live in cold
environments with low oxygen tensions, is grey-white to pale
yellow, and it turns dark blue when exposed to the oxygen in the
air, as seen when they bleed. This is due to change in color of
hemocyanin when it is oxidized.
Hemocyanin carries oxygen in
extracellular fluid, which is in contrast to the intracellular oxygen
transport in mammals by hemoglobin in RBCs.
Main article: Chlorocruorin
The blood of most annelid worms and some marine polychaetes use
chlorocruorin to transport oxygen. It is green in color in dilute
Main article: Hemerythrin
Hemerythrin is used for oxygen transport in the marine invertebrates
sipunculids, priapulids, brachiopods, and the annelid worm, magelona.
Hemerythrin is violet-pink when oxygenated.
Main article: Hemovanadin
The blood of some species of ascidians and tunicates, also known as
sea squirts, contains proteins called vanadins. These proteins are
based on vanadium, and give the creatures a concentration of vanadium
in their bodies 100 times higher than the surrounding sea water.
Unlike hemocyanin and hemoglobin, hemovanadin is not an oxygen
carrier. When exposed to oxygen, however, vanadins turn a mustard
General medical disorders
Disorders of volume
Injury can cause blood loss through bleeding. A healthy adult can
lose almost 20% of blood volume (1 L) before the first symptom,
restlessness, begins, and 40% of volume (2 L) before shock sets
Thrombocytes are important for blood coagulation and the formation
of blood clots, which can stop bleeding. Trauma to the internal organs
or bones can cause internal bleeding, which can sometimes be severe.
Dehydration can reduce the blood volume by reducing the water content
of the blood. This would rarely result in shock (apart from the very
severe cases) but may result in orthostatic hypotension and fainting.
Disorders of circulation
Shock is the ineffective perfusion of tissues, and can be caused by a
variety of conditions including blood loss, infection, poor cardiac
Atherosclerosis reduces the flow of blood through arteries, because
atheroma lines arteries and narrows them. Atheroma tends to increase
with age, and its progression can be compounded by many causes
including smoking, high blood pressure, excess circulating lipids
(hyperlipidemia), and diabetes mellitus.
Coagulation can form a thrombosis, which can obstruct vessels.
Problems with blood composition, the pumping action of the heart, or
narrowing of blood vessels can have many consequences including
hypoxia (lack of oxygen) of the tissues supplied. The term ischemia
refers to tissue that is inadequately perfused with blood, and
infarction refers to tissue death (necrosis), which can occur when the
blood supply has been blocked (or is very inadequate).
See also: Hematology
Insufficient red cell mass (anemia) can be the result of bleeding,
blood disorders like thalassemia, or nutritional deficiencies, and may
require one or more blood transfusions.
Anemia can also be due to a
genetic disorder in which the red blood cells simply do not function
Anemia can be confirmed by a blood test if the hemoglobin
value is less than 13.5 gm/dl in men or less than 12.0 gm/dl in
women. Several countries have blood banks to fill the demand for
transfusable blood. A person receiving a blood transfusion must have a
blood type compatible with that of the donor.
Disorders of cell proliferation
Leukemia is a group of cancers of the blood-forming tissues and cells.
Non-cancerous overproduction of red cells (polycythemia vera) or
platelets (essential thrombocytosis) may be premalignant.
Myelodysplastic syndromes involve ineffective production of one or
more cell lines.
Disorders of coagulation
Hemophilia is a genetic illness that causes dysfunction in one of the
blood's clotting mechanisms. This can allow otherwise inconsequential
wounds to be life-threatening, but more commonly results in
hemarthrosis, or bleeding into joint spaces, which can be crippling.
Ineffective or insufficient platelets can also result in coagulopathy
Hypercoagulable state (thrombophilia) results from defects in
regulation of platelet or clotting factor function, and can cause
Infectious disorders of blood
Blood is an important vector of infection. HIV, the virus that causes
AIDS, is transmitted through contact with blood, semen or other body
secretions of an infected person.
Hepatitis B and C are transmitted
primarily through blood contact. Owing to blood-borne infections,
bloodstained objects are treated as a biohazard.
Bacterial infection of the blood is bacteremia or sepsis. Viral
Infection is viremia.
