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EPITHELIAL CELLS
HISTOLOGY
| Term | Definition |
|---|---|
| epithelial, connective, muscular, nervous tissues | four basic tissue types |
| connective tissue | several types of fixed and wandering cells; abundant amount of ECM; support and protection of tissues/organs |
| muscle tissue | elongated contractile cells; moderate amount of ECM; strong contraction; body movements |
| nervous tissue | elongated cells with extremely fine processes, very amount ECM; transmission of nerve impulses |
| parenchyma | composed of cells responsible for the organ's specialized functions |
| stroma | cells of which have a supporting role in the organ |
| brain and spinal cord | organ of which stroma is not always a connective tissue |
| epithelial tissues | composed of closely aggregated polyhedral cells, adhering strongly to one another and to a thin layer of ECM, forming cellular sheets that line the cavities of organs and cover the body surface. |
| epithelia | line all external and internal surfaces of the body and all substances that enter or leave an organ must cross this type of tissue |
| covering, lining, protecting surfaces, absorption, secretion | principal functions of epithelial tissue |
| columnar cells | elongated nuclei, |
| squamous cells | flattened nuclei |
| cuboidal/pyramidal cells | spherical nuclei |
| nuclei | also allows to determine the number of cell layers in an epithelium. |
| adjacent | most epithelia are ________ to connective tissues containing blood vessels from which the epithelial cells receive nutrients and O2. |
| lamina propria | connective tissue that underlies the epithelia lining the organs of the digestive, respiratory, and urinary systems |
| papillae | small evaginations that can increase the area of contact between the two tissues |
| papillae | occur most frequently in epithelial tissues subject to friction (covering of the skin or tongue) |
| basal pole | the region of the cell contacting the ECM and connective tissue |
| apical pole | opposite end of basal pole, usually facing a space |
| lateral surfaces | cell membranes here often have numerous folds that increase the are and functional capacity f that surface |
| basement membrane | a thin extracellular felt-like sheet of macromolecules where basal surface of all epithelia rests on |
| basal lamina | nearest; a thin, electron-dense, sheetlike layer of the fibrils |
| reticular lamina | beneath basal lamina that is a more diffuse and fibrous lamina; contains collagen III fibers |
| hemidesmosomes | bind the basal surface of the epithelial cell to the basal lamina |
| laminin | major glycoprotein within basal laminae |
| basal lamina | fine extracellular layer seen ultra structurally |
| basement membrane | entire structure beneath the epithelial cells visible with light microscope |
| macromolecules | basal lamina; secreted from the basal sides of the epithelial celss and form a sheetlike array. |
| type IV collagen | monomers of type IV collagen self-assemble into a two dimensional network of evenly spaced subunits resembling the mesh of a window screen |
| laminin | large glycoproteins that attach to transmembrane integrin protein in the basal membrane and project through the mesh formed by the type IV collagen |
| nidogen and perlecan | a short, rodlike protein and proteoglycan; cross-link laminins to the type IV collagen network; helping provide basal lamina's 3D structure; bind epithelium to that structure; determine its porosity and the size of molecules able to filter through it |
| external laminae | basal laminae are often called _____; thin sleeves surrounding muscle cells, nerves, and fat-storing cells, where they serve a semipermeable barriers regulating macromolecular exchange between the enclosed cells and connective tissue |
| type III collagen | the more diffuse meshwork of the reticular lamina contains, bound to the basal lamina by anchoring fibrils of type VII collagen |
| type III collagen and type VII collagen | proteins that are produced by the connective tissues |
| basement membrane | filters; structural support; attach EP underlying connective tissue; mediate cell-to-cell interactions involving EP, mark routes for certain cell migration EP; serves as a scaffolding that allows rapid epithelial repair and regeneration |
| basal lamina | components help organize integrins & other proteins in plasma membrane of epithelial cells, maintaining cell polarity & helping localize endocytosis, signal transduction, and other activities |
| tight or occluding junctions | form a seal between adjacent cells |
| tight junctions (zonulae occludens) and adherent junction (zonulae adherens) | forms continuous band around the cell |
| tight junctions (zonulae occludens) | multiple ridges prevent passive flow of material between cells but are not very strong; most apical of the junctions |
| adherent junction (zonulae adherens) | below tight junctions, serves to stabilize and strengthen the circular occluding bands, helping hold cell together |
| demosomes (macula adherens) | form very strong attachment points that supplement zonula adherens and play a major role to maintain integrity of an epithelium |
| gap junctions (nexus) | each a patch patch of many connexons in the adjacent cell membranes, have little strength but serves as intercellular channels for flow of molecules |
| occludins, claudins, ZO proteins | type of tight junction; seal adjacent cells to one another, control passage of molecules between them; separates apical and basolateral membrane |
| e-cadherin, catenin complexes | type of adherens junction; provides points linking the cytoskeletons of adjacent cells; strengthens and stabilizes nearby tight junctions |
| cadherin family proteins (desmogleins, desmocollin) | type of desmosomes; provides points of strong intermediate filament coupling between adjacent cells, strengthening the tissue |
| integrins | type of hemidesmosomes; anchors cytoskeleton to the basal lamina |
| connexin | gap junction; allows direct tarnsfer of small molecules and ions from one cells to another |
| adherent or anchoring junctions | sites of strong cell adhesion |
| gap junctions | channels for communication between adjacent cells |
| zonula/zonulae | indicates junction forms a band completely encircling each cell |
| apical cell membrane | membrane domain of epithelia, part of the luminal compartment of tissue or an organ |
