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 tissue Covers all free body surfaces Functions include: --Protection --Absorption --Filtration --Secretion

Special Characteristics Forms continuous sheets Cells packed close together Have an apical surface (free edge) that is exposed Epithelial tissue rests on a Basement Membrane Avascular—Epithelials have no direct blood supply Epithelials 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. Stratified Simple 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

STRATIFIEDSTRATIFIED

Simple Squamous Single layer of this squamous cells Rests on a basement membrane Cells fit closely together Function in Absorption or Rapid Diffusion Form serous membranes that line the ventral cavity

Simple Squamous Found in air sacs of lungs Forms the walls of capillaries

Simple Cuboidal Single layer of cuboidal cells Rests on a basement membrane Found in glands Helps to form glandular ducts

Simple Cuboidal Forms the walls of the Kidney’s tubules Covers the surface of the ovaries

Simple Columnar Made up of a single layer of columnar cells Tall cells that are fit close together Rests on a basement membrane

Simple Columnar Lines the entire length of the digestive tract

Pseudostratified Columnar Single layer of cells Varying sizes of cells with nuclei at differing heights Rests on a basement membrane Functions in absorption and secretions

Pseudostratified Columnar Lines the respiratory tract Goblet cells are present and produce mucus Mucus traps debris and dust

Stratified Squamous Most common stratified epithelial tissue Consists of several layers of cells Found at sites of friction Durable tissue

Stratified Squamous Found in the esophagus, mouth and outer skin

Stratified Cuboidal Multi-layered tissue type Found in ducts of large organs

Stratified Columnar Multi-layered tissue type Found in ducts of large organs

Transitional Highly modified, stratified squamous epithelium Forms the lining of the urinary bladder and ureters Urinary system organs have the ability to stretch Cells can slide past one another and stretch Greater volume is created More 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 product Ex.) Endocrine or Exocrine Glands Secretion  protein 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 directly ex.) Thyroid, Adrenal and Pituitary Glands Exocrine gland  contain ducts  secretions empty to the surface ex.) Sweat & Oil Glands, Liver and Pancreas