Red blood cells are the most common type of blood cell and the vertebrate body's principal means of delivering oxygen from the lungs or gills to body tissues via the blood. A blood cell (also called blood corpuscle) is any cell of any type normally found in Blood. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes With regard to living things, a body is the integral physical material of an individual Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive A gill is an anatomical structure found in many aquatic organisms Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells ��such as nutrients and oxygen—and transports Waste products ^[1]

Human red blood cells

Red blood cells are also known as RBCs, red blood corpuscles (an archaic term), haematids or erythrocytes (from Greek erythros for "red" and kytos for "hollow", with cyte nowadays translated as "cell"). Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly

A schistocyte is a red blood cell undergoing cell fragmentation, or a fragmented part of a red blood cell. In Cell biology, fragmentation is the breaking apart of cells or Cell organelles into smaller parts

Vertebrate erythrocytes

From left to right: human erythrocyte, thrombocyte, leukocyte. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood Platelets, or Thrombocytes, are small cytoplasmic bodies derived from cells They circulate in the Blood of Mammals and are involved

Erythrocytes consist mainly of hemoglobin, a complex molecule containing heme groups whose iron atoms temporarily link to oxygen molecules in the lungs or gills and release them throughout the body. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by A heme ( American English) or haem ( British English) is a Prosthetic group that consists of an Iron atom contained in the center of Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Oxygen can easily diffuse through the red blood cell's cell membrane. Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Hemoglobin also carries some of the waste product carbon dioxide back from the tissues. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single (In humans, less than 2% of the total oxygen, and most of the carbon dioxide, is held in solution in the blood plasma). Blood plasma is the Liquid component of Blood, in which the Blood cells are suspended A related compound, myoglobin, acts to store oxygen in muscle cells. Myoglobin is a single-chain globular Protein of 153 Amino acids containing a Heme ( Iron -containing Porphyrin) Prosthetic Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the ^[2]

The color of erythrocytes is due to the heme group of hemoglobin. The blood plasma alone is straw-colored, but the red blood cells change color depending on the state of the hemoglobin: when combined with oxygen the resulting oxyhemoglobin is scarlet, and when oxygen has been released the resulting deoxyhemoglobin is darker, appearing bluish through the vessel wall and skin. Blood plasma is the Liquid component of Blood, in which the Blood cells are suspended Pulse oximetry takes advantage of this color change to directly measure the arterial blood oxygen saturation using colorimetric techniques. Pulse oximetry is a non-invasive method allowing the monitoring of the Oxygenation of a patient's Hemoglobin. Arteries are Blood vessels that carry blood away from the Heart. Oxygen saturation is a relative measure of the amount of Oxygen that is Dissolved or carried in a given medium Colorimetry or Colourimetry can refer to the quantitative study of Color perception

The sequestration of oxygen carrying proteins inside specialized cells (rather than having them dissolved in body fluid) was an important step in the evolution of vertebrates; it allows for less viscous blood, higher concentrations of oxygen, and better diffusion of oxygen from the blood to the tissues. eVolution is the third Album by eLDee, it was due to be released in 2008 Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. The size of erythrocytes varies widely among vertebrate species; erythrocyte width is on average about 25% larger than capillary diameter and it has been hypothesized that this improves the oxygen transfer from erythrocytes to tissues. Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange ^[3]

The only known vertebrates that don't use erythrocytes for oxygen transport are the ice fishes (family Channichthyidae); they live in very oxygen rich cold water and transport oxygen freely dissolved in their blood. The icefishes (or white-blooded fishes) are a family ( Channichthyidae) of Perciform Fish found in the cold waters around Antarctica ^[4]

In 2007 it was reported that erythrocytes also play a part in the body's immune response: when lysed by pathogens such as bacteria, their hemoglobin releases free radicals that break down the pathogen's cell wall and membrane, killing it. An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor Lysis ( Greek, lysis from lyein = to separate refers to the death of a cell by breaking of the cellular membrane often by viral or osmotic In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell ^[5][6]

Mammalian erythrocytes

Erythrocytes in mammals are anucleate when mature, meaning that they lack a cell nucleus and as a result, have no DNA. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Red blood cells have nuclei during early phases of development, but extrude them as they mature in order to provide more space for hemoglobin. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein In comparison, the erythrocytes of nearly all other vertebrates have nuclei; the only known exception being salamanders of the Batrachoseps genus. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Salamander (orig from Persian: sām, "fire" and andarūn, "within" is the common name for a group of approximately 500 Species Slender salamander is the name often given to Plethodontid (lungless Salamanders of the genus Batrachoseps. ^[7] Mammalian erythrocytes also lose their other organelles such as their mitochondria. In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. As a result, red blood use none of the oxygen they transport; they produce the energy carrier ATP by fermentation, via glycolysis of glucose followed by lactic acid production. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy Fermentation is the process of deriving energy from the oxidation of organic compounds such as carbohydrates using an endogenous electron acceptor which is See also Gluconeogenesis, which carries out a process wherein glucose is synthesized rather than catabolized Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role Furthermore, red cells do not have an insulin receptor and thus glucose uptake is not regulated by insulin. In Molecular biology, the insulin receptor is a transmembrane receptor that is activated by Insulin. Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance Because of the lack of nucleus and organelles, the red blood cells cannot synthesize any RNA, and consequently they cannot divide or repair themselves. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units

