EXSC%223:%Week%of%9/19/16%%Notes%from%the%textbook%Ch.%4.2%4.2$Epithelial$tissue$covers$body$surfaces,$lines$cavities,$and$forms$glands$• Epithelial$tissue:$sheet$of$cells$that$covers$a$body$surface$or$lines$a$body$cavity$• Two$forms$exist$in$the$body$o Covering$and$lining$epithelium$§ Forms$outer$layer$of$skin$§ Lines$open$cavities$of$urogenital,$digestive,$and$respiratory$systems$§ Covers$walls$and$organs$of$closed$ventral$body$cavity$o Glandular$epithelium$§ Fashions$the$glands$of$the$body$• Epithelia$form$boundaries$between$different$environments$• Functions$o Protection$o Absorption$o Filtration$o Excretion$o Secretion$o Sensory$reception$• Characteristics$of$epithelia$o Polarity:$all$epithelia$have$an$apical$surface$(upper,$free$surface$exposed$to$body$exterior$or$cavity$of$internal$organ)$and$a$basal$surface$(lower,$attached)$§ Apical-basal$polarity$o Specialized$contacts$§ Fit$close$together$and$form$continuous$sheets$§ Tight$junctions$and$desmosomes$bind$adjacent$cells$together$§ Tight$junctions$keep$proteins$in$the$apical$region$from$going$to$the$basal$region$o Supported$by$connective$tissue$§ Epithelial$sheets$supported$by$connective$tissue$o Avascular$but$innervated$§ Avascular:$no$blood$vessels$§ Innervated:$supplied$by$nerve$fibers$§ Cells$nourished$by$substance$diffusing$from$blood$vessels$o Regeneration$§ High$regenerative$capacity$• Classification$of$epithelial$tissue$o Number$of$cells$present$§ Simple:$single$cell$layer$• Absorption,$secretion,$filtration$§ Stratified:$2$or$more$cell$layers$stacked$• High$abrasion$areas,$protection$needed$o Shapes$of$cells$§ Squamous:$flattened,$scale-like$§ Cuboidal:$boxlike,$approximately$as$tall$as$it$is$wide$§ Columnar:$tall,$column$shaped$• Types$o Simple$squamous$§ Single$layer,$flat$cells$§ Allows$diffusion$and$filtration$§ Ex:$blood$vessels$o Simple$cuboidal$§ Single$layer,$cube-like$cells$§ Secretion$and$absorption$§ Ex:$kidney$tubules$o Simple$columnar$§ Single$layer$of$tall$cells$§ Absorption,$secretion$of$mucus$§ Ex:$digestive$tract$o Pseudostratified$columnar$§ Single$layer,$differing$heights,$nuclei$seen$at$different$levels$§ Secrete$things,$especially$mucus$§ Ex:$trachea$o Stratified$squamous$§ Several$layers,$basal$cells$are$cuboidal,$surface$are$squamous$§ Protects$underlying$tissues$from$abrasion$§ Ex:$esophagus,$mouth,$vagina,$skin$(keratinized$version)$o Transitional$epithelium$§ Resembles$stratified$squamous$and$stratified$cuboidal$§ Basal$cells$are$cuboidal$or$columnar,$surface$cells$are$dome$shaped/squamous-like$§ Stretches$readily$§ Ex:$ureter,$bladder,$urethra$• Glandular$epithelia$o Gland:$one$or$more$cells$that$make$and$secrete$a$particular$product$(secretion)$§ Exocrine:$externally$secreting$• Secrete$products$onto$the$skin$or$into$body$cavities$• Ex:$salivary$glands$§ Endocrine:$internally$secreting$• Ductless$• Produce$hormones$$Lecture%Notes%9/19%Epithelial$tissue$• Simple$squamous$o Sheets$of$cells,$held$together$by$cell$junctions$o Thin$flat$cells$§ Good$for$diffusion$• Oxygen$crossing$the$epithelia$into$blood$vessels$• Simple$cuboidal$o