| basolateral cell membrane | membrane domain of epithelia, part of basal compartment that encompasses the underlying connective tissue |
| cadherins | mediate cell adhesion; transmembrane glycoproteins of each cell that bind together in the presences if CA2+; binds catenins |
| terminal web | a cytoskeletal feature at the apical pole in many epithelial cells; formed by actin filaments linked adherence |
| desmosomes | "spot weld"; disc-shaped structures at the sur- face of one cell that are matched with identical structures at an adjacent cell surface |
| desmogleins and desmocollins | cadherin family |
| plakoglobins | catenin-like proteins that link to desmoplankins |
| desmoplankins | larger proteins; bind intermediate filament proteins rather than actins |
| tonofilaments | cable-like filaments of cytokeratin; where epithelial desmosomes are attached |
| gap junctions | mediate intercellular communication; abundant in many epithelia |
| cryofracture preparations | shows a junctions consist of aggregated transmembrane protein complexes forms circular patches in the plasma membrane |
| connexins | transmembran gap junction |
| connexons | hexameric complexes produced by connexins; each of which has a central hydrophilic pore about 1.5nm in diameter. |
| hemidesmosomes | anchoring junctions attached to the basal lamina |
| integrins | bind primarily to laminin molecules in the basal lamina |
| focal adhesion (focal contact) | basal anchoring junction found in cells, moving during epithelial repair of reorganization; smaller (than hemidesmosomes) more numerous, ad consist of integrins link indirectly to bundled actiin filaments |
| focal adhesion kinase | initiates cascade of intracellular protein phosphorylation affecting cell adhesion,mobility, and gene expression; important in migrating nonepithelial cells such as fibroblasts. |
| microvilli | visible as a brush or striated border projecting into the lumen |
| thick glycocalyx | includes membrane-bound proteins and enzymes for digestion of certain macromolecules. |
| microfilament arrays | undergo various myosin-based movements, which help maintain optimal conditions for absorption via numerous channels, receptors, and other proteins in the plasmalemma. |
| stereocilia | less common type of apical process, best seen on the absorptive epithelial cells lining the male reproductive system; increase the cells’ surface area, facilitating absorption. |
| cilia | long, highly motile apical structures, larger than microvilli, and containing internal arrays of microtubules not microfilaments. |
| primary cilium | one short projection of cilia; enriched with receptors and signal transduction complexes for detection of light, odors, motion, and flow of liquid past the cells |
| motile cilia | abundant on cuboidal or columnar cells of many epithelia. |
| axoneme | This 9 + 2 assembly of microtubules |
| kinesin and cytoplasmic dynein motors | motors move along the peripheral microtubules for the transport of molecular components into and out of these structures. |
| basal bodies | apical cytoplasmic structures just below the cell membrane |
| Ciliary motion | motion occurs through successive changes in the conformation of the axoneme, in which various accessory proteins make each cilium relatively stiff, but elastic. |
| axonemal dynein | bound to one microtubule in each doublet extend as “arms” toward a microtubule of the next doublet. |
| covering epithelia (lining) and secretory (glandular) epithelia | an arbitrary functional division for there are lining epithelia in which all the cells also secrete or in which cells are distributed among the lining cells |
| covering or lining epithelia | organized into one or more layers that cover the surface or line the cavities of an organ. |
| Simple epithelia | epithelia containing one cell layer |
| stratified epithelia | epithelia containg two or more layers. |
| squamous | (thin cells), |
| cuboidal | (cell width and thickness roughly similar), |
| columnar | cells taller than they are wide |
| Stratified squamous keratinized epithelium | epidermis of skin, where it helps prevent dehydration from the tissue |
| Stratified non keratinized epithelium | line moist internal cavities where water loss is not a problem |
| stratified cuboidal and stratified columnar epithelia | both rare epithelia |
| stratified cuboidal | occurs in the excretory ducts of salivary and sweat glands |
| stratified columnar | seen in the conjunctive lining the eyelids, where it is both protective and mucus secreting |
| transitional epithelium or urothelium | lines much of the urinary tract, from kidney to proximal part of the urethra; characterized by a superficial layer of large, dome-like cells (umbrella cells) |
| trancytosis | the vesicular transport of macromolecules from one side of a cell to the other |
| simple squamous | single layer of thin cells |
| simple cuboidal | tall as they are wide; high level of active transport across the epithelium |
| simple columnar | tall than they are wide; apical cilia or microvilli, often specialized for absorption |
| transitional epithelium | specialized to protect underlying tissues from the hypertonic and potentially cytotoxic effects of urine |
| pseudostratified columnar epithelium | tall, irregular cells all are attached to the basement membrane but their nuclei are at different levles and cells extend to the free surfcae |
| exocrine gland | deliver secreted material where it is used |
| endocrine gland | lose the connection to their original epithelium and lack ducks |
| merocrine secretion | common method od protein or glycoprotein secretion |
| holocrine secretion | cells accumulate product continuously as the enlarge and undergo terminal differentiation |
| apocrine secretion | accumulates ate the cells' apical end, when pinched off to release product surrounded by a small amount of cytoplasm and cell membrane |
| serous cells | synthesize protein that are mostly not glycosylated, digestive enzymes |
| mucous | filled apically with secretory glandules but contains heavily glycosylated protein called mucins |
| mucins | heavily glycosylated protein |
| mucus | hydrated mucins |
| seromucous glands | both acini and mucous tubules with clustered serous cells |
| myoepithelial cells | lone processes of this cells embrace an acinus |
Created by:
snwugf(real)