layer

layer (la´er)

A sheet of one substance lying on another and distinguished from it by a difference in texture or color or by not being continuous with it. See also stratum, lamina.
ameloblastic l. the internal l. of the enamel organ.enamel l;
anterior elastic l. anterior limiting l. of cornea
anterior limiting l. of cornea a transparent homogeneous acellular layer, 6 to 9 mum thick, lying between the basal l. of the outer layer of stratified epithelium and the substantia propria of the cornea; considered to be a basement membrane.lamina limitans anterior corneae [NA], anterior elastic l., Bowman's membrane, lamina elastica anterior, limiting l.'s of cornea;
anterior l. of rectus abdominis sheath the portion of the rectus sheath that lies anterior to the muscle, consisting in its upper two-thirds of contributions from the aponeuroses of the external and internal oblique muscles, and in its lower third (below the arcuralt line) of contributions from the aponeuroses of all three muscles of the anterolateral abdominal wall.lamina anterior vaginae musculi recti abdominis [NA];
bacillary l. l. of rods and cones
basal l. stratum basale (1)
basal cell l. stratum basale epidermidis
basal l. of choroid lamina basalis choroideae
basal l. of ciliary body basal lamina of ciliary body
l. of Bechterew band of Kaes-Bechterew
blastodermic l.'s the primordial cell l.'s on the yolk surface of a telolecithal egg; in the earliest stages they consist of protoderm, and they later differentiate into ectoderm, endoderm, and mesoderm.
brown l. lamina fusca of sclera
cambium l. 1. the inner osteogenic l. of the periosteum; 2. a highly cellular zone immediately beneath the epithelium covering a botryoid sarcoma.
l.'s of cerebellar cortex See cerebellar cortex.
l.'s of cerebral cortex See cerebral cortex.
cerebral l. of retina the internal l. of the retina containing the neural elements, as distinguished from the outer leaf of the retina, or pigmented layer.pars optica retinae [NA], neural l. of retina, optic part of retina, stratum cerebrale retinae;
Chievitz' l. in the developing retina of an embryo, a transitory zone between the inner and outer neuroblastic l.'s that is devoid of nuclei.
choriocapillary l. the internal layer of the choroidea of the eye, composed of a very close capillary network.lamina choroidocapillaris [NA], choriocapillaris, entochoroidea, lamina choriocapillaris, membrana choriocapillaris, Ruysch's membrane;
circular l. of muscular coat the inner, circular l. of the smooth muscle of the muscular coat. Nomina Anatomica lists circular l.'s of muscular coats (stratum circulare tunicae muscularis...) of the following: 1) colon (... coli [NA]); 2) rectum (... recti [NA]); 3) small intestine (... intestini tenuis [NA]); 4) stomach (... gastrici [NA]).stratum circulare tunicae muscularis gastricae [NA], stratum circulare tunicae [NA];
circular l.'s of muscular tunics See circular l. of muscular coat.
circular l. of tympanic membrane stratum circulare membranae tympani
claustral l. the l. of subcortical gray matter between the external capsule and the white matter of the insula or extreme capsule.
clear l. of epidermis stratum lucidum
columnar l. stratum basale epidermidis
conjunctival l. of bulb bulbar conjunctiva
conjunctival l. of eyelids palpebral conjunctiva
corneal l. of epidermis stratum corneum epidermidis
cornified l. of nail stratum corneum unguis
cutaneous l. of tympanic membrane stratum cutaneum membranae tympani
deep l. in a stratified structure, the stratum which lies beneath all others, furthest from the surface. See deep l. of levator palpebrae superioris muscle, deep l. of temporalis fascia.lamina profunda [NA], deep lamina;
deep gray l. of superior colliculus a l. of myelinated fibers, the deepest layer of the colliculus superior, delimiting the latter from the central gray substance surrounding the cerebral aqueduct.stratum album profundum;
deep l. of levator palpebrae superioris muscle the deeper fibers of the levator muscle of the superior eyelid which are inserted into the superior tarsal plate.lamina profunda musculi levatoris palpebrae superioris;
deep l. of temporalis fascia the deep part of the temporal fascia attaching to the medial surface of the zygomatic arch;lamina profunda fasciae temporalis;
deep white l. of superior colliculus See gray l. of superior colliculus.
elastic l.'s of arteries elastic laminae of arteries, under lamina
elastic l.'s of cornea See anterior limiting l. of cornea, posterior limiting l. of cornea.
enamel l. ameloblastic l
ependymal l. an inner epithelial l. of cells bordering the lumen of the embryonic neural tube and brain, formed during the latter's stratification, and persisting in modified form throughout life.ependymal zone, ventricular l;
epithelial l.'s See epithelium.
epithelial choroid l. epithelial lamina
epitrichial l. the superficial flattened-cell l. of the epidermis of a young embryo before the definitive stratification has developed.
external nuclear l. of retina neuroepithelial l. of retina
fatty l. of superficial fascia Camper's fascia
fibrous l. the outer dense connective tissue l. of the periosteum.
fillet l. stratum lemnisci
fusiform l. l. 6 of the cortex cerebri.multiform l., polymorphous l., spindle-celled l;
ganglionic l. of cerebellar cortex piriform neuron l
ganglionic l. of cerebral cortex l. 5 of the cortex cerebri.
ganglionic l. of optic nerve the inner l. of multipolar neurons in the retina consisting of the relatively large neurons that give rise to the fibers of the optic nerve.stratum ganglionare nervi optici;
ganglionic l. of retina the intermediate l. of neurons in the retina composed largely of bipolar cells.internal nuclear l. of retina, stratum ganglionare retinae, stratum nucleare internum retinae;
germ l. one of the three primordial cell l.'s (ectoderm, endoderm, mesoderm) established in an embryo during gastrulation and the immediately following stages.
germinative l. stratum basale epidermidis
germinative l. of nail stratum germinativum unguis
glomerular l. of olfactory bulb a l. composed of spherical bodies, called glomeruli, formed by the synapses of mitral cells with the olfactory nerve fibers derived from the cells of the olfactory epithelium.
granular l. of cerebellar cortex granular l. of cerebellum
granular l. of cerebellum the deepest of the three l.'s of the cortex; it contains large numbers of granule cells, the dendrites of which synapse with incoming mossy fibers in cerebellar glomeruli. Thin, unmyelinated axons of granule cells ascend perpendicularly into the molecular l. in which they bifurcate into fibers coursing parallel to the long axis of the cerebellar folia. Parallel fibers form numerous synapses with the dendrites of Purkinje cells, basket cells, and stellate cells.stratum granulosum cerebelli [NA], granular l. of cerebellar cortex;
granular l.'s of cerebral cortex l.'s 2 (outer) and 4 (inner) of the cortex cerebri.
granular l. of epidermis a l. of somewhat flattened cells containing basophilic granules of keratohyalin and lying just above the stratum spinosum and deeply to the stratum corneum.stratum granulosum epidermidis [NA];
granular l.'s of retina nuclear l.'s of retina
granular l. of a vesicular ovarian follicle stratum granulosum folliculi ovarici vesiculosi
gray l. of superior colliculus term applied to any one of the three major l.'s of gray matter of the superior colliculus that alternate with l.'s composed chiefly of nerve fibers: 1) the superficial gray l. of superior colliculus, above the largely white layer of the incoming fibers of the optic tract (optic l.); 2) the middle gray l. of superior colliculus, placed between the optic l. and a more deeply located l. of fibers, the l. lemnisci; 3) the deep gray layer of superior colliculus, between the l. lemnisci and the central gray substance surrounding the cerebral aqueduct, and containing the large nerve cells from which most of the colliculus descending connections (tectobulbar, tectopontine, and tectospinal tract) originate.stratum griseum colliculi superioris [NA], stratum cinereum colliculi superioris;
half-value l. (HVL) the thickness of a specific absorber (e.g., Al) that will reduce the intensity of a beam of radiation to one-half its initial value.
Henle's l. the outer l. cells of the inner root sheath of the hair follicle.
Henle's fiber l. the l. of inner cone fibers in the central area of the retina.
