![Hematopoiesis simple](https://upload.wikimedia.org/wikipedia/commons/f/f0/Hematopoiesis_simple.svg)
A blood cell, also called a hematopoietic cell, hemocyte, or hematocyte, is a
cell
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...
produced through
hematopoiesis
Haematopoiesis (, from Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. ...
and found mainly in the
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
. Major types of blood cells include
red blood cell
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s (erythrocytes),
white blood cell
White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...
s (leukocytes), and
platelet
Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ini ...
s (thrombocytes). Together, these three kinds of blood cells add up to a total 45% of the blood tissue by volume, with the remaining 55% of the volume composed of
plasma
Plasma or plasm may refer to:
Science
* Plasma (physics), one of the four fundamental states of matter
* Plasma (mineral), a green translucent silica mineral
* Quark–gluon plasma, a state of matter in quantum chromodynamics
Biology
* Blood pla ...
, the liquid component of blood.
Red blood cells
Red blood cell
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s or ''erythrocytes'', primarily carry
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
and collect
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
through the use of
hemoglobin
Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...
. Hemoglobin is an
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
-containing protein that gives red blood cells their color and facilitates transportation of
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
from the
lung
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s to tissues and
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
from tissues to the lungs to be exhaled. Red blood cells are the most abundant cell in the blood, accounting for about 40-45% of its volume. Red blood cells are circular, biconcave, disk-shaped and deformable to allow them to squeeze through narrow capillaries. They do not have a nucleus. Red blood cells are much smaller than most other human cells.
RBCs are formed in the red bone marrow from
hematopoietic stem cell
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within t ...
s in a process known as
erythropoiesis
Erythropoiesis (from Greek 'erythro' meaning "red" and 'poiesis' "to make") is the process which produces red blood cells (erythrocytes), which is the development from erythropoietic stem cell to mature red blood cell.
It is stimulated by decrea ...
. In adults, about 2.4 million RBCs are produced each second. The normal RBCs count is 4.5 to 5 millions per cu.mm. RBCs have a lifespan of approximately 100-120 days. After they have completed their lifespan, they are removed from the bloodstream by the
spleen
The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes . .
Mature red blood cells are unique among cells in the human body in that they lack a nucleus (although
erythroblasts
A nucleated red blood cell (NRBC), also known by several other names, is a red blood cell that contains a cell nucleus. Almost all vertebrate organisms have hemoglobin-containing cells in their blood, and with the exception of mammals, all of t ...
do have a nucleus).
The condition of having too few red blood cells is known as
anemia
Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...
, while having too many is
polycythemia
Polycythemia (also known as polycythaemia) is a laboratory finding in which the hematocrit (the volume percentage of red blood cells in the blood) and/or hemoglobin concentration are increased in the blood. Polycythemia is sometimes called eryth ...
.
Erythrocyte sedimentation rate (ESR) is the rate at which RBCs sink to the bottom (when placed in a vertical column after adding an anticoagulant). Normal values of ESR are:
• 3 to 5 mm per hour in males.
• 4 to 7 mm per hour in females.
White blood cells
White blood cell
White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...
s or ''leukocytes'', are cells of the
immune system
The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
involved in defending the body against both
infectious disease
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
and foreign materials. They are produced and derived from multipotent cells in the
bone marrow
Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoietic ce ...
known as
hematopoietic stem cell
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within t ...
s. Leukocytes are found throughout the body, including the blood and
lymphatic system
The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid o ...
. There are a variety of types of white bloods cells that serve specific roles in the human immune system. WBCs constitute approximately 1% of the blood volume.
White blood cells are divided into
granulocyte
Granulocytes are
cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear. They ha ...
s and
agranulocyte
In immunology, agranulocytes (also known as nongranulocytes or mononuclear leukocytes) are one of the two types of leukocytes (white blood cells), the other type being granulocytes. Agranular cells are noted by the absence of Granule (cell biol ...
s, distinguished by the presence or absence of
granules in the cytoplasm. Granulocytes include
basophils
Basophils are a type of white blood cell. Basophils are the least common type of granulocyte, representing about 0.5% to 1% of circulating white blood cells. However, they are the largest type of granulocyte. They are responsible for inflammator ...
,
eosinophils
Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells (WBCs) and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. A ...
,
neutrophils
Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying in ...
, and
mast cells
A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a par ...
. Agranulocytes include
lymphocytes
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adap ...
and
monocytes.
The condition of having too few white blood cells is
leukopenia
Leukopenia () is a decrease in the number of leukocytes (WBC). Found in the blood, they are the white blood cells, and are the body's primary defense against an infection. Thus the condition of leukopenia places individuals at increased risk of inf ...
, while having too many is
leukocytosis
Leukocytosis is a condition in which the white cell (leukocyte count) is above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, but may also occur following certain parasi ...
. There are individual terms for the lack or overabundance of specific types of white blood cells. The number of white blood cells in circulation is commonly increased in the incidence of
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
. Many
hematological cancers are based on the inappropriate production of white blood cells.
Platelets
Platelet
Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ini ...
s, or ''thrombocytes'', are very small, irregularly shaped clear cell fragments, 2–3 µm in diameter, which derive from fragmentation of
megakaryocytes
A megakaryocyte (''mega-'' + '' karyo-'' + '' -cyte'', "large-nucleus cell") is a large bone marrow cell with a lobated nucleus responsible for the production of blood thrombocytes (platelets), which are necessary for normal blood clotting. In hum ...