In$kidneys$(proximal$and$convoluted$tubules$of$nephrons)$o Function:$excretion$and$absorption$• Simple$columnar$o Nuclei$are$on$the$same$level$across$the$cells$o Ex:$microvilli,$goblet$cells$o Non-ciliated$ones$are$in$the$digestive$tract$• Pseudostratified$columnar$o Nuclei$not$on$the$same$level,$they$are$scattered$o In$the$trachea$§ Ciliated:$helps$move$mucous$out$of$the$lungs$• Stratified$squamous$o Cuboidal$shaped$cells$towards$the$basal$layer$o Flatten$and$become$more$squamous$towards$the$apical$layer$• Transitional$o Characteristics$combination$between$stratified$squamous$and$stratified$cuboidal$Glandular$epithelium$• Gland:$consist$of$one$or$more$cells$that$make$and$secrete$a$particular$product$o Secretion$made$of$protein$o Two$types$of$glands:$endocrine$and$exocrine$• Endocrine$o Ductless$o Produce$hormones$secreted$directly$into$the$extracellular$space$within$the$body$• Exocrine$o Has$ducts$o Secretes$through$ducts$onto$body$surfaces$of$cavities$o Excretions$include:$mucous,$sweat,$oil,$saliva,$bile$• Classifications$of$exocrine$glands$o Unicellular$§ Single$cells$scattered$in$an$epithelial$sheet$with$other$cell$types$• No$duct$• Ex:$goblet$cells$§ Goblet$cell$• Associated$with$simple$columnar$pseudostratified$epithelium$• Needs$a$lot$of$energy$to$produce$and$secrete$mucin$(glycoprotein)$o Mixes$with$waste$to$form$mucous$• In$respiratory$and$intestinal$tract$• Mucin=protein$component$of$mucus$by$exocytosis$• Lots$of$vesicles,$rough$ER,$golgi$o Function$for$exocytosis$o Principle$of$complementarity$o Multicellular$§ Epithelium$derived$duct$and$secretory$unit$of$secretory$cells$o 2$parts$of$exocrine$gland$§ duct$§ secretory$region$o simple$vs$compound$§ number$of$ducts$§ simple:$1$duct$§ compound:$more$than$1$duct$o tubular$vs$alveolar$§ shape$of$secretory$region$§ tubular:$tube$shaped$§ alveolar:$round$sac$shaped$o modes$of$secretion$§ merocrine:$products$secreted$by$exocytosis$• ex:$pancreas,$sweat$glands,$salivary$glands$§ holocrine:$products$secreted$by$rupture$of$gland$cells,$“puking”$• ex:$sebaceous$glands$$Notes%from%textbook%Ch.%4.4-4.5%4.4$Muscle$tissue$is$responsible$for$body$movement$• Muscle$tissue$o Highly$cellular$o Well-vascularized$o Responsible$for$most$types$of$body$movement$o Possess$myofilaments$§ Elaborate$networks$of$actin$and$myosin$filaments$o Three$types$§ Skeletal$§ Cardiac$§ Smooth$o Voluntary$§ Muscle$under$conscious$control$§ Skeletal$o Involuntary$§ Muscle$not$consciously$controlled$§ Cardiac$and$smooth$• Skeletal$muscle$o Structure:$long,$cylindrical,$multinucleated,$obvious$striations$o Function:$voluntary$movement,$locomotion,$manipulation$of$the$environment$o Location:$in$skeletal$muscles$attached$to$bones$or$skin$• Cardiac$muscle$o Structure:$branching,$striated,$generally$uninucleated$o Function:$as$it$contracts,$it$propels$blood$into$circulation,$involuntary$control$o Location:$walls$of$the$heart$• Smooth$muscle$o Structure:$spindle$shaped,$elongated,$central$nuclei,$cells$arranged$closely$to$form$sheets$o Function:$propels$substances$or$objects$along$internal$passageways,$involuntary$control$o