epithelia Flashcards
introduce specialised cell surface epithelia
in polarized epithelial cells (cuboidal/columnar)
apical domain: tall cuboidal epithelial cells face lumen F: absorb +move substances (cilia, sterocilia, and microvilli)
lateral domain- many junctions connect cell-cell for diff purposes. tight j- tight barrier control transport of mol. desmosomes attach IF to cell. zona adherens under zona occludens+intercalated dic of heart. modulate cell-cell adhesion + respo transmission of signals between cells. communicating j:channel for diff of ions, direct comm between cells
basal domain- binds to basal lamina via hemidesmosome or focal contacts.
basal labyrinth-cell membrane invagination (enlarge SA) abundant in mito (contain pumps, source of energy for ion transporting cells)
basal domain
binds to basal lamina via hemidesmosome or focal contacts. Striation, caused by attachment of epithelium due to hemi+focal striation looks like linear arrangement of cytoskeletal elemental+adhesion complexes (also bc if mitochondria). have invagination of cell membrane that enlarge the area of basal cell surface= enhance power of enzymes located there. vertically position mitochondria inside the invagination. typical in ions transporting cells (proximal+distal renal tubules, cells of striated ducts in salivary glands.)
1) Hemidesmone- proteins of IF anchored to intercellular plaque bound to INTEGRIN (receptor to laminin+fibronectin in basal lamina)
2) focal contacts- actin F anchored to them via adaptor proteins+ INTEGRIN.
- Infolding of basement membrane (has ion-transporting epithelia)
basal labyrinth-cell membrane invagination (enlarge SA) abundant in mito (contain pumps, source of energy for ion transporting cells)
Basement membrane
basal lamina
lucida- 20-100um, e- dense, under epithelia, extracellular portion of integrin has LAMININ+FIBRONECTIN receptors
densa: e- dense, adj to CT composed of collagen IV fibrils+ENTACTIN+ proteoglycans + LAMININ)
- attach to CT through collagen IV+FIBRILILN
- laminin+ collagen form network help together by ENTACTIN, NIDOGEN +PERLECAN
Reticular lamina: layer of reticular fibres under basal domain. Not produced by epithelia (belong to CT). more diffusible in fibrous layer, stains PAS+ and eosinophilic due to collagen III (bind to basal lamina through IV)
- F: support structure, polarity for epithelial cells, and helps organization of proteins affect endocytosis and signal trasnduction. proteins of lamina help w filter conc of mitotic growth factors. forming scaffold for epithelial repair
Communicating junctions
(lateral j) aggregated transmembrane protein complex in circular patches of PM.
- protein CONNEXIN forms hexametric complexes= CONNEXONS (hydrophilic core 1.5nm; 1000x or more between cells move in coordinated manner- cardiac cells.
- injury, channel close to prevent spread)
zona adherens
(lateral j) zona adheres (anchoring junctions)- lateral surface of neighbouring cells under zona occludens in epithelial tissue. In intercalated disc of cardiac. Actin F anchored to attached plaque (site of cell membrane that attaches junction). Actin bind to E-CADHERIN (transmembrane glycoprotein) through linking protein (ALPHA ACTININ, VINCULIN+ CATENIN) - depend on Ca2+
apical domain
apical domain- tall cuboidal epithelial cells face lumen F: absorb +move substances
cilia- 5-10um, 0,2diameter (longer than microvilli twice wide)
- one cilia=primary cilia non-motile.
- has receptor +signal transduction complexes: light, odour, mov, flow of fluid
- abundant in columnar+cuboidal at apical
- lung, resp tract+ ear
- motile in epithelial cells w organized microtubular core. basal bodies (similar to centriole-cylindrical w 9 microtubules in triplets. make up cilia + control axoneme assemble) + axoneme (9 doublets surround 2 central microtubules, peripheral joined by NEXIN and joined to central sheath by RADIAL SPOKES. responsible for motility bc of protein motors dynein+kinase).
sterocilia 5-10um, long motile microvilli. in hair cells, men (reproductive system) : epithelium of ductus deferens+epidydimus.
- no VILLIN at tip of sterocili (unlike microvilli)
microvilli 1um and 0.1um diameter
- intestinal microvilli has glycocalyx has enzyme for digestion of macromol.
- bundles of actin f capped+crosslinked to eachother+PM via actin-binding proteins (MYOSIN, FIMBRIN, FASCIN).
- intestinal microvilli has actin F anchored to villin extend processes to apical cytoskeleton interacting w/ terminal web (provide support+rigidity)
- (intestinal fluid has striated border and PCT has brish border)
