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Cells can be separated into prokaryotic and eukaryotic categories. Eukaryotic cells contain a nucleus. They comprise protists (single-celled organisms), fungi, plants, and animals, and are generally 5–100 micrometers in linear dimension. Prokaryotic cells contain no nucleus, are relatively small (1–10 μm in diameter), and have a simple internal structure. They include two classes of bacteria: eubacteria (including photosynthetic organisms, or cyanobacteria), which are common bacteria inhabiting soil, water, and larger organisms; and archaebacteria, which grow under unusual conditions. See also Eukaryotae; Prokaryotae.

Prokaryotic (bacterial) cells

All eubacteria have an inner (plasma) membrane which serves as a semipermeable barrier allowing small nonpolar and polar molecules such as oxygen, carbon dioxide, and glycerol to diffuse across (down their concentration gradients), but does not allow the diffusion of larger polar molecules (sugars, amino acids, and so on) or inorganic ions such as Na⁺, K⁺, Cl⁻, Ca²⁺ (sodium, potassium, chlorine, calcium). The plasma membrane, which is a lipid bilayer, utilizes transmembrane transporter and channel proteins to facilitate the movement of these molecules. Eubacteria can be further separated into two classes based on their ability to retain the dye crystal violet. Gram-positive cells retain the dye; their cell surface includes the inner plasma membrane and a cell wall composed of multiple layers of peptidoglycan. Gram-negative bacteria are surrounded by two membranes: the inner (plasma) membrane and an outer membrane that allows the passage of molecules of less than 1000 molecular weight through porin protein channels. Between the inner and outer membranes is the peptidoglycan-rich cell wall and the periplasmic space. See also Cell permeability.

Eubacteria contain a single circular double-stranded molecule of deoxyribonucleic acid (DNA), or a single chromosome. As prokaryotic cells lack a nucleus, this genomic DNA resides in a central region of the cell called the nucleoid. The bacterial genome contains all the necessary information to maintain the structure and function of the cell.

Many bacteria are able to move from place to place, or are motile. Their motility is based on a helical flagellum composed of interwoven protein called flagellin. The flagellum is attached to the cell surface through a basal body, and propels the bacteria through an aqueous environment by rotating like the propeller on a motor boat. The motor is reversible, allowing the bacteria to move toward chemoattractants and away from chemorepellants.

Eukaryotic cells

In a light microscopic view of a eukaryotic cell, a plasma membrane can be seen which defines the outer boundaries of the cell, surrounding the cell's protoplasm or contents. The protoplasm includes the nucleus, where the cell's DNA is compartmentalized, and the remaining contents of the cell (the cytoplasm). The eukaryotic cell's organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, cytoskeleton, and plasma membrane. The organelles occupy approximately half the total volume of the cytoplasm. The remaining compartment of cytoplasm (minus organelles) is referred to as the cytosol or cytoplasmic ground substance. Eukaryotic cells also differ from prokaryotic cells in having a cytoskeleton that gives the cell its shape, its capacity to move, and its ability to transport organelles and vesicles from one part of the cell cytoplasm to another. Eukaryotic cells are generally larger than prokaryotic cells and therefore require a cytoskeleton and membrane skeleton to maintain their shape, which is related to their functions.

Eukaryotic cells contain a large amount of DNA (about a thousandfold more than bacterial cells), only approximately 1% of which encodes protein. The remaining DNA is structural (involved in DNA packaging) or regulatory (helping to switch on and off genes).

Plasma membrane

The plasma membrane serves as a selective permeability barrier between a cell's environment and cytoplasm. The fundamental structure of plasma membranes (as well as organelle membranes) is the lipid bilayer, formed due to the tendency of amphipathic phospholipids to bury their hydrophobic fatty acid tails away from water. Human and animal cell plasma membranes contain a varied composition of phospholipids, cholesterol, and glycolipids.

Cytoskeleton

The cytoskeleton is involved in establishing cell shape, polarity, and motility, and in directing the movement of organelles within the cell. The cytoskeleton includes microfilaments, microtubules, intermediate filaments, and the two-dimensional membrane skeleton that lines the cytoplasmic surface of cell membranes. See also Cytoskeleton.

