cell (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
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.
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.
Alpha cell of the pancreas.
A monocyte or macrophage that participates in the immune response. See: antigen-presenting cell; macrophage
A cell present in the acinus of an acinous gland, e.g., of the pancreas.
adult stem cell
A precursor cell that can also give rise to identical precursor cells: daughters of a stem cell can develop into a terminally-differentiated cell type or they can remain a stem cell. Adult stem cells are found in many tissues, such as bone marrow, brain, retina, skin, intestines, liver, testis, and pancreas. Synonym: somatic stem cell See: embryonic stem cell
A macrophage along a blood vessel, together with perivascular undifferentiated cells associated with it.
An air-filled sinus cavity in a bone.
1. An enteroendocrine cell that produces glucagon and is found in the pancreatic islets. Synonym: A cell
2. An acidophil of the adenohypophysis (anterior pituitary gland).
1. In the lung, either of two types of epithelial cells lining the alveoli. Type I cells are simple thin squamous epithelial cells. Type II cells secrete pulmonary surfactant. Type II cells are smaller and more numerous than Type I cells.
2. In the mammary glands, the milk-secreting epithelial cells, which are activated during lactation.
A modified nerve cell in the retina that has dendrites but no axon. See: neuron
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
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.
A cell in the epithelium of the stomach, intestines, and appendix that secretes serotonin.
atypical glandular cells Abbreviation: AGC
An abnormal finding on a Pap test. This classification is divided into “favor neoplasia” or “not otherwise specified (NOS).” NOS is subdivided into endocervical or endometrial origin. Atypical endocervical cells are important because of their risk for significant disease. Synonym: atypical glandular cells of undetermined significance
atypical glandular cells of undetermined significance Abbreviation: AGUS
Atypical glandular cells.
A lymphocyte that synthesizes and secretes antibodies. B lymphocytes originate and differentiate in the bone marrow and then populate the spleen, lymph nodes, and other lymphoid tissues. When exposed to an antigen, a B cell divides to form (a) plasma cells, which produce antigen-specific antibodies, and (b) a lesser number of memory B cells, which can quickly differentiate into plasma cells upon a second exposure to the original antigen. Antibody production is a key part of the humoral immune response of adaptive immunity. The humoral immune response is effective against bacteria, viruses, and other pathogens, and provides the rationale for vaccination. Synonym: B lymphocyte
See: ; T cell
2. Pancreatic beta cell.
The developing leukocyte at a stage at which the nucleus is not segmented.
1. A rounded or cuboidal epithelial stem cell found in the bottom layer of pseudostratified epithelia, such as the epidermis and the lining of the airways of the lung.
2. Either of two types of cell found in the bottom layer of the olfactory epithelium; one type is a flattened "basal cell proper", and the other is a rounded stem cell called a globose cell.
3. A rounded stem cell found in the taste buds and a progenitor of the specialized taste receptor cells.
1. Myoepithelial cell.
2. One of the nonspiny granule cells found in the cerebral cortex.
3. One of the small interneurons found in the outermost layer of the cerebellar cortex along with stellate cells.
1. Any of the insulin-secreting cells of the pancreas that constitute the bulk of the islets of Langerhans. Synonym: B cell
2. A basophil cell of the adenohypophysis (anterior pituitary gland).
Betz cell See: Betz cells
1. A precursor cell for a specific cell type.
2. An immature cell of a specific type.
Any cell normally found circulating in the blood stream. Blood cells include red cells and white cells; red cells generally remain inside blood vessels, while white cells can also more into the tissues outside the blood vessel walls. See: blood for illus.
An osteoblast, osteoclast, or osteocyte.
bone marrow cell
An epithelial cell found sparsely in the lining of the bronchial tree. The cell's surface has long stiff microvilli, and the cell has the appearance of an absorptive cell.
An erythrocyte with 10 to 30 spicules distributed over the surface of the cell, as seen in heart disease, stomach cancer, kidney disease, and dehydration. Synonym: echinocyte
A cell present in a neoplasm and differentiated from normal tissue cells because of its degree of anaplasia, irregularity of shape, nuclear size, changes in the structure of the nucleus and cytoplasm, increased number of mitoses, and ability to metastasize.
capsule cellSatellite cell.
An enlarged and vacuolated basophil cell seen in the pituitary in gonadal insufficiency or following castration.
Helper T cell.
A suppressor T cell, e.g., a cytotoxic T cell.
CD 34+ cell
A cell with the CD34 protein on its surface membrane. Some CD34 cells that are hemopoietic stem cells can be separated out from peripheral blood.
Any of the cells trapped within cementum that maintain cementum as a living calcified tissue by their metabolic activity.
A duct cell of the pancreas more or less invaginated into the lumen of an acinus.
chalice cellGoblet cell.
1. Any of the cells of the parathyroid gland that secretes the parathyroid hormone.
2. Any of the cells of the gastric glands that secretes pepsinogen.
A cell that produces, stores, and secretes catecholamines (dopamine and norepinephrine). Chromaffin cells are found in the medulla of the adrenal glands and in small clusters in the sympathetic ganglia.
A cuboidal epithelial cell found in the lining of the terminal and the respiratory bronchioles of the lungs. Clara cells are nonciliated, and they secrete surfactant, like the type II alveolar epithelial cells found deeper in the bronchial tree.
A vaginal epithelial cell, thickly coated with coccobacillary organisms. Clue cells are a hallmark of bacterial vaginosis.
An epithelial cell with height greater than its width.
columnar epithelial cell
A cell in the retina whose scleral end forms a cone that serves as a light receptor. Vision in bright light, color vision, and acute vision depend on the function of the cones. See: rod cell
A T cell that inhibits the activity of suppressor T cells. Although a contrasuppressor cell shares this functional capability with T helper cells, it is distinguished from other CD4+ cells by its other cell surface markers and the unique group of cytokines it produces.
A cell in the cortex of an organ, e.g., a neuron in the cerebral cortex.
A cell – usually epithelial – with a height about equal to its width and depth.
Cytotoxic T cell.
cytotoxic T cell
A CD8+ T lymphocyte that can destroy microorganisms directly through the release of perforin and proteolytic enzymes. These cells are particularly important in the defense against viruses, rejection of allografts, and, possibly, new malignant cells. Synonym: CD8 cell; cytotoxic cel; killer T cell
An enteroendocrine cell that produces somatostatin and is found in the pancreatic islets, stomach, and small intestine. Synonym: delta cell; somatostatin cell
A cell formed by cell division.
A cell found in the urine with inclusion bodies in its nucleus. It indicates infection with BK virus in renal transplant recipients.
Pancreatic D cell.
One type of antigen-presenting cell that helps T cells respond to foreign antigens. Dendritic cells are found in epithelial tissues and include the Langerhans' cells of the skin and the interdigitating cells in lymph nodes; they also circulate in the blood.
Downey cell See: Downey 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.
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.
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. See: leukocyte
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
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'.
One of the scattered hormone-producing cells found in the pancreatic islets and throughout the gastrointestinal (mainly, small intestinal) mucosa.
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.
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
ethmoid air cell
The type of cell composing multicellular, as well as a number of unicellular, organisms. Unlike prokaryotic cells, eukaryotic cells have many of their intracellular functions organized within structures called organelles. Some organelles -- notably, the nucleus, which contains the DNA -- are enclosed by intracellular membranes.
An enteroendocrine cell that produces pancreatic polypeptide and is found in the pancreatic islets.
A bone marrow cell with a bright red cytoplasm, occasionally found in the marrow of patients with multiple myeloma.
An optical cell used in photometers and cell counters, through which the sample and any standards are passed for detection and measured or counted by optical or electrometric means. See: cytometry
A cell that contains vacuoles; a lipid-filled macrophage.
1. The secretory cell of the thyroid gland; it produces the thyroid hormones, T3 (triiodothyronine) and T4 (tetraiodothyronine or thyroxine).
2. Any of the flattened somatic cells that form a monolayer around each primary oocyte in the ovary. After puberty, when an oocyte matures, during a monthly cycle, its follicular cells divide, become cuboidal, and form a multilayered coating for the oocyte; at this stage, the follicular cells are called granulosa cells.