Malaria and trypanosomiasis are blood-borne
Carbon monoxide poisoning
Carbon monoxide poisoning
Substances other than oxygen can bind to hemoglobin; in some cases
this can cause irreversible damage to the body. Carbon monoxide, for
example, is extremely dangerous when carried to the blood via the
lungs by inhalation, because carbon monoxide irreversibly binds to
hemoglobin to form carboxyhemoglobin, so that less hemoglobin is free
to bind oxygen, and fewer oxygen molecules can be transported
throughout the blood. This can cause suffocation insidiously. A fire
burning in an enclosed room with poor ventilation presents a very
dangerous hazard, since it can create a build-up of carbon monoxide in
the air. Some carbon monoxide binds to hemoglobin when smoking
Venous blood collected during blood donation
Blood for transfusion is obtained from human donors by blood donation
and stored in a blood bank. There are many different blood types in
humans, the ABO blood group system, and the Rhesus blood group system
being the most important. Transfusion of blood of an incompatible
blood group may cause severe, often fatal, complications, so
crossmatching is done to ensure that a compatible blood product is
Other blood products administered intravenously are platelets, blood
plasma, cryoprecipitate, and specific coagulation factor concentrates.
Many forms of medication (from antibiotics to chemotherapy) are
administered intravenously, as they are not readily or adequately
absorbed by the digestive tract.
After severe acute blood loss, liquid preparations, generically known
as plasma expanders, can be given intravenously, either solutions of
salts (NaCl, KCl, CaCl2 etc.) at physiological concentrations, or
colloidal solutions, such as dextrans, human serum albumin, or fresh
frozen plasma. In these emergency situations, a plasma expander is a
more effective life-saving procedure than a blood transfusion, because
the metabolism of transfused red blood cells does not restart
immediately after a transfusion.
Main article: bloodletting
In modern evidence-based medicine, bloodletting is used in management
of a few rare diseases, including hemochromatosis and polycythemia.
However, bloodletting and leeching were common unvalidated
interventions used until the 19th century, as many diseases were
incorrectly thought to be due to an excess of blood, according to
Jan Janský is credited with the first classification of blood into
four types (A, B, AB, and O)
According to the Oxford English Dictionary, the word "blood" dates to
the oldest English, circa 1000 CE. The word is derived from
Middle English, which is derived from the Old English word blôd,
which is akin to the Old High German word bluot, meaning blood. The
modern German word is (das) Blut.
Classical Greek medicine
Fåhræus (a Swedish physician who devised the erythrocyte
sedimentation rate) suggested that the Ancient Greek system of
humorism, wherein the body was thought to contain four distinct bodily
fluids (associated with different temperaments), were based upon the
observation of blood clotting in a transparent container. When blood
is drawn in a glass container and left undisturbed for about an hour,
four different layers can be seen. A dark clot forms at the bottom
(the "black bile"). Above the clot is a layer of red blood cells (the
"blood"). Above this is a whitish layer of white blood cells (the
"phlegm"). The top layer is clear yellow serum (the "yellow
ABO blood group system
ABO blood group system was discovered in the year 1900 by Karl
Jan Janský is credited with the first classification of
blood into the four types (A, B, AB, and O) in 1907, which remains in
use today. In 1907 the first blood transfusion was performed that used
the ABO system to predict compatibility. The first non-direct
transfusion was performed on March 27, 1914. The Rhesus factor was
discovered in 1937.
Cultural and religious beliefs
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Due to its importance to life, blood is associated with a large number
of beliefs. One of the most basic is the use of blood as a symbol for
family relationships through birth/parentage; to be "related by blood"
is to be related by ancestry or descendence, rather than marriage.
This bears closely to bloodlines, and sayings such as "blood is
thicker than water" and "bad blood", as well as "
Blood is given particular emphasis in the Jewish and Christian
Leviticus 17:11 says "the life of a creature is in
the blood." This phrase is part of the Levitical law forbidding the
drinking of blood or eating meat with the blood still intact instead
of being poured off.
Mythic references to blood can sometimes be connected to the
life-giving nature of blood, seen in such events as childbirth, as
contrasted with the blood of injury or death.
In many indigenous Australian Aboriginal peoples' traditions, ochre
(particularly red) and blood, both high in iron content and considered
Maban, are applied to the bodies of dancers for ritual. As Lawlor
In many Aboriginal rituals and ceremonies, red ochre is rubbed all
over the naked bodies of the dancers. In secret, sacred male
ceremonies, blood extracted from the veins of the participant's arms
is exchanged and rubbed on their bodies. Red ochre is used in similar
ways in less-secret ceremonies.
