Blood, The Blood
, There Will Be Blood
, In the Blood
, Blood for Blood
, Blood on Blood
, blood transfusion
, Blood in Blood out
, Talk:Blood in Blood out
is a highly specialized circulating tissue
consisting of several types of cells suspended in a fluid medium known as plasma
. The cellular constituents are: red blood cell
s, which carry respiratory gases and give it its red color, white blood cell
s (leukocytes), which fight disease, and platelet
s, cell fragments which play an important part in the clotting of the blood.
Medical terms related to blood often begin with hemo-
) from the Greek
" for "blood." Anatomically, blood is considered a connective tissue
from both its origin in the bones and its function.
Functions of blood are:
* Supply of oxygen
to tissues (bound to hemoglobin
which is carried in red cells)
* Supply of nutrients such as glucose
, amino acids
and fatty acids
(dissolved in the blood or bound to plasma proteins)
* Removal of waste such as carbon dioxide
and lactic acid
* Immunological functions, including circulation of white cells, and detection of foreign material by antibodies
, which is one part of the body's self-repair mechanism
* Messenger functions, including the transport of hormones
and the signalling of tissue damage
* Regulation of body pH
* Regulation of core body temperature
functions, including erection
(see also jumping spider
Problems with blood composition or circulation can lead to downstream tissue dysfunction. The term ischaemia
refers to tissue which is inadequately perfused with blood.
The blood is circulated around the lungs
and body by the pump
ing action of the heart
. Additional return pressure may be generated by gravity and the actions of skeletal muscles. In mammals, blood is in equilibrium with lymph
, which is continuously formed from blood (by capillary ultrafiltration) and returned to the blood (via the thoracic duct
). The lymphatic circulation has been called the "second circulation".
Anatomy of mammalian blood
Blood is composed of several kinds of cells (occasionally called corpuscles
); these formed elements
of the blood constitute about 45% of whole blood. The other 55% is blood plasma
, a fluid that is the blood's liquid medium, appearing yellow in color. thumb|right|230px|A red blood cell
s, several white blood cell
s including knobby lymphocyte
s, a monocyte
, a neutrophil
, and many small disc-shaped platelet
s.">[scanning electron microscope (SEM) image of normal circulating human blood. One can see red blood cell
s, several white blood cell
s including knobby lymphocyte
s, a monocyte
, a neutrophil
, and many small disc-shaped platelet
The normal pH
of human arterial blood is approximately 7.40 (normal range is 7.35-7.45), a weak alkaline solution. Blood that has a pH below 7.35 is acidic
, while blood pH above 7.45 is alkaline
. Blood pH along with arterial carbon dioxide tension (PaCO2
) and HCO3
readings are helpful in determining the acid-base balance of the body. The respiratory system
and urinary system
normally control the acid-base balance of blood as part of homeostasis
. Blood is about 7% of the human body weight,
so the average adult has a blood volume of about 5 litre
s, of which 2.7-3 litres is plasma. Human blood density is around 1060 kg/m³.
[cite web | url = http://hypertextbook.com/facts/2004/MichaelShmukler.shtml | title = Density of Blood | accessdate = 2006-10-04 | year = 2004 | publisher = http://hypertextbook.com/facts/ The Physics Factbook ]
The combined surface area of all the red cells in the human body would be roughly 2,000 times as great as the body's exterior
The cells are:
*Red blood cells or erythrocytes
(96%). In mammals, mature red blood cells lack a nucleus
s. They contain the blood's haemoglobin
and distribute oxygen. The red blood cells (together with endothelial
vessel cells and some other cells) are also marked by glycoprotein
s that define the different blood types
*White blood cells or leukocytes
(3.0%), are part of the immune system
; they destroy infectious agents, pathogens
*Platelets or thrombocytes
(1.0%) are responsible for blood clotting (coagulation
). They change fibrinogen into fibrin. This fibrin creates a mesh onto which red blood cells collect and clot. This clot stops more blood from leaving the body and also helps to prevent bacteria from entering the bodyBlood plasma
is essentially an aqueous
solution containing 92% water, 8% blood plasma protein
s, and trace amounts of other materials. Some components are:
* Serum albumin
* Blood clotting factors (to facilitate coagulation
* Various other protein
* Various electrolyte
s (mainly sodium
Together, plasma and cells form a non-Newtonian fluid
whose flow properties are uniquely adapted to the architecture of the blood vessels.