Henle's nervous l. entoretina
horny l. of epidermis stratum corneum epidermidis
horny l. of nail stratum corneum unguis
Huxley's l. a l. of cells interposed between Henle's l. and the cuticle of the inner root sheath of the hair follicle.Huxley's membrane, Huxley's sheath;
infragranular l. the cellular band deep to the inner granular l. of the developing human cerebral cortex, which differentiates into the ganglionic l. and multiform l. by the sixth fetal month.
intermediate l. mantle l
internal nuclear l. of retina ganglionic l. of retina
investing l. of deep cervical fascia the part of the cervical fascia investing the sternocleidomastoid and trapezius muscles and completely encircling the neck.lamina superficialis fasciae cervicalis [NA], investing fascia, superficial l. of deep cervical fascia;
Kölliker's l. the l. of connective tissue in the iris.
Langhans' l. cytotrophoblast
lateral cartilaginous l. lateral lamina of cartilaginous auditory tube
lateral l. of cartilaginous auditory tube lateral lamina of cartilaginous auditory tube
latticed l. a cortical cell l. in the hippocampus.
limiting l.'s of cornea anterior limiting l. of cornea, posterior limiting l. of cornea
longitudinal l. of muscular coat the outer, longitudinal l. of the smooth muscle of the muscular coat. Nomina Anatomica lists longitudinal l.'s of muscular coats (stratum longitudinale tunicae muscularis...) of the following: 1) colon (... coli [NA]); 2) rectum (... recti [NA]); 3) small intestine (... intestini tenuis [NA]); 4) stomach (... gastrici [NA]).stratum longitudinale tunicae muscularis gastricae [NA], stratum longitudinale tunicae muscularis [NA];
longitudinal l.'s of muscular tunics See longitudinal l. of muscular coat.
malpighian l. malpighian stratum
mantle l. the nuclear zone of the developing neural tube between the marginal l. and the ependymal l.; forms the gray matter of the central nervous system.intermediate l., mantle zone (1);
marginal l. the outer, nonnuclear l. of the embryonic neural tube; into its fibrous network grow the longitudinal nerve fibers which eventually become the white matter of the cord and brain stem.marginal zone;
medial cartilaginous l. medial lamina of cartilaginous auditory tube
medial l. of cartilaginous auditory tube medial lamina of cartilaginous auditory tube
medullary l.'s of thalamus medullary laminae of thalamus, under lamina
membranous l. membranous lamina of cartilaginous auditory tube
membranous l. of superficial fascia 1. superficial fascia of perineum 2. Scarpa's fascia
meningeal l. of dura mater See dura mater of brain.
Meynert's l. pyramidal cell l
middle gray l. of superior colliculus See gray l. of superior colliculus.
molecular l. term applied to any l. of brain tissue that contains few nerve-cell bodies and is composed largely of terminal arborizations of dendrites and axons; notable examples are the superficial l. (first l.) of the cerebral cortex and the molecular l. of cerebellum.plexiform l., stratum moleculare;
molecular l. of cerebellar cortex molecular l. of cerebellum
molecular l. of cerebellum the outer lamina of the cortex, containing the cell bodies and dendrites of Purkinje cells, the axons of the granule cells, and the cell bodies, dendrites, and axons of basket cells.stratum moleculare cerebelli [NA], molecular l. of cerebellar cortex;
molecular l. of cerebral cortex l. 1 of the cortex cerebri.plexiform l. of cerebral cortex;
molecular l.'s of olfactory bulb the l.'s, composed mainly of nerve fibers, on the outer and inner sides of the l. of mitral cells of the bulb.
molecular l. of retina name applied to each of the plexiform l.'s of the retina.stratum moleculare retinae;
multiform l. fusiform l
muscular l. of mucosa muscularis mucosae
neural l. of optic retina See retina.
