Difference between revisions of "Blood" - New World Encyclopedia

Latest revision as of 18:13, 31 October 2023

A human blood smear showing red blood cells (a) and three types of white blood cells (neutrophil, eosinophil, and lymphocyte) (b-d).

Blood is a highly specialized, circulating tissue that consists of several types of cells suspended in a fluid medium. Along with the heart (a pump) and blood vessels (a series of conduits), blood forms an essential part of the circulatory system, a system of gas exchange in all terrestrial vertebrates.

There are two main components of blood: Blood cells (collectively known as the hematocrit) and an aqueous medium for transporting the cellular materials (called the plasma). The hematocrit consists of three types of cells responsible for the blood's crucial functions:

Red blood cells (erythrocytes) transport respiratory gases. Erythrocytes give vertebrate blood its distinctive color due to the presence of hemoglobin, an iron-containing protein that binds oxygen in the lungs and transports it to tissues in the body.
White blood cells (leukocytes) serve an immunological function, defending the body against foreign materials.
Platelets (thrombocytes) are cell fragments that play an important part in the clotting of the blood.

In addition to the roles outlined above, blood performs a range of functions, supplying nutrients such as glucose, amino acids, and fatty acids to various tissues; removing waste products such as carbon dioxide, urea, and lactic acid; transporting hormones and signaling tissue damage; and regulating the body pH and core body temperature required for a stable internal environment (homeostasis).

The term "blood" may also refer to a related circulatory fluid in certain invertebrates, such as arthropods and most mollusks, which is also known as the hemolymph. In these animals, there is no distinction between blood and interstitial fluid (the solution that bathes and surrounds the cells of multicellular animals).

Given its importance to life, blood has come to be associated with a number of cultural beliefs and practices. Blood continues to function as a symbol of family relationships: For example, to be "related by blood" is to be related by ancestry rather than by marriage. In both Islamic and Jewish dietary laws (Kashrut), consumption of food containing blood is forbidden. In certain Aboriginal Australian traditions, the ritual use of blood as adornment helps to attune the dancers to the invisible energetic realm of the Dreamtime (Lawlor 1991). Among certain Germanic tribes (such as the Anglo-Saxons and the Norsemen), blood was ritually sprinkled after battle (Blóts), as it was considered to retain the power of its originator. The vampiric folklore of Eastern Europe, in which the undead derive sustenance from the blood of living beings, attests to the mythological power of blood as well as to fears about contamination through blood.

Components and properties

Blood contributes about 7 percdent of the human body weight (Alberts 2005), with an average density of approximately 1060 kg/m³ (Shmukler 2004). The average adult has a blood volume of roughly 5 liters. Blood cells constitute about 45 percent of whole blood by volume, with the other 55 percent represented by plasma, a fluid that is the blood cells' liquid medium, appearing golden-yellow in color.

A scanning electron microscope (SEM) image of normal circulating human blood. Visible components include red blood cells; several types of white blood cells; and many small, disc-shaped platelets.

Types of blood cells

Each liter of human blood contains the following cellular components:

5 × 10¹² erythrocytes (45.0 percent of blood volume): Red blood cells (erythrocytes) are shaped like discs, giving them a large surface for gas exchange; their flexibility also enables them to squeeze through capillaries. In mammals, mature red blood cells lack a nucleus and organelles. They contain the blood's hemoglobin and distribute oxygen. The red blood cells (together with endothelial vessel cells and some other cells) are also marked by glycoproteins that define the different blood types (see below). The combined surface area of all the red blood cells in the human body would be roughly 2,000 times as great as the body's exterior surface.
9 × 10⁹ leukocytes (1.0 percent of blood volume): White blood cells are part of the immune system; they destroy and remove old or aberrant cells and cellular debris as well as attack infectious agents (pathogens) and foreign substances.
3 × 10¹¹ thrombocytes (<1.0 percent of blood volume): Platelets are responsible for blood clotting (coagulation). They are activated when they come into contact with exposed collagen fibers, and work in tandem with components in the blood plasma, called blood clotting factors.

Blood plasma

Blood plasma is essentially an aqueous solution containing 92 percent water, 8 percent blood plasma proteins, and trace amounts of other materials. It includes a variety of components, from gases and ions (mostly sodium and chloride ions, which give blood its salty taste) to nutrients, hormones, and immunoglobulins (antibodies). The most abundant blood plasma protein in humans and other mammals is serum albumin, which is essential for maintaining the osmotic pressure needed for proper distribution of body fluids.

Properties of blood vary by species

The normal pH of human arterial blood is approximately 7.40, a weak alkaline solution. Blood that has a pH below 7.35 is considered overly acidic, while blood pH above 7.45 is too alkaline. Blood pH, along with arterial carbon dioxide tension (PaCO₂) and HCO₃ readings, is 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.