Mammalian erythrocytes are biconcave disks: flattened and depressed in the center, with a dumbbell-shaped cross section. This shape (as well as the loss of organelles and nucleus) optimizes the cell for the exchange of oxygen with its surroundings. The cells are flexible so as to fit through tiny capillaries, where they release their oxygen load. Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange Erythrocytes are circular, except in the camel family Camelidae, where they are oval. Camels are Even-toed ungulates within the Genus Camelus. The Dromedary, one-humped or Arabian camel has a single hump and the Camelids are members of the biological family Camelidae, the only living family in the suborder Tylopoda.

In large blood vessels, red blood cells sometimes occur as a stack, flat side next to flat side. This is known as rouleaux formation, and it occurs more often if the levels of certain serum proteins are elevated, as for instance during inflammation. Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens

The spleen acts as a reservoir of red blood cells, but this effect is somewhat limited in humans. The spleen is an organ found in all Vertebrate animals In humans the spleen is located in the abdomen of the body where it functions in the destruction of redundant Red In some other mammals such as dogs and horses, the spleen sequesters large numbers of red blood cells which are dumped into the blood during times of exertion stress, yielding a higher oxygen transport capacity. The dog ( Canis lupus familiaris) is a domesticated Subspecies of the gray wolf, a Mammal of the Canidae family of the order The horse ( Equus caballus) is a hoofed ( Ungulate) Mammal, one of eight living species of the family Equidae.

Erythrocytes: (a) seen from surface; (b) in profile, forming rouleaux; (c) rendered spherical by water; (d) rendered crenate by salt. (c) and (d) do not normally occur in the body.

Human erythrocytes

The diameter of a typical human erythrocyte disk is 6–8 µm, much smaller than most other human cells. To help compare different Orders of magnitude this page lists some items with Lengths between 10&minus6 and 10&minus5 m (between 1 and There are about 210 known distinct human Cell types. Keratinizing epithelial cells Epidermal Keratinocyte (differentiating A typical erythrocyte contains about 270 million hemoglobin molecules, with each carrying four heme groups.

Adult humans have roughly 2–3 × 10¹³ red blood cells at any given time (women have about 4 to 5 million erythrocytes per microliter (cubic millimeter) of blood and men about 5 to 6 million; people living at high altitudes with low oxygen tension will have more). This list compares various sizes of positive Numbers including counts of things Dimensionless quantity and probabilities. The litre or liter (see spelling differences) is a unit of Volume. Red blood cells are thus much more common than the other blood particles: There are about 4,000–11,000 white blood cells and about 150,000–400,000 platelets in each microliter of human blood. Platelets, or Thrombocytes, are small cytoplasmic bodies derived from cells They circulate in the Blood of Mammals and are involved

The red blood cells of an average adult human male store collectively about 2. 5 grams of iron, representing about 65% of the total iron contained in the body. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 ^[8][9] (See Human iron metabolism. Human iron metabolism is the set of chemical reactions maintaining Human homeostasis of Iron. )

Life cycle

The process by which red blood cells are produced is called erythropoiesis. Erythropoiesis is the process by which Red blood cells (erythrocytes are produced Erythrocytes are continuously being produced in the red bone marrow of large bones, at a rate of about 2 million per second. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of (In the embryo, the liver is the main site of red blood cell production. An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular The liver is a vital organ in the human body and is present in Vertebrates and some other animals ) The production can be stimulated by the hormone erythropoietin (EPO), synthesised by the kidney; which is used for doping in sports. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body Erythropoietin (ɨˌɹɪθɹoʊˈpɔɪɨtɨn /ɨˌɹɪθɹoʊˈpɔɪtən/ or /ɨˌɹiːθɹoʊ-/ or EPO is a Glycoprotein Hormone that controls Just before and after leaving the bone marrow, they are known as reticulocytes which comprise about 1% of circulating red blood cells. Reticulocytes are immature Red blood cells typically composing about 1% of the red cells in the human body

Erythrocytes develop from committed stem cells through reticulocytes to mature erythrocytes in about 7 days and live a total of about 120 days.

