What is a Red Blood Cell? (with pictures) What is a Red Blood Cell? Originally Written By: Michael Anissimov Revised By: Jillian O Keeffe Edited By: Bronwyn Harris Last Modified Date: 08 December 2016 Copyright Protected: Top 10 facts about the world A red blood cell, or erythrocyte , is the most common type of cell in blood. It carries oxygen throughout the circulatory system, from the lungs to the rest of the body, and brings carbon dioxide waste back the other way. All of the body's tissues are dependent upon oxygen from these cells — if the flow is cut off, the tissue dies. There are several medical conditions associated with red blood cells specifically, including sickle-cell anemia, thalassemia, and spherocytosis, but changes in the amount of these cells can also be a sign of other disorders. Characteristics Red blood cells have a diameter of about 6 to 8 micrometers (millionths of a meter), which is similar in size to most cells in the body. They are round and red, with a depression in the center.

Adult humans have 20 to 30 trillion of these cells in their bodies, with men having more on average than women, and each one lives for about 120 days before being broken down. They are very flexible, which is important for their functioning, since they often have to squeeze through small openings. Ad Function The main purpose of red blood cells is to transport oxygen and carbon dioxide through the circulatory system. The reason they can do this is that they contain an iron-containing protein called hemoglobin, which binds to oxygen. When the oxygen and the hemoglobin combine, they cause the cells to become bright red. This is why blood looks red when it goes outside of the body as well — when exposed to the open through a cut, the cells become exposed to a lot of atmospheric oxygen. Once all the oxygen connected to the cells is used up, then they collect carbon dioxide and other waste gases from the body and bring it back to the lungs, where they swap it for oxygen and start the cycle again. Related Disorders There are a variety of medical disorders associated with red blood cells, with one of the most common being sickle-cell disease. This is a genetic disorder that causes the cells to become stiff and sickle-shaped.

This makes them unable to move properly throughout the circulatory system, and can lead to a variety of problems, including strokes, blindness, and chronic pain. Spherocytosis is another genetic condition that changes the shape of cells and makes them brittle, but unlike sickle-cell disease, it makes them spherical. Several other conditions cause red blood cell abnormalities by disrupting the proper production of hemoglobin. This includes thalassemia, a genetic disorder that causes abnormal hemoglobin molecules, and pernicious anemia, in which the body doesn't absorb enough B12, which is needed for making hemoglobin. Additionally, conditions like G6PD deficiency, hemolytic disease of the fetus and newborn, and aplastic anemia can cause problems with the creation and life of red blood cells. Besides conditions that affect the cells themselves, having an increase or decrease in the number of red blood cells in the body can be a symptom of several conditions. A high red blood cell count, also called polycythemia, can be caused by poor circulation to the kidneys, genetic heart problems, Chronic Obstructive Pulmonary Disease ( COPD ), and pulmonary fibrosis .

Some people are also born with genetic variants that cause them to have higher than normal red blood cell counts. A lower than normal count can be a sign of poor nutrition, problems with bone marrow, and leukemia , among other things. Ad Definition of Red blood cells Definition of Red blood cells Causes of a Heart Attack Slideshow Red blood cells: The blood cells that carry oxygen. Red cells contain hemoglobin and it is the hemoglobin which permits them to transport oxygen (and carbon dioxide). Hemoglobin, aside from being a transport molecule, is a pigment. It gives the cells their red color (and their name). The abbreviation for red blood cells is RBCs. Red blood cells are sometime simply called red cells. They are also called erythrocytes or, rarely today, red blood corpuscles. Last Editorial Review: 5/13/2016 What Are Red Blood Cells? - Health Encyclopedia - University of Rochester Medical Center What Are Red Blood Cells? Red blood cells play an important role in your health by carrying fresh oxygen throughout the body. Click to Enlarge Red blood cells are round with a flattish, indented center, like doughnuts without a hole.

Your healthcare provider can check on the size, shape, and health of your red blood cells using tests, such as the complete blood count screening. Red blood cells at work Hemoglobin is the protein inside red blood cells that carries oxygen. Red blood cells also remove carbon dioxide from your body, transporting it to the lungs for you to exhale. Red blood cells are made inside your bones, in the bone marrow. They typically live for about 120 days, and then they die. Click to Enlarge Nutrition and red blood cells Foods rich in iron help you maintain healthy red blood cells. Vitamins are also necessary to build healthy red blood cells. These include vitamin E, found in foods such as dark green vegetables, nuts and seeds, mango, and avocados; vitamins B2, B12, and B3, found in foods such as eggs, whole grains, and bananas; and folate, available in fortified cereals, dried beans and lentils, orange juice, and green leafy vegetables. Illnesses of the red blood cells Most people don't think about their red blood cells unless they have a disease that affects these cells.