In humans and other hemoglobin-using creatures, oxygenated blood is bright red, due to the oxygenated iron-containing hemoglobin found in 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 skin pigments, blood vessel coverings, and an optical effect caused by the way in which light penetrates through the skin, veins typically appear blue in color.

The blood of horseshoe crabs is blue, which is a result of its high content of copper-based hemocyanin instead of the iron-based hemoglobin. Members of the lizard-family, called skinks, which belong to the genus Prasinohaema, have green blood due to a buildup of the waste product biliverdin.

Other functions

In addition to the roles in respiration, transport, immunology, and blood clotting described above, blood's additional functions may include:

Thermoregulation: Blood circulation transports heat through 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, while decreasing blood flow to the surface conserves heat.
Hydraulic function: The restriction of blood flow can also be used in specialized tissues (such as the mammalian penis, clitoris, or nipple) to cause engorgement resulting in an erection of that tissue. Another example of blood's hydraulic function is found in the jumping spider, in which blood forced into the legs under pressure causes them to straighten for a powerful jump.

Properties and functions of blood in invertebrates

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 hemolymph moves nutrients to the tissues and removes waste products in an open system.

Other invertebrates use respiratory proteins to increase their oxygen-carrying capacity. While hemoglobin is the most common respiratory protein found in nature, hemocyanin is found in crustaceans and mollusks, giving a blue pigmentation to their blood. It is thought that tunicates (sea squirts) might use vanabins (proteins containing vanadium) for respiratory pigmentation, which can be bright green, blue, or orange in color.

In many invertebrates, oxygen-carrying proteins are freely soluble in the blood, whereas 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 particularly complex hemoglobins that allow them to live in especially harsh aquatic environments. These hemoglobins carry sulfides that are normally fatal in other animals.

Physiology of blood

Production and degradation

Blood cells are produced by specialized stem cells, located in the bone marrow, through a process termed hematopoiesis. The protein components of plasma (including clotting proteins) are produced overwhelmingly in the liver, while hormones are produced by the endocrine glands. The watery fraction is regulated by the hypothalamus and maintained by the kidney and indirectly by the gut.

Blood cells 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. Healthy erythrocytes have a plasma half-life of 120 days before they are systematically replaced by new erythrocytes created through hematopoiesis.

Transport

The blood is circulated around the lungs and body through the pumping action of the heart. Additional return pressure may be generated by gravity and by 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 may be thought of as the "second circulation."

Blood type

Blood type (or blood group) is determined, in part, by the ABO blood group antigens present on red blood cells.

A blood type (also called a blood group) is a classification of blood based on the presence or absence of inherited antigens on the surface of red blood cells. These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system.

While antigens from the human ABO blood group system are also found in apes, such as chimpanzees, bonobos and gorillas, the structure of the blood-group antigens in other animals and bacteria is not always identical to those typically found in humans. The classification of most animal blood groups therefore uses different blood typing systems than those used for classification of human blood.

If an individual is exposed to a blood group antigen that is not recognized as part of the self, the immune system will produce antibodies that can specifically bind to that particular blood-group antigen, and an immunological memory against that antigen is formed. These antibodies can bind to antigens on the surface of transfused red blood cells (or other tissue cells), often leading to destruction of the cells by recruitment of other components of the immune system. Thus, it is vital that compatible blood is selected for transfusions, and that compatible tissue is selected for organ transplantation. Transfusion reactions involving minor antigens or weak antibodies may lead to minor problems. However, more serious incompatibilities can lead to a more vigorous immune response with massive destruction of red blood cells, low blood pressure, and even death.

Blood-related diseases and disorders

Medical terms related to blood often begin with hemo- or hemato- from the Greek word for blood (haima). The study of blood, the blood-forming organs, and blood-related diseases is referred to as hematology, a branch of biology (physiology), pathology, clinical laboratory, internal medicine, and pediatrics. Hematology includes the study of the etiology, diagnosis, treatment, prognosis, and prevention of blood diseases, which affect the production of blood and its components, such as blood cells, hemoglobin, blood proteins, and the mechanism of coagulation.

The most common disorder of the blood is anemia, a deficiency of red blood cells and/or hemoglobin. This deficiency results in a reduced ability of blood to transfer oxygen to the tissues, causing tissue hypoxia. There are several types of anemia, produced by a variety of underlying causes. Since all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences. The three main classes of anemia include excessive blood loss, excessive blood cell destruction (hemolysis), or deficient red blood cell production (ineffective hematopoiesis). In menstruating women, dietary iron deficiency is a common cause of deficient red blood cell production.