Nucleus

One of the most prominent organelles within a eukaryotic cell is the nucleus. The nuclear compartment is separated from the rest of the cell by a specialized membrane complex built from two distinct lipid bilayers, referred to as the nuclear envelope. However, the interior of the nucleus maintains contact with the cell's cytoplasm via nuclear pores. The primary function of the nucleus is to house the genetic apparatus of the cell; this genetic machinery is composed of DNA (arranged in linear units called chromosomes), RNA, and proteins. Nuclear proteins aid in the performance of nuclear functions and include polypeptides that have a direct role in the regulation of gene function and those that give structure to the genetic material. See also Cell nucleus.

Endoplasmic reticulum

The endoplasmic reticulum is composed of membrane-enclosed flattened sacs or cisternae. The enclosed compartment is called the lumen. The endoplasmic reticulum is morphologically separated into rough (RER) and smooth (SER). PER is studded with ribosomes and SER is not. RER is the site of protein synthesis, while lipids are synthesized in both RER and SER. See also Endoplasmic reticulum.

Golgi apparatus

The final posttranslational modifications of proteins and glycolipids occur within a series of flattened membranous sacs called the Golgi apparatus. Vesicles which bud from the endoplasmic reticulum fuse with a specialized region of the cis Golgi compartment called the cis Golgi network. In the trans Golgi network, proteins and lipids are sorted into transport vesicles destined for lysosomes, the plasma membrane, or secretion. See also Golgi apparatus.

Lysosomes

Lysosomes are membrane-bound organelles with a luminal pH of 5.0, filled with acid hydrolyses. Lysosomes are responsible for degrading materials brought into the cell by endocytosis or phagocytosis, or autophagocytosis of spent cellular material. See also Endocytosis; Lysosome.

Mitochondria

The mitochondrion contains a double membrane: the outer membrane, which contains a channel-forming protein named porin, and an inner membrane, which contains multiple infolds called cristae. The inner membrane, which contains the protein complexes responsible for electron transport and oxidative phosphorylation, is folded into numerous cristae that increase the surface area per volume of this membrane. The transfer of electrons from nicotinamide adenine dinucleotide (NADH) or flavin adenine dinucleotide (FADH₂) down the electron transfer chain to oxygen causes protons to be pumped out of the mitochondrial matrix into the intermembrane space. The resulting proton motive force drives the conversion of ADP plus inorganic orthophosphate (P_i) to ATP by the enzyme ATP synthetase. See also Mitochondria.

Peroxisomes

Within the peroxisome, hydrogen atoms are removed from organic substrates and hydrogen peroxide is formed. The enzyme catalase can then utilize the hydrogen peroxide to oxidize substrates such as alcohols, formaldehydes, and formic acid in detoxifying reactions. See also Peroxisome.

Plant cells

Plant cells are distinguished from other eukaryotic cells by various features. Outside their plasma membrane, plant cells have an extremely rigid cell wall. This cell wall is composed of cellulose and other polymers and is distinct in composition from the cell walls found in fungi or bacterial cells. The plant cell wall expands during cell growth, and a new cell wall partition is created between the two daughter cells during cell division. Similar cell walls are not observed in animal cells.

Most plant cells contain membrane-encapsulated vacuoles as major components of their cytoplasm. These vacuoles contain water, sucrose, ions, nitrogen-containing compounds formed by nitrogen fixation, and waste products.

Chloroplasts are the other major organelle in plant cells that is not found in other eukaryotic cells. Like mitochondria, they are constantly in motion within the cytoplasm. One of the pigments found in chloroplasts is chlorophyll, which is the molecule that absorbs light and gives the green coloration to the chloroplast. Chloroplasts, like mitochondria, have an outer and inner membrane. Within the matrix of the chloroplast there is an intricate internal membrane system. The internal membranes are made up of flattened interconnected vesicles that take on a disc-like structure (thylakoid vesicles). The thylakoid vesicles are stacked to form structures called grana, which are separated by a space called the stroma. Within the stroma, carbon dioxide (CO₂) fixation occurs, in which carbon dioxide is converted to various intermediates during the production of sugars. Chlorophyll is found within the thylakoid vesicles; it absorbs light and, with the involvement of other pigments and enzymes, generates ATP during photosynthesis. See also Plant cell.

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(1) A geographic area in a cellular phone system. See cellphone.

(2) In a spreadsheet, the intersection of a row and column.

(3) Short for "cellphone."

(4) An elementary unit of storage for data (bit) or power (battery).

(5) See Cell chip.

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Layout production: single frame on a storyboard.

Motion picture or television production: single frame on a roll of film or videotape.

Research: component of a sample group used in research.

