histologyhistology

Types of EpitheliaTypes of Epithelia

A pictorial essayA pictorial essay

Epithelial TermsEpithelial Terms

Simple: Simple: one layer thickone layer thick

Stratified: Stratified: more than one layer thick, obvious by linear more than one layer thick, obvious by linear arrangement of stained nucleiarrangement of stained nuclei

Pseudo-Stratified: Pseudo-Stratified: looks like more than one layer looks like more than one layer thick, but is actually only one layer thick.thick, but is actually only one layer thick.

Transitional: Transitional: like a super pseudo-stratified layer it is like a super pseudo-stratified layer it is used for epithelial tissue that expands and contracts many used for epithelial tissue that expands and contracts many times (like bladders, etc.)times (like bladders, etc.)

Epithelial cell typesEpithelial cell types

SquamousSquamous

CuboidalCuboidal

ColumnarColumnar

Simple squamous epitheliumSimple squamous epitheliumSquamous epithelium has that “dinner plate” look Squamous epithelium has that “dinner plate” look

(thin on edge, roundish from the top.(thin on edge, roundish from the top.

Simple Squamous Cont’dSimple Squamous Cont’d

LocationsLocations– lining of ventral body cavitieslining of ventral body cavities– lining of heart and blood vesselslining of heart and blood vessels– lining of portions of kidney tubuleslining of portions of kidney tubules– cornea of eye, and alveoli of lungscornea of eye, and alveoli of lungs

FunctionsFunctions– reduce frictionreduce friction– control permeabilitycontrol permeability– perform absorption and secretion functionsperform absorption and secretion functions

Stratified squamous epitheliumStratified squamous epitheliumLayers of Squamous cells on the apical side with Layers of Squamous cells on the apical side with

layers of stem cells on the basal side.layers of stem cells on the basal side.

Stratified squamous cont’dStratified squamous cont’d

LocationLocation– surface of skinsurface of skin– lining of mouth, throat, esophagus, rectum, lining of mouth, throat, esophagus, rectum,

anus and vaginaanus and vagina

FunctionFunction– provide physical protection against abrasion, provide physical protection against abrasion,

pathogens, and chemicalspathogens, and chemicals

Simple cuboidal epitheliumSimple cuboidal epitheliumCells shaped like cubes, with very large nucleiCells shaped like cubes, with very large nuclei

Simple cuboidal cont’dSimple cuboidal cont’d

LocationLocation– