what is epithelial tissue and where can you find it in the body?

What is epithelial tissue

and where can you find

it in the body?

What is Epithelial Tissue?Acts as a lining, covering or glandular body

tissueCovers all free body surfacesFunctions include:

--Protection--Absorption--Filtration--Secretion

Special CharacteristicsForms continuous sheetsCells packed close togetherHave an apical surface (free edge) that is

exposedEpithelial tissue rests on a Basement

MembraneAvascular—Epithelials have no direct blood

supplyEpithelials regenerate easily (if well

nourished)

Shapes of epithelial cells:Epithelial Cells can be one of three shapes:1.) Squamous

2.) Cuboidal

3.) Columnar

Simple vs. StratifiedSimple Epithelial Tissue:

--Single layer of cells--Work in Absorption, Secretion or

Filtration--Not a protective tissue

Stratified Epithelial Tissue:--Consists of two or more layers--Function to protect

STRATIFIED

Simple SquamousSingle layer of this squamous cellsRests on a basement membraneCells fit closely togetherFunction in Absorption or Rapid DiffusionForm serous membranes that line the ventral

cavity

Simple Squamous

Found in air sacs of lungsForms the walls of capillaries

Simple CuboidalSingle layer of cuboidal cellsRests on a basement membraneFound in glandsHelps to form glandular ducts

Simple Cuboidal

Forms the walls of the Kidney’s tubulesCovers the surface of the ovaries

Simple Columnar

Made up of a single layer of columnar cellsTall cells that are fit close togetherRests on a basement membrane

Simple Columnar

Lines the entire length of the digestive tract

Pseudostratified Columnar

Single layer of cellsVarying sizes of cells with nuclei at differing

heightsRests on a basement membraneFunctions in absorption and secretions

Pseudostratified Columnar

Lines the respiratory tractGoblet cells are present and produce mucusMucus traps debris and dust

Stratified SquamousMost common stratified epithelial tissueConsists of several layers of cellsFound at sites of frictionDurable tissue

Stratified Squamous

Found in the esophagus, mouth and outer skin

Stratified CuboidalMulti-layered tissue typeFound in ducts of large organs

Stratified ColumnarMulti-layered tissue typeFound in ducts of large organs

Transitional Highly modified, stratified squamous

epitheliumForms the lining of the urinary bladder and

uretersUrinary system organs have the ability to

stretchCells can slide past one another and stretchGreater volume is createdMore Urine is able to be stored

Transitional Epithelium

Glands--cells obtain what they need from the blood

and use them to make their secretion

Glands contains cells that secrete a productEx.) Endocrine or Exocrine Glands

Secretionprotein molecules in a water based fluid

Secretion is discharged once produced

Glandular Epithelium

Endocrine vs. Exocrine

Endocrine gland ductless gland secretions diffuse into the blood directlyex.) Thyroid, Adrenal and Pituitary Glands

Exocrine glandcontain ductssecretions empty to the surfaceex.) Sweat & Oil Glands, Liver and

Pancreas