Hemophilia is a genetic illness that causes dysfunction in one of the blood's clotting mechanisms This disorder can allow otherwise inconsequential wounds to be life-threatening, but more commonly results in hemarthrosis, or bleeding into joint spaces, which can be crippling.

Leukemia refers to a group of cancers of the blood-forming tissues; it is characterized by an abnormal proliferation of blood cells (usually leukocytes).

Blood is also an important vector of infection. HIV, the virus that causes AIDS, is transmitted through contact with blood, semen, or the bodily secretions of an infected person. Hepatitis B and C are transmitted primarily through blood contact. Malaria and trypanosomiasis are blood-borne parasitic infections.

Blood in ancient medicine

Hippocratic medicine considered blood to be 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 and leeching were a common intervention until the nineteenth 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.

References
ISBN links support NWE through referral fees

Alberts, B. 2005. Leukocyte leocyte functions and percentage breakdown. From B. Alberts, Molecular Biology of the Cell. NCBI Bookshelf. Retrieved April 14, 2007.
Lawlor, R. 1991. Voices Of The First Day: Awakening in the Aboriginal Dreamtime. Rochester, VT: Inner Traditions International. ISBN 0892813555.
Martini, F. et al. 2006. Human Anatomy, 5th ed. San Francisco: Pearson. ISBN 0805372113.
Purves, W., D. Sadava, G. Orians, and C. Heller. 2004. Life: The Science of Biology, 7th edition. Sunderland, MA: Sinauer. ISBN 0716766728.
Shmukler, M. 2004. Density of blood. The Physics Factbook. Retrieved October 4, 2006.

External links

All links retrieved October 31, 2023.

Blood Online, a journal published by the American Society of Hematology.

Cardiovascular system - edit
Blood \| Heart → Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Vena cava → Heart → Pulmonary arteries → Lungs → Pulmonary veins → Heart