. The average lifespan of a platelet is normally just 5 to 9 days. Platelets are a natural source of growth factors. They circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots. Platelets release thread-like fibers to form these clots.
The normal range (99% of population analyzed) for platelets is 150,000 to 450,000 per cubic millimeter. If the number of platelets is too low, excessive bleeding can occur. However, if the number of platelets is too high, blood clots can form thrombosis, which may obstruct blood vessels and result in such events as a
stroke
A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
,
myocardial infarction
A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may ...
,
pulmonary embolism
Pulmonary embolism (PE) is a blockage of an pulmonary artery, artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include dyspnea, shortness of breath, chest pain p ...
, or blockage of blood vessels to other parts of the body, such as the extremities of the arms or legs. An abnormality or disease of the platelets is called a thrombocytopathy, which can be either a low number of platelets (
thrombocytopenia
Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients an ...
), a decrease in function of platelets (thrombasthenia), or an increase in the number of platelets (thrombocytosis). There are disorders that reduce the number of platelets, such as
heparin-induced thrombocytopenia
Heparin-induced thrombocytopenia (HIT) is the development of thrombocytopenia (a low platelet count), due to the administration of various forms of heparin, an anticoagulant. HIT predisposes to thrombosis (the abnormal formation of blood clots ...
(HIT) or
thrombotic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in blood clots forming in small blood vessels throughout the body. This results in a low platelet count, low red blood cells due to their breakdown, and often kidney, h ...
(TTP), that typically cause thromboses, or clots, instead of bleeding.
Platelets release a multitude of growth factors including
platelet-derived growth factor
Platelet-derived growth factor (PDGF) is one among numerous growth factors that regulate cell growth and division. In particular, PDGF plays a significant role in blood vessel formation, the growth of blood vessels from already-existing blood v ...
(PDGF), a potent chemotactic agent, and
TGF beta
Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other ...
, which stimulates the deposition of extracellular matrix. Both of these growth factors have been shown to play a significant role in the repair and regeneration of connective tissues. Other healing-associated growth factors produced by platelets include
basic fibroblast growth factor
Fibroblast growth factor 2, also known as basic fibroblast growth factor (bFGF) and FGF-β, is a growth factor and signaling protein encoded by the ''FGF2'' gene. It binds to and exerts effects via specific fibroblast growth factor receptor '' ...
(bFGF),
insulin-like growth factor 1
Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults.
IGF-1 is a protein that in humans is ...
(IGF-1), platelet-derived epidermal growth factor, and
vascular endothelial growth factor
Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, ...
(VEGF). Local application of these factors in increased concentrations through platelet-rich plasma (PRP) has been used as an adjunct to wound healing for several decades.
Complete blood count
A complete blood count (CBC) is a test panel requested by a doctor or other medical professional that gives information about the cells in a patient's blood. A scientist or lab technician performs the requested testing and provides the requesting medical professional with the results of the CBC. In the past, counting the cells in a patient's blood was performed manually, by viewing a slide prepared with a sample of the patient's blood under a microscope. Today, this process is generally automated by use of an automated analyzer, with only approximately 10-20% of samples now being examined manually. Abnormally high or low counts may indicate the presence of many forms of disease, and hence blood counts are amongst the most commonly performed blood tests in medicine, as they can provide an overview of a patient's general health status.
Discovery
In 1658 Dutch naturalist
Jan Swammerdam
Jan Swammerdam (February 12, 1637 – February 17, 1680) was a Dutch biologist and microscopist. His work on insects demonstrated that the various phases during the life of an insect—egg, larva, pupa, and adult—are different forms of the ...
was the first person to observe red blood cells under a microscope, and in 1695,
microscopist
Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...
Antoni van Leeuwenhoek
Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch microbiologist and microscopist in the Golden Age of Dutch science and technology. A largely self-taught man in science, he is commonly known as " the ...
, also Dutch, was the first to draw an illustration of "red corpuscles", as they were called. No further blood cells were discovered until 1842 when French physician
Alfred Donné
Alfred may refer to:
Arts and entertainment
*''Alfred J. Kwak'', Dutch-German-Japanese anime television series
* ''Alfred'' (Arne opera), a 1740 masque by Thomas Arne
* ''Alfred'' (Dvořák), an 1870 opera by Antonín Dvořák
*"Alfred (Interlu ...
discovered platelets. The following year leukocytes were first observed by
Gabriel Andral
Gabriel Andral (6 November 1797 – 13 February 1876) was a distinguished French pathologist and a professor at the University of Paris.
In 1828 Andral was appointed professor of hygiene, and in 1839 succeeded François-Joseph-Victor Broussais (17 ...
, a French professor of medicine, and
William Addison, a British physician, simultaneously. Both men believed that both red and white cells were altered in disease. With these discoveries,
hematology
Hematology ( always spelled haematology in British English) is the branch of medicine concerned with the study of the cause, prognosis, treatment, and prevention of diseases related to blood. It involves treating diseases that affect the produc ...
, a new field of medicine, was established. Even though agents for staining tissues and cells were available, almost no advances were made in knowledge about the morphology of blood cells until 1879, when
Paul Ehrlich
Paul Ehrlich (; 14 March 1854 – 20 August 1915) was a Nobel Prize-winning German physician and scientist who worked in the fields of hematology, immunology, and antimicrobial chemotherapy. Among his foremost achievements were finding a cure ...
published his technique for staining blood films and his method for differential blood cell counting.
References
External links
*
{{DEFAULTSORT:Blood Cell
1658 in science
Blood