EPITHELIAL TISSUEEPITHELIAL TISSUE

General Features of General Features of EpitheliumEpithelium• Consists of packed cells with little Consists of packed cells with little

extracellular material between themextracellular material between them• Cells are arranged in continuous sheets, in Cells are arranged in continuous sheets, in

either single or multiple layerseither single or multiple layers• Have a free surface and a basal surfaceHave a free surface and a basal surface• Are Are avascular : a- avascular : a- without without vascular-vascular- blood blood

vesselsvessels• Have nerve supplyHave nerve supply• High capacity for renewal by cell divisionHigh capacity for renewal by cell division

Covering and Lining Covering and Lining EpitheliumEpithelium

Classification by shapeClassification by shape

• Squamous - flatSquamous - flat

• Cuboidal – cubes or hexagonsCuboidal – cubes or hexagons

• Columnar – tall, rectangular and Columnar – tall, rectangular and cylindricalcylindrical

• Transitional – range in shape from flat Transitional – range in shape from flat to columnar and often change shapeto columnar and often change shape

Classification by Arrangement of LayersClassification by Arrangement of Layers

• Simple – single layer in areas of diffusion, Simple – single layer in areas of diffusion, osmosis, filtration, secretion and osmosis, filtration, secretion and absorptionabsorption

• Stratified – two or more layers used for Stratified – two or more layers used for protecting underlying tissuesprotecting underlying tissues

• Pseudostratified columnar – contains one Pseudostratified columnar – contains one layer, appears to have several layers but layer, appears to have several layers but not all cells reach the surface, ciliated or not all cells reach the surface, ciliated or secrete mucoussecrete mucous

Types of Epithelial Tissue

Simple Squamous Simple Squamous EpitheliumEpithelium

Single layer, flat cells, central nucleusSingle layer, flat cells, central nucleus

Lines the heart, blood vessels, lymphatic Lines the heart, blood vessels, lymphatic vessels, alveoli, glomerular capsules, and vessels, alveoli, glomerular capsules, and

forms the epithelial layer of serous forms the epithelial layer of serous membranesmembranes

Function: filtration, diffusion, osmosis, Function: filtration, diffusion, osmosis, secretion in serous membranessecretion in serous membranes

Simple Squamous Epithelium

Simple Cuboidal EpitheliumSimple Cuboidal Epithelium

Single layer, cube shaped, central Single layer, cube shaped, central nucleusnucleus

Lines the tubes and smaller ducts of Lines the tubes and smaller ducts of the kidneysthe kidneys

Function: secretion and absorptionFunction: secretion and absorption

Glomerular CapsulesRenal Cortex

Simple Cubiodal Epithelium

Nonciliated Simple Columnar Nonciliated Simple Columnar EpitheliumEpithelium

Single layer, nonciliated, rectangular, Single layer, nonciliated, rectangular, cylindrical cells, nucleus at base, contain cylindrical cells, nucleus at base, contain goblet cells, some have microvilligoblet cells, some have microvilli

Lines GI, respiratory, reproductive and Lines GI, respiratory, reproductive and urinary tractsurinary tracts

Function: secretion and absorptionFunction: secretion and absorption

Simple Columnar Epithelium in Small Intestine

Stratified Squamous Stratified Squamous EpitheliumEpitheliumSeveral layers, cuboidal or columnar deep, Several layers, cuboidal or columnar deep,

squamous superficial, basal cells replace squamous superficial, basal cells replace surface cellssurface cells

Keratinized epidermis, nonkeratinized lines Keratinized epidermis, nonkeratinized lines the mouth, esophagus, vagina and tonguethe mouth, esophagus, vagina and tongue

Function: protectionFunction: protection

Stratified Squamous Stratified Squamous EpitheliumEpithelium

Transitional EpitheliumTransitional Epithelium

Variable cell shapes, superficial cells Variable cell shapes, superficial cells squamous when stretched, cuboidal squamous when stretched, cuboidal when relaxedwhen relaxed

Lines urinary bladder and portions of Lines urinary bladder and portions of ureters and urethraureters and urethra

Function: permits organs to stretch Function: permits organs to stretch without rupturingwithout rupturing

Transitional EpitheliumTransitional Epithelium

Pseudostratified Columnar Pseudostratified Columnar EpitheliumEpithelium

Not true stratified tissue, cells at different Not true stratified tissue, cells at different layers, all cells attached to basement layers, all cells attached to basement membrane, only some reach surfacemembrane, only some reach surface

Ciliated lines airways of most of the upper Ciliated lines airways of most of the upper respiratory tract (trachea)respiratory tract (trachea)

Function: secretion and movement of mucusFunction: secretion and movement of mucus

Ciliated Pseudostratified Columnar Epithelium

Glandular EpitheliumGlandular Epithelium

• Endocrine –Endocrine – ductless glands ductless glands

Pituitary, thyroid, and adrenal glandsPituitary, thyroid, and adrenal glands

• Exocrine –Exocrine – glands with ducts glands with ducts

Sweat and salivary glandsSweat and salivary glands