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@@ Line 1: / Line 1: @@
-{{Claimed}}{{Contracted}}
+{{Approved}}{{Images OK}}{{Submitted}}{{Paid}}{{copyedited}}
-[[Image:Blood smear.jpg|350px|thumb|right|Human [[blood smear]]: a - [[erythrocytes]]; b - [[neutrophil]]; c - [[eosinophil]]; d - [[lymphocyte]].]]
+[[Image:Blood smear.jpg|350px|thumb|right|A human [[blood smear]] showing red blood cells (a) and three types of white blood cells ([[neutrophil]], [[eosinophil]], and [[lymphocyte]]) (b-d).]]
-'''Blood''' is a highly specialized [[circulation (physiology)|circulating]] [[biological tissue|tissue]] that consists of several types of cells suspended in a fluid medium. Along with the [[heart]] (a pump) and [[blood vessel]]s (a series of conduits), blood forms an essential part of the [[circulatory system]], a system of gas exchange in all terrestrial vertebrates.
+'''Blood''' is a highly specialized, circulating [[biological tissue|tissue]] that consists of several types of [[cell (biology)|cells]] suspended in a fluid medium. Along with the [[heart]] (a pump) and [[blood vessel]]s (a series of conduits), blood forms an essential part of the [[circulatory system]], a system of gas exchange in all terrestrial [[vertebrate]]s.
-There are two main components of blood: its cellular components (collectively known as the ''hematocrit'') and an aqueous medium for transporting the cellular materials (called the  ''plasma''). The hematocrit consists of three types of cells responsible for the blood's crucial functions:
+There are two main components of blood: Blood cells (collectively known as the ''hematocrit'') and an aqueous medium for transporting the cellular materials (called the  ''plasma''). The hematocrit consists of three types of cells responsible for the blood's crucial functions:
 *'''[[Red blood cell]]s (erythrocytes)''' transport respiratory gases. Erythrocytes give vertebrate blood its distinctive color due to the presence of [[hemoglobin]], an iron-containing protein that binds oxygen in the lungs and transports it to tissues in the body.
 *'''[[White blood cell]]s (leukocytes)''' serve an immunological function, defending the body against foreign materials.
 *'''[[Platelet]]s (thrombocytes)''' are cell fragments that play an important part in the clotting of the blood.
-In addition to the roles in respiration and outlined above, blood performs a range of functions, supplying nutrients such as [[glucose]], [[amino acids]] and [[fatty acids]] to various tissues; removing waste products such as [[carbon dioxide]], [[urea]] and [[lactic acid]]; transporting [[hormones]] and the signaling of tissue damage; and regulating the body [[pH]] and core [[body temperature]] required for a stable internal environment (homeostasis).
+In addition to the roles outlined above, blood performs a range of functions, supplying nutrients such as [[glucose]], [[amino acid]]s, and [[fatty acid]]s to various tissues; removing waste products such as [[carbon dioxide]], [[urea]], and [[lactic acid]]; transporting [[hormone]]s and signaling tissue damage; and regulating the body [[pH]] and core [[body temperature]] required for a stable internal environment (''homeostasis'').
-Invertebrates xyz.
+The term "blood" may also refer to a related circulatory fluid in certain [[invertebrate]]s, such as [[arthropod]]s and most [[mollusk]]s, which is also known as the ''hemolymph.'' In these animals, there is no distinction between blood and [[interstitial fluid]] (the solution that bathes and surrounds the cells of multicellular animals).
+{{toc}}
+Given its importance to life, blood has come to be associated with a number of cultural beliefs and practices. Blood continues to function as a symbol of family relationships: For example, to be "related by blood" is to be related by ancestry rather than by marriage. In both Islamic and Jewish dietary laws (Kashrut), consumption of food containing blood is forbidden. In certain Aboriginal Australian traditions, the ritual use of blood as adornment helps to attune the dancers to the invisible energetic realm of the Dreamtime (Lawlor 1991). Among certain Germanic tribes (such as the Anglo-Saxons and the Norsemen), blood was ritually sprinkled after battle (''Blóts''), as it was considered to retain the power of its originator. The [[vampire|vampiric]] folklore of Eastern Europe, in which the undead derive sustenance from the blood of living beings, attests to the mythological power of blood as well as to fears about contamination through blood.
 ==Components and properties==
-Blood is about 7% of the human body weight (Alberts, 2005), with an average density of approximately 1060 kg/m³ (Shmukler, 2004).The average adult has a blood volume of roughly 5 [[litre]]s, composed of plasma (see below) and several kinds of cells (occasionally called ''corpuscles''); these ''formed elements'' of the blood are ''erythrocytes'' ([[red blood cell]]s), ''leukocytes'' ([[white blood cell]]s), and ''thrombocytes'' ([[platelet]]s). The cells constitute about 45% of whole blood by volume.
+Blood contributes about 7 percdent of the human body weight (Alberts 2005), with an average density of approximately 1060 kg/m³ (Shmukler 2004). The average adult has a blood volume of roughly 5 [[liter]]s. Blood cells constitute about 45 percent of whole blood by volume, with the other 55 percent represented by plasma, a fluid that is the blood cells' liquid medium, appearing golden-yellow in color.
-[[Image:SEM blood cells.jpg|thumb|right|230px|A [[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]]s.]]
+[[Image:SEM blood cells.jpg|thumb|right|230px|A [[scanning electron microscope]] (SEM) image of normal circulating human blood. Visible components include red blood cells; several types of white blood cells; and many small, disc-shaped platelets.]]