A supporting cell in the adenohypophysis (anterior pituitary gland); it produces bioactive peptides, including growth factors and cytokines.
foreign body giant cell
An enteroendocrine cell found in the stomach that produces the hormone gastrin.
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.
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
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
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.
One of three types of nonneuronal cell in the central nervous system: astrocytes, oligodendrocytes, and microglial cells. SYN neuroglial cell Synonym: neuroglial cell
A macrophage present at sites of brain injury. The cells are packed with lipoid granules from phagocytosis of damaged brain cells. See: microglia
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.
A mucous cell sitting between nonsecretory cells, such as is found in the intestinal epithelium.
Golgi cell See: Golgi, Camillo
graft facilitating cell
Any of a group of CD8 positive, t-cell receptor negative cells that help donated bone marrow engraft in the recipient.
1. Any of the small neurons that pack the granular cell layer of the cerebellar cortex, immediately below the Purkinje cell layer. Granule cells receive inputs (mossy fibers) from the spinal cord and brainstem (except the inferior olive). Axons of granule cells run perpendicular to the Purkinje cell dendrites, on which they synapse.
2. Any of the neurons of the cerebral cortex that are not pyramidal cells. Cortical granule cells are categorized as spiny or nonspiny. Synonym: stellate cell
3. A small axon-less neuron found in the olfactory bulb.
One of the many cuboidal cells that surround and nurture the maturing oocyte. See: follicular cell (2)
An epithelial cell possessing stereocilia in the maculae, cristae ampullaris, and the organ of Corti. These cells are receptors for the senses of position and hearing.
heart failure cell
A red-colored (from ingested red cells) lung macrophage often found in the sputum of patients with congestive heart failure.
A line of human epithelial cells that grows well in culture. It is an immortal cancer cell that has been maintained in continuous tissue cultures for decades from a patient with carcinoma of the cervix. It is named for the first two letters of the patient's first and last names, Henrietta Lacks. HeLa cells have been used in thousands of experiments on cell growth, differentiation, and cancer, and in virology, pharmacology, and other fields.
HELMET CELLS: (Orig. mag. ×640)
A schistocyte or fragmented blood cell, seen in hemolytic anemias. See: illustration
A type of T lymphocyte whose surface is marked by CD4 receptors; it is involved in both cell-mediated and antibody-mediated immune responses. It secretes cytokines that stimulate the activity of B cells and other T cells and binds with class II histocompatibility antigens, which are processed by macrophages and other antigen-presenting cells. Synonym: helper T cell See: antigen processing
; T cell
; cell-mediated immunity
helper T cell
hematopoietic stem cell
A progenitor cell in the bone marrow that can replicate itself as well as produce precursor cells of the various blood cell lineages.
An androgen-producing cell found in the ovarian hilum. It is analogous to the male Leydig cell.
holly leaf cell
A cell found in blood smears of persons with sickle cell anemia.
A neuron of the inner nuclear layer of the retina. The axons of these cells run horizontally and connect various parts of the retina.
Hürthle cell See: Hürthle cell
hybridoma cell See: hybridoma
A cell that contains more than the normal number of chromosomes and hence stains more densely.
An enteroendocrine cell that produces the enzyme cholecystokinin-pancreozymin (pancreaticozymin) and is found in the small intestine.
A type of antigen-presenting cell found in lymph nodes and lymphoid tissue.
Any of the many cells found in connective tissue of the ovary, in the seminiferous tubules of the testes, and in the medulla and cortex of the kidney. The cells in the testes and ovaries produce hormones such as testosterone and estrogen.
intestinal absorptive cell
In the small intestine, any of the tall columnar cells topped with a brush border made of thousands of microvilli.
A cell of the islets of Langerhans of the pancreas.
The early developmental form of a leukocyte.
A modified smooth muscle cell in the wall of the afferent arteriole leading to a glomerulus of the kidney. This type of cell secretes renin when blood pressure decreases to activate the renin-angiotensin mechanism, which increases sodium retention, thus elevating the blood pressure.
An enteroendocrine cell that produces gastric inhibitory peptide (glucose-dependent insulinotropic peptide) and is found in the small intestine. This peptide stimulates the beta cells of the pancreas to secrete insulin.
Natural killer cell.
killer T cellCytotoxic T cell.
An APUD cell found in the lung.
Kupffer cell See: Kupffer cell
An enteroendocrine cell that produces glucagon-like peptide-1 and is found in the small intestine. This peptide signals the pancreas to secrete insulin after a meal.
A cell that is always mitotically active, such as the epithelial cells lining the stomach and the stem cells in the red bone marrow.
Abbreviation for lymphokine-activated killer cell. These natural killer cells, obtained from the patient's blood, have been activated in culture with interleukin-2.LAK cells; the cells can then be used to treat patients with solid malignant tumors.
A type of dendritic antigen-presenting cell that typically resides in the skin.
L.E. CELL (center): (Orig. mag. ×1000)
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.
Leydig cell See: Leydig's cell
A macrophage found in the sinuses of lymphatic tissue.
A cell of the corpus luteum of the ovary that contains fatty yellowish granules. Granulose lutein cells are hypertrophied follicle cells; these lutein (paralutein) cells develop from the theca interna.
An obsolete term for lymphocyte.
lymphokine-activated killer cell
1. A microfold cell, which is a cell in the gastrointestinal epithelium covering patches of lymphoid tissue. M cells transport antigens from the intestinal lumen to the underlying lymphoid tissues for recognition and processing.
2. An APUD cell that produces melanotropin and is found in the pituitary gland.
An astrocyte or an oligodendrocyte.
Bone marrow cell.
A large tissue cell resembling a basophil, which is essential for inflammatory reactions mediated by immunoglobulin E (IgE) but does not circulate in the blood. Mast cells are present throughout the body in connective tissue, but are concentrated beneath the skin and the mucous membranes of the respiratory and digestive tracts. Mast cells are covered with IgE molecules, which bind with foreign antigens and stimulate degranulation, releasing such mediators as histamine, prostaglandins, leukotrienes, and proteinases from densely packed granules within the cytoplasm. These mediators produce type I (immediate) hypersensitivity reactions (e.g., urticaria, allergic rhinitis, asthma, angioedema, and systemic anaphylaxis). See: illustration
Mastoid air cell.
mastoid air cell
Any of the variable-sized, air-filled sinuses inside the mastoid antrum. About 20% of adult skulls have no mastoid air cells.
matrix stem cell
A stem cell derived from Wharton's jelly.
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.
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.
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
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.
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.
An astrocyte or other glial cell with many branching processes. See: neuroglia
A cell that gives rise to similar cells through fission or budding. Synonym: parent cell
Any cell in a mucosal epithelium.
An epithelial cell that secretes mucus and IgA antibodies. Mucous cells and serous cells are the two varieties of secretory cells found in exocrine glands. Synonym: mucus cell
multinucleated giant cell
muscle cell See: muscle
Any white blood cell other than lymphocytes.
A cell present in the bone marrow of patients with multiple myeloma.
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
neural crest cell
Embryonic cells of the neuron-glia lineage that form along the ridges (neural folds) of the neural plate and that migrate into the developing organism to produce a variety of tissues. The migratory ability of these embryonic epithelial cells is similar to the motility of mesenchyme cells; this has led neural crest cells to be called mesectodermal cells. In the neural lineage, neural crest cells give rise to the dorsal root ganglia, the placodes that will develop into the olfactory and auditory sensory organs, the pituitary gland, the peripheral autonomic nervous system, and the neurenteric and APUD cells. In the glial lineage, neural crest cells give rise to Schwann cells and other peripheral satellite cells. In addition, neural crest cells of the cranial region give rise to certain facial connective tissue, including the bones of the nasal cavities, the roof of the mouth, and the sella turcica.
Niemann-Pick cell See: Niemann-Pick cell
Natural killer cell.
Any cell found in the bone marrow that cannot reconstitute the marrow or give rise to more differentiated blood cells.
A large lymphocyte without the cell markers of either a T cell or a B cell. Natural killer cells are examples of null cells.
