Epithelia Flashcards
germinal epithelium
develop gamete-haploid. Males: seminiferous tbules has sertoli cells produce spermatozoa. Females:ovarian surface (waldeyer) simple squamous and cuboidal cells.
secretory epithelium
planar+trabecular epithelium. both secretory glands (endo+exo) units supported by stroma of CT. in larger glands layer of CT also surround duct forming separate lobules (w secretory units ) enclosed w capsule (capsulated)
Endocrine- secrete hormones absorbed +trasnported to blood. single cells or groups+no duct (obliterated connection w surface epithelium)
Exocrine: secretion enter duct, cavity/body surface. unicellular (goblet cells) muticellular (glands w duct: connection preserved w epithelium)
Paracrine: secrete material reach target cell through diffusion by extra cellular space. subjacent to CT.
serous cells
- has serous cells: large enzyme= ALPHA AMYLASE non glycosylated stain PAS - and EOSINOPHILIC but cyto BASOPHILIC has well filled rer+GA w secretory granules. round nucleus, euchromatin. apical domain has tight+ adherent junction- accinar in shape.
acini of pancreas + parotid/salivary glands. epner glands in tongue conc in circumvallate papillae
(parotid- serous acini drain to intercalated duct then form large striated duct. lined w columnar epithelium)
mucous cells vs seromucous
- mucous cells: goblet cells; low columnar cells, nuclei flat +condensed, cyto mucigenous (mucins) hydrate to make musoucs- glycosylated proteins stain PAS + and ALCIAN BLUE (basophilic bc mucin is GAG). Mucin is hydrophilic so stains poorly w eosin (washes away). tubulsar in shape
minor glands (distributed throughout oral+submucosa+has plasma cells), weber glands (salivary- open at lingual tonsil. serous but has mucous membrane). palatine glands. glands are developed from covering epithelia in featus by cell proliferation onto CT- serous mucous: on some salivary galnds (serousa cinar+tubules) product watery mucous +digestive enzyme
mechanism of exocrine secretion
merocrine- secretory procuduct released into vesicles of apical surface of cell. fise w PM+ excrudes contents by exocytosis serous+mucous cell. Eccrine sweat gland+salivary and mammary glands.
eccrine glands: simple tubular coiled, myoepithelium+stratified duct (2 layers unfolding of basolateral membrane along elongated mitochondria). cuboidal epithelial on surface
apocrine: secretory product accumulated on apical cell ends, excruded to release w a but of cytoplasm and portion of PM. how droplets of lipids released in mammary glands+aromatic glands of skins=axilla
holocrine: not apoptosis, secretory product accumulate within maturing cell. cause rupture of cells releasing product+cell debris onto lumen. sabecous glands
sabecous glands
branched acinar, ducts, hair follicles in surface of vermilion zone (stratified squamous becoming thinner lose epithelium at junction and become non keratinized, highly innervated and vascularised area, has melanocytes)+ areola
appocrine sweat glands
in axila+perineal region
coiled tubular merocrine glands
2 layers of stratified duct w cuboidal cells
myoepithelium
composed pheromones
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 0.5um 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)
lateral domain
lateral domain tight junction (occludens) forms tight relationships w neighbouring cells- most apical, forms band encircles each cell. transmembrane proteins act sealing strands to form barrier on apical end (CLAUDINS+OCCLUDIN).
- F: control transport of mol by redirecting to go through cell=trasncellular rather than paracellular. force to go through intracellular cleft
- few in PCT- very permeable to water
- prevents membrane protein at one apical end to move= two domains basolateral and apical
- diffusion of outer memb= pentalaminar sheets help reg permeability
Desmosome- disc-shaped.
- F: attach IF to cell. contain large member of cadherin fam DESMOGLEIN+DESMOCOLLIN- insert to dense attachment plaque of anchoring proteins= DESMOPLANKIN+PLAKOGLOBIN.
- non-epithelial cells, intermediate f attach to desmososme via VIEMENTIN+DESMIN. most common cable-like filament is CYTOKERRATIN.
- in most stratified squamous spithelia keratinized to protect against water loss.
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+
Communicating junctions- 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)
basal domain+basement membrane
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. 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)
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 lmaina 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