-Each litre of blood contains:
-*'''5 × [[SI prefix#List of SI prefixes|10<sup>12</sup>]] erythrocytes''' (45.0% of blood volume) : In mammals, mature red blood cells lack a [[Cell nucleus|nucleus]] and [[organelle]]s. They contain the blood's [[hemoglobin]] 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 [[Human blood group systems|blood types]]. The proportion of blood occupied by red blood cells is referred to as the [[hematocrit]]. 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 surface.
-*'''9 × [[SI prefix#List of SI prefixes|10<sup>9</sup>]] leukocytes''' (1.0% of blood volume) : White blood cells are part of the [[immune system]]; they destroy and remove old or aberrant cells and cellular debris, as well as attack infectious agents ([[pathogens]]) and foreign substances.
-*'''3 × [[SI prefix#List of SI prefixes|10<sup>11</sup>]] thrombocytes''' (<1.0% of blood volume) : Platelets 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 body.
-The other 55% (making up a total of 2.7-3.0 litres in an average human) is [[blood plasma]], a fluid that is the blood's liquid medium, appearing golden-yellow in color.  [[Blood plasma]] is essentially an [[water|aqueous]] solution containing 92% water, 8% blood plasma [[protein]]s, and trace amounts of other materials. Some components are:
+===Types of blood cells===
+Each liter of human blood contains the following cellular components:
+*'''5 × 10<sup>12</sup> erythrocytes''' (45.0 percent of blood volume): Red blood cells (erythrocytes) are shaped like discs, giving them a large surface for gas exchange; their flexibility also enables them to squeeze through capillaries. In [[mammal]]s, mature red blood cells lack a [[Cell nucleus|nucleus]] and [[organelle]]s. They contain the blood's [[hemoglobin]] 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 [[Human blood group systems|blood types]] (see below). The combined surface area of all the red blood cells in the human body would be roughly 2,000 times as great as the body's exterior surface.
+*'''9 × 10<sup>9</sup> leukocytes''' (1.0 percent of blood volume): White blood cells are part of the [[immune system]]; they destroy and remove old or aberrant cells and cellular debris as well as attack infectious agents ([[pathogens]]) and foreign substances.
+*'''3 × 10<sup>11</sup> thrombocytes''' (<1.0 percent of blood volume): Platelets are responsible for blood clotting ([[coagulation]]). They are activated when they come into contact with exposed [[collagen]] fibers, and work in tandem with components in the blood plasma, called ''blood clotting factors.''
-* [[Serum albumin]]
+===Blood plasma===
-* Blood clotting factors (to facilitate [[coagulation]])
+[[Blood plasma]] is essentially an [[water|aqueous]] solution containing 92 percent water, 8 percent blood plasma [[protein]]s, and trace amounts of other materials. It includes a variety of components, from gases and ions (mostly sodium and chloride ions, which give blood its salty taste) to nutrients, hormones, and [[immunoglobulin]]s (antibodies). The most abundant blood plasma protein in humans and other mammals is ''serum albumin,'' which is essential for maintaining the [[osmosis|osmotic pressure]] needed for proper distribution of body fluids.
-* [[Immunoglobulins]] (antibodies)
-* [[Hormone]]s
-* Carbon dioxide
-* Various other [[protein]]s
-* Various [[electrolyte]]s (mainly [[sodium]] and [[chloride]])
-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 [[antibody|immunoglobulins]].
+===Properties of blood vary by species===
+The normal [[pH]] of human arterial blood is approximately 7.40, a weak alkaline solution. Blood that has a pH below 7.35 is considered overly [[acidic]], while blood pH above 7.45 is too [[alkaline]]. Blood pH, along with arterial carbon dioxide tension (PaCO<sub>2</sub>) and [[Bicarbonate|HCO<sub>3</sub>]] readings, is 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.
-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 considered overly [[acidic]], while blood pH above 7.45 is too [[alkaline]]. Blood pH along with arterial carbon dioxide tension (PaCO<sub>2</sub>) and [[Bicarbonate|HCO<sub>3</sub>]] 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]].
+In humans and other hemoglobin-using creatures, oxygenated blood is bright red, due to the oxygenated iron-containing hemoglobin found in 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 skin pigments, blood vessel coverings, and an optical effect caused by the way in which light penetrates through the skin, veins typically appear blue in color.
-In humans and other hemoglobin-using creatures, oxygenated blood is bright red. This is due to oxygenated iron-containing hemoglobin found 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 skin pigments, blood vessel coverings and 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 rare condition [[sulfhemoglobinemia]] results in green blood.
+The blood of [[horseshoe crab]]s is blue, which is a result of its high content of [[copper]]-based hemocyanin instead of the iron-based hemoglobin. Members of the lizard-family, called [[skink]]s, which belong to the genus ''[[Prasinohaema]],'' have green blood due to a buildup of the waste product [[biliverdin]].
-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.  [[Skink]]s in the genus ''[[Prasinohaema]]'' have green blood due to a buildup of the waste product [[biliverdin]].
+==Other functions==
+In addition to the roles in respiration, transport, immunology, and blood clotting described above, blood's additional functions may include:
-==Functions==
+*''Thermoregulation:'' Blood circulation transports [[heat]] through 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, while decreasing blood flow to the surface conserves heat.