Point of intersection between a row and column in an electronic spreadsheet. The spreadsheet's cells can be related to one another, through arithmetic and logical formulas, to create financial data.When data in one cell is changed such as in "what-if" analysis, the software instantly calculates the effects of the change on all cells displaying the results.

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The cell is the fundamental unit of all living things. The simplest forms of life are single-celled organisms; these include both ‘prokaryotes’ — bacteria, which have a simple internal structure — and the much more complex ‘eukaryotes’ (pro, before or preceding; eu, good, normal, and karyon, a kernel). Higher organisms, such as man, are sophisticated communities in which groups of eukaryotic cells carry out specialized functions and communicate with each other. Prokaryotes are usually about one thousandth of a millimetre in diameter. Eukaryotic cells are much larger, typically around one to two hundredths of a millimetre. There are about 100 million million cells in the human body. Both prokaryotes and eukaryotes usually multiply by dividing in two, although in multicellular organisms cell division is under strict control.

It was the invention of the microscope, in the seventeenth century, that allowed scientists the first glimpses of individual cells. In particular, the Dutchman, Antoni van Leeuwenhoek described the extraordinary variety of motile single-celled organisms (which he called ‘animalcules’) present in pond water. The word ‘cell’ (from the Latin cella, ‘a small room’) was first coined in 1665, by the English physicist Robert Hooke, to refer to the microscopic structure of cork. Technical improvements in microscopy in the eighteenth and nineteenth centuries allowed more precise observation. It gradually became apparent that cells had a complicated internal structure, and that some features (for example, what we now refer to as the nucleus) were common to most cells, even though the appearance of the cells themselves varied enormously. This in turn hinted that a common basic organization might underlie all living matter.

The first simple distinction had been between nucleus and cytoplasm — the rest of the cellular substance — but by the end of the nineteenth century the principal internal components of cells that we are familiar with today (sub-cellular structures or organelles) had been identified. These included the endoplasmic reticulum (an extensive network of membranes within the cell), mitochondria (cylindrical, membrane-limited structures) and the Golgi complex (a stack of flattened membrane sacs, named after the Italian anatomist who described those and other intracellular structures in 1898, and later shared a Nobel prize with Spaniard Ramón y Cajal). The true complexity of the internal structure of cells, however, only became apparent in the 1950s, when cells were examined with the newly-invented electron microscope, which had much greater resolving power than the conventional light microscope — magnifying 20-30 000 times. It was around this time that the field now known as cell biology began to come to prominence, with the goal of understanding how the various organelles acted together to allow the cell to carry out its many functions. As well as simply observing cell structure, cell biologists now began to take cells apart and purify the different organelles using high-speed centrifugation. It was also shown that the purified organelles could be made to work in isolation, which allowed a detailed study of their functions, and the identification of the mechanisms underlying them.

Diagram of the components of a cell with central nucleus and the different organelles in the surrounding cytoplasm; in reality the organelles are very much smaller in relation to the size of the cell and very much more numerous. Inset: enlarged diagram of the cell membrane. The hydrophilic 'heads' of the molecules of the lipid bilayer form both surfaces of the membrane


Our current view of the cell is as an organism-in-miniature. The blueprint is contained in the DNA, packaged into chromosomes in the nucleus. Parts of the DNA sequence are replicated into ‘messenger’ RNA, which exits the nucleus and specifies the sequences of the cell's proteins, which are constructed in the cytoplasm. The power-houses of the cell are the mitochondria, which use nutrients taken up from outside to generate ATP, the energy currency of the cell. (Plant cells have additional organelles, the chloroplasts, which contain chlorophyll, the molecule responsible for capturing the energy of sunlight and initiating the process of photosynthesis. This results in the production of carbon-containing molecules for use by the cell and the generation of oxygen, which is essential for the continuation of life on earth.)

Many cells are responsible for secreting substances which will have external effects. In the pancreas, for instance, some cells secrete enzymes into the gut, where they digest our food, whereas other cells secrete insulin into the bloodstream, which instructs cells in the rest of the body to take up glucose. Both the digestive enzymes and the insulin are packaged into the endoplasmic reticulum and are then transported to the surface of the cell via the Golgi apparatus. Thus although each organelle is a discrete structure, there is extensive communication between organelles. This intracellular trafficking system demands that there be strict controls on the movement of proteins between organelles, and that individual proteins be ‘tagged’ for delivery to particular destinations. Without this control, the organization of the cell would quickly disintegrate.