Olfactory receptor cell.
olfactory receptor cell
A cell of the olfactory mucosa that has receptors for the sense of smell. Olfactory cells are continuously replaced from stem cells throughout adult life. Synonym: olfactory cell
Any of the mesenchyme precursor cells committed to the bone lineage and capable of producing osteoblasts and osteocytes. Osteoprogenitor cells are found in bone, bone marrow, and other connective tissue.
A parietal cell of the gastric glands; it produces hydrochloric acid and the intrinsic factor.
An abnormal but not malignant cell seen in some cytologic specimens obtained during Papanicolaou tests (Pap tests). It is found in women with vaginal atrophy, in some postpartum women, some women suffering from anorexia or starvation, and some who have used progesterone for contraception.
parent cellMother cell.
One of the cells supporting the hair cells of the organ of Corti. These cells form several rows of outer phalangeal cells (Deiters' cells) and a single row of inner phalangeal cells.
phantom cell See: red cell ghost
Any cell that normally contains pigment granules.
A cell derived from a B lymphocyte that has been sensitized to a specific foreign antigen and produces antibodies to that particular antigen. It may be found in the blood or in tissue fluid. Synonym: plasmacyte
An enteroendocrine endocrine cell found in the pancreatic islets that produces pancreatic polypeptide.
The immediate precursor of a lymphocytic B cell.
A cell with spiny processes that connect with similar processes of adjoining cells. These are found in the stratum spinosum of the keratinized epithelium of the epidermis.
In physical therapy, a device consisting of a container, two solid conducting elements, and an electrolyte for the production of electric current by chemical energy.
Primordial germ cell.
primordial germ cell
A germ cell before it begins its maturation into a haploid gamete. Synonym: primordial cell
progenitor cellA cell (sometimes a stem cell) that produces cells of a particular lineage, e.g., a neuroblast.
The form of cell composing many primitive unicellular organisms, such as bacteria. Prokaryotic cells do not have nuclei, which are partitioned by an intracellular membrane; instead the DNA forms one main coil in the cell cytoplasm.
Purkinje cell See: Purkinje, Johannes E. von
A leukocyte present in pus. Pus cells are often degenerated or necrotic.
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.
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 Abbreviation: RBC
Renshaw cell See: Renshaw cell
2. A cell not performing its normal function (i.e., a nerve cell that is not conducting an impulse or a muscle cell that is not contracting).
1. An undifferentiated cell of the spleen, bone marrow, or lymphatic tissue that can develop into one of several types of connective tissue cells or into a macrophage.
An out-of-date term for a cell of the mononuclear phagocytic system.
Rieder cell See: Rieder cell
A cell in the retina of the eye whose scleral end is long and narrow, forming a rod-shaped sensory receptor. Rods are stimulated by light and are essential for vision in dim light. See: cone cell
A rose-shaped cluster of phagocytes surrounding lysed nuclear material or red blood cells. Rosette cells occur frequently in blood in which L.E. cells are present. Rosette cells are not diagnostic of lupus erythematosus. See: L.E. cell
Rouget cell See: Rouget cell
An enteroendocrine cell that produces secretin and is found in the small intestine.
1. A stem cell associated with skeletal muscle that may form a limited number of new muscle cells after injury.
2. One of the neuroglia cells enclosing the cell bodies of sensory neurons in spinal ganglia. Synonym: capsule cell
A phagocyte that cleans up disintegrating tissues or cells.
Schwann cell See: Schwann 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
A cell that when stimulated gives rise to nerve impulses that are conveyed to the central nervous system.
A type II alveolar cell that secretes pulmonary surfactant; it is adjacent to a septum of the alveoli.
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: Sertoli cell
SICKLED CELLS IN SICKLE CELL DISEASE
A vacuolated cell with the nucleus off center. Mucus-secreting adenocarcinomas usually contain these cells.
skeletal muscle cell See: muscle
smooth muscle cell See: muscle
Any cell that is not a germ cell.
somatic stem cell
Adult stem cell.
spiculed red cell
Crenated red blood cells with surface projections. In most instances, this is a normal variation in red cell equilibrium and is reversible. See: acanthocyte
A flat epithelial cell. Synonym: squamous epithelial cell
squamous epithelial cell
1. Granule cell of the cerebral cortex.
2. One of the small interneurons found in the outer layer of the cerebellar cortex along with basket cells.
stellate reticuloendothelial cell
A Kupffer cell, one of the macrophages that line the sinusoids of the liver.
An embryonic stem cell or an adult stem cell.
Sternberg-Reed cell See: Reed-Sternberg 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.
A supporting cell, as in the acoustic macula, organ of Corti, olfactory epithelium, taste buds, or testes.
One of the large epithelial cells that occur in groups in the hilus of the ovary. They are thought to be chromaffin cells.
A chromaffin cell of ectodermal origin present in the fetal adrenal gland. Sympathetic and medullary cells originate from these cells.
syncytial giant cell
A lymphocyte that responds to specific antigens, with the assistance of antigen-presenting cells (APCs). T cells arise in the bone marrow and migrate to the thymus gland, where they mature; then they circulate between blood and lymph, serving as one of the primary cells of the adaptive immune response. Immature T cells are called thymocytes. Mature T cells are antigen specific. Their surface receptors (T cell receptors, abbrev. TCRs) respond only to a single antigen. T cells are further categorized using another family of surface protein markers called clusters of differentiation (CDs). All T cells have a CD3 marker. Additional markers differentiate the subclasses of T cells. CD4 T helper cells serve primarily as regulators, secreting cytokines that stimulate the activities of other white blood cells. CD8 T cells (cytotoxic T cells) directly lyse (kill) organisms, an important defense against viruses; most CD8 T cells also produce gamma interferon (INF?), one of the strongest stimulators of macrophage activity. Synonym: T lymphocyte
See: immune response
; immunological surveillance
; T-cell receptor
A T cell can only recognize the "foreignness" of antigens after they have been modified by macrophages and other antigen-presenting cells (APCs). After this, T cells dominate the adaptive immune response by mobilizing B cells and other T cells of the cell-mediated immune pathways. T cells are responsible for type IV hypersensitivity reactions, such as graft rejection, and for tumor cell recognition and destruction.
; cell-mediated immunity
TARGET CELLS: In hemoglobin C disease (×600)
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
2. . The cell at which a signal (e.g., hormone or nerve impulse) is aimed.illustration
A phagocyte that has ingested the unaltered nuclei of cells. These nuclei can be observed unchanged within the phagocytes.
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
taste receptor celltaste cell.
An abnormally shaped blood cell, sometimes found on blood smears of patients with bone marrow fibrosis, iron deficiency, or thalassemias. Synonym: dacrocyte
Any of the fibroblasts of white fibrous connective tissue of tendons arranged in parallel rows.
terminally differentiated cell
A cell sufficiently committed to a particular function that it can no longer divide, e.g. a red cell.
thymic epithelial cell
The epithelial cells that form the internal scaffolding of the thymus. These cells vary in shape and size but generally align in sheets and cords, partitioning the thymus into islands of close-packed lymphocytes in the organ's cortex. Thymic epithelial cells are not simply structural and they interact actively with adjacent lymphocytes.
Any cell characteristic of the thymus, including thymic epithelial cells and thymocytes (thymic lymphocytes).
Any cell characteristic of the thyroid gland, but usually referring to a thyroid follicular cell.
An undifferentiated embryonic cell that has the potential to develop into any type of cell.
Touton giant cell See: Touton cell
The stretchable epithelial cells that compose the transitional epithelium (uroepithelium), which lines most of the urinary tract. Transitional cells are strongly interconnected. They are cuboidal when not under pressure, and they become flattened and squamous when stretched. Transitional epithelia are 4-6 cells thick, and the top transitional cells -- those on the lumenal surface -- fuse to become larger and polyploid.
One of the epithelial cells forming the surface of the spherical blastocyst stage embryo. Trophoblast cells are destined to give rise to many of the extraembryonic tissues.
tufted See: mitral cell
Türk irritation cell See: Türk irritation cell
Tzanck cell See: Tzanck cell
A cell resembling an embryonic cell in that it does not have the specific morphologic or functional characteristics of any particular adult cell type.
A cell with a single cell process.
A lineage of cells used in cell cultures and isolated from kidney epithelial cells of the African green monkey (Cercopithecus aethiops).