-*Respiration. With the exception of [[Pulmonary artery|pulmonary]] and [[Umbilical artery|umbilical arteries]] and their corresponding veins, [[artery|arteries]] carry oxygenated blood away from the [[heart]] and deliver it to the body via [[arteriole]]s and [[capillary|capillaries]], where the oxygen is consumed; afterwards, [[venule]]s and [[vein]]s carry deoxygenated blood back to the heart.
+*''Hydraulic function:'' The restriction of blood flow can also be used in specialized tissues (such as the mammalian [[penis]], [[clitoris]], or [[nipple]]) to cause engorgement resulting in an [[erection]] of that tissue. Another example of blood's hydraulic function is found in the [[jumping spider]], in which blood forced into the legs under pressure causes them to straighten for a powerful jump.
-*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.
+==Properties and functions of blood in invertebrates==
+In [[insect]]s, the blood (more properly called [[hemolymph]]) is not involved in the transport of oxygen. (Openings called [[invertebrate trachea|trachea]]e allow oxygen from the air to diffuse directly to the tissues.) Insect hemolymph moves nutrients to the tissues and removes waste products in an open system.
-*Transport of hydrogen ions. Some oxyhemoglobin loses oxygen and becomes deoxyhemoglobin. Deoxyhemoglobin has a much greater affinity for hydrogen ion (H<sup>+</sup>) than does oxyhemoglobin so it binds most of the hydrogen ions.
+Other invertebrates use respiratory proteins to increase their oxygen-carrying capacity. While hemoglobin is the most common respiratory protein found in nature, [[hemocyanin]] is found in [[crustacean]]s and [[mollusk]]s, giving a blue pigmentation to their blood. It is thought that [[tunicate]]s (sea squirts) might use [[vanabins]] ([[protein]]s containing [[vanadium]]) for respiratory pigmentation, which can be bright [[green]], blue, or [[orange (color)|orange]] in color.
-*Thermoregulation. Blood circulation transports [[heat]] through 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, while decreasing surface blood flow conserves heat.
+In many invertebrates, oxygen-carrying proteins are freely soluble in the blood, whereas 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]].
-*Hydraulic function. The restriction of blood flow can also be used in specialized tissues to cause engorgement resulting in an [[erection]] of that tissue. Examples of this would occur in a mammalian [[penis]], [[clitoris]] or [[nipple]].
+[[Giant tube worms]] have particularly complex hemoglobins that allow them to live in especially harsh aquatic environments. These hemoglobins carry sulfides that are normally fatal in other animals.
-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.
-===Invertebrates===
-In [[insect]]s, the blood (more properly called [[hemolymph]]) is not involved in the transport of oxygen. (Openings called [[invertebrate trachea|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.
-Other invertebrates use respiratory proteins to increase their oxygen-carrying capacity. Hemoglobin is the most common respiratory protein found in nature. [[Hemocyanin]] ([[blue]]) contains [[copper]] and is found in [[crustacean]]s and [[mollusk]]s. It is thought that [[tunicate]]s (sea squirts) might use [[vanabins]] ([[protein]]s containing [[vanadium]]) for respiratory pigment (bright [[green]], blue, or [[orange (colour)|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]].
-[[Giant tube worms]] have extraordinary hemoglobins that allow them to live in extraordinary environments.  These hemoglobins also carry sulfides normally fatal in other animals.
 ==Physiology of blood==
 ===Production and degradation===
-Blood cells are produced in the [[bone marrow]]; this 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 is regulated by the [[hypothalamus]] and maintained by the [[kidney]] and indirectly by the [[gut]].
+Blood cells are produced by specialized ''[[stem cell]]s,'' located in the [[bone marrow]], through a process termed ''hematopoiesis.'' The protein components of plasma (including clotting proteins) are produced overwhelmingly in the [[liver]], while hormones are produced by the [[endocrine gland]]s. The watery fraction is 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]]. Healthy erythrocytes have a plasma [[half-life]] of 120 days before they are systematically replaced by new erythrocytes created by the process of hematopoiesis.
+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]]. Healthy erythrocytes have a plasma [[half-life]] of 120 days before they are systematically replaced by new erythrocytes created through [[hematopoiesis]].
 ===Transport===
-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 may be thought of as the "second circulation".
+The blood is circulated around the [[lung]]s and body through the [[pump]]ing action of the [[heart]]. Additional return pressure may be generated by gravity and by 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 may be thought of as the "second circulation."
-==Blood-related diseases and disorders==
+==Blood type==
-Medical terms related to blood often begin with '''''hemo-''''' or '''''hemato-''''' ([[British English|BE]]: ''haemo-'' and ''haemato-'') from the [[Greek language|Greek]] word "''haima''" for "blood."
+[[Image:ABO blood type.svg|thumb|left|400px|'''Blood type''' (or blood group) is determined, in part, by the ABO blood group antigens present on red blood cells.]]
+A ''blood type'' (also called a ''blood group'') is a classification of blood based on the presence or absence of [[Inheritance|inherited]] [[antigen]]s on the surface of red blood cells. These antigens may be [[protein]]s, [[carbohydrate]]s, [[glycoprotein]]s, or [[glycolipids]], depending on the blood group system.
