- Fiber
- The parts of plants that cannot be digested, namely complex carbohydrates. Also known as bulk or roughage. Complex carbohydrates from plants are rich in starch and fiber. Examples of plants that provide complex carbohydrates (fiber) are fresh fruits and vegetables, whole-grain breads, and cereal grains. Simple carbohydrates, such as common table sugar, have no fiber. Dietary fiber can have many benefits including promoting bowel regularity, lowering the level of cholesterol in the blood, and easing conditions such as hemorrhoids, colitis, and diverticulosis. Dietary fiber can also aid in weight maintenance as it requires more chewing and promotes hunger satisfaction by giving the stomach a sense of fullness. A salient benefit of dietary fiber was thought to be that it lowered the risk of colon cancer. Then in 1999 it was reported that dietary fiber seemed to have no effect on the chance of developing colon cancer. And in 2000 a kind of dietary fiber was discovered to increase the risk of the adenomas, the forerunners of cancer of the colon. The fiber under study was from ispaghula husk, which is not normally found in the diet but is found in laxatives containing mucilage. Ispaghula husk fiber is similar to psyllium, a fiber derived from plant husks that is found in many bulk laxatives. It appears that a high-fiber diet should be avoided by anyone who may have colorectal adenomas.
* * *A slender thread or filament. 1. Extracellular filamentous structures such as collagenic or elastic connective tissue fibers. 2. The nerve cell axon with its glial cell or Schwann cell envelope. 3. Elongated, hence threadlike, cells such as muscle cells and the epithelial cells composing the major part of the eye lens. 4. Nutrients in the diet that are not digested by gastrointestinal enzymes. SYN: fibra [TA], fibre. [L. fibra]- A fibers myelinated nerve fibers in somatic nerves, measuring 1–22 μm in diameter, conducting nerve impulses at a rate of 6–120 m/sec.- accelerator fibers postganglionic sympathetic nerve fibers originating in the superior, middle, and inferior cervical ganglia of the sympathetic trunk, conveying nervous impulses to the heart that increase the rapidity and force of the cardiac pulsations. SYN: augmentor fibers.- adrenergic fibers nerve f.'s that transmit nervous impulses to other nerve cells (or smooth muscle or gland cells) by the medium of the adrenalinelike transmitter substance norepinephrine (noradrenaline).- afferent fibers those that convey impulses to a ganglion or to a nerve center in the brain or spinal cord.- alpha fibers large somatic motor or proprioceptive nerve fibers with conducting impulses at rates of 80–120 m/sec.- anastomosing fibers, anastomotic fibers individual fibers passing from one nerve trunk or muscle bundle to another.- arcuate fibers nervous or tendinous fibers passing in the form of an arch from one part to another. See arcuate fibers of cerebrum, external arcuate fibers, internal arcuate fibers.- arcuate fibers of cerebrum [TA] short association fibers that connect adjacent gyri in the cerebral cortex. SYN: fibrae arcuatae cerebri [TA].- argyrophilic fibers reticular connective tissue fibers that react with silver salts and appear black microscopically.- association fibers nerve fibers interconnecting subdivisions of the cerebral cortex of the same hemisphere or different segments of the spinal cord on the same side. SYN: endogenous fibers, intrinsic fibers.- astral fibers fibers (fibrils) radiating from the centrosphere toward the periphery of the cell as seen with a light microscope; revealed as microtubules under the electron microscope. Cf.:kinetochore fibers, polar fibers.- augmentor fibers SYN: accelerator fibers.- autonomic nerve fibers [TA] any of the pre- and/or postsynapatic nerve fibers that collectively comprise the sympathetic and parasympathetic parts of the autonomic division of the peripheral nervous system. SYN: neurofibrae autonomicae [TA], visceral motor fibers.- B fibers myelinated fibers autonomic nerves, with a diameter of 2 μm or less, conducting at a rate of 3–15 m/sec.- Bergmann fibers filamentous glia fibers traversing the cerebellar cortex perpendicular to the surface.- bulbar corticonuclear fibers [TA] nerve fibers projecting from the motor and somatic sensory cortices to motor and sensory relay nuclei of the medulla oblongata, such as the hypoglossal nucleus, accessory nucleus and gracile and cuneate nuclei. See corticonuclear fibers. SYN: fibrae corticonucleares bulbi [TA].