A rod cell or cone cell of the retina.
A rarely used term for a cell (such as a macrophage) that moves like an ameba.
white blood cell Abbreviation: WBC
muscle (mus'el ) [L. musculus, diminutive of mus, mouse]
MORPHOLOGICAL FORMS OF MUSCLE
MORPHOLOGICAL FORMS OF MUSCLE
MORPHOLOGICAL FORMS OF MUSCLE
MORPHOLOGICAL FORMS OF MUSCLE
MORPHOLOGICAL FORMS OF MUSCLE
MORPHOLOGICAL FORMS OF MUSCLE
A type of tissue composed of contractile cells. Each muscle cell is filled with parallel actin and myosin filaments. When activated by an internal release of calcium, the filaments use the energy in ATP to crawl along each other in opposite directions. This movement shortens the length of the cell, which then contracts.
The three general classes of muscle cells (myocytes) are skeletal (striated), cardiac (striated), and smooth; most of the muscle in humans is skeletal. A typical muscle has a central portion called the belly and two or more attachment ends with tendons; the more stationary of the attachments is called the muscle's origin, while the more movable attachment is called the muscle's insertion. See: illustration
MUSCLES OF THE TRUNK
The abdominal muscles are made up of the cremaster, external abdominal oblique, iliacus, psoas major, pyramidalis, quadratus lumborum, rectus abdominis, and transversus abdominis muscles.illustration
abducens muscle, abducens oculi
Lateral rectus muscle, one of the extraocular muscles. Nerve: cranial nerve (CN VI). In clinical practice, referred to as the lateral rectus muscle.
A muscle that on contraction draws a part away from the median plane of the body or the axial line of an extremity. See: adductor muscle
abductor digiti minimi muscle
Hand muscle. Origin: pisiform bone of wrist. Insertion: base of proximal phalanx of digit 5. Nerve: ulnar (C8-T1). Action: abducts digit 5.
abductor pollicis brevis muscle
Hand muscle. Origin: flexor retinaculum of wrist, scaphoid and trapezium bones. Insertion: lateral base of proximal phalanx of thumb. Nerve: median (C8-T1). Action: abducts thumb, aides in opposition with digit 5. See: armfor illus. (Muscles of the Arm)
A muscle that draws toward the midline. See: abductor muscle
adductor brevis muscle
A muscle of the medial thigh originating on the ramus of the pubis and inserted in the linea aspera of the femur. It adducts, flexes, and medially rotates the thigh and is controlled by the obturator nerve.
adductor longus muscle
Hip and thigh muscle. Origin: front of pubis (below crest). Insertion: linea aspera of femur. Nerve: obturator (L2-L4). Action: adducts, flexes, and rotates thigh medially. See: leg for illus. (Muscles of the leg)
adductor magnus muscle
Hip and thigh muscle. Origin: inferior ramus of pubis, ramus of ischium, ischial tuberosity. Insertion: linea aspera and adductor tubercle of femur. Nerve: obturator and sciatic (L2-L4). Action: adducts, flexes, and rotates thigh medially. See: leg for illus. (Muscles of the leg)
adductor pollicis muscle
Hand muscle. Origin: capitate bone of wrist and metacarpals 2-3. Insertion: proximal phalanx of thumb and medial sesamoid bone. Nerve: ulnar (C8-T1. Action: adducts thumb, aides in opposition with digit 5.
Controlled movements involve two opposing muscles: the agonist muscle produces the main action, while the antagonist muscle produces the opposite action to a lesser degree. The balance between agonist and antagonist muscles allows precise control of the final action. Synonym: antagonist muscle See: PNF Stretching Techniques
A short muscle along the back of and outside the elbow. It originates from the lateral epicondyle of the humerus, crosses the back of the elbow joint on the same side, attaches to the lateral surface of the olecranon process and the adjacent surface of the ulna. It extends the forearm and abducts the elbow as the forearm pronates. It is innervated by the radial nerve (C7, C8, T1).
antagonist muscleAgonist muscle.
Muscles that pull against gravity to maintain normal posture. Synonym: postural muscles
One of the skeletal muscles of the limbs.
arrector pili muscleArrector pili.
Arm: biceps brachii, brachialis, coracobrachialis, and triceps muscles. Forearm, anterior: flexor carpi radialis, flexor carpi ulnaris, flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus, and pronator quadratus muscles. Forearm, posterior: abductor pollicis longus, anconeus, brachioradialis, extensor carpi radialis brevis, extensor carpi radialis longus, extensor carpi ulnaris, extensor digitorum, extensor digitorum minimi, extensor indicis, extensor pollicis brevis, extensor pollicis longus, and supinator muscles. See: arm for illus. (Muscles of the Arm)
A muscle attached to the capsule of a joint.
The oblique or the transverse arytenoid -- laryngeal muscles. Origins: arytenoid cartilage. Insertions: contralateral arytenoid cartilage. Nerve: recurrent laryngeal and superior laryngeal of the vagus (CN X). Action: closes laryngeal inlet by bringing arytenoid cartilages toward each other.
The tensor tympani and stapedius muscles.
A skeletal muscle that moves or stabilizes the head or the trunk.
Superficial: latissimus dorsi and trapezius muscles. Middle layer: levator scapulae, rhomboid major, and rhomboid minor muscles. Deep layer: erector spinae and splenius. Deepest layer: interspinalis, intertransverse, multifidus, rotatores, semispinalis, and spinalis capitis.
biceps brachii muscle
Arm muscle. Origin: supraglenoid tubercle, coracoid process of scapula. Insertion: tuberosity of radius, posterior border of ulna (via bicipital aponeurosis). Nerve: musculocutaneous (C5-C6). Action: flexes forearm, supinates hand. See: arm for illus. (Muscles of the Arm)
biceps femoris muscle
Leg muscle. Origin: ischial tuberosity, linea aspera and second supracondylar ridge of femur. Insertion: lateral condyle of tibia, head of fibula. Nerve: sciatic (L5-S2). Action: flexes leg, rotates leg laterally, extends thigh. See: leg for illus. (Muscles of the leg)
A muscle in which the fibers converge from both sides to a central tendon.illustration
Arm muscle. Origin: anterior surface of lower (distal) humerus. Insertion: coronoid process of ulna. Nerve: musculocutaneous and radial (C5-C7). Action: flexes forearm. See: arm for illus. (Muscles of the Arm)
Arm muscle. Origin: lateral supracondylar ridge of distal humerus. Insertion: distal end of radius. Nerve: radial (C5-C7). Action: flexes forearm. See: arm for illus. (Muscles of the Arm)
Facial muscle. Origin: pterygomandibular raphe and alveolar processes of jaws. Insertion: orbicularis oris muscle at angle of mouth. Nerve: facial (CN VII). Action: compresses check against teeth, retracts angle of mouth.
A tissue composed of mitochondrion-filled muscle cells that also contain neatly packed actin and myosin filaments; the filaments are arranged in cylindrical bundles called myofibrils. In each cell, the myofibrils are all aligned in the same direction and are parceled into longitudinal blocks (called sarcomeres) of similar lengths. Under the microscope, the ends of the blocks appear as lines, making cardiac muscle cells appear to have regularly arranged striations. In the muscle tissue, the cardiac muscle cells are connected in branching networks.
Cardiac muscle is innervated by both sympathetic and parasympathetic autonomic motor axons. In addition, cardiac muscle: is stimulated by blood—borne molecules, can conduct electrical impulses from cell to cell, and can independently generate rhythmical contractions. Cardiac muscle, which is found only in the heart, cannot be controlled consciously.
chest wall muscle
Pectoralis major, pectoralis minor, serratus anterior, subclavius, subscapularis, or teres major muscle.
chewing muscleMastication muscle.
Internal eye muscle. Origin: edges of sclera. Insertion: ciliary process of lens. Nerve: oculomotor (CN III). Action: allows lens to become more curved to focus on near objects.
constrictor muscle of pharynx
A muscle that constricts the pharynx; it is important for swallowing.
One of the major muscles that stabilizes and controls the pressure inside the trunk; these are the pelvic floor, abdominal wall, back, and diaphragm muscles.