The aging erythrocyte undergoes changes in its plasma membrane, making it susceptible to recognition by phagocytes and subsequent phagocytosis in the spleen, liver and bone marrow. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Phagocytes are cells that are found in the blood bone marrow and other tissues of Vertebrates. Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole The spleen is an organ found in all Vertebrate animals In humans the spleen is located in the abdomen of the body where it functions in the destruction of redundant Red Much of the important breakdown products are recirculated in the body. The heme constituent of hemoglobin are broken down into Fe³⁺ and biliverdin. Biliverdin is a green Pigment formed as a byproduct of Heme breakdown The biliverdin is reduced to bilirubin, which is released into the plasma and recirculated to the liver bound to albumin. Bilirubin (formerly referred to as hematoidin) is the yellow breakdown product of normal Heme Catabolism. Albumin (Latin albus white refers generally to any Protein with water Solubility, which is moderately soluble in concentrated salt solutions and experiences The iron is released into the plasma to be recirculated by a carrier protein called transferrin. Transferrin is a Blood plasma Protein for Iron Ion delivery Transferrin is a Glycoprotein, which binds iron very tightly but reversibly Almost all erythrocytes are removed in this manner from the circulation before they are old enough to hemolyze. Hemolysis (or haemolysis)—from the Greek Hemo-, Greek meaning blood - Lysis, meaning to break open—is the breaking Hemolyzed hemoglobin is bound to a protein in plasma called haptoglobin which is not excreted by the kidney. Haptoglobin (abbreviated as Hp) is a Protein in the Blood plasma that binds free Hemoglobin released from Erythrocytes

Surface proteins

There are two main types of proteins on the surface:

• Band 3
• Glycophorins such as glycophorin C

The blood types of humans are due to variations in surface glycoproteins of erythrocytes. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Anion Exchanger 1 ( AE1) or Band 3 is a Phylogenetically preserved Transport protein responsible for mediating the electroneutral exchange of A Glycophorin is a Sialoglycoprotein of the Membrane of a Red blood cell. Glycophorin C (GYPC CD236/CD236R glycoprotein beta glycoconnectin PAS-2' is an Integral membrane protein of the Erythrocyte and acts as the receptor A blood type (also called a blood group) is a classification of Blood based on the presence or absence of inherited Antigenic substances on the Not to be confused with Peptidoglycan. Glycoproteins are proteins that contain Oligosaccharide chains ( Glycans) covalently attached

Separation and blood doping

Red blood cells can be separated from blood plasma by centrifugation. Blood plasma is the Liquid component of Blood, in which the Blood cells are suspended Centrifugation is a process that involves the use of the Centrifugal force for the separation of mixtures used in industry and in laboratory settings During plasma donation, the red blood cells are pumped back into the body right away, and the plasma is collected. Some athletes have tried to improve their performance by blood doping: first about 1 litre of their blood is extracted, then the red blood cells are isolated, frozen and stored, to be reinjected shortly before the competition. Blood doping is the practice of boosting the number of Red blood cells (RBCs in the circulation in order to enhance athletic performance (Red blood cells can be conserved for 5 weeks at −79 °C. ) This practice is hard to detect but may endanger the human cardiovascular system which is not equipped to deal with blood of the resulting higher viscosity. This is an article about the rock music band "Circulatory System" Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress.

Diseases and diagnostic tools

Affected by Sickle-cell disease, red blood cells alter shape and threaten to damage internal organs. Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid

Blood diseases involving the red blood cells include:

• Anemias (or anaemias) are diseases characterized by low oxygen transport capacity of the blood, because of low red cell count or some abnormality of the red blood cells or the hemoglobin. Hematology ( American English) or haematology ( British English) is the branch of biology (physiology Pathology, Clinical laboratory Anemia ( AmE) or anæmia/anaemia ( BrE) (from the Ancient Greek grc-Latn anaîmia, meaning “without blood” is defined as a qualitative
  • Iron deficiency anemia is the most common anemia; it occurs when the dietary intake or absorption of iron is insufficient, and hemoglobin, which contains iron, cannot be formed
  • Sickle-cell disease is a genetic disease that results in abnormal hemoglobin molecules. For a discussion of iron deficiency more broadly see the Wikipedia article iron deficiency. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid When these release their oxygen load in the tissues, they become insoluble, leading to mis-shaped red blood cells. These sickle shaped red cells are rigid and cause blood vessel blockage, pain, strokes, and other tissue damage.
  • Thalassemia is a genetic disease that results in the production of an abnormal ratio of hemoglobin subunits. Thalassemia (from Greek θαλασσα thalassa sea + αίμα haima blood British spelling "thalassaemia" is an inherited Autosomal recessive
  • Spherocytosis is a genetic disease that causes a defect in the red blood cell's cytoskeleton, causing the red blood cells to be small, sphere-shaped, and fragile instead of donut-shaped and flexible. Spherocytosis is an auto- hemolytic Anemia (a disease of the blood) characterized by the production of Red blood cells (RBCs or erythrocytes cytoskeleton (also CSK is a cellular " Scaffolding " or " Skeleton " contained within the Cytoplasm.
  • Pernicious anemia is an autoimmune disease wherein the body lacks intrinsic factor, required to absorb vitamin B12 from food. Pernicious anemia (also known as Biermer's anemia, Addison's anemia, or Addison-Biermer anemia) is a form of Megaloblastic anemia due to Autoimmune diseases arise from an overactive Immune response of the body against substances and tissues normally present in the body Intrinsic factor is a Glycoprotein produced by the Parietal cells of the Stomach. Vitamin B12 is needed for the production of hemoglobin.
  • Aplastic anemia is caused by the inability of the bone marrow to produce blood cells. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of
  • Pure red cell aplasia is caused by the inability of the bone marrow to produce only red blood cells. Acquired pure red cell aplasia (or PRCA refers to a type of Anemia affecting the precursors to Red blood cells but not to White blood cells.
  • Hemolysis is the general term for excessive breakdown of red blood cells. Hemolysis (or haemolysis)—from the Greek Hemo-, Greek meaning blood - Lysis, meaning to break open—is the breaking It can have several causes.
• The malaria parasite spends part of its life-cycle in red blood cells, feeds on their hemoglobin and then breaks them apart, causing fever. Malaria is a vector -borne Infectious disease caused by Protozoan Parasites It is widespread in tropical and subtropical regions including Both sickle-cell disease and thalassemia are more common in malaria areas, because these mutations convey some protection against the parasite. Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid Thalassemia (from Greek θαλασσα thalassa sea + αίμα haima blood British spelling "thalassaemia" is an inherited Autosomal recessive
• Polycythemias (or erythrocytoses) are diseases characterized by a surplus of red blood cells. Polycythemia (or polycythaemia or erythrocytosis) is a condition in which there is a net increase in the total number of Blood cells, primarily Red The increased viscosity of the blood can cause a number of symptoms.
  • In polycythemia vera the increased number of red blood cells results from an abnormality in the bone marrow. Primary Polycythemia, often called Polycythemia vera (PCV polycythemia rubra vera (PRV or erythremia occurs when excess red blood cells are produced
• Several microangiopathic diseases, including disseminated intravascular coagulation and thrombotic microangiopathies, present with pathognomonic (diagnostic) RBC fragments called schistocytes. Disseminated intravascular coagulation ( DIC) also known as consumptive coagulopathy, is a pathological activation of Coagulation (blood clotting mechanisms Pathognomonic (often misspelled as pathognomic and sometimes as pathomnemonic) is an adjective of Greek origin (παθογνωμονικό) often used in Medicine These pathologies generate fibrin strands that sever RBCs as they try to move past a thrombus. Fibrin (also called Factor Ia) is a Protein involved in the clotting of blood A thrombus, or blood clot, is the final product of the Blood coagulation step in Hemostasis.

Several blood tests involve red blood cells, including the RBC count (the number of red blood cells per volume of blood) and the hematocrit (percentage of blood volume occupied by red blood cells). A blood test is a laboratory analysis performed on a Blood sample that is usually extracted from a Vein in the arm using a needle, or via The hematocrit ( Ht or HCT) or packed cell volume ( PCV) or erythrocyte volume fraction (EVF is the proportion of Blood The blood type needs to be determined to prepare for a blood transfusion or an organ transplantation. A blood type (also called a blood group) is a classification of Blood based on the presence or absence of inherited Antigenic substances on the Blood transfusion is the process of transferring Blood or blood-based products from one person into the Circulatory system of another

History

The first person to describe red blood cells was probably the young Dutch biologist Jan Swammerdam, who had used an early microscope in 1658 to study the blood of a frog. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Jan Swammerdam ( February 12, 1637, Amsterdam - February 17, 1680) was a Dutch biologist and microscopist A microscope ( Greek: ( micron) = small + ( skopein) = to look or see is an instrument for viewing objects that are ^[10] Unaware of this work, Anton van Leeuwenhoek provided another microscopic description in 1674. Antonie Philips van Leeuwenhoek (October 24 1632 &ndash August 30 1723 was a Dutch tradesman and Scientist from Delft, the Netherlands ^[11]

References

External links

• Blood Groups and Red Cell Antigens by Laura Dean. Searchable and downloadable online textbook in the public domain.
• Database of vertebrate erythrocyte sizes.
• Red Gold, PBS site containing facts and history