Problems with red blood cells can be caused by illnesses or a lack of iron or vitamins in your diet. Some diseases of the red blood cells are inherited. Diseases of the red blood cells include many types of anemia, a condition in which there are too few red blood cells to carry sufficient oxygen throughout the body. People with anemia may have red blood cells that have an unusual shape or that look normal, larger than normal, or smaller than normal. Symptoms of anemia include tiredness, irregular heartbeats, pale skin, feeling cold, and, in severe cases, heart failure. Children who don't have enough healthy red blood cells grow and develop more slowly than other children. These symptoms demonstrate how important red blood cells are to your daily life. These are common types of anemia: Iron-deficiency anemia. If you don't have enough iron in your body, your body won't be able to make enough red blood cells. Iron-deficiency anemia is the most common form of anemia. Among the causes of iron deficiency are a diet low in iron, a sudden loss of blood, a chronic loss of blood (such as from heavy menstrual periods), or the inability to absorb enough iron from food. Sickle cell anemia.

In this inherited disease, the red blood cells are shaped like half moons rather than the normal indented circles. This change in shape can make the cells "sticky" and unable to flow smoothly through blood vessels. This causes a blockage in blood flow. This blockage may cause acute or chronic pain and can also lead to infection or organ damage. Sickle cells die much more quickly than normal blood cells—in about 10 to 20 days instead of 120 days—causing a shortage of red blood cells. Normocytic anemia. This type of anemia happens when your red blood cells are normal in shape and size, but you don't have enough of them to meet your body's needs. Diseases that cause this type of anemia are usually long-term conditions, like kidney disease, cancer, or rheumatoid arthritis. Hemolytic anemia. This type of anemia happens when red blood cells are destroyed by an abnormal process in your body before their lifespan is over. As a result, your body doesn't have enough red blood cells to function, and your bone marrow cannot make enough to keep up with demand. Fanconi anemia.

This is a rare inherited disorder in which your bone marrow isn't able to make enough of any of the components of blood, including red blood cells. Children born with this disorder often have serious birth defects because of the problems with their blood and may develop leukemia. Medical Reviewers: Red Blood Cell Count: The Test | Red Blood Cell Count Test: RBC Count; Erythrocyte Count; Red Count | Lab Tests Online Is there anything else I should know? How is it used? A red blood cell (RBC) count is typically ordered as part of a complete blood count (CBC) and may be used as part of a health checkup to screen for a variety of conditions. This test may also be used to help diagnose and/or monitor a number of diseases that affect the production or lifespan of red blood cells. Red blood cells circulate in the blood and carry oxygen throughout the body. They are produced in the bone marrow and then released into the bloodstream as they mature. RBCs have a typical lifespan of about 120 days and are continuously renewed and replaced as they age and degrade or are lost through bleeding.

A relatively stable number of RBCs is maintained in the circulation by increasing or decreasing the rate of production by the bone marrow. Some conditions affect RBC production and may cause an increase or decrease in the number of mature RBCs released into the blood circulation. Other conditions may affect the lifespan of RBCs in circulation, especially if the RBCs are deformed due to an inherited or acquired defect or abnormality. If RBCs are lost or destroyed faster than they can be replaced, if bone marrow production is disrupted, or if the RBCs produced do not function normally, then a person will become anemic , which affects the amount of oxygen reaching tissues. If too many RBCs are produced and released, then a person can develop polycythemia . This can cause decreased blood flow and related problems. While an RBC count can be used to detect a problem with red blood cell production and/or lifespan, it cannot determine the underlying cause. In addition to the full CBC, some other tests may be performed at the same time or as follow up to help establish a diagnosis. Examples include: ^ Back to top What does the test result mean?

Since an RBC count is performed as part of a complete blood count (CBC) , results from other components are taken into consideration. A rise or drop in the RBC count must be interpreted in conjunction with other parameters, such as hemoglobin , hematocrit , reticulocyte count , and/or red blood cell indices . Blood or red cell loss that occurs suddenly or over time and diseases and conditions that decrease red blood cell production in the bone marrow will result in a low RBC count. Some causes of a low RBC count ( anemia ) include: Trauma Red blood cell destruction, for example hemolytic anemia caused by autoimmunity or defects in the red cell itself; the defects could be a hemoglobinopathy (e.g., sickle cell anemia ), thalassemia , an abnormality in the RBC membrane (e.g., hereditary spherocytosis), or enzyme defect (e.g., G6PD deficiency ).