A single higher organism contains a huge variety of cell types: compare, for example, a neuron with a lymphocyte, or a skeletal muscle cell with a liver cell (hepatocyte). All of these cells were produced from a single fertilized egg, by processes including cell division, migration, differentiation, and death. We are only just beginning to understand how these processes are orchestrated to produce the complete organism. One aspect that is crucial to the development and maintenance of multicellular organisms is communication between cells. Cells are continually signalling to their neighbours through the release of molecules that are detected by specialized receptors on the surface of other cells. In the brain, for example, neurons ‘talk’ to each other by means of small molecules. These molecules, or ‘neurotransmitters’, are packaged in small sacs within the neurons, and are released when an electrical impulse passes to the end of its axon. The neurotransmitter then binds to receptors on the neighbouring neurons and changes the electrical properties of these neurons, making them more or less likely to initiate an electrical impulse themselves. In other parts of the body, neurons communicate in similar fashion with muscle cells, causing them to contract, or with glandular cells, causing them to secrete. Many drugs work by blocking or mimicking the action of these neurotransmitters. Again, some cells release molecules which travel in the blood: messengers which communicate with remotely distant cells that have the appropriate receptors on their surface.

Once tissues and organs have been formed it is essential that cell division be strictly controlled in order to maintain normal function. Many proteins are now known which control cell division, often in response to external stimuli. Mutations in these proteins can result in uncontrolled cell division. This can lead eventually to the formation of tumours, which can be life threatening.

We are now familiar with the idea that cells are produced by the division of progenitor cells. This idea, of course, begs the question as to how the first cell was produced. It has been shown that simple organic molecules can form under conditions believed to be similar to those that existed on earth in its early history. How these molecules became assembled into proteins, and more particularly how the self-replicating ‘blueprint’ molecules such as DNA came about, are fundamental unanswered questions.

— Michael Edwardson

See also cell membranes; cell signalling.

n. a small group of individuals who work together for clandestine or subversive purposes.

See the Introduction, Abbreviations and Pronunciation for further details.

1. The basic unit of spatial information in any raster depiction of spatial entities.

2. see atmospheric cell.

1. See core.
2. A single small cavity surrounded partially or completely by walls.
3. A segment of a ribbed vault.
4. The small sleeping apartment of a monk or a prisoner.
5. In electrical systems, a single raceway of a cellular or underfloor duct system.
6. In electrical batteries, a single voltage-producing component used in series with other similar components to provide the desired output voltage.

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The structural and functional unit of living organisms. Typical cell components include a nucleus and cytoplasm enveloped by a cell surface membrane. The cytoplasm contains a number of membrane-bound organelles, including mitochondria, the sites of aerobic metabolism.

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A cell is a membrane-bound unit that contains hereditary material (DNA) and cytoplasm; it is the basic structural and functional unit of life.

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Single unit used to convert chemical energy into a DC electrical voltage.

(DOD) Small group of individuals who work together for clandestine or subversive purposes.

The basic structural unit of an organism.

A region of the atmosphere in which air tends to circulate without flowing outward.

cell

The basic unit of all living things except viruses. In advanced organisms, cells consist of a nucleus (which contains genetic material), cytoplasm, and organelles, all of which are surrounded by a cell membrane.

Groups of cells with similar structure and function form tissues.

The simplest part of the living structure. It is the cell that undergoes either mitotic (or replicative) division as in normal growth, or miotic or split division for sex base cells, ready to combine with other halves to provide a new cell, the basis of a new organism. The mystery of cell growth is to determine what makes a cell form certain organs while others form other structures. These pre-differentiated cells are called stem cells. When cells are cloned, differentiation does not occur easily, and a multi-cell mass called a callus is first developed. Recent strides in cloning techniques have gone a long way to solve these dilemmas.

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1. the basic structural unit of all living organisms; it typically comprises a small, usually microscopic, discrete mass of organelle-containing cytoplasm, bounded externally by a membrane. Each cell is capable of interacting with other cells and performing all the fundamental functions of life. In plants the cell usually also includes the cell wall. Originally the term referred to the bounding wall of a plant cell that had lost its living content. See also +cyte, cyto+.
2. a container for liquid during measurement or separation procedures, such as dialysis, electric conductivity measurement, electrolysis, microdiffusion, moving boundary electrophoresis, analytical ultracentrifugation, ultrafiltration, and (spectro)photometry; see also cuvette.
3. or electric cell a device for producing electric current by converting chemical energy into electric energy; it consists of two electrodes in contact with an electrolyte.
4. (in crystallography) see unit cell.

—cellular adj.