+While antigens from the human [[ABO blood group system]] are also found in [[ape]]s, such as [[chimpanzee]]s, [[bonobo]]s and [[gorilla]]s, the structure of the blood-group antigens in other animals and [[bacteria]] is not always identical to those typically found in humans. The classification of most animal blood groups therefore uses different blood typing systems than those used for classification of human blood.
-[[Hippocrates|Hippocratic]] 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]] and [[leeching]] were a common intervention until the [[19th century]] (it is still used for some rare blood disorders).
+If an individual is exposed to a blood group antigen that is not recognized as part of the self, the [[immune system]] will produce [[Antibody|antibodies]] that can specifically bind to that particular blood-group antigen, and an immunological memory against that antigen is formed. These antibodies can bind to antigens on the surface of transfused [[red blood cell]]s (or other tissue cells), often leading to destruction of the cells by recruitment of other components of the immune system. Thus, it is vital that compatible blood is selected for transfusions, and that compatible tissue is selected for [[organ transplant]]ation. [[Transfusion reactions]] involving minor antigens or weak antibodies may lead to minor problems. However, more serious incompatibilities can lead to a more vigorous [[immune]] response with massive destruction of red blood cells, [[Hypotension|low blood pressure]], and even [[death]].
-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]].
+==Blood-related diseases and disorders==
+Medical terms related to blood often begin with ''hemo-'' or ''hemato-'' from the [[Greek language|Greek]] word for blood (''haima''). The study of blood, the blood-forming organs, and blood-related diseases is referred to as ''hematology,'' a branch of biology (physiology), [[pathology]], [[clinical laboratory]], [[internal medicine]], and [[pediatrics]].  Hematology includes the study of the [[etiology]], [[diagnosis]], treatment, [[prognosis]], and [[prevention]] of blood diseases, which affect the production of blood and its components, such as blood cells, hemoglobin, blood proteins, and the mechanism of coagulation.
-Problems with blood circulation and composition play a role in many diseases.
+The most common disorder of the blood is [[anemia]], a deficiency of red blood cells and/or hemoglobin. This deficiency results in a reduced ability of blood to transfer [[oxygen]] to the [[tissue (biology)|tissues]], causing tissue [[Hypoxia (medical)|hypoxia]].  There are several types of anemia, produced by a variety of underlying causes. Since all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences. The three main classes of anemia include excessive blood loss, excessive blood cell destruction ([[hemolysis]]), or deficient red blood cell production (ineffective hematopoiesis). In menstruating women, dietary iron deficiency is a common cause of deficient red blood cell production.
-* [[Injury|Wounds]] can cause major blood loss (see [[bleeding]]). The [[thrombocyte]]s cause the blood to [[coagulation|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]].
+[[Hemophilia]] is a genetic illness that causes dysfunction in one of the blood's [[coagulation|clotting mechanisms]] This disorder can allow otherwise inconsequential wounds to be life-threatening, but more commonly results in [[hemarthrosis]], or bleeding into joint spaces, which can be crippling.
-* Circulation blockage can also create many medical conditions from [[ischemia]] in the short term to tissue [[necrosis]] and [[gangrene]] in the long term.
-* [[Hemophilia]] is a genetic illness that causes dysfunction in one of the blood's [[coagulation|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.
-* [[Leukemia]] is a group of [[cancer (medicine)|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]] and [[thalassemia]], 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.
-* Overproduction of red blood cells is called [[polycythemia]].
-* 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]] and [[Hepatitis C|C]] are transmitted primarily through blood contact. Owing to [[blood-borne infection]]s, bloodstained objects are treated as a [[Biological hazard|biohazard]].
-* Bacterial infection of the blood is [[bacteremia]] or [[sepsis]]. Viral Infection is viremia. [[Malaria]] and [[trypanosomiasis]] are blood-borne parasitic infections.
-Problems with blood composition or circulation can lead to downstream tissue dysfunction. The term ''ischaemia'' refers to tissue which is inadequately perfused with blood.
+[[Leukemia]] refers to a group of [[cancer]]s of the blood-forming tissues; it is characterized by an abnormal proliferation of blood cells (usually leukocytes).
-[[Blood transfusion]] 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.
+Blood is also an important vector of infection. [[HIV]], the [[virus]] that causes [[AIDS]], is transmitted through contact with blood, [[semen]], or the bodily secretions of an infected person. [[Hepatitis B]] and [[Hepatitis C|C]] are transmitted primarily through blood contact. [[Malaria]] and [[trypanosomiasis]] are blood-borne parasitic infections.
-Other blood products administered [[intravenous]]ly are platelets, blood plasma, cryoprecipitate and specific coagulation factor concentrates.
+===Blood in ancient medicine===
+[[Hippocrates|Hippocratic]] medicine considered blood to be 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]] and [[leeching]] were a common intervention until the nineteenth 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]].