The term serum
refers to plasma from which the clotting proteins have been removed. Most of the protein remaining is albumin and immunoglobulins
Physiology of blood
Production and degradation
Blood cells are produced in the bone marrow
; the process is termed hematopoiesis
. The proteinaceous component (including clotting proteins) is produced overwhelmingly in the liver
, while hormones are produced by the endocrine gland
s and the watery fraction regulated by the hypothalamus
and maintained by the kidney
and indirectly by the gut
Blood cells are degraded by the spleen
and the Kupffer cell
s in the liver. The liver also clears some proteins, lipids and amino acid
s. The kidney actively secretes waste products into the urine
. Erythrocytes usually live up to 120 days before they are systematically replaced by new erythrocytes created by the process of hematopoiesis.
Transport of oxygen
See Oxygen transportation
Blood oxygenation is measured in several ways, but the most important measure is the hemoglobin (Hb) saturation percentage. This is a non-linear (sigmoidal) function of the partial pressure
of oxygen. About 98.5% of the oxygen in a sample of arterial blood in a healthy human breathing air at normal pressure is chemically combined with the Hb. Only 1.5% is physically dissolved in the other blood liquids and not connected to Hb. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species (for exceptions, see below).
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 arteriole
s and capillaries
, where the oxygen is consumed; afterwards, venule
s and vein
s carry deoxygenated blood back to the heart.
Differences in infrared absorption between oxygenated and deoxygenated blood form the basis for realtime oxygen saturation measurement in hospitals and ambulances.
Under normal conditions in humans at rest, haemoglobin in blood leaving the lungs is about 98-99% saturated with oxygen. In a healthy adult at rest, deoxygenated
blood returning to the lungs is still approximately 75% saturated.
[http://home.hia.no/~stephens/ventphys.htm Ventilation and Endurance Performance] [http://groups.msn.com/TransplantSupportLungHeartLungHeart/oxygen2.msnw Transplant Support- Lung, Heart/Lung, Heart MSN groups]
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 conditions.
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1464731 J Physiol. 2005 July 1]
Oxygen saturation this low is considered dangerous in an individual at rest (for instance, during surgery under anesthesia): "As a general rule, any condition which leads to a sustained mixed venous saturation of less than 50% will be poorly tolerated and a mixed venous saturation of less than 30% should be viewed as a medical emergency."
[http://www.manbit.com/PAC/chapters/P30.cfm The 'St George' Guide To Pulmonary Artery Catheterisation]
A fetus, receiving oxygen via the placenta, is exposed to much lower oxygen pressures (about 20% of the level found in an adult's lungs) and so fetuses produce another form of hemoglobin with a much higher affinity for oxygen (hemoglobin F) in order to extract as much oxygen as possible from this sparse supply.
[http://members.aol.com/Bio50/LecNotes/lecnot20.html Oxygen Carriage in Blood - High Altitude]
Substances other than oxygen can bind to the haemoglobin; in some cases this can cause irreversible damage to the body. Carbon monoxide
for example is extremely dangerous when absorbed into the blood. When combined with the haemoglobin, it irreversibly makes carboxyhaemoglobin which reduces the volume of oxygen that can be carried in the blood. This can very quickly cause suffocation as oxygen is vital to many organisms (including humans). This damage can occur when smoking a cigarette
(or similar item) or in event of a fire. Thus carbon monoxide is considered far more dangerous than the actual fire itself because it reduces the oxygen carrying content of the blood.
s, the blood (more properly called hemolymph
) is not involved in the transport of oxygen. (Openings called trachea
e 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.