Sudden ( acute ) or chronic bleeding from the digestive tract (e.g., ulcers , polyps , colon cancer ) or other sites, such as the bladder or uterus (in women, heavy menstrual bleeding, for example) Red blood cell | definition of red blood cell by Medical dictionary Red blood cell | definition of red blood cell by Medical dictionary Related to red blood cell: red blood cell count e·ryth·ro·cyte red blood cell n. Abbr. RBC A cell in the blood of vertebrates that transports oxygen and carbon dioxide to and from the tissues. In mammals, the red blood cell is disk-shaped and biconcave, contains hemoglobin, and lacks a nucleus. Also called erythrocyte, red cell, red corpuscle. red blood cell See erythrocyte . erythrocyte A mature, non-nucleated cell averaging 7–8 µm in diameter, which is round or ovoid on peripheral smear, contains haemoglobin and has a zone of central pallor due to the cell’s biconcavity.

Erythrocytes are normally confined to blood vessels (aorta, arteries, arterioles, capillaries, venules, veins, inferior vena cava and superior vena cava), the heart and pulmonary vasculature. Haemoglobin, the main erythrocyte protein, is tasked with transporting O2 to tissues and CO2 away from tissues. Erythrocytes have an average lifespan of 120 days. e·ryth·ro·cyte (sel) [L. cella, a chamber] GENERALIZED HUMAN CELL AND ORGANELLES The basic unit of life. A cell is a group of self-sustaining biochemical reactions that are isolated from the environment by a selectively permeable lipid membrane. Among the key reactions are those that maintain a stable intracellular concentration of ions; for mammalian cells, typical internal concentrations include 140 mM K+, 5-15 mM Na+, 5-15 mM Cl-, and a pH of 7.2, which can be significantly different from their concentrations outside the cell. Other key reactions move molecules and molecular complexes within the cell, sometimes changing the cell's shape.

These reactions, along with many others, require energy, and the generation of energy by breaking apart preexisting hydrocarbon molecules ("food") is the job of glycolysis and other characteristic intracellular metabolic reactions. See: glycolysis ; metabolism ; mitochondrion . Structure Intracellular chemical reactions are controlled by enzymes that are organized in stable molecular complexes called organelles. The polymer-based organelles include centrioles and the cytoskeleton; nucleic acid-based organelles include ribosomes; and membrane-enclosed organelles include the nucleus, endoplasmic reticula, Golgi complexes, lysosomes, peroxisomes, mitochondria, and storage and transport vesicles. See: illustrationIndividual mammalian cells are usually microscopic, typically ranging from 5 µm to 50 µm in diameter. In humans, lymphocytes are small cells (~6 µm in diameter), columnar epithelial cells (10 µm x 20 µm) are medium-size cells, and mature ova (120-150 µm) are some of the largest cells.

Cell Division In mammals, all new cells arise from existing cells through cell division, and an animal's growth results largely from increases in the number of its cells, most of which differentiate into specialized cell types to form the body's various tissues. Cell division involves two major processes: karyokinesis, the division of the nucleus, and cytokinesis, the division of the remainder of the cell. When generating somatic daughter cells, karyokinesis uses a process called mitosis, which produces daughter cells with a full complement of chromosomes. When generating germ cells, karyokinesis includes a process called meiosis, which produces daughter cells with half the normal number of chromosomes. See: meiosis and mitosis for illus. A cell Ameloblast. anterior horn cell A somatic motor neuron that has its cell body in the ventral (anterior) horn of the gray matter of the spinal cord; its axon passes out through a ventral root and innervates skeletal muscle. antigen-presenting cell Abbreviation: APC A cell that breaks down antigens and displays their fragments on surface receptors next to major histocompatibility complex molecules. This presentation is necessary for some T lymphocytes that are unable to recognize soluble antigens.

Macrophages are the primary antigen-presenting cells, but B cells and dendritic cells also can act as APCs. See: T cell ; macrophage processing cell APUD The abbreviated name for an 'amine precursor uptake and decarboxylation cell'. These cells are the constituents of a diffuse neuroendocrine system and all have metabolic pathways that make and utilize serotonin (5-HT). APUD cells include chromaffin cells, enterochromaffin cells, and SIF cells as well as certain cells found in the parathyroid gland, thyroid gland, pituitary gland, hypothalamus, and placenta. argentaffin cell See: Downey cell dust cell A macrophage that migrates into the lumen of lung aveoli and ingests debris, particles of air pollution, and pathogens to keep the airspaces clear. EC cell 1. An embryonal carcinoma cell, which is a cultured cell line. 2. An enterochromaffin cell that secretes substance P and is found in the stomach and small intestine. effector cell A cell that carries out the final response or function of a particular process.