Blood is also used to fasten the
feathers of birds onto people's bodies. Bird feathers contain a
protein that is highly magnetically sensitive.
Lawlor comments that blood employed in this fashion is held by these
peoples to attune the dancers to the invisible energetic realm of the
Dreamtime. Lawlor then connects these invisible energetic realms and
magnetic fields, because iron is magnetic.
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Among the Germanic tribes, blood was used during their sacrifices; the
Blóts. The blood was considered to have the power of its originator,
and, after the butchering, the blood was sprinkled on the walls, on
the statues of the gods, and on the participants themselves. This act
of sprinkling blood was called blóedsian in Old English, and the
terminology was borrowed by the
Roman Catholic Church
Roman Catholic Church becoming to
bless and blessing. The Hittite word for blood, ishar was a cognate to
words for "oath" and "bond", see Ishara. The Ancient Greeks believed
that the blood of the gods, ichor, was a substance that was poisonous
As a relic of Germanic Law, the cruentation, an ordeal where the
corpse of the victim was supposed to start bleeding in the presence of
the murderer, was used until the early 17th century.
In Genesis 9:4, God prohibited
Noah and his sons from eating blood
(see Noahide Law). This command continued to be observed by the
It is also found in the Bible that when the Angel of Death came around
to the Hebrew house that the first-born child would not die if the
angel saw lamb's blood wiped across the doorway.
At the Council of Jerusalem, the apostles prohibited certain
Christians from consuming blood—this is documented in Acts 15:20 and
29. This chapter specifies a reason (especially in verses 19–21): It
was to avoid offending Jews who had become Christians, because the
Mosaic Law Code prohibited the practice.
Christ's blood is the means for the atonement of sins. Also, ″…
the blood of Jesus Christ his [God] Son cleanseth us from all sin." (1
John 1:7), “… Unto him [God] that loved us, and washed us from our
sins in his own blood." (Revelation 1:5), and "And they overcame him
(Satan) by the blood of the Lamb [Jesus the Christ], and by the word
of their testimony …” (Revelation 12:11).
Some Christian churches, including Roman Catholicism, Eastern
Orthodoxy, Oriental Orthodoxy, and the Assyrian Church of the East
teach that, when consecrated, the Eucharistic wine actually becomes
the blood of Jesus for worshippers to drink. Thus in the consecrated
wine, Jesus becomes spiritually and physically present. This teaching
is rooted in the Last Supper, as written in the four gospels of the
Bible, in which Jesus stated to his disciples that the bread that they
ate was his body, and the wine was his blood. "This cup is the new
testament in my blood, which is shed for you." (Luke 22:20).
Most forms of Protestantism, especially those of a Wesleyan or
Presbyterian lineage, teach that the wine is no more than a symbol of
the blood of Christ, who is spiritually but not physically present.
Lutheran theology teaches that the body and blood is present together
"in, with, and under" the bread and wine of the Eucharistic feast.
In Judaism, animal blood may not be consumed even in the smallest
Leviticus 3:17 and elsewhere); this is reflected in Jewish
dietary laws (Kashrut).
Blood is purged from meat by rinsing and
soaking in water (to loosen clots), salting and then rinsing with
water again several times. Eggs must also be checked and any blood
spots removed before consumption. Although blood from fish is
biblically kosher, it is rabbinically forbidden to consume fish blood
to avoid the appearance of breaking the Biblical prohibition.
Another ritual involving blood involves the covering of the blood of
fowl and game after slaughtering (
Leviticus 17:13); the reason given
Torah is: "Because the life of the animal is [in] its blood"
(ibid 17:14). In relation to human beings,
Kabbalah expounds on this
verse that the animal soul of a person is in the blood, and that
physical desires stem from it.