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1. the basic structural unit of living organisms.
2. a small more or less enclosed space.
All living cells arise from other cells, either by division of one cell to make two, as in mitosis and meiosis, or by fusion of two cells to make one, as in the union of the sperm and ovum to make the zygote in sexual reproduction.
All cells are bounded by a structure called the cell membrane or plasma membrane, which is a lipid bilayer composed of two layers of phospholipids. Each layer is one molecule thick with the charged, hydrophilic end of the lipid molecules on the surface of the membrane and the uncharged hydrophobic fatty acid tails in the interior of the membrane.
Cells are divided into two classes, eukaryotic cells and prokaryotic cells:
Eukaryotic cells have a true nucleus, which contains the genetic material, composed of the chromosomes, each of which is a long linear deoxyribonucleic acid (DNA) molecule associated with protein. The nucleus is bounded by a nuclear membrane, which is composed of two lipid bilayer membranes.
Prokaryotic cells, the bacteria, have no nucleus, and their genetic material, consisting of a single circular naked DNA molecule, is not separated from the rest of the cell by a nuclear membrane.
Eukaryotic cells are larger and more complex than prokaryotic cells. They also have membrane-bounded structures, such as mitochondria, chloroplasts, Golgi apparatus, endoplasmic reticulum and lysosomes, that prokaryotic cells lack.
The contents of a cell are referred to collectively as the protoplasm. In eukaryotic cells the contents of the nucleus are referred to as nucleoplasm and the rest of the protoplasm as the cytoplasm.
The lipid bilayer of eukaryotic cells is impermeable to many substances, such as ions, sugars and amino acids; however, membrane proteins selectively move specific substances through the cell membrane by active or passive transport. Water, gases such as oxygen and carbon dioxide, and nonpolar compounds pass through the cell membrane by diffusion. Materials can also be engulfed and taken into the cell enclosed in a portion of the cell membrane. This is called phagocytosis when solids are ingested and pinocytosis when liquids are ingested. The reverse process is called exocytosis. All of these processes permit the cell to maintain an internal environment different from its exterior. See also body fluids.
The cells of the body differentiate during development into many specialized types with specific tasks to perform. Cells are organized into tissues and tissues into organs. Embedded in the cell membrane are a wide range of molecules that vary with the cell type and are typically composed of proteins or glycoproteins that have a cytoplasmic transmembrane and external domains. These molecules serve as cell receptors and are involved in signal transduction for a wide range of ligands, including hormones, cytokines and incidentally serve as receptors for viruses and drugs.
See also betz cells, gaucher's cells, golgi's cells, hela cells, hürthle cell, kupffer's cells, merkel cell, mesangial cell, neuroendocrine cell.

Structure of the cell as seen by light microscopy. By permission from Guyton R, Hall JE, Textbook of Medical Physiology, Saunders, 2000