- C fibers unmyelinated fibers, 0.4–1.2 μm in diameter, conducting nerve impulses at a velocity of 0.7–2.3 m/sec.- cerebellohypothalamic fibers nerve fibers originating from cells of the cerebellar nuclei and projecting, via the superior cerebellar peduncle, to the contralateral hypothalamus, mainly its dorsal, lateral, and posterior areas and dorsomedial nucleus.- cerebelloolivary fibers [TA] axons that arise from neurons in the cerebellar nuclei, exit via the superior cerebellar peduncle, cross in its decussation, and descend in association with the central tegmental tract. Depending of their origin, these fibers terminate in the accessory and principal olivary nuclei; anterior and posterior interposed nuclei to the dorsal accessory and medial accessory olivary nuclei respectively, the medial cerebellar nucleus to the medial accessory olivary nucleus, and the lateral cerebellar nucleus to the principal olivary nucleus. SYN: fibrae cerebelloolivares [TA].- cerebellospinal fibers fibers that originate from the fastigial and interposed (primarily the posterior) cerebellar nuclei and descend to the contralateral side of the spinal cord. See fastigiospinal fibers. SEE ALSO: fastigiospinal fibers.- cholinergic fibers nerve fibers that transmit impulses to other nerve cells, muscle fibers, or gland cells by the medium of the transmitter substance acetylcholine.- chromatic f. SYN: chromonema.- circular fibers the circular fibers of the ciliary muscle. SYN: fibrae circulares [TA], Müller fibers (1), Müller muscle (2), Rouget muscle.- climbing fibers nerve fibers in the cerebellar cortex that synapse upon smooth branchlets of Purkinje cell dendrites.- collagen f., collagenous f. an individual f. that varies in diameter from less than 1 μm to about 12 μm and is composed of fibrils; the fibers' which are usually arranged in bundles, undergo some branching and are of indefinite length; chemically the f. is a glycoprotein, collagen, which yields gelatin upon boiling; they make up the principal element of irregular connective tissue, tendons, aponeuroses, and most ligaments, and occur in the matrix of cartilage and osseous tissue. SYN: white f. (2).- commissural fibers nerve fibers crossing the midline and connecting two corresponding parts or regions of the nervous system.- cone f. a part of the cone cell of the retina; the inner cone f. is a slender axon-like part of the cone extending from the cell body to the pedicle located in the outer plexiform layer of the retina; in the outer fovea, where the cones are much elongated, they narrow to an outer cone f., located between the inner segment and the cell body.- corticobulbar fibers term formerly used to describe projections of the motor and sensory cortices to nuclei of the rhombencephalon innervating the musculature of the face, tongue, and jaws and some fibers to rhombencephalic relay nuclei; replaced by bullar corticonuclear fibers (to medulla), pontine corticonuclear fibers (to pons), mesencephalic corticonuclear fibers (to midbrain). See these individual entries.- corticomesencephalic fibers [TA] axons that originate in the cerebral cortex and terminate in mesencephalic structures such as the tectum, substantia nigra, or tegmentum. SYN: fibrae corticomesencephalicae [TA].- corticonuclear fibers descriptive term connotating fibers from a cortical structure (cerebral or cerebellar) passing to subcortical cell groups; fibers comprising the fibrae corticonucleares bulbi [TA], fibrae corticonucleares pontis [TA] and fibrae corticonucleares mesencephali [TA]; cerebellar corticonuclear fibers (Purkinje cell axons to the cerebellar nuclei). SYN: fibrae corticonucleares [TA].- corticopontine fibers [TA] the fibers that compose the corticopontine tract. SYN: fibrae corticopontinae [TA].- corticoreticular fibers [TA] corticofugal fibers distributed to the reticular formation of the mesencephalon and rhombencephalon. SEE ALSO: corticonuclear fibers. SYN: fibrae corticoreticulares [TA].- corticorubral fibers [TA] nerve fibers projecting from the cerebral cortex (primarily precentral and premotor regions) to the red nucleus of the midbrain. SYN: fibrae corticorubrales [TA].- corticospinal fibers [TA] SYN: pyramidal fibers.- corticothalamic fibers a general term designating nerve fibers originating from any area of the cerebral cortex and terminating in the nuclei of the thalamus.- cuneocerebellar fibers [TA] SYN: cuneocerebellar tract.