The main effector cells of the immune system, for example, are activated lymphocytes and phagocytes—the cells involved in destroying pathogens and removing them from the body. embryonic stem cell Abbreviation: ES cell A cell from the inner cell mass of the blastocyst (the 3-5 day old mammalian embryo) that can give rise to all the somatic cells of the body. Embryonic stem cells can be maintained as pure stem cell cultures. See: adult stem cell endothelial cell The type of epithelial cell that lines blood vessels and lymph vessels; these cells are usually squamous (flattened) and form sheets one layer thick. Endothelial cells are derived from mesenchyme cells of the embryo. A sheet of endothelial cells is called an endothelium. See: endothelium enterochromaffin cell Abbreviation: EC cell An enteroendocrine cell that produces serotonin and is found in the small intestine. Enterochromaffin cells are very similar to the cells, found throughout the peripheral sympathetic nervous system, that are called simply 'chromaffin cells'.

enteroendocrine cell One of the scattered hormone-producing cells found in the pancreatic islets and throughout the gastrointestinal (mainly, small intestinal) mucosa. ependymal cell Any of the epithelial cells that form a one-cell-thick layer lining the ventricles and the central canal of the central nervous system. The ventricular (apical) surfaces of many ependymal cells are covered with cilia or microvilli. In most places, the ependymal layer does not have a basal lamina. Specialized regions of ependymal cells include the covering of the blood vessels and loose connective tissue of the choroid plexuses; here, the ependyma is specialized to secrete cerebrospinal fluid. epithelial cell Any of the cells forming the cellular sheets that cover surfaces, both inside and outside the body. Epithelial cells are closely packed and take on polyhedral shapes, from tall (columnar) through squat (cuboidal) to flat (squamous). Epithelial cells adhere strongly to one another, and one of their surfaces -- the basal surface -- sticks firmly to a thin extracellular film of fibrils called a basal lamina.

A sheet of epithelial cells derived from embryonic epithelia (the ectoderm or the endoderm) is called an epithelium. See: epithelium ethmoidcell An enteroendocrine cell found in the stomach that produces the hormone gastrin. ganglion cell 1. Any neuron whose cell body is located within a ganglion. 2. A neuron of the retina of the eye whose cell body lies in the ganglion cell layer. The axons of ganglion cells form the optic nerve. germ cell A cell whose function is to reproduce the organism. Early in development, primordial germ cells are found in the genital ridges of the embryo. Later, in the testis, the primordial germ cells are called spermatogonia, and in the ovary, they are called oogonia. When they mature, the germ cells (i.e., spermatogonia and oogonia) differentiate into haploid gametes (i.e., spermatozoa and ova). Synonym: primordial germ cell giant cell 1.

A multinucleated phagocyte created by several individual macrophages that have merged around a large pathogen or a substance resistant to destruction, such as a splinter or surgical suture. See: granuloma ; tuberculosis 2. A large multinucleated (40-60 nuclei) tumor cell characteristic of certain bone and tendon tumors. 3. A large multinucleated cell that invades the walls of the aorta and its major branches in giant cell arteritis. glial cell One of three types of nonneuronal cell in the central nervous system: astrocytes, oligodendrocytes, and microglial cells. SYN neuroglial cell Synonym: neuroglial cell gitter cell A macrophage present at sites of brain injury. The cells are packed with lipoid granules from phagocytosis of damaged brain cells. See: microglia globus cell One of the two varieties of basal cell found in the olfactory epithelium. It is a rounded neuroblast or neural stem cell for the olfactory receptor cells. goblet cell A type of dendritic antigen-presenting cell that typically resides in the skin. L.E. CELL (center): (Orig. mag.