Facial muscle. Origin: medial part of supraorbital margin. Insertion: skin above middle of eyebrow. Nerve: facial (CN VII). Action: pulls eyebrows toward midline and downward. Synonym: Corrugator supercilii
Spermatic cord muscle. Origin: inguinal ligament and pubic tubercle. Insertion: cremasteric fascia covering spermatic cord. Nerve: genitofemoral (L1-L2). Action: elevates testis in males. See: penis for illus.
The lateral or the posterior cricoarytenoid -- laryngeal muscles. Origin: cricoid cartilage. Insertion: muscular process of arytenoid cartilage. Nerve: recurrent laryngeal of the vagus (CN X). Action: rotates arytenoid cartilages for vocalizations.
Laryngeal muscle. Origin: cricoid cartilage. Insertion: lower edges of thyroid cartilage. Nerve: superior laryngeal of the vagus (CN X). Action: tenses (stretches) vocal cords See: thyroidfor illus.
deep neck muscle
One of the various neck muscles that surround the vertebral column and base of the skull and which are contained in the prevertebral cylinder of deep cervical fascia. All these muscles are innervated by cervical spinal nerves, and most of these muscles act primarily to move and stabilize the head.
Shoulder muscle. Origin: a bony ellipse from the lateral third of the clavicle over the acromial process and along the spine of the scapula. Insertion: deltoid tuberosity on the lateral shaft of the humerus. Nerve: axillary (C5-C6). Action: abducts arm. See: arm for illus. (Muscles of the Arm)
The three-layered muscular wall of the urinary bladder. Nerve: primarily parasympathetic (S2-S4), secondarily sympathetic (T11-L2). Action: empties bladder.
Origin: internal surfaces of lower six ribs, xiphoid process, vertebral bodies L1-L3. Insertion: central tendon (of diaphragm). Nerve: phrenic, lower six intercostals. Action: inflates lungs
Neck muscle with two bellies. Origin: anterior belly attaches to the digastric fossa in mandible at base of anterior midline, posterior belly attaches to mastoid process. Insertion: tendon connecting both bellies in a loop of fascia that is attached to hyoid bone. Nerve: anterior belly -- trigeminal (CN V), posterior belly -- facial (CN VII). Action: lowers mandible and raises hyoid bone. See: neck for illus.
erector spinae muscle
Three adjacent vertical bands of deep back muscles -- the iliocostalis, longissimus, and spinalis muscles. Origins: a wide tendon running along the iliac crest to the sacrum, the lower lumbar and sacral spinous processes. Insertions: along the back in the angles of the lower ribs, transverse processes of the thoracic and cervical vertebrae. Nerves: dorsal rami of the spinal nerves. Actions: extends (bends backward) the vertebral column and neck, twists the back.
extensor carpi ulnaris muscle
Forearm muscle. Origin: lateral epicondyle of humerus, proximal edge of ulna. Insertion: proximal end of fifth metacarpal. Nerve: radial (C7-C8). Action: adducts hand, extends wrist. See: arm for illus. (Muscles of the Arm)
extensor digitorum muscle
Forearm muscle. Origin: lateral epicondyle of humerus. Insertion: common extensor tendon of fingers. Nerve: radial (C7-C8). Action: extends fingers and wrist. See: arm for illus. (Muscles of the Arm)
extensor digitorum brevis muscle
Foot muscle. Origin: dorsolateral surface of calcaneus. Insertion: extensor tendons of toes. Nerve: deep peroneal (S1-S2). Action: extends toes. See: leg for illus. (Muscles of the leg)
extensor digitorum longus muscle
Foot muscle. Origin: lateral condyle of tibia, upper three-fourths of fibula. Insertion: extensor tendons of toes 2-5. Nerve: deep peroneal (L5-S1). Action: extends toes, dorsiflexes foot. See: leg for illus. (Muscles of the leg)
extensor hallucis longus muscle
Foot muscle. Origin: middle of fibula. Insertion: base of proximal phalanx of big toe. Nerve: deep peroneal (S1-S2). Action: dorsiflexes big toe. See: leg for illus. (Muscles of the leg)
external intercostal muscles
The outer layer of muscles between the ribs, originating on the lower margin of each rib and inserted on the upper margin of the next rib. During inspiration, they draw adjacent ribs together, pulling them upward and outward, and increasing the volume of the chest cavity. They are controlled by the intercostal nerves.
external oblique muscle
Abdominal wall muscle. Origin: lower costal margin. Insertion: anterior half of iliac crest, rectus sheath, inguinal ligament. Nerve: intercostals 8-12, iliohypogastric, ilioinguinal (L1). Action: tenses and compresses abdomen, flexes and laterally rotates spine, lowers rib cage.
external pterygoid muscleLateral pterygoid muscle.
extraocular muscle Abbreviation: EOM
Six muscles that attach outside the eyeball and that move the eye in its socket. The EOM are: the inferior and superior oblique muscles, and the lateral, medial, inferior, and superior rectus muscles. See: extraocular for illus.
extrinsic muscle Abbreviation: EM
The muscles outside an organ that control its position, such as the EM of the eye or tongue.
muscles of facial expression
Thin muscles that insert into the skin of the face; all are innervated by the facial nerve (CN VII). Scalp: frontalis and occipitalis muscles. Ear: anterior, posterior, and superior auricular muscles. Eye: orbicularis oculi. Nose: depressor septi, nasalis, and procerus muscles. Mouth: buccinator, depressor anguli oris, depressor labii inferioris, levator anguli oris, levator labii superioris, mentalis, orbicularis oris, risorius, and zygomaticus muscle. Neck: platysma. See: face and headfor illus.
muscles of facial expression
The newer name for the peroneus muscles.
fibularis longus musclePeroneus longus muscle.
A muscle that steadies a part so that more precise movements in a related structure may be accomplished.
flexor carpi radialis muscle
Forearm muscle. Origin: medial epicondyle of humerus. Insertion: bases of second and third metacarpals. Nerve: median (C6-C7). Action: abducts hand, flexes wrist. See: Arm, muscles of the arm (illus.)
flexor carpi ulnaris muscle
Forearm muscle. Origin: medial epicondyle of humerus, medial side of olecranon, proximal posterior edge of ulna. Insertion: pisiform, hamate, and base of fifth metacarpal. Nerve: ulnar (C7-C8). Action: adducts hand, flexes wrist.
flexor digitorum longus muscle
Foot muscle. Origin: posterior surface of middle tibia. Insertion: distal phalanges of toes 2-5. Nerve: tibial (S2-S3). Action: flexes toes 2-5, plantarflexes foot. See: leg for illus. (Muscles of the leg)
flexor digitorum profundus muscle
Forearm muscle. Origin: proximal three-fourths of ulna. Insertion: distal phalanges of fingers (digits 2-5). Nerve: ulnar, median (C8-T1). Action: flexes distal finger joints, aids in wrist flexion.
flexor digitorum superficialis muscle
Forearm muscle. Origin: medial epicondyle of humerus, coronoid process of ulna. Insertion: middle phalanges of fingers (digits 2-5). Nerve: median (C7-T1). Action: flexes fingers and wrist. See: arm for illus. (Muscles of the Arm)
flexor hallucis longus muscle
Foot muscle. Origin: distal two-thirds of posterior tibia. Insertion: plantar side of distal phalanx of big toe. Nerve: tibial (S2-S3). Action: flexes big toe, plantarflexes foot.
flexor pollicis brevis muscle
A muscle of the hand originating on the flexor retinaculum and trapezium, trapezoid, and capitate and inserted on the lateral side of the base of the first phalanx of the thumb. It flexes the thumb at both the carpometacarpal joint and the metacarpophalangeal joint and is controlled by the median and the ulnar nerves.
flexor pollicis longus muscle
Forearm muscle. Origin: coronoid process of ulna, anterior surface of radius. Insertion: distal phalanx of thumb. Nerve: median (C8-T1). Action: flexes thumb. See: arm for illus. (Muscles of the Arm)
Dorsal: dorsal interosseous, extensor digitorum brevis, extensor digitorum longus, extensor hallucis longus, and tibialis anterior muscles. Plantar: abductor digiti minimi, abductor hallucis, adductor hallucis, flexor digitorum brevis, flexor digiti minimi brevis, flexor hallucis brevis, lumbrical, plantar interosseous, and quadratus plantae muscles. See: leg for illus. (Muscles of the leg)
Front half of occipitofrontalis muscle – a facial muscle. Origin: epicranial (scalp) aponeurosis. Insertion: skin of eyebrows, root of nose. Nerve: facial (CN VII). Action: elevates eyebrows, wrinkles forehead. See: face and head for illus.