- cuneospinal fibers [TA] axons that originate in the cuneate nucleus of the medulla oblongata and descend ipsilaterally in the cuneate fasciculus to terminate primarily in the posterior horn of the spinal cord in cervical and upper thoracic levels. SYN: fibrae cuneospinales [TA].- dentatorubral fibers nerve fibers arising in the dentate nucleus of the cerebellum and projecting, via the superior cerebellar peduncle and its decussation, to the contralateral red nucleus of the midbrain. SYN: fibrae dentatorubrales.- dentatothalamic fibers nerve fibers projecting from the dentate nucleus of the cerebellum to the contralateral thalamus via the superior cerebellar peduncle (and its decussation); enter the thalamus as one component of the thalamic fasciculus.- dentinal fibers, dental fibers 1. the processes of the pulpal cells, the odontoblasts, which extend in radial fashion through the dentin to the dentoenamel junction and are contained within the dentinal tubules; SYN: Tomes fibers. 2. the intertubular fine collagenous fibers that with the dentinal ground substance infiltrated with calcium salts constitutes the dentinal matrix.- depressor fibers sensory nerve fibers having pressure-sensitive nerve endings in the wall of certain arteries capable of activating blood pressure-lowering brainstem mechanisms when stimulated by an increase in intraarterial pressure.- dietary f. the plant polysaccharides and lignin that are resistant to hydrolysis by the digestive enzymes in humans.- efferent fibers those fibers conveying impulses to effector tissues (muscle : smooth, cardiac or striated; or glands) in the periphery; those fibers exiting a specific cell group ( i.e., efferent fibers of the basilar pons), used in reference to a cell group.- elastic fibers fibers that are 0.2–2 μm in diameter but may be larger in some ligaments; they branch and anastomose to form networks and fuse to form fenestrated membranes; the fibers and membranes consist of microfibrils about 10 nm wide and an amorphous substance containing elastin. SYN: yellow fibers.- enamel fibers SYN: prismata adamantina, under prisma.- endogenous fibers SYN: association fibers.- exogenous fibers nerve fibers by which a given region of the central nervous system is connected with other regions; the term applies to both afferent and efferent f. connections.- external arcuate fibers they include: 1) posterior external arcuate fibers [TA] that arise from cells in the accessory or lateral cuneate nucleus and pass to the cerebellum; 2) anterior external arcuate fibers [TA] that arise from the arcuate nuclei at the base of the medulla oblongata and pass around the lateral surface of the medulla; both enter the cerebellum as components of the restiform portion of the inferior cerebellar peduncle. SYN: fibrae arcuatae externae.- fastigiobulbar fibers nerve fibers projecting from the fastigial nuclei of the cerebellum to the brainstem; crossed and uncrossed fibers that terminate mainly in the vestibular and reticular nuclei, and in the medial accessory olivary nucleus.- fastigiospinal fibers crossed descending fibers originating in the fastigial nucleus of the cerebellum and ending in the spinal cord gray matter at cervical, and possibly lower, levels.- frontopontine fibers [TA] a large group of fibers arising from the frontal lobe of the cerebral hemisphere, especially the precentral gyrus, descending in the internal capsule, farther caudally composing the medial part of the crus cerebri through which they extend caudalward to end in the gray matter (pontine nuclei) of the ventral part of the pons. SEE ALSO: corticopontine tract. SYN: fibrae frontopontinae [TA].- gracilespinal fibers [TA] axons that arise from neurons of the gracile nucleus of the medulla oblongata and descend ipsilaterally in the gracile fasciculus to terminate primarily in the posterior horn of the spinal cord in lower thoracic and lumbosacral levels. SYN: fibrae gracilispinales [TA].- Gratiolet fibers SYN: optic radiation.- gray fibers SYN: unmyelinated fibers.- hypothalamocerebellar fibers nerve fibers originating from cells in the hypothalamus and projecting to the cerebellar cortex and nuclei.- hypothalamospinal fibers [TA] a group of fibers that originates primarily from the paraventricular nucleus and lateral and posterior hypothalamic areas, descends ipsilaterally through the ventrolateral brainstem and into the lateral funiculus of the spinal cord, and terminates in relation to neurons of the intermediolateral nucleus. SYN: fibrae hypothalamospinales [TA].