×1000) L.E. cell Historically, an abbreviation for lupus erythematosus cell, a polymorphonuclear leukocyte that contains the phagocytized nucleus of another cell. It is characteristic but not diagnostic of lupus erythematosus. This distinctive cell may form when the blood of patients with systemic lupus erythematosus is incubated and further processed according to a specified protocol. The plasma of some patients contains an antibody to the nucleoprotein of leukocytes. These altered nuclei, which are swollen, pink, and homogeneous, are ingested by phagocytes. These are the L.E. cells. The ingested material, when stained properly, is lavender and displaces the nucleus of the phagocyte to the inner surface of the cell membrane. The L.E. cell phenomenon can be demonstrated in most patients with systemic lupus erythematosus but is not essential for diagnosis. illustration A stem cell derived from Wharton's jelly. memory cell A cell derived from B or T lymphocytes that can quickly recognize a foreign antigen to which the body has been previously exposed.

Memory T cells stimulate T helper lymphocytes and cytotoxic T cells; memory B cells stimulate the production of antigen-specific antibodies by B plasma cells. Both types of memory cells survive for years, providing a durable adaptive immune response against foreign antigens. mesenchyme cell One of the two basic somatic cell lineages -- the other being epithelial cells. In contrast to epithelial cells, mesenchyme cells are not polarized and are frequently motile. In the early embryo, mesenchyme cells fill many of the spaces enclosed by epithelia. Later, mesenchyme cells will secrete the space-filling extracellular matrix molecules, such as collagen and glycoproteins, that characterize connective tissue. mesenchymal stem cell A stem cell found in connective tissue and capable of producing cells of the connective tissue lineages, such as cartilage, bone, muscle, and fat cells. mesothelial cell The type of epithelial cell that lines serous (pleural, peritoneal, and pericardial) cavities, blood vessels, and lymph vessels; these cells are usually squamous (flattened) and form sheets one layer thick. Mesothelial cells are derived from mesenchyme cells of the embryo.

A sheet of mesothelial cells is called a mesothelium. See: mesothelium microglial cell A small glial cell of the central nervous system and retina. Microglia have spiky branched processes and are arranged homogeneously throughout the brain and spinal cord. They are activated by disease and injury, after which they become phagocytic and sometimes resume their embryonic motility like a macrophage. mitral cell One of the two principal neurons of the olfactory bulb -- the other being the tufted cell. In a complex synaptic formation called a glomerulus, each of the mitral and tufted cells receives synaptic inputs from axons of the olfactory nerve. The axons of the mitral and tufted cells form the olfactory tract and synapse in the olfactory cortex. mossy cell A cell present in the bone marrow of patients with multiple myeloma. myoepithelial cell A smooth muscle cell found in some epithelia; it lies between glandular cells and the basal lamina of sweat, mammary, lacrimal, and salivary glands.

Synonym: basket cell natural killer cell Abbreviation: NK cell A large granular lymphocyte – a defensive cell of innate immunity – that bonds to cells and lyses them by releasing cytotoxins. Natural killer cells are null cells, lymphocytes that do not have B cell or T cell surface markers, and they can be activated without previous antigen exposure. NK cells destroy cells infected with viruses and some types of tumor cells in cultures. They also secrete gamma interferon (INF?), tumor necrosis factor alpha (TNFa), and granulocyte-macrophage colony-stimulating factor (GMCSF), enhancing the effect of T lymphocytes. Synonym: killer cell A leukocyte present in pus. Pus cells are often degenerated or necrotic. pyramidal cell A large, common neuron found in the cerebral cortex. Pyramidal cells are flask-shaped or triangular, and, in the parts of the cortex with six layers, they occupy the fifth layer. Pyramidal cell dendrites project up into the most superficial layer of the cortex, while pyramidal cell axons run in the opposite direction, i.e., downward and out of the cortex.

Synonym: pyramidal neuron radial glial cell A structural macroglial cell that is a key component of the developing nervous system. Radial glial cells first appear in the neural tube, where their cell bodies are suspended between two thin cell processes; the apical process attaches to the inner (ventricular) surface of the neural tube, and the basal process attaches to the outer (pial) surface. Early in development, neuroblasts migrate radially along the scaffolding formed by the radial glial cell processes, and growing axons may follow the scaffolding longitudinally. Later, many radial glial cells retract their processes and differentiate into astrocytes. red cell A small cell that is filled with hemoglobin, has no nucleus, and is shaped like a biconcave disc. Red cells transport oxygen to tissues and carbon dioxide to the lungs. Individual red cells have a life span of 3-4 months, and new red cells are continually being produced in the bone marrow. In a healthy person, 99% of the cells circulating in the blood are red cells.