In some small invertebrate
s like insects
, oxygen is simply dissolved in the plasma. Larger animals use respiratory proteins to increase the oxygen carrying capacity. Hemoglobin is the most common respiratory protein found in nature. Hemocyanin
) contains copper
and is found in crustacean
s and mollusk
s. It is thought that tunicate
s (sea squirts) might use vanabins
s 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 cell
s, allowing for a higher concentration of respiratory pigments without increasing viscosity
or damaging blood filtering organs like the kidneys
Deep sea invertebratesGiant tube worms
have extraordinary hemoglobins that allow them to live in extraordinary environments. These hemoglobins also carry sulfides normally fatal in other animals.
Transport of carbon dioxide
When systemic arterial blood flows through capillaries, carbon dioxide diffuses from the tissues into the blood. Some carbon dioxide is dissolved in the blood. Some carbon dioxide reacts with hemoglobin and other proteins to form carbamino
compounds. The remaining carbon dioxide is converted to bicarbonate
and hydrogen ion
s through the action of RBC carbonic anhydrase
. Most carbon dioxide is transported through the blood in the form of bicarbonate ions.
Transport of hydrogen ions
Some oxyhemoglobin loses oxygen and becomes deoxyhemoglobin. Deoxyhemoglobin has a much greater affinity for H+ than does oxyhemoglobin so it binds most of the hydrogen ions.
In humans and other hemoglobin-using creatures, oxygenated blood is bright red. This is due to oxygenated iron in the red blood cells. Deoxygenated blood is a darker shade of red, which can be seen during blood donation and when venous blood samples are taken. However, due to an optical effect caused by the way in which light penetrates through the skin, veins typically appear blue in color. This has led to a common misconception that venous blood is blue before it is exposed to air. Another reason for this misconception is that medical charts always show venous blood as blue in order to distinguish it from arterial blood which is depicted as red on the same chart.
The blood of horseshoe crab
s is blue, which is a result of its high content in copper-based hemocyanin instead of the iron-based hemoglobin found, for example, in humans.
Provision of force
In mammals the restriction of blood flow is commonly used as a temporary provision of force, as in an erection
Health and disease
medicine considered blood one of the four humors
(together with phlegm
, yellow bile
and black bile
). As many diseases were thought to be due to an excess of blood, bloodletting
were a common intervention until the 19th century
(it is still used for some rare blood disorders).
In classical Greek medicine, blood was associated with air, springtime, and with a merry and gluttonous (sanguine
) personality. It was also believed to be produced exclusively by the liver
and blood test
s are amongst the most commonly performed diagnostic investigations that directly concern the blood.
Problems with blood circulation and composition play a role in many diseases.
can cause major blood loss (see bleeding
). The thrombocyte
s cause the blood to coagulate
, blocking relatively minor wounds, but larger ones must be repaired at speed to prevent exsanguination
. Damage to the internal organs can cause severe internal bleeding
, or hemorrhage
* Circulation blockage can also create many medical conditions from ischemia
in the short term to tissue necrosis
in the long term.
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.
is a group of cancers
of the blood-forming tissues.
* Major blood loss, whether traumatic or not (e.g. during surgery), as well as certain blood diseases like anemia
, can require blood transfusion
. Several countries have blood bank
s to fill the demand for transfusable blood. A person receiving a blood transfusion must have a blood type
compatible with that of the donor.
* Blood is an important vector of infection. HIV
, the virus
which causes AIDS
, is transmitted through contact between blood, semen
, or the bodily secretions of an infected person. Hepatitis B
are transmitted primarily through blood contact. Owing to blood-borne infection
s, bloodstained objects are treated as a biohazard
* Bacterial infection of the blood is bacteremia
. Viral Infection is viremia. Malaria
are blood-borne parasitic infections.
is the most direct therapeutic use of blood. It is obtained from human donors by blood donation
. As there are different blood type
s, and transfusion of the incorrect blood may cause severe complications, crossmatching
is done to ascertain the correct type is transfused.
Other blood products administered intravenous
ly are platelets, blood plasma, cryoprecipitate and specific coagulation factor concentrates.