neural l. of retina cerebral l. of retina
neuroepithelial l. of retina the outermost l. of the cerebral l. of retina, composed of the primary receptor cells of the retina; the stratum consists of two sublayers: 1) an external l. made up of the rods and cones, the photosensitive processes of the receptor cells, and 2) the external nuclear l. containing the cell bodies of these cells; the external limiting membrane forms a perforated supporting plate between the two sublayers; the name refers to the fact that the retinal receptor cells are a specialized form of (epithelial) ependyma cell and thus, in a sense, are comparable to the neuroepithelial cells (e.g., hair cells) of other sense organs.external nuclear l. of retina, stratum neuroepitheliale retinae, stratum nucleare externum retinae;
Nitabuch's l. Nitabuch's membrane
nuclear l.'s of retina the outer nuclear l., l. 4, of the retina, neuroepithelial l. of retina, and the inner l., l. 6, of the retina, ganglionic l. of retina.granular l.'s of retina, stratum nucleare externum et internum retinae;
odontoblastic l. a l. of connective tissue cells at the periphery of the dental pulp of the tooth.
optic l. 1. a layer of white matter interspersed with nerve-cell bodies, immediately below the superficial gray l. of the superior colliculus, composed of myelinated fibers originating in the retina and striate cortex; 2. the inner l. of the retina, consisting of the fibers originating from the cells of the ganglionic l. of optic nerve; in their further course these fibers combine to form the optic nerve or optic tract.stratum opticum;
orbital l. of ethmoid bone orbital plate of ethmoid bone
osteogenetic l. the inner bone-forming l. of the periosteum.
palisade l. stratum basale epidermidis
papillary l. stratum papillare corii
parietal l. the outer l. of an enveloping sac or bursa, usually lining the walls of the cavity or space occupied by the enveloped structure, the structure itself being covered with the inner or visceral layer of the enveloping sac; an actual or potential space is enclosed by the two layers and intervenes between parietal and visceral layers. The parietal l. is usually the more substantial l.lamina parietalis [NA];
parietal l. of leptomeninges arachnoid
parietal l. of serous pericardium the outer part of the serous pericardium suported by the fibrous pericardium.lamina parietalis pericardii;
parietal l. of tunica vaginalis the outer part of the tunica vaginalis testis supported by the internal spermatic fascia.lamina parietalis tunicae vaginalis testis;
perforated l. of sclera lamina cribrosa sclerae
periosteal l. of dura mater See dura mater of brain.
pigmented l. of ciliary body stratum pigmenti corporis ciliaris
pigmented l. of iris stratum pigmenti iridis
pigmented l. of retina the outer l. of the retina, consisting of pigmented epithelium.ectoretina, stratum pigmenti bulbi, stratum pigmenti retinae, tapetum nigrum, tapetum oculi;
piriform neuron l. the layer of Purkinje cells between the molecular and granular layers of the cerebellar cortex.stratum neuronorum piriformium [NA], ganglionic l. of cerebellar cortex, l. of piriform neurons, Purkinje's l., stratum gangliosum cerebelli;
l. of piriform neurons piriform neuron l
plasma l. still l
plexiform l. molecular l
plexiform l. of cerebral cortex molecular l. of cerebral cortex
plexiform l.'s of retina l.'s of the retina where synapses occur; in the external l., processes of rods and cones synapse with bipolar neuron dendrites; in the internal l., axon terminals of bipolar cells synapse with ganglion cell dendrites. See retina.stratum plexiforme externum et internum retinae;
polymorphous l. fusiform l
posterior elastic l. posterior limiting l. of cornea
posterior limiting l. of cornea a transparent homogeneous acellular layer between the substantia propria and the endothelial layer of the cornea; considered to be a highly developed basement membrane.lamina limitans posterior corneae [NA], membrana vitrea [NA], Descemet's membrane, Duddell's membrane, entocornea, hyaloid membrane, lamina elastica posterior, limiting l.'s of cornea, membrana hyaloidea, posterior elastic l., tunica vitrea, vitreous membrane (1);
posterior l. of rectus abdominis sheath the portion of the sheath of the rectus abdominis muscle that lies posterior to the muscle covering only its upper two-thirds; it is formed by contributions from the aponeuroses of the internal oblique and transversus abdominis muscles; its free inferior margin forms the arcuate line; it is deficient below this, the posterior aspect of the muscle being covered only by transversalis fascia and peritoneum.lamina posterior vaginae musculi recti abdominis [NA];
pretracheal l. pretracheal fascia
prevertebral l. prevertebral fascia
prickle cell l. stratum spinosum epidermidis
Purkinje's l. piriform neuron l
pyramidal cell l. l. 3 of the cortex cerebri.Meynert's l;
radiate l. of tympanic membrane stratum radiatum membranae tympani
Rauber's l. 1. the thinned-out trophoblastic membrane over the embryonic disk in developing carnivores and ungulates; 2. outermost cell layer which helps form the blastodisk; called blastodermic or primitive ectoderm.