Leg muscle. Origin: medial condyle of femur, lateral condyle of femur. Insertion: calcaneus (via Achilles tendon). Nerve: tibial (S1-S2). Action: plantarflexes foot, flexes knee. See: leg for illus. (Muscles of the leg)
Either of the two muscles that attach to the medial surface of the greater trochanter of the femur (the trochanteric fossa) where they mesh with the tendon of the obturator internus muscle. The superior gemellus muscle arises from the ischial spine and is innervated by the nerve to the obturator internus; the inferior arises from the ischial tuberosity and is innervated by the femoral nerve. Both muscles hold the head of the femur in the acetabulum, rotate (laterally) the thigh in extension, and abduct the thigh when it is flexed.
Tongue muscle. Origin: genial tubercle on inside of mandibular symphysis. Insertion: ventral tongue, hyoid bone. Nerve: hypoglossal (CN XII). Action: protrudes and depresses tongue.
gluteus maximus muscle
Thigh muscle. Origin: upper outer edge of ilium and sacrum. Insertion: iliotibial tract of fascia lata, gluteal tuberosity of femur. Nerve: inferior gluteal (L5-S2). Action: extends, abducts, and laterally rotates thigh.
gluteus medius muscle
Thigh muscle. Origin: lower half of ilium. Insertion: proximal medial tibia. Nerve: obturator (L2-L3). Action: adducts, flexes, and medially rotates thigh.
Thigh muscle. Origin: lower half of pubis. Insertion: proximal medial tibia. Nerve: obturator (L2-L3). Action: adducts, flexes, and medially rotates thigh. See: leg for illus. (Muscles of the leg)
Posterior thigh muscles that originate on the ischial tuberosity and act across both the hip and knee joints; they are the biceps femoris, gracilis, sartorius, semitendinosus, and semimembranosus muscles.
Abductor digiti minimi, abductor pollicis brevis, adductor pollicis, dorsal interosseous, flexor digiti minimi, flexor pollicis brevis, lumbrical, opponens digiti minimi, opponens pollicis, palmaris brevis, and palmar interosseous muscles.
Hilton muscle See: Hilton, John
A sheet of muscle extending up from the hyoid bone to the ipsilateral base and sides of the tongue. It depresses the sides of the tongue and is innervated by cranial nerve XII (hypoglossal nerve).
Thigh muscle. Origin: iliac fossa. Insertion: lesser trochanter of femur, psoas major tendon. Nerve: femoral (L2-L3). Action: flexes thigh.
The iliacus and psoas major muscles considered together. See: leg for illus. (Muscles of the leg)
inferior oblique muscle
Extraocular muscle. Origin: inside front lower margin of maxillary part of orbit. Insertion: lateral surface of eyeball behind its equator. Nerve: oculomotor (CN III). Action: turns eye up and outward with lateral rotation. See: extraocular for illus.
inferior rectus muscle
Extraocular muscle. Origin: tendinous ring around optic nerve at rear of orbit. Insertion: lower edge of eyeball in front of its equator. Nerve: oculomotor (CN III). Action: turns eye down and medially. See: extraocular for illus.
Shoulder muscle. Origin: medial two-thirds of infraspinatus fossa of scapula. Insertion: posterior side of greater tubercle of humerus. Nerve: suprascapular (C4-C6). Action: rotates arm laterally.
internal intercostal muscles
The muscles between the ribs, lying beneath the external intercostals. During expiration, they pull the ribs downward and inward, decreasing the volume of the chest cavity and contributing to a forced exhalation.
internal pterygoid muscleMedial pterygoid muscle.
A muscle that has both its origin and insertion within a structure, as intrinsic muscles of the tongue, eye, hand, or foot.
A muscle not under conscious control: smooth, cardiac, and some skeletal muscles.
Any of six short muscles inside the larynx that move the vocal apparatus and (except for the cricothyroid muscle) are innervated by the recurrent laryngeal branch of the vagus nerve (CN X).
lateral pterygoid muscle
One of the mastication muscles. Origin: greater wing of sphenoid bone, lateral pterygoid plate. Insertion: pterygoid fovea of condyle of mandible. Nerve: trigeminal (CN V). Action: opens mouth, protrudes mandible. Synonym: external pterygoid muscle See: arm for illus.
lateral rectus muscle
Extraocular muscle. Origin: tendinous ring around optic nerve at rear of orbit. Insertion: temporal edge of eyeball in front of its equator. Nerve: abducens (CN VI). Action: turns eye laterally. See: extraocular for illus.
latissimus dorsi muscle
Back muscle. Origin: spinous processes of vertebrae T7-S3, thoracolumbar fascia, iliac crest. Insertion: bicipital groove of humerus. Nerve: thoracodorsal (C6-C8). Action: adducts, extends, and medially rotates arm.
Anterior and lateral: extensor digitorum longus, extensor hallucis longus, peroneus, peroneus longus, peroneus tertius, and tibialis anterior muscles. Posterior: flexor digitorum longus, flexor hallucis longus, gastrocnemius, plantaris, popliteus, soleus, and tibialis posterior muscles. See: leg for illus. (Muscles of the leg)
levator ani muscle
The set of pelvic floor muscles, which include the iliococcygeus, levator prostatae or vaginal sphincter, pubococcygeus, and puborectalis muscles. Origins: insides of pelvic bones (pubis, arcus tendinaeus, ischial spine, and sacrospinous ligament). Insertions: perineal body, coccyx, anococcygeal ligament, lower sacrum. Nerve: perineal of spinal S4, pudendal. Action: supports pelvic viscera, contributes to urethral, vaginal, and anal sphincter actions.
levator palpebrae muscle
Eyelid muscle. Origin: inner roof of orbit. Insertion: skin and tarsal plate of upper eyelid. Nerve: oculomotor (CN III). Action: raises upper eyelid. See: extraocular for illus.
Hand and foot muscles. Origins: tendons of flexor digitorum profundus or flexor digitorum longus. Insertions: extensor tendons of digits 2-5. Nerve, hand: median (C8-T1), ulnar (C8-T1). Nerve, foot: medial plantar (S2-S3), lateral plantar (S2-S3). Action: flex the straightened digits (specifically, flex the metacarpophalangeal or metatarsophalangeal joints while extending the interphalangeal joints).
Muscle of mastication. Origin: zygomatic process of maxilla, zygomatic arch. Insertion: coronoid process, lower half of ramus, and angle of mandible. Nerve: trigeminal (CN V). Action: elevates mandible to close jaw. See: headfor illus.
The chewing muscle, which is innervated by the mandibular division of the trigeminal nerve (CN V). These muscles include the masseter, temporalis, and medial and lateral pterygoid muscles. Synonym: chewing muscle
medial pterygoid muscle
Muscle of mastication. Origin: lateral pterygoid plate. Insertion: medial surface of ramus and angle of mandible. Nerve: trigeminal (CN V). Action: closes mouth, protrudes mouth, moves jaw sideways. Synonym: internal pterygoid muscle
medial rectus muscle
Extraocular muscle. Origin: tendinous ring around optic nerve at rear of orbit. Insertion: nasal edge of eyeball in front of its equator. Nerve: oculomotor (CN III). Action: turns eye medially.
Facial muscle. Origin: incisive fossa at front of mandible. Insertion: skin of chin. Nerve: facial (CN VII). Action: raises and protrudes lower lip. See: face and headfor illus.
A muscle with several tendons of origin and several tendons of insertion, in which fibers pass obliquely from a tendon of origin to a tendon of insertion on each side. See: bipennate muscle
Neck muscle. Origin: mylohyoid line of mandible. Insertion: hyoid bone, mylohyoid raphe. Nerve: trigeminal (CN V). Action: elevates hyoid and larynx, lowers jaw.