- inhibitory fibers nerve fibers that inhibit the activity of the nerve cells with which they have synaptic connections, or of the effector tissue (smooth muscle, heart muscle, glands) in which they terminate.- intercrural fibers of superficial ring [TA] horizontal arched fibers that pass from the inguinal ligament across the medial and lateral crura of the superficial inguinal ring. SYN: fibrae intercrurales anuli inguinalis superficialis [TA], intercolumnar fasciae, intercolumnar fibers.- internal arcuate fibers [TA] fibers that arise in the cuneate and gracile nuclei, pass in a curving course across the midline of the medulla oblongata, and form the contralateral medial lemniscus; may also designate other fibers such as those of the olivocerebellar tract that arch through the substance of the medulla and may traverse the sensory decussation. SYN: fibrae arcuatae internae [TA].- intrathalamic fibers [TA] fibers that arise in one nucleus of the dorsal thalamus and terminate in another. SYN: fibrae intrathalamicae [TA].- intrinsic fibers SYN: association fibers.- James fibers atrio-His bundle connections thought to be the basis for the short P-R interval syndrome; these fibers should be distinguished from the controversial internodal tracts of the atrium, sometimes referred to as “James tracts.” SYN: James tracts.- kinetochore fibers fibers of the mitotic spindle attached to the centromere and extending toward the poles. Cf.:astral fibers, polar fibers.- Korff fibers argyrophilic fibers that pass between odontoblasts at the periphery of the dental pulp and fan out into the dentin.- Kühne f. artificial muscle f. made by filling the intestine of an insect with a growth of myxomycetes; used to demonstrate the contractility of protoplasm.- fibers of lens the elongated cells of ectodermal origin forming the substance of the crystalline lens of the eye. SYN: fibrae lentis.- long association fibers [TA] nerve fibers interconnecting lobes or gyri of the cerebral cortex of the same hemisphere that are not immediately adjacent to each other; nerve fibers connecting noncontiguous segments of the spinal cord on the same side; fibers that interconnect distant points. SYN: fibrae associationes longae [TA].- longitudinal pontine fibers [TA] See longitudinal pontine fasciculi, under fasciculus. SYN: fibrae pontis longitudinales [TA].- Mahaim fibers paraspecific fibers originating from the A-V node, the His bundle, or the bundle branches and inserting into the ventricular myocardium; they are potential pathways for reentrant dysrhythmias. SYN: nodoventricular fibers.- meridional fibers of ciliary muscle [TA] the longitudinal fibers of the ciliary muscle. SYN: fibrae meridionales muscularis ciliaris [TA].- mesencephalic corticonuclear fibers [TA] nerve fibers projecting primarily from the motor cortex to motor nuclei of the mesencephalon such as the oculomotor and trochlear; these inputs are relayed via nuclei located adjacent to these motor nuclei. See corticonuclear fibers. SYN: fibrae corticonucleares mesencephali [TA].- mossy fibers highly branched nerve f.'s in the cerebellar cortex that terminate in rosette formations and synapse upon granule cell dendrites.- motor fibers nerve fibers that transmit impulses that activate effector cells, e.g., in muscle or gland tissue.- Müller fibers 1. SYN: circular fibers. 2. sustentacular neuroglial cells of the retina, running through the thickness of the retina from the internal limiting membrane to the bases of the rods and cones where they form a row of junctional complexes. SYN: Müller radial cells, sustentacular fibers of retina.- myelinated nerve f. an axon enveloped by a myelin sheath formed by oligodendroglia cells (in brain and spinal cord) or Schwann cells (in peripheral nerves). SYN: medullated nerve f..- Nélaton fibers SYN: Nélaton sphincter.- nerve f. the axon of a nerve cell, ensheathed by oligodendroglia cells in brain and spinal cord, and by Schwann cells in peripheral nerves.- nodoventricular fibers SYN: Mahaim fibers.- nonmedullated fibers SYN: unmyelinated fibers.- nuclear bag f. the largest type of intrafusal muscle fibers in a neuromuscular spindle, containing a central aggregation of nuclei (nuclear bag).- nuclear chain f. the shortest and most numerous type of intrafusal muscle fibers in a neuromuscular spindle, containing a single row of centrally positioned nuclei.