reticular l. of corium stratum reticulare corii
l.'s of retina See retina.
l. of rods and cones the l. of the retina next to the pigment l. and containing the visual receptors. See also retina, granular l.'s of retina, neuroepithelial l. of retina.bacillary l;
rostral l. rostral lamina
Sattler's elastic l. the middle l. of the choroid.
serous l. of peritoneum simple squamous epithelium that forms the glistening surface of the parietal and visceral layers of peritoneum.tunica serosa peritonei [NA];
l.'s of skin See epidermis, dermis.
sluggish l. still l
somatic l. the external l. of the lateral mesoderm of the embryo, lying adjacent to the ectoderm and together with it constituting the somatopleure.
spindle-celled l. fusiform l
spinous l. stratum spinosum epidermidis
splanchnic l. the internal l. of the lateral mesoderm, lying adjacent to the endoderm and together with it forming the splanchnopleure.
still l. the l. of the bloodstream in the capillary vessels, next to the wall of the vessel, that flows slowly and transports the white blood cells along the l. wall, while in the center the flow is rapid and transports the red blood cells.plasma l., Poiseuille's space, sluggish l;
subendocardial l. the loose connective tissue l. that joins the endocardium and myocardium; in the ventricles, it contains branches of the conducting system of the heart.
subendothelial l. the thin l. of connective tissue lying between the endothelium and elastic lamina in the intima of blood vessels.
subpapillary l. the vascular l. of the corium.
subserous l. the layer of connective tissue beneath a serous membrane such as that of the periconeum or pericardium.tela subserosa [NA];
superficial l. in a stratified structure, the outermost or topmost of the strata; the stratum nearest the surface. See superficial l. of deep cervical fascia, superficial l. of the levator palpebrae superioris muscle, superficial l. of temporalis fascia.lamina superficialis [NA], superficial lamina;
superficial l. of deep cervical fascia investing l. of deep cervical fascia
superficial gray l. of superior colliculus See gray l. of superior colliculus.
superficial l. of the levator palpebrae superioris muscle the superficial fibers of the levator muscle of the superior eyelid which are inserted into the skin of the superior eyelid.lamina superficialis musculi levatoris palpebrae superioris [NA];
superficial l. of temporalis fascia the superficial part of the temporal fascia attaching to the lateral surface of the zygomatic arch.lamina superficialis fasciae temporalis [NA];
suprachoroid l. suprachoroid lamina
Tomes' granular l. a thin l. of dentin adjacent to the cementum, appearing granular in ground sections; the granules are small uncalcified spaces.
vascular l. vascular lamina of choroid
vascular l. of choroid coat of eye vascular lamina of choroid
ventricular l. ependymal l
visceral l. the inner l. of an enveloping sac or bursa which lines the outer surface of the enveloped structure, as opposed to the parietal layer which lines the walls of the occupied space or cavity. The visceral l. is usually thin, delicate and not apparent as being separate, but rather appears to be the outer surface of the structure itself.lamina visceralis [NA];
visceral l. of serous pericardium the inner part of the serous pericardium applied directly on the heart.epicardium [NA], lamina visceralis pericardii [NA];
visceral l. of tunica vaginalis of testis the inner part of the tunica vaginalis testis applied directly to the testis and epididymis.lamina visceralis tunicae vaginalis testis [NA];
Waldeyer's zonal l. dorsolateral fasciculus
Weil's basal l. the l. beneath the odontoblasts of the tooth; it contains reticular fibers but few if any cells.Weil's basal zone;
zonular l. 1. a thin l. of white substance covering the upper surface of the thalamus and forming part of the floor of the body of the lateral ventricle; 2. a l. of white substance on the surface of the superior colliculus.stratum zonale [NA];

 

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