The major nose muscle and a muscle of facial expression.
Anterior and lateral: digastric, geniohyoid, mylohyoid, omohyoid, platysma, sternocleidomastoid, sternohyoid, sternothyroid, stylohyoid, and thyrohyoid muscles. Posterior: levator scapulae, scalene muscles, and trapezius. Suboccipital: obliquus capitis and rectus capitis muscles. See: headfor illus.
nonstriated muscleSmooth muscle.
Either of the two muscles on each side of the pelvic region that rotate the thighs outward.
opponens pollicis muscle
A muscle of the hand originating on the trapezium and flexor retinaculum and inserted in the first metacarpal. It flexes and adducts the thumb (brings it across the palm) and is controlled by the median nerve.
A muscle encircling an opening.
orbicularis oculi muscle
Facial muscle. Origin: completely surrounds eye, attaches to medial palpebral ligament (and adjacent bones) and lacrimal crest (and adjacent bones). Insertion: medial palpebral raphe (after encircling orbit), lateral palpebral raphe, tarsi of eyelids. Nerve: facial (CN VII) Action: closes eyelids, lifts cheeks, compresses lacrimal sac. See: face and headfor illus.
orbicularis oris muscle
Facial muscle. Origin: adjacent facial muscles that surround mouth. Insertion: into itself and skin of lips while encircling mouth. Nerve: facial (CN VII). Action: closes and purses lips. See: face and headfor illus.
muscles of the palate
Levator veli palatini, musculus uvulae, palatoglossus, palatopharyngeus, pharyngeal constrictor, salpingopharyngeus, and tensor veli palatine muscles.
palmaris longus muscle
Forearm muscle. Origin: medial epicondyle of humerus. Insertion: palmar surface of flexor retinaculum, palmar aponeurosis. Nerve: median (C7-C8). Action: flexes hand. See: arm for illus. (Muscles of the Arm)
Internal conical heart muscles. Origin: ventricular wall. Insertion: tricuspid and mitral valve leaflets via chordae tendinae. Action: anchor leaflets of valves during heart contractions.
A ridge of myocardium on the inner wall of either atrium of the heart.
pectoralis major muscle
Chest wall muscle. Origin: medial half of clavicle, sternum, costal cartilages 4-6. Insertion: lateral edge of bicipital groove of humerus. Nerve: lateral and medial pectoral (C5-T1). Action: adducts and medially rotates arm.
pectoralis minor muscle
Chest wall muscle. Origin: Anterior medial surface of ribs 3-5. Insertion: coracoid process of scapula. Nerve: lateral and medial pectoral (C6-C8). Action: pulls shoulder forward and down, elevates rib cage.
peroneus longus muscle
Leg muscle. Origin: lateral two-thirds of fibula. Insertion: medial cuneiform bone, base of first metatarsal. Nerve: superficial peroneal (L5-S1). Action: everts and plantar flexes foot. Synonym: fibularis longus muscle See: leg for illus. (Muscles of the leg)
pharynx and tongue muscles
Cricothyroid, genioglossus, geniohyoid, hyoglossus, palatoglossus, pharyngeal constrictor, styloglossus, stylopharyngeus, salpingopharyngeus, and thyrohyoid muscles.
Thigh muscle. Origin: anterior surface of sacrum. Insertion: upper part of greater trochanter of femur. Nerve: spinal L5-S2. Action: laterally rotates thigh.
Neck and facial muscle. Origin: superficial fascia of upper chest. Insertion: skin of lower face. Nerve: facial (CN VII). Action: lowers jaw, widens neck. See: face and headfor illus.
A muscle on the posterior or dorsal aspect of a limb.
postural musclesAntigravity muscles.
A muscle on the anterior or ventral aspect of a limb.
A muscle that arises in the skin over the nose and is connected to the forehead. It acts to draw the eyebrows down.
pronator teres muscle
Arm muscle. Origin: medial epicondyle of humerus, coronoid process of ulna. Insertion: lateral side of middle of radius. Nerve: median (C6-C7). Action: pronates forearm.
psoas major muscle
Thigh muscle. Origin: bodies of vertebrae T12-L1. Insertion: lesser trochanter of femur. Nerve: lumbar L1-L3. Action: flexes thigh.
The lateral or the medial pterygoid muscle.
Pelvic muscle, part of levator ani. Origin: back surface of pubis. Insertion: joins other levator ani muscles forming a bowl shaped diaphragm, encircles anal canal, and attaches to sacrum and coccyx. Nerve: inferior rectal and sacral (S4). Action: supports pelvis, holds anal canal at right angle to rectum.
The rectus femoris, vastus intermedius, vastus lateralis, and vastus medius muscles together.
rectus abdominis muscle
Abdominal wall muscle. Origin: crest and symphysis of pubis. Insertion: xiphoid process, costal cartilages 5-7. Nerve: spinal T7-T12. Action: tenses abdomen, flexes vertebral column.
rectus femoris muscle
Thigh muscle. Origin: anterior inferior iliac spine, upper edge of acetabulum. Insertion: tibial tuberosity (via the patellar ligament). Nerve: femoral (L2-L4). Action: extends leg, flexes thigh. See: leg for illus. (Muscles of the leg)
Twitch skeletal muscle cells containing myoglobin and many mitochondria. These cells largely generate energy via aerobic oxidation and are suited for maintaining contractions for an extended time.
muscle of respiration
Any of the muscles used in breathing, including the diaphragm, the muscles of the rib cage, and the abdominal muscles. See: diaphragm
The major or the minor rhomboid muscle -- shoulder muscles. Origins: nuchal ligament, spinous processes of vertebrae C7-T5. Insertion: vertebral edge of scapula. Nerve: dorsal scapular (C4-C5). Action: pulls scapulae toward each other. See: illus. (Muscles of the Trunk)
rotator cuff muscles
Shoulder muscles -- the infraspinatus, subscapularis, supraspinatus, and teres minor muscles -- which hold the head of the humerus in the glenoid fossa of the scapula.
Thigh muscle. Origin: anterior superior iliac spine. Insertion: medial side of proximal tibia. Nerve: femoral (L2-L3). Action: flexes thigh and leg, laterally rotates thigh. See: leg for illus. (Muscles of the leg)
The anterior, the middle, or the posterior scalene muscle -- neck muscles. Origins: transverse processes of vertebrae C1-C7. Insertions: upper surfaces of ribs 1-2. Nerves: cervical spinal C4-C8. Actions: raises ribs 1-2, bends neck ipsilaterally.
Thigh muscle. Origin: ischial tuberosity. Insertion: medial condyle of tibia. Nerve: sciatic (L5-S2). Action: extends thigh, flexes and medially rotates leg. See: leg for illus. (Muscles of the leg)
Thigh muscle. Origin: ischial tuberosity. Insertion: upper medial tibia near tuberosity. Nerve: sciatic L5-S2). Action: extends thigh, flexes and medially rotates leg. See: leg for illus. (Muscles of the leg)
Any of several muscles arising from the ribs or vertebrae by separate slips.
serratus anterior muscle
Chest muscle. Origin: outer surface of ribs 1-8. Insertion: anterior side of vertebral edge of scapula. Nerve: long thoracic (C5-C7). Action: pulls scapula forward (anterior) and laterally (abduction), rotates scapula upward.
Deltoid, infraspinatus, subscapularis, supraspinatus, teres major and teres minor muscles.
MORPHOLOGICAL FORMS OF MUSCLE
MORPHOLOGICAL FORMS OF MUSCLE
MORPHOLOGICAL FORMS OF MUSCLE
A tissue composed of muscle cells (often multinucleated) that contain neatly packed actin and myosin filaments; these filaments are arranged in cylindrical bundles called myofibrils. In each cell, the myofibrils are all aligned in the same direction and are parceled into longitudinal blocks (called sarcomeres) of similar lengths. Under the microscope, the ends of the blocks look like lines, making skeletal muscle cells appear to have regularly arranged striations. See: illustration
Skeletal muscle is innervated by somatic (as opposed to autonomic) motor axons at a synaptic structure called a motor endplate, where acetylcholine is the neurotransmitter. Most skeletal muscles can be controlled consciously, and skeletal muscle is sometimes referred to as voluntary muscle. Skeletal muscle cells contract more forcefully than smooth or cardiac muscle cells.