- nucleocortical fibers general term for projections from a nucleus to an overlying cortical structure; specifically used to designate axons of cerebellar nuclear cells that project to the cerebellar cortex (cerebellar nucleocortical fibers) where they end as mossy fibers.- oblique fibers of muscular layer of stomach [TA] the smooth muscle fibers of the innermost layer of the muscular coat of the stomach; the fibers occur chiefly at the cardiac end of the stomach and spread over the anterior and posterior surfaces. SYN: fibrae obliquae tunicae muscularis [TA].- occipitopontine fibers [TA] a group of fibers originating in the occipital lobe of the cerebral hemisphere and descending in the internal capsule and lateral part of the crus cerebri to the pontine nuclei of the basilar part of the pons. SEE ALSO: corticopontine tract. SYN: fibrae occipitopontinae [TA].- occipitotectal fibers [TA] fibers originating in visual regions of the occipital lobe and passing, via the retrolenticular limb of the internal capsule, to the tectum where they end mainly in the superior colliculus. SYN: fibrae occipitotectales [TA].- olivocochlear fibers See olivocochlear tract.- olivospinal fibers a slender bundle of nerve fibers in the peripheral zone of the lateral funiculus of the spinal cord, composed, more likely, of spinoolivary fibers than of olivospinal fibers. SYN: fibrae olivospinales [TA], Helwig bundle.- osteogenetic fibers the fibers in the osteogenetic layer of the periosteum.- parietopontine fibers [TA] a system of fibers originating in the parietal lobe of the cerebral hemisphere that descend in the internal capsule and lateral part of the crus cerebri to terminate in the pontine nuclei in the ventral part of the pons. SEE ALSO: corticopontine tract. SYN: fibrae parietopontinae [TA].- perforating fibers bundles of collagenous fibers that pass into the outer circumferential lamellae of bone or the cementum of teeth. SYN: Sharpey fibers.- periodontal f. desmodentium.- periventricular fibers [TA] a heterogeneous system of thin nerve fibers in the periventricular gray matter of the hypothalamus; the dorsal longitudinal fasciculus is a caudal continuation of the system. SYN: fibrae periventriculares [TA].- pilomotor fibers nerve fibers that innervate the erector muscles of hair follicles responsible for piloerection.- polar fibers those fibers of the mitotic spindle extending from the two poles of the spindle toward the equator. Cf.:astral fibers, kinetochore fibers.- pontine corticonuclear fibers [TA] nerve fibers projecting from the motor and sensory cortices to motor and sensory relay nuclei in the pontine tegmentum such as the facial, abducens, and trigeminal nuclei; fibers may be direct or relayed via the adjacent reticular nuclei. See corticonuclear fibers. SYN: fibrae corticonucleares pontis [TA].- pontocerebellar fibers [TA] fibers arising from the nuclei of the basilar pons and primarily crossing the midline (there is a modes uncrossed projection), centering the cerebellum via the middle cerebellar peduncle and terminating as mossy fibers in the cerebellar cortex. SYN: fibrae pontocerebellares [TA].- postcommissural fibers [TA] fibers in the column of fornix that pass caudal (posterior) to the anterior commissure to enter the mammillary nuclei; the largest part of the column of fornix. SYN: fibrae postcommissurales [TA].- postganglionic fibers a f. whose cell body is located in an autonomic (motor) ganglion and whose peripheral process will terminate on smooth muscle, cardiac muscle, or glandular epithelium; associated with sympathetic or parasympathetic parts of the autonomic nervous system.- precollagenous fibers immature, argyrophilic fibers.- precommissural fibers [TA] fibers in the column of fornix that pass rostral (anterior) to the anterior commissure to enter primarily the septal nuclei. SYN: fibrae precommissurales [TA].- preganglionic fibers a f. whose cell body is located in an autonomic nucleus in the spinal cord or brain stem and whose axon terminates in an autonomic (motor) ganglion; found in nerves conveying sympathetic or parasympathetic fibers.- pressor fibers sensory nerve fibers whose stimulation causes vasoconstriction and rise of blood pressure.- pretectoolivary fibers [TA] fibers originating from the pretectal nuclei and projecting primarily to the ipsilateral medial accessory olivary nucleus. SYN: fibrae pretectoolivares [TA].- projection fibers nerve fibers connecting the cerebral cortex with other centers in the brain or spinal cord; fibers arising from cells in the central nervous system that pass to distant loci.