Synonym: erythrocyte; red blood cell; red blood corpuscle See: erythrocyte red blood cell See: Schwann cell segmented cell A segmented neutrophil (i.e., one with a nucleus of two or more lobes connected by slender filaments). selenoid cell See: red cell ghost sensory cell A cell that when stimulated gives rise to nerve impulses that are conveyed to the central nervous system. septal cell A type II alveolar cell that secretes pulmonary surfactant; it is adjacent to a septum of the alveoli. serous cell An epithelial cell that secretes a watery fluid containing proteins, glycoproteins, and often antibodies (IgA, IgG, and IgM). Serous cells and mucous cells are the two varieties of secretory cells found in exocrine glands. Sertoli cell See: Reed-Sternberg cell stipple cell A red blood cell that contains small basophilic-staining dots. It is seen in lead poisoning, malaria, severe anemia, and leukemia.

striated muscle See: muscle suppressor T cell A subpopulation of regulatory T lymphocytes that develop in the thymus gland, that slows or stops a specific immune response. sustentacular cell A supporting cell, as in the acoustic macula, organ of Corti, olfactory epithelium, taste buds, or testes. sympathicotrophic cell One of the large epithelial cells that occur in groups in the hilus of the ovary. They are thought to be chromaffin cells. sympathochromaffin cell A chromaffin cell of ectodermal origin present in the fetal adrenal gland. Sympathetic and medullary cells originate from these cells. syncytial giant cell TARGET CELLS: In hemoglobin C disease (×600) target cell 1. . An erythrocyte with a dark rounded central area surrounded by a lightly stained clear ring, which in turn is surrounded by a dense ring of peripheral cytoplasm. It is present in certain blood disorders, such as thalassemia, and in patients who have no spleen. See: hemoglobin C disease for illus Synonym: codocyte ; leptocyte 2. .

The cell at which a signal (e.g., hormone or nerve impulse) is aimed. illustration tart cell A phagocyte that has ingested the unaltered nuclei of cells. These nuclei can be observed unchanged within the phagocytes. taste cell Any of the neuroepithelial cells within a taste bud that are receptors for the sense of taste. Each possesses on the free surface a short gustatory hair that projects through the inner taste pore. Synonym: taste receptor cell Red Blood Cells - How Blood Works | HowStuffWorks Red Blood Cells Photo courtesy Garrigan.Net Microscopic image of red blood cells During formation, the RBC eventually loses its nucleus and leaves the bone marrow as a reticulocyte. At this point, the reticulocyte contains some remnants of organelles. Eventually these organelles leave the cell and a mature erythrocyte is formed. RBCs last an average of 120 days in the bloodstream. When RBCs age, they are removed by macrophages in the liver and spleen. A hormone called erythropoietin and low oxygen levels regulate the production of RBCs.

Any factor that decreases the oxygen level in the body, such as lung disease or anemia (low number of RBCs), increases the level of erythropoietin in the body. Erythropoietin then stimulates production of RBCs by stimulating the stem cells to produce more RBCs and increasing how quickly they mature. Ninety percent of erythropoietin is made in the kidneys . When both kidneys are removed, or when kidney failure is present, that person becomes anemic due to lack of erythropoietin. Iron, vitamin B-12 and folate are essential in the production of RBCs. Red blood cells (RBCs) are by far the most abundant cells in the blood. RBCs give blood its characteristic red color. In men , there are an average of 5,200,000 RBCs per cubic millimeter (microliter), and in women there are an average of 4,600,000 RBCs per cubic millimeter. RBCs account for approximately 40 to 45 percent of the blood.

This percentage of blood made up of RBCs is a frequently measured number and is called the hematocrit. The ratio of cells in normal blood is 600 RBCs for each white blood cell and 40 platelets. There are several things about RBCs that make them unusual: An RBC has a strange shape -- a biconcave disc that is round and flat, sort of like a shallow bowl. An RBC has no nucleus. The nucleus is extruded from the cell as it matures. An RBC can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries. (Capillaries are minute blood vessels through which oxygen, nutrients and waste products are exchanged throughout the body.) An RBC contains hemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it. The primary function of red blood cells is to transport oxygen from the lungs to the cells of the body. RBCs contain a protein called hemoglobin that actually carries the oxygen. In the capillaries, the oxygen is released to be used by the cells of the body.