Skeletal muscle got its name because it usually attaches at one end to bone. Skeletal muscle is by far the most common type of muscle in the body and it plays a major role in normal metabolism, e.g., after a meal, excess glucose is removed from the blood stream primarily by skeletal muscle.
Synonym: nonstriated muscle.; unstriated muscle. See: table
A tissue composed of muscle cells that contain loosely-organized actin and myosin filaments. The lack of tight organization means that smooth muscle cells do not appear striated when examined under a microscope. Smooth muscle tissue tends to occur as sheets and is typically found in the walls of tubes, e.g., arteries, and sacs, e.g., the gastrointestinal system.
Smooth muscles are innervated by both sympathetic and parasympathetic autonomic motor axons; they are also stimulated by blood-borne molecules. Smooth muscles cannot be consciously controlled, and this form of muscle tissue is called involuntary muscle. Smooth muscle cells contract more slowly than skeletal or cardiac muscle cells.
Leg muscle. Origin: proximal ends of tibia and fibula. Insertion: calcaneus via Achilles tendon. Nerve: tibial (S1-S2). Action: plantarflexes foot. See: leg for illus. (Muscles of the leg)
Muscle derived from mesodermal somites, including most skeletal muscle.
A muscle that encircles a duct, tube, or orifice, thus controlling its opening.
sphincter muscle of urinary bladder
The smooth muscle fibers around the origin of the urethra. Contraction of this muscle prevents urination; relaxation permits it.
A muscle that supports a body segment so muscles attached to it can function.
Middle ear muscle. Origin: posterior wall of middle ear. Insertion: neck of stapes. Nerve: facial (CN VII). Action: tilts stapes, dampens excessive vibrations.
Neck muscle. Origin: upper edge of manubrium, middle of upper clavicle. Insertion: mastoid process. Nerve: accessory (CN XI), spinal C2. Action: contralaterally rotates head. See: face and headfor illus.
striated muscle See: table
Shoulder muscle. Origin: medial subscapular fossa. Insertion: lesser tubercle of humerus. Nerve: upper and lower subscapular (C5-C7). Action: medially rotates arm.
superior oblique muscle
Extraocular muscle. Origin: sphenoid bone deep in medial side of orbit. Insertion: lateral surface of eyeball behind its equator. Nerve: trochlear (CN IV). Action: turns eye down and outward with medial rotation.
superior rectus muscle
Extraocular muscle. Origin: tendinous ring around optic nerve at rear of orbit. Insertion: upper edge of eyeball in front of its equator. Nerve: oculomotor (CN III). Action: turns eye up and medially. See: extraocular for illus.
Shoulder muscle. Origin: medial supraspinous fossa of scapula. Insertion: greater tubercle of humerus. Nerve: suprascapular (C4-C6). Action: abducts arm.
Muscles aiding one another in function.
Muscle of mastication. Origin: temporal fossa of skull. Insertion: coronoid process of mandible. Nerve: trigeminal (CN V). Action: closes mouth, clenches teeth, retracts jaw. See: headfor illus.
tensor fascia lata muscle
Thigh muscle. Origin: iliac crest, anterior superior iliac spine. Insertion: iliotibial tract of fascia lata. Nerve: superior gluteal (L4-L5). Action: stabilizes (abducts) thigh, extends and laterally rotates leg.
tensor tympani muscle
Middle ear muscle. Origin: wall of auditory tube. Insertion: handle of malleus. Nerve: trigeminal (CN V). Action: tenses tympanic membrane, dampens excessive vibrations.
teres major muscle
Shoulder muscle. Origin: lower lateral edge of scapula. Insertion: bicipital groove of humerus. Nerve: lower scapular (C6-C7). Action: adducts and medially rotates arm.
teres minor muscle
Shoulder muscle. Origin: upper lateral edge of scapula. Insertion: greater tubercle of humerus. Nerve: axillary (C4-C6). Action: laterally rotates arm.
The abductor or flexor muscle of the thumb.
Anterior: iliopsoas, quadriceps (rectus femoris, vastus intermedius, vastus lateralis, and vastus medius), and sartorius muscles. Medial: adductor brevis, adductor longus, adductor magnus, gracilis, and pectineus muscles. Gluteal region: gemelli, gluteus maximus, gluteus medius, gluteus minimus, obturator externus, obturator, internus, piriformis, quadratus femoris, and tensor fasciae lata muscles. Posterior: biceps femoris, semimembranosus, and semitendinosus muscles. See: leg for illus. (Muscles of the leg)
A muscle arising on the inner surface of the thyroid cartilage. It extends upward and backward and is inserted on the epiglottis. It depresses the epiglottis.
tibialis anterior muscle
Leg muscle. Origin: lateral side of proximal tibia. Insertion: medial side of cuneiform bone, base of metatarsal 1. Nerve: deep peroneal (L4-L5). Action: inverts and dorsiflexes foot.
tibialis posterior muscle
Leg muscle. Origin: anterior tibia and fibula. Insertion: navicular, cuneiform, and cuboid bones; metatarsals 2-4. Nerve: tibial (L4-L5). Action: inverts and plantarflexes foot.
Skeletal muscle fibers that contract slowly and that cannot propagate an action potential along their cell membranes. Tonic muscles are uncommon in humans and are found only in the extraocular muscles, stapedius muscle, and intrafusal fibers of the muscle spindles. The remainder of human skeletal muscle contains only twitch fibers.
Neck and back muscle. Origin: occipital bone (superior nuchal line), nuchal ligament, spinous processes of vertebrae C7-T12. Insertion: posterior edge of lateral clavicle, acromion, posterior edge of spine of scapula. Nerve: accessory (CN XI), spinal C3-C4. Action: elevates, retracts, and rotates scapula. See: face and headfor illus.
A flat muscle with a broad origin and narrow insertion.
Arm muscle. Origin: infraglenoid tubercle of scapula, posterior of proximal humerus, posterior of distal humerus. Insertion: olecranon process. Nerve: radial (C6-C8). Action: extends forearm. Synonym: triceps brachii muscle See: arm for illus. (Muscles of the Arm)
triceps brachii muscleTriceps muscle.
A muscle with three tendons of origin and a single, common insertion.
Muscle fibers that can conduct axon potentials along their cell membranes. Almost all skeletal muscle in humans is twitch muscle. A very small number of muscles in humans are tonic muscles. Twitch muscles cells can be categorized into a number of types on the basis of the biochemical cycle that they use to produce their energy: red (oxidative), white (glycolytic), or intermediate (oxidative/glycolytic). Most human muscles are composed of a mix of twitch muscle cell types.
A muscle whose fibers converge on only one side of a tendon. See: bipennate muscle
unstriated muscleSmooth muscle.
uterine muscle See: myometrium
vastus intermedius muscle
Thigh muscle. Origin: anterior and lateral sides of proximal femur. Insertion: common tendon of quadratus muscles, tibial tuberosity via patellar ligament. Nerve: femoral (L2-L4). Action: extends leg.
vastus lateralis muscle
Thigh muscle. Origin: lateral side of proximal femur. Insertion: common tendon of quadratus muscles, tibial tuberosity via patellar ligament. Nerve: femoral (L2-L4). Action: extends leg. See: leg for illus. (Muscles of the leg)
vastus medialis muscle
Thigh muscle. Origin: medial side of femur Insertion: common tendon of quadratus muscles, tibial tuberosity via patellar ligament. Nerve: femoral (L2-L4). Action: extends leg.
Laryngeal muscle. Origin: midline of inner surface of thyroid cartilage. Insertion: arytenoid cartilage. Nerve: recurrent laryngeal of vagus (CN X). Action: changes tension of vocal cords.
A muscle that can be controlled voluntarily; most skeletal muscles are voluntary.
| Length (in/m)||50–200||25,000|
| Thickness (in/m)|| 4–8|| 75|
| Markings||No striation||Striation||Marked striation|
|Effects of cutting related nerve||Slight||Regulation of heart rate is lost||Complete paralysis|