- pyramidal fibers the fibers that compose the corticospinal tract. SEE ALSO: corticospinal tract. SYN: corticospinal fibers [TA], fibrae corticospinales [TA], fibrae pyramidales.- raphespinal fibers nerve fibers originating from cells of the nuclei raphe magnus, pallidus, and obscurus of the pons and medulla and terminating in the spinal cord gray matter; fibers involved in the descending inhibition of nociceptive input in the dorsal (posterior) horn; they contain serotonin.- red fibers red striated muscle fibers that are rich in sarcoplasm, myoglobin, and mitochondria; they are smaller in diameter and contract more slowly than white fibers.- Reissner f. a rodlike, highly refractive f. running caudally from the subcommissural organ throughout the length of the central canal of the brainstem and spinal cord.- Remak fibers SYN: unmyelinated fibers.- reticular fibers the collagen (type III) fibers forming the distinctive loose connective tissue stroma of embryonic tissues, mesenchyme, red pulp of the spleen, cortex and medulla of lymph node s, and the hematopoietic compartments of bone marrow and accounting for a substantial portion of the collagen fibers of the skin, blood vessel s, synovial membrane, uterine tissue, and granulation tissue; characterized by organization as a reticular meshwork of fine filaments and by an affinity for silver and for periodic acid -Schiff stains.- rod f. a part of the rod cell of the retina that extends to either side of the cell body; the inner rod f. terminates in the spherule, a synaptic ending located in the outer plexiform layer.- Rosenthal f. an oval or elongated eosinophilic mass believed to represent a modified process of an astrocyte; seen in large numbers in certain slowly growing astrocytomas and areas of chronic reactive gliosis.- rubroolivary fibers [TA] axons that arise from cells of the parvocellular part of the red nucleus, descend ipsilaterally as one component of the central tegmental tract, and terminate primarily in the principal olivary nucleus. SYN: fibrae rubroolivares [TA].- Sharpey fibers SYN: perforating fibers.- short association fibers [TA] nerve fibers that may interconnect adjacent lobes or gyri of the cerebral cortex of the same hemisphere or contiguous segments of the spinal cord on the same side; fibers that interconnect close or adjacent points. SYN: fibrae associationes breves [TA].- skeletal muscle fibers multinucleated contractile cells varying from less than 10 to 100 μm in diameter and from less than 1 mm to several centimeters in length; the f. consists of sarcoplasm and cross-striated myofibrils, which in turn consist of myofilaments; human skeletal muscles are a mixture of red, white, and intermediate type fibers.- somatic nerve fibers [TA] afferent or efferent fibers distributed outside the body cavities, i.e., to the parietes; the majority of somatic afferent fibers conduct impulses centrally stimulating conscious sensation; all somatic efferent fibers stimulate somatic (voluntary/striated/skeletal) muscle. SYN: neurofibrae somaticae [TA].- spinocuneate fibers axons that originate from cells in the posterior horn of cervical and upper thoracic spinal levels, ascend ipsilaterally in the cuneate fasciculus, and terminate in the cuneate nucleus. These are part of the postsynaptic–dorsal column system. SYN: fibrae spinocuneatae [TA].- spinogracile fibers [TA] axons that originate from neurons in the posterior horn of lower thoracic and lumbosacral spinal cord levels, ascend ipsilaterally in the gracile fasciculus, and terminate in the gracile nucleus. These are part of the postsynaptic–dorsal column system. SYN: fibrae spinograciles [TA].- spinohypothalamic fibers [TA] axons that originate in the spinal cord gray matter, ascend as part of the anterolateral system, and terminate in the hypothalamus SYN: fibrae spinohypothalamicae [TA].- spinomesencephalic fibers [TA] a composite group of fibers traveling in the spinal lemniscus (anterolateral system) and ending in the mesencephalon; includes spinotectal fibers [TA] to the deeper layers of the superior colliculus and spinoperiaqeductal fibers [TA] that terminate in the periaqueductal gray matter. SYN: fibrae spinomesencephalicae [TA].- spinoolivary fibers [TA] fibers that arise in the spinal cord and ascend primarily on the ipsilateral side to terminate in the accessory nuclei of the inferior olivary complex. SYN: fibrae spinoolivares [TA].