Ninety-seven percent of the oxygen that is carried by the blood from the lungs is carried by hemoglobin; the other three percent is dissolved in the plasma. Hemoglobin allows the blood to transport 30 to 100 times more oxygen than could be dissolved in the plasma alone. Hemoglobin combines loosely with oxygen in the lungs, where the oxygen level is high, and then easily releases it in the capillaries, where the oxygen level is low. Each molecule of hemoglobin contains four iron atoms, and each iron atom can bind with one molecule of oxygen (which contains two oxygen atoms, called O2) for a total of four oxygen molecules (4 * O2) or eight atoms of oxygen for each molecule of hemoglobin. The iron in hemoglobin gives blood its red color. Thirty-three percent of an RBC is hemoglobin. The normal concentration of hemoglobin in blood is 15.5 grams per deciliter of blood in men, and 14 grams per deciliter of blood in women.

(A deciliter is 100 milliliters, or one-tenth of a liter.) Besides carrying oxygen to the cells of the body, the RBCs help to remove carbon dioxide (CO2) from the body. Carbon dioxide is formed in the cells as a byproduct of many chemical reactions. It enters the blood in the capillaries and is brought back to the lungs and released there and then exhaled as we breathe. RBCs contain an enzyme called carbonic anhydrase which helps the reaction of carbon dioxide (CO2) and water (H2O) to occur 5,000 times faster. Carbonic acid is formed, which then separates into hydrogen ions and bicarbonate ions: Carbonic Anhydrase CO2 + H2O ===> H2CO3 + H+ + HCO3- carbon dioxide + water ==> carbonic acid + hydrogen ion + bicarbonate ion The hydrogen ions then combine with hemoglobin and the bicarbonate ions go into the plasma. Seventy percent of the CO2 is removed in this way. Seven percent of the CO2 is dissolved in the plasma. The remaining 23 percent of the CO2 combines directly with hemoglobin and then is released into the lungs.

In the next section, we'll learn about the different types of white blood cells. Up Next Functions of Red Blood Cells, White Blood Cells & Platelets - Video & Lesson Transcript | Study.com Functions of Red Blood Cells, White Blood Cells & Platelets Watch short & fun videos Start Your Free Trial Today An error occurred trying to load this video. Try refreshing the page, or contact customer support. You must create an account to continue watching Register for a free trial Are you a student or a teacher? I am a student Start Your Free Trial To Continue Watching As a member, you'll also get unlimited access to over lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed. Coming up next: Fibrous Connective Tissue: Function & Types You're on a roll. Keep up the good work! Your next lesson will play in 10 seconds 0:06 Blood Connective Tissue 3:58 Remembering White Blood Cells 4:10 Platelets Add to Add to Add to Want to watch this again later? Log in or sign up to add this lesson to a Custom Course. Custom Courses are courses that you create from Study.com lessons.

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Create an account to start this course today Try it free for 5 days! Lesson Transcript Instructor: Laura Enzor Laura has a Master's degree in Biology and is working on her PhD in Biology. She specializes in teaching Human Physiology at USC. Blood is a connective tissue vital to our body's survival. In this lesson, we will explore the three functions of blood by delving into red blood cells, white blood cells and platelets - the three individual components that make up blood as a whole. Blood, A Connective Tissue Types of living cells in the blood In the human body, one of the most important connective tissues is blood. Blood is considered a connective tissue because it consists of a non-living fluid in which living cells are suspended. The blood matrix surrounding the cells is known as plasma, which accounts for about 55% of our blood volume. There are three types of living cells in blood: red blood cells (or erythrocytes), white blood cells (or leukocytes) and platelets (or thrombocytes). These make up the remaining 45% of our blood volume. Red Blood Cells Blood has three main functions: transportation, regulation and protection.

Our erythrocytes, or red blood cells, are the most abundant cell type in the human body. Additionally, erythrocytes are anucleated, which means they don't have a nucleus. This extra room allows for more hemoglobin to be stored in our red blood cells. Hemoglobin is a respiratory pigment , which binds to either oxygen or carbon dioxide. This allows oxygen to be transported around our body to our tissues and organs (and carbon dioxide to be taken away). Hemoglobin is largely comprised of iron, which when combined with oxygen, gives blood its red color. Additionally, blood helps cycle nutrients and hormones throughout our bodies. Process of transporting oxygen throughout the body Blood also helps us maintain homeostasis by regulating our internal body pH and temperature as well as how much water is in our bodies at a given time. Plasma, our connective tissue matrix, is about 90% water. Blood is also vital in protecting our bodies. Blood loss is controlled with clotting mechanisms, and white blood cells provide immune response. Let's examine this function in more detail.