• accessory c's — macrophages involved in the processing and presentation of antigens making them immunogenic.
• acinar c., acinous c. — any of the cells lining an acinus, especially applied to the zymogen-secreting cells of the pancreatic acini.
• adherent c. — one that adheres to the glass or plastic container in cell cultures, to form the monolayer. See also cell culture.
• alpha c's — 1. cells in the islets of Langerhans that secrete glucagon.
— 2. acidophilic cells of the anterior pituitary.
• APUD c's — see apud cells.
• argentaffin c's — enterochromaffin cells containing cytoplasmic granules capable of reducing silver compounds, located throughout the gastrointestinal tract, chiefly in the basilar portions of the gastric glands and the crypts of Lieberkühn. They secrete serotonin.
• band c. — an immature neutrophil in which the nucleus is not lobulated but is in the form of a continuous band, horseshoe shaped, twisted or coiled. Called also band-form granulocyte and stab cell.
• basal c. — an early keratinocyte, present in the basal layer of the epidermis.
• basket c's — cells in the cerebellar cortex whose axons carry basket-like groups of fibrils which enclose the cell body of each Purkinje cell.
• beta c's — 1. basophilic cells in the pancreas that secrete insulin and make up most of the bulk of the islets of Langerhans; they contain granules that are soluble in alcohol.
— 2. basophilic cells of the anterior pituitary.
• blood c. — one of the formed elements of the blood. See also blood.
• c. body — the nucleus of the cell and the adjacent cytoplasm in cells which have processes, e g. neurons which consist of a cell body, an axon and dendrites.
• bone c. — a nucleated cell in the lacunae of bone. Called also osteocyte.
• cartilage c. — chondrocyte.
• chromaffin c's — cells whose cytoplasm shows fine brown granules when stained with potassium bichromate, occurring in the adrenal medulla and in scattered groups in various organs and throughout the body.
• cleavage c. — any of the cells derived from the fertilized ovum by mitosis; a blastomere.
• c. count — see erythrocyte, leukocyte, milk cell counts.
• c. culture — see cell culture.
• c. cycle — see cell cycle.
• daughter c. — a cell formed by division of a mother cell.
• c. dehydration — fluid loss from cells due to elevation of the osmotic pressure of blood and tissue fluid; a potent stimulus to thirst.
• dendritic c. — macrophage-like cells with long, filamentous processes located in the cortex of lymph nodes and the skin. Important in antigen trapping, processing and presentation. See also langerhans’ cell.
• c. differentiation — the process whereby cells become specialized usually with concurrent loss of reproductive capacity.
• embryonic stem c. — a stem cell of fetal origin. See stem cell (below).
• epithelioid c. — enlarged macrophages with enlarged lysosomes and much endoplasmic reticulum. May fuse to form multinucleated giant cell (below).
• epsilon c. — one of the groups of acidophilic cells in the adenohypophysis. Contains granules that stain with azocarmine dye.
• foam c. — a cell with a vacuolated appearance due to the presence of complex lipoids; seen in xanthoma.
• c. fusion — see syncytial giant cell.
• ganglion c. — a large nerve cell, especially one of those of the spinal ganglia.
• germ c. — see germ cell.
• giant c. — a very large, multinucleate cell; applied to megakaryocytes of bone marrow, to giant cells formed by coalescence and fusion of macrophages occurring in infectious granulomas and about foreign bodies, and to certain cancer cells.
• glial c's — neuroglial cells.
• goblet c. — a unicellular mucous gland found in the epithelium of various mucous membranes, especially that of the respiratory passages and intestines.
• granular c. — one containing granules, such as a keratinocyte in the stratum granulosum of the epidermis, when it contains a dense collection of darkly staining granules.
• gustatory c. — see taste bud.
• heart failure c's, heart lesion c's — iron-containing, rust-colored macrophages found in the pulmonary alveoli in congestive heart failure.
• helmet c. — schistocyte.
• helper c. — a subset of T lymphocytes which cooperate with B and other T lymphocytes for the synthesis of antibodies to many antigens; they play an integral role in immunoregulation.
• hybrid c. — a mononucleate cell produced from a binucleate heterokaryon after the latter undergoes mitosis. Such cells are initially unstable, tending to lose randomly some of the double complement of chromosomes. Used for mapping genes to particular chromosomes. See also heterokaryon, hybridoma.
• immunologically competent c. — see immunocyte.
• interstitial c's — the cells of the connective tissue of the ovary or of the testis (Leydig's cells) which furnish the internal secretion of those structures, i.e. testosterone.
• islet c's — cells composing the islets of Langerhans in the pancreas. See alpha cells, beta cells (above).
• juxtaglomerular c's — specialized cells, containing secretory granules, located in the tunica media of the afferent glomerular arterioles. They cause aldosterone production by secreting the enzyme renin and play a role in the regulation of blood pressure and fluid balance.
• K c's, killer c's — T lymphocytes or null lymphocytes that have cytotoxic activity against target cells coated with specific IgG antibody.
• lacis c. — accumulation of cells between the arterioles at the glomerular hilus. Called also granular cell.
• lacunar c. — precursor of the malignant interdigitating reticular cell in Hodgkin-like lymphoma in humans.
• LE c. — a mature neutrophilic polymorphonuclear leukocyte characteristic of lupus erythematosus. See also lupus erythematosus (le) cell.
• Leydig's c's — interstitial cells of the testis, which secrete testosterone.