-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 a topical plasma volume expander as a non-blood alternative, and these alternatives where used are rivaling blood use when used.
-==The role of blood in religion, myth, and culture==
-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."  This phrase is part of the Levitical law forbidding the drinking blood, due to its practice in idol worship by surrounding societies.
-In many [[Indigenous Australians|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 (Lawlor, 1991).
-Among the [[Germanic tribe]]s (such as the [[Anglo-Saxons]] and the [[Norsemen]]), blood was used during the sacrifices, the ''[[Blót]]s''. 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 language|Old English]] and the terminology was borrowed by the [[Roman Catholic Church]] becoming ''to bless'' and ''blessing''. The [[Hittite language|Hittite]] word for blood, ''ishar'' was a cognate to words for "oath" and "bond", see [[Ishara]].
-The [[Ancient Greece|Ancient Greeks]] believed that the blood of the Gods, ''[[ichor]]'', was a mineral that was poisonous to mortals.
-In [[Judaism]], blood cannot be consumed even in the smallest quantity ([[Leviticus]] 3:17 and elsewhere); this is reflected in Jewish [[diet (nutrition)|dietary]] laws ([[Kashrut]]). Blood is purged from [[meat]] by [[salting (food)|salting]] and soaking in water.
-Other rituals involving blood are the covering of the blood of [[fowl]] and [[game]] 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 [[sacrifice|sacrificial service]] (known as the ''[[korbanot]]''), in the [[Temple in Jerusalem]]. Blood (the blood of a lamb) was also the means for atonement of sins for the Jews.
-Some Christian churches, including [[Roman Catholic Church|Roman Catholicism]], [[Eastern Orthodox Church|Eastern Orthodoxy]], branches of [[Anglicanism]], and the [[Moravians (religion)|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 [[Twelve Apostles|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 |chapter=22|verse=20}})''. Various forms of Protestantism, especially those of a [[Wesley]]an 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.
-[[Mormons]] believe that before [[Adam]] and [[Eve (Bible)|Eve]] ate the forbidden fruit, blood was not present in their bodies. It is said to have formed after the Fall when they became mortal.
-Consumption of food containing blood is forbidden by [[Islamic dietary laws]].
-Due to Bible-based beliefs, [[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.
-[[Vampire]]s are mythological beings which live forever by drinking the blood of the living. Stories of creatures of this kind are known all over the world. European versions of this myth are mostly inspired by folklore based on the stories regarding [[Vlad Dracula]].{{Fact|date=February 2007}}
-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 [[China|Chinese-language]] and [[Hong Kong]] [[film]]s.
-This is also evident in [[Japan]]ese culture and is parodied in [[anime]] and [[manga]]. 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 fantasy.{{Fact|date=February 2007}}
-Various religious and other groups have been falsely accused of using human blood in rituals; such accusations are known as [[blood libel]]. The most common form of this is [[blood libel against Jews]]. Although there is no ritual involving human blood in Jewish law or custom, fabrications of this nature (often involving the murder of children) were widely used during the Middle Ages to justify [[anti-Semitism|anti-Semitic]] persecution and some have persisted into the 21st century.
-Blood is one of the body fluids that has been used in art. In particular, the performances of [[Viennese Actionism|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.  [[Marc Quinn]] has made sculptures using frozen blood, including a cast of his own head made using his own blood.
 ==References==
-*Alberts, B. 2005. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&rid=mboc4.table.4143|title=Leukocyte Leocyte functions and percentage breakdown.] From ''Molecular Biology of the Cell''. NCBI Bookshelf. Retrieved April 14, 2007.
+*Alberts, B. 2005. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&rid=mboc4.table.4143 Leukocyte leocyte functions and percentage breakdown.] From B. Alberts, ''Molecular Biology of the Cell''. NCBI Bookshelf. Retrieved April 14, 2007.
 *Lawlor, R. 1991. ''Voices Of The First Day: Awakening in the Aboriginal Dreamtime.'' Rochester, VT:  Inner Traditions International. ISBN 0892813555.
-*Martini, F. et al. 2006. ''Human Anatomy,'' 5th ed. San Francisco, CA: Pearson.  ISBN 0805372113.
+*Martini, F. et al. 2006. ''Human Anatomy,'' 5th ed. San Francisco: Pearson. ISBN 0805372113.
 *Purves, W., D. Sadava, G. Orians, and C. Heller. 2004. ''Life: The Science of Biology,'' 7th edition. Sunderland, MA: Sinauer. ISBN 0716766728.
-*Shmukler, M. 2004. [http://hypertextbook.com/facts/2004/MichaelShmukler.shtml Density of Blood.] The Physics Factbook. Retrieved October 4, 2006.
+*Shmukler, M. 2004. [http://hypertextbook.com/facts/2004/MichaelShmukler.shtml Density of blood.] ''The Physics Factbook''. Retrieved October 4, 2006.
 ==External links==
-{{wiktionary}}
+All links retrieved October 31, 2023.
-{{commonscat|Blood}}
-*[http://www.bloodjournal.org/ ''Blood Online''], a journal published by the [[American Society of Hematology]]
+*[http://www.bloodjournal.org/ ''Blood Online''], a journal published by the American Society of Hematology.
-{{blood}}
 {{cardiovascular_system}}
-{{credit|Blood|145249632}}
+{{credit|Blood|145249632|Anemia|153693685|Leukemia|151394685|Hematology|152924849|Serum_albumin|151987968|Blood_type|153762479|Blood_type_(non-human)|151481349|Interstitial_fluid|151442410|skink|150979197}}
 [[Category:Life sciences]]
+[[Category:Anatomy and physiology]]