White Blood Cells The types of leukocytes in the blood There are five different types of white blood cells, or leukocytes, in our bodies, and we can break them up into two main categories. These are granulocytes and agranulocytes. These terms simply refer to how these cells look when stained. Granulocytes have visible granules in their cell bodies, and agranulocytes do not. There are three types of granulocytes. They are neutrophils , eosinophils and basophils. Granulocytes Neutrophils Neutrophils are the most abundant type of white blood cell in our body. These are primarily responsible for killing off foreign bacteria. Neutrophils are the first responders when we are injured or sick, and they help keep us healthy by phagocytizing (or consuming) bacteria in our bodies. Eosinophils Eosinophils are responsible for fighting infections of parasitic worms. These cells release toxins that kill the worms and are also involved in the inflammatory response when we have an allergic reaction. Basophils Basophils release two chemicals, histamine and heparin.

Histamine is also involved in allergic reactions, and heparin is an anticoagulant. Anticoagulants keep blood from clotting, which helps bring more blood to a damaged area in our body, which, in turn, helps promote healing. Agranulocytes Blood Basics Blood Basics Home For Patients Blood Basics Blood is a specialized body fluid. It has four main components: plasma, red blood cells, white blood cells, and platelets. Blood has many different functions, including: transporting oxygen and nutrients to the lungs and tissues forming blood clots to prevent excess blood loss carrying cells and antibodies that fight infection bringing waste products to the kidneys and liver, which filter and clean the blood regulating body temperature The blood that runs through the veins, arteries, and capillaries is known as whole blood, a mixture of about 55 percent plasma and 45 percent blood cells. About 7 to 8 percent of your total body weight is blood. An average-sized man has about 12 pints of blood in his body, and an average-sized woman has about 9 pints.

Jump To: The Components of Blood and Their Importance Many people have undergone blood tests or donated blood , but hematology - the study of blood - encompasses much more than this. Doctors who specialize in hematology (hematologists) are leading the many advances being made in the treatment and prevention of blood diseases. If you or someone you care about is diagnosed with a blood disorder, your primary care physician may refer you to a hematologist for further testing and treatment. back to top Plasma The liquid component of blood is called plasma, a mixture of water, sugar, fat, protein, and salts. The main job of the plasma is to transport blood cells throughout your body along with nutrients, waste products, antibodies, clotting proteins, chemical messengers such as hormones, and proteins that help maintain the body's fluid balance. back to top Red Blood Cells (also called erythrocytes or RBCs) Known for their bright red color, red cells are the most abundant cell in the blood, accounting for about 40-45 percent of its volume.

The shape of a red blood cell is a biconcave disk with a flattened center - in other words, both faces of the disc have shallow bowl-like indentations (a red blood cell looks like a donut). Production of red blood cells is controlled by erythropoietin, a hormone produced primarily by the kidneys. Red blood cells start as immature cells in the bone marrow and after approximately seven days of maturation are released into the bloodstream. Unlike many other cells, red blood cells have no nucleus and can easily change shape, helping them fit through the various blood vessels in your body. However, while the lack of a nucleus makes a red blood cell more flexible, it also limits the life of the cell as it travels through the smallest blood vessels, damaging the cell's membranes and depleting its energy supplies. The red blood cell survives on average only 120 days. Red cells contain a special protein called hemoglobin, which helps carry oxygen from the lungs to the rest of the body and then returns carbon dioxide from the body to the lungs so it can be exhaled. Blood appears red because of the large number of red blood cells, which get their color from the hemoglobin.

The percentage of whole blood volume that is made up of red blood cells is called the hematocrit and is a common measure of red blood cell levels. back to top Where Do Blood Cells Come From? Blood cells develop from hematopoietic stem cells and are formed in the bone marrow through the highly regulated process of hematopoiesis. Hematopoietic stem cells are capable of transforming into red blood cells, white blood cells, and platelets. These stem cells can be found circulating in the blood and bone marrow in people of all ages, as well as in the umbilical cords of newborn babies. Stem cells from all three sources may be used to treat a variety of diseases, including leukemia, lymphoma, bone marrow failure, and various immune disorders. back to top Where Can I Find More Information? If you are interested in learning more about blood diseases and disorders, here are a few other resources that may be of some help: Red Blood Cells Red Blood Cells Red Blood Cells The red blood cells carry oxygen to the body's tissues and remove carbon dioxide and other wastes. Credits Primary Medical ReviewerE.

Gregory Thompson, MD - Internal Medicine Specialist Medical ReviewerBrian Leber, MDCM, FRCPC - Hematology Current as ofFebruary 20, 2015 WebMD Medical Reference from Healthwise This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.© 1995-2015 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. Top Picks

Question: What is the name for a red blood cell?
Answer: Erythrocyte