• c. line — see cell culture.
• lutein c's — the plump, pale-staining, polyhedral cells of the corpus luteum.
• lymph c. — lymphocyte.
• lymphoid c's — lymphocytes and plasma cells.
• mast c. — a connective tissue cell that has basophilic, metachromatic cytoplasmic granules that contain histamine, heparin, hyaluronic acid, slow-reacting substance of anaphylaxis (SRS-A), and, in some species, serotonin. Have Fc receptors specific for IgE in the cell membrane.
• c.-mediated immune reaction — see cellular immunity.
• c. migration — movement of cells from their place of origin to other tissues; one of the fundamental processes of development.
• microglial c. — see microglia. See also neuroglia cells (below).
• milk c. count — see milk cell counts.
• mother c. — a cell that divides to form new, or daughter, cells.
• Mott c. — a plasma cell with large, clear cytoplasmic pockets.
• natural killer c's, NK c's — cells capable of mediating cytotoxic reactions without themselves being specifically sensitized against the target.
• nerve c. — any cell of the nervous system; a neuron.
• c. nests — see isogenous groups.
• neuroglia c's, neuroglial c's — see neuroglia.
• null c's — lymphocyte-like cells that lack specific antigen receptors and other surface markers characteristic of B and T lymphocytes; they include K and NK cells; their numbers are elevated in active systemic lupus erythematosus and other disease states.
• olfactory c's — a set of specialized cells of the mucous membrane of the nose; the receptors for smell.
• parafollicular c's — see c cell.
• Pick's c's — round, oval or polyhedral cells with foamy, lipid-containing cytoplasm found in the bone marrow and spleen in Niemann–Pick disease.
• plasma c. — a spherical or ellipsoidal cell with a single, eccentrically placed nucleus containing dense masses of chromatin in a wheel-spoke arrangement, an area of perinuclear clearing which contains the Golgi apparatus, and generally abundant cytoplasm. Plasma cells are produced by cell division of B lymphocytes following antigen stimulation and are involved in the synthesis and release of antibody. Called also plasmacyte and plasmocyte.
• prickle c. — a dividing keratinocyte of the prickle-cell layer of the epidermis, with delicate radiating process connecting with other similar cells.
• prokaryotic c. — see prokaryote.
• Purkinje's c's — large branching cells of the middle layer of the cerebellar cortex.
• red c., red blood c. — erythrocyte.
• Reed–Sternberg c's — giant histiocytic cells, typically multinucleate, which are the common histological characteristic of Hodgkin's disease in humans.
• reticular c's — the cells forming the reticular fibers of connective tissue; those forming the framework of lymph nodes, bone marrow and spleen. They are weakly phagocytic, stromal in origin and are distinct from the monocyte–macrophage system.
• reticuloendothelial c. — a cell of the reticuloendothelial system.
• Schwann c. — any of the large nucleated cells whose cell membrane spirally enwraps the axons of myelinated peripheral neurons supplying the myelin sheath between two nodes of Ranvier.
• Sertoli c's — elongated cells in the tubules of the testes to which the spermatids become attached; they provide support, protection and, apparently, nutrition until the spermatids are transformed into mature spermatozoa.
• sickle c. — a crescentic or sickle-shaped erythrocyte seen in some humans and deer. The abnormal shape caused by the presence of varying proportions of hemoglobin S.
• signet-ring c. — a cell in which the nucleus has been pressed to one side by an accumulation of intracytoplasmic mucin.
• somatic c's — the cells of the body other than the germ cells.
• c. sorting — see fluorescence-activated cell sorter.
• c. specialization — conversion of a simple cell type into a specialized cell type capable of a special function, e.g. a secretory cell; a major part of the growth of an embryo and the differentiation of basic mesenchymal tissue into specialized organs.
• spindle c. — spindle shaped cells of the dermis or subcutis; principal component of spindle cell tumors.
• spur c. — spiculed mature erythrocyte.
• squamous c's — flat, scalelike epithelial cells.
• stab c. — see band cell (above).
• stellate c. — any star-shaped cell, as a Kupffer cell or astrocyte, having many filaments extending in all directions.
• stem c. — 1. any precursor cell.
— 2. a primitive hematopoietic cell that is capable of self-replicating or differentiating into precursor cells of erythrocytes or any of the leukocytes.
• stipple c. — an erythrocyte containing granules that take a basic or bluish stain with Wright's stain.
• suppressor c's — a not well defined subset of T lymphocytes that are reported to inhibit antibody and cell-mediated immune responses. They may play a role in immunoregulation, and are believed to be abnormal in various autoimmune and other immunological disease states. See also T lymphocytes.
• target c. — 1. an abnormally thin erythrocyte showing, when stained, a dark center and a peripheral ring of hemoglobin, separated by a pale, unstained zone containing less hemoglobin; seen in various anemias and other disorders. Called also codocyte.
— 2. any cell selectively affected by a particular agent, such as a hormone or drug. — 3. cell containing nonself antigens in its cell membranes that is a target for nonimmune and immune cytolysis, e.g. virus-infected or tumor cell.
• taste c's — cells in the taste buds associated with the nerves of taste.
• c. therapy — see glandular therapy.
• totipotential c. — an embryonic cell that is capable of developing into any type of body cell.
• Türk's c. — a lymphocyte with increased basophilia.
• visual c's — the neuroepithelial elements of the retina.
• white c., white blood c. — leukocyte.