- spinoperiaqueductal fibers [TA] axons originating from cell bodies of the posterior horn, ascending as part of the contralateral anterolateral system, and terminating in the periaqueductal gray of the mesencephalon; involved in descending pathways for pain suppression. SEE ALSO: spinomesencephalic fibers. SYN: fibrae spinoperiaqueductales [TA].- spinoreticular fibers [TA] nerve fibers originating from the spinal cord and terminating in the reticular formation of the brainstem; some ascend as part of the anterolateral system. SYN: fibrae spinoreticulares [TA], spinoreticular tract [TA].- spinotectal fibers [TA] axons originating from cell bodies in the posterior horn, crossing in the anterior white commissure, ascending as part of the anterolateral system, and primarily terminating in the deeper layers of the superior colliculus. SEE ALSO: spinomesencephalic fibers. SYN: fibrae spinotectales [TA].- stress fibers long bundles of microfilaments made up of actin; believed to be involved in the attachment of cultured cells to a substratum and also in the determination of the shape of cells such as fibroblasts; may be involved in cellular mobility.- striatonigral fibers SYN: strionigral fibers.- strionigral fibers nerve fibers originating from cells of the caudate and putamen and terminating mainly in the pars reticulata of the substantia nigra; they utilize GABA and substance P. SYN: striatonigral fibers.- sudomotor fibers postganglionic and cholinergic sympathetic nerve fibers that innervate the sweat glands.- sustentacular fibers of retina SYN: Müller fibers (2).- T f. a f. that branches at right angles to the right and left; term used to describe the branching patterns of granular cell axons in the molecular layer of the cerebellum.- tautomeric f.s nerve fibers of the spinal cord that do not extend beyond the limits of the spinal cord segment in which they originate.- tectoolivary fibers [TA] fibers that originate in the deep layers of the superior colliculus and project primarily to the contralateral medial accessory olivary nucleus. SYN: fibrae tectoolivares [TA].- tectopontine fibers [TA] fibers arising in the tectum of the mesencephalon and terminating in the ipsilateral nuclei of the basilar pons and in the reticulotegmental nucleus. SYN: fibrae tectopontinae [TA].- tectoreticular fibers [TA] fibers that originate in the superior colliculus and project bilaterally to the reticular formation, primarily that of the midbrain. SYN: fibrae tectoreticulares [TA].- temporopontine fibers [TA] a f. group originating in the cerebral cortex of the temporal lobe, particularly the superior and middle temporal gyri, following the sublenticular limb of the internal capsule into the lateral margin of the crus cerebri in which it descends to its termination in the pontine nuclei in the basilar part of the pons. SEE ALSO: corticospinal tract. SYN: fibrae temporopontinae [TA].- thalamocortical fibers a general term identifying nerve fibers arising from nuclei of the thalamus and projecting to, and terminating in, the cerebral cortex.- transverse pontine fibers [TA] fibers arising from the pontine nuclei, decussate and pass into the cerebellum as the middle cerebellar peduncles. SYN: fibrae pontis transversae [TA].- unmyelinated fibers a f. having no myelin covering (CNS); a naked axon; in the PNS represented by all axons lying in troughs in a single Schwann cell (Schwann cell unit); a slow conducting f.. SYN: gray fibers, nonmedullated fibers, Remak fibers.- vasomotor fibers postganglionic visceral efferent fibers innervating the smooth muscles of vessel walls.- white f. 1. white mammalian muscle fibers; larger in diameter than red fibers they have less myoglobin, sarcoplasm, and mitochondria, and contract more quickly; 2. SYN: collagen f..- zonular fibers [TA] delicate fibers that pass from the equator of the lens to the ciliary body, collectively known as the ciliary zonule. SYN: fibrae zonulares [TA].
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fi·ber or chiefly Brit fi·bre 'fī-bər n1) a thread or a threadlike structure or object: asb) one of the filaments composing most of the intercellular matrix of connective tissuec) one of the elongated contractile cells of muscle tissue2) mostly indigestible material in food that stimulates the intestine to peristalsis called also bulk, dietary fiber, roughage* * *
fi·ber (fiґbər) 1. an elongated, threadlike structure; see also fibra [TA]. 2. neurofibra. 3. dietary f.For anatomic structures not listed here, see under fibra and see under the terms listed in def. 2 above.
Medical dictionary. 2011.