Many forms of medication (from antibiotic
s to chemotherapy
) are administered intravenously, as they are not readily or adequately absorbed by the digestive tract.
As stated above, some diseases are still treated by removing blood from the circulation.
It is the fluid part of the blood that saves lives where severe blood loss occurs, other preparations can be given such as ringers atopical plasma volume expander as a non-blood alternative, and these alternatives where used are rivalling blood use where used.
Mythology and religion
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; to be "related by blood" is to be related by ancestry or descendance, rather than marriage. This bears closely to bloodline
s, and sayings such as "blood is thicker than water" and "bad blood", as well as "Blood brother
". Blood is given particular emphasis in the Jewish and Christian religions because (Leviticus
17:11) says "the life of a creature is in the blood."
The differences in sugars and protein sequences sets human blood apart from animal blood and this has been used as an argument for creation in religious circles.
Among the Germanic tribe
s (such as the Anglo-Saxons
and the Viking
s), blood was used during the 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 bleodsian
in Old English
and the terminology was borrowed by the Roman Catholic Church
becoming to bless
. 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 mineral that was poisonous to mortals.
, blood cannot be consumed even in the smallest quantity (Leviticus
3:17 and elsewhere); this is reflected in Jewish dietary
). Blood is purged from meat
Other rituals involving blood are the covering of the blood of fowl
after slaughtering (Leviticus
17:13); the reason given by the Torah
is: "Because the life of every animal is in
his blood" (ibid 17:14), although from its context in Leviticus
3:17 it would appear that blood cannot be consumed because it is to be used in the sacrificial service
(known as the korbanot
), in the Temple in Jerusalem
. Blood (the blood of a lamb) was also the means for antonement of sins for the Jews.
has historically been the religion to be most affected by blood libel
Some Christian churches, including Roman Catholicism
, Eastern Orthodoxy
, branches of Anglicanism
, and the Moravian Church
, teach that when consecrated the Eucharist wine becomes
the material Blood of Jesus
. Thus in the consecrated wine (now the Most Precious Blood of Christ), 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 which 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." (sourcetext|source=Bible|version=King James|book=Luke )
. Various 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 not physically but spiritually present. Blood (the blood of Jesus Christ) is also seen as the means for atonement for sins for Christians. Lutheran
theology teaches that the body and blood is present together "in, with, and under" the bread and wine of the eucharist feast.
Consumption of food containing blood is forbidden by Islamic dietary laws
main|Jehovah's Witnesses and Jehovah's Witnesses
do not eat blood or accept tranfusions of whole blood or its four major components namely, red blood cells, white blood cells, platelets (thrombocytes), and whole plasma. Members are instructed to personally decide whether or not to accept fractions, and medical procedures that involve their own blood.
s are fictional beings thought to cheat death by drinking the blood of the living. This myth is mostly inspired by European folklore based on the stories regarding Vlad III the Impaler
and rare variations of dementia
specific to the
Chinese and Japanese culture
In Chinese culture, it is often said that if a man's nose produces a small flow of blood, this signifies that he is experiencing sexual desire. This often appears in Chinese-language
and Hong Kong film
This is also evident in Japan
ese culture and is parodied in anime
. Male characters will often be shown with a nosebleed
if they have just seen a female nude
or in little clothing, or if they have had an erotic thought or
Blood is one of the body fluids that has been used in art.
[http://artscad.com/A.nsf/Opra/SRVV-6MDNX5 "Nostalgia" Artwork in blood]
In particular, the performances of Viennese Actionist Hermann Nitsch
, Franko B
, Lennie Lee
, Ron Athey
, Yang Zhichao
and Kira O' Reilly
along with the photography of Andres Serrano
, have incorporated blood as a prominent visual element.
* Artificial blood
* List of human blood components
* Blood as food
: see black pudding
* Blood and video game censorship
* Taboo food and drink#Blood
*http://www.bloodjournal.org/ Blood Online
, a journal published by the American Society of Hematology Category:Cardiovascular systemCategory:TissuesCategory:Body fluids
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