Likewise, the mystical reason for salting temple sacrifices and
slaughtered meat is to remove the blood of animal-like passions from
the person. By removing the animal's blood, the animal energies and
life-force contained in the blood are removed, making the meat fit for
Consumption of food containing blood is forbidden by Islamic dietary
laws. This is derived from the statement in the Qur'an, sura Al-Ma'ida
(5:3): "Forbidden to you (for food) are: dead meat, blood, the flesh
of swine, and that on which has been invoked the name of other than
Blood is considered unclean, hence there are specific methods to
obtain physical and ritual status of cleanliness once bleeding has
occurred. Specific rules and prohibitions apply to menstruation,
postnatal bleeding and irregular vaginal bleeding. When an animal has
been slaughtered, the animal's neck is cut in a way to ensure that the
spine is not severed, hence the brain may send commands to the heart
to pump blood to it for oxygen. In this way, blood is removed from the
body, and the meat is generally now safe to cook and eat. In modern
times, blood transfusions are generally not considered against the
Jehovah's Witnesses and blood transfusions
Based on their interpretation of scriptures such as Acts 15:28, 29
("Keep abstaining...from blood."), many
Jehovah's Witnesses neither
consume blood nor accept transfusions of whole blood or its major
components: red blood cells, white blood cells, platelets
(thrombocytes), and plasma. Members may personally decide whether they
will accept medical procedures that involve their own blood or
substances that are further fractionated from the four major
East Asian culture
In south East Asian popular culture, it is often said that if a man's
nose produces a small flow of blood, he is experiencing sexual desire.
This often appears in Chinese-language and Hong Kong films as well as
in Japanese and Korean culture parodied in anime, manga, and drama.
Characters, mostly males, will often be shown with a nosebleed if they
have just seen someone nude or in little clothing, or if they have had
an erotic thought or fantasy; this is based on the idea that a male's
blood pressure will spike dramatically when aroused.[unreliable
Main article: Vampire
Vampires are mythical creatures that drink blood directly for
sustenance, usually with a preference for human blood. Cultures all
over the world have myths of this kind; for example the 'Nosferatu'
legend, a human who achieves damnation and immortality by drinking the
blood of others, originates from Eastern European folklore. Ticks,
leeches, female mosquitoes, vampire bats, and an assortment of other
natural creatures do consume the blood of other animals, but only bats
are associated with vampires. This has no relation to vampire bats,
which are new world creatures discovered well after the origins of the
In the applied sciences
Blood residue can help forensic investigators identify weapons,
reconstruct a criminal action, and link suspects to the crime. Through
bloodstain pattern analysis, forensic information can also be gained
from the spatial distribution of bloodstains.
Blood residue analysis is also a technique used in archeology.
Blood is one of the body fluids that has been used in art. In
particular, the performances of Viennese Actionist Hermann Nitsch,
Istvan Kantor, Franko B, Lennie Lee, Ron Athey, Yang Zhichao, Lucas
Abela and Kira O' Reilly, along with the photography of Andres
Serrano, have incorporated blood as a prominent visual element. Marc
Quinn has made sculptures using frozen blood, including a cast of his
own head made using his own blood.
In genealogy and family history
The term blood is used in genealogical circles to refer to one's
ancestry, origins, and ethnic background as in the word bloodline.
Other terms where blood is used in a family history sense are
blue-blood, royal blood, mixed-blood and blood relative.
Blood as food
Blood substitutes ("artificial blood")
List of human blood components
Luminol, a visual test for blood left at crime scenes.
Taboo food and drink: Blood
Oct-1-en-3-one ("Smell" of blood)
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Wikiquote has quotations related to: Blood
Look up blood in Wiktionary, the free dictionary.
Wikimedia Commons has media related to Blood.
Blood Groups and Red Cell Antigens. Free online book at NCBI Bookshelf
Blood on In Our Time at the BBC.
The main cell types in blood
Langhans giant cells, Foreign-body giant cell
Touton giant cells
Antigen presenting cells
Red blood cells
Megakaryocyte–erythroid progenitor cell
Hematopoietic stem cell
αβ (Cytotoxic CD8+
Helper CD4+ / TFH / Th3 / Th17 / Regulatory)
Natural killer T cell
Cytokine-induced killer cell
Lymphokine-activated killer cell
Hematopoietic stem cell
Apheresis (plasmapheresis, plateletpheresis, leukapheresis)
Coombs test (direct and indirect)
International Society of
Intraoperative blood salvage
Blood group systems /
Rh and RHAG
Blood products /
Red blood cells
Plasma / Fresh frozen plasma / PF24 (
BNF: cb11934902m (d