n

The basic unit of vital tissue. One of a large variety of microscopic protoplasmic masses that make up organized tissues. Each cell has a cell membrane, protoplasm, nucleus, and a variety of inclusion bodies. Each type of cell is a living unit with its own metabolic requirements, functions, permeability, ability to differentiate into other cells, reproducibility, and life expectancy.

For a list of words related to cell, see:

• Cell Structure and Function - cell: basic structural and functional unit of living organisms; smallest unit into which living thing can be divided and retain characteristics associated with life
• Tools, Tests, Units, and Scales - cell: system in which two electrodes are in contact with an electrolyte
• Electricity and Electronics - cell: housing for electrodes and electrolyte, used to generate electricity or in electrolysis
• Rooms - cell: small, single room for one person, esp. in prison or monastery
• Revolution and Antigovernment Activity - cell: smallest group within party organization, esp. Communist party
• Intrigues, Plots, and Corruption - cell: small group acting as a unit within larger organization, often in secret
• Prison and Punishment - cell: small room in which prisoner is held or lives

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See words rhyming with "cell."

  See crossword solutions for the clue Cell.

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Dansk (Danish)
n. - celle, deling, element
v. tr. - anbringe i celle
v. intr. - opbevare i celle

idioms:

• cell phone    mobiltelefon

Nederlands (Dutch)
cel

Français (French)
n. - cellule, (Biol, Bot) cellule, alvéole (ruche), (Élec, Chim) élément, (Pol) cellule
v. tr. - mettre/confiner dans une cellule, ranger dans une ruche
v. intr. - vivre en cellule

idioms:

• cell phone    radiotéléphone

Deutsch (German)
n. - (Biol. u.a.) Zelle, (Pol.) Zelle, Gruppe, (Elektr.) galvanische Voltzelle, (Phys.) elektrolytische Zelle
v. - in einer Zelle wohnen

idioms:

• cell phone    Handy

Ελληνική (Greek)
n. - κελί, (βιολ.) κύτταρο, (Η/Υ) κελί/κυψέλη λογιστικού φύλλου, (ηλεκτρ.) στοιχείο (συσσωρευτή), (μτφ.) ομάδα, κλίκα

idioms:

• cell phone    κινητό τηλέφωνο

Italiano (Italian)
cella, cellula

idioms:

• monk's cell    cella, cella di convento
• prison cell    cella, cella di prigione

Português (Portuguese)
n. - célula (f), cárcere (m)

idioms:

• monk's cell    retiro (m) de monge
• prison cell    cela (f) de prisão

Русский (Russian)
камера, клетка

idioms:

• monk's cell    келья
• prison cell    камера

Español (Spanish)
n. - celda, célula, célula fotoeléctrica
v. tr. - poner en celdas o células, enceldar
v. intr. - ponerse en celdas o células, enceldarse

idioms:

• cell phone    teléfono celular

Svenska (Swedish)
n. - cell (biol.), kloster-/fängelsecell, element (elektr.)

中文（简体）(Chinese (Simplified))
单元, 电池, 细胞, 贮...于巢室, 住牢房或小室

idioms:

• cell phone    便携式电话, 移动电话, 大哥大, 手机

中文（繁體）(Chinese (Traditional))
n. - 單元, 電池, 細胞
v. tr. - 貯...於巢室
v. intr. - 住牢房或小室

idioms:

• cell phone    攜帶型電話, 行動電話, 大哥大, 手機

한국어 (Korean)
n. - 작은 방, 세포, 전지, 독방
v. tr. - 독방 살이를 시키다, 작은 방에 넣다
v. intr. - 독방 살이를 하다, 작은 방에 들어 박히다

日本語 (Japanese)
n. - 独房, 個室, 電池, 細胞, 小室

idioms:

• monk's cell    修道士の小部屋
• padded cell    精神病患者室

العربيه (Arabic)
‏(الاسم) حجرة صغيرة, زنزانه, خليه‏

עברית (Hebrew)
n. - ‮תא, מנזר קטן המסונף למנזר גדול יותר‬
v. tr. - ‮כלא בתא, אחסן במבנה דמוי חלת-דבש‬
v. intr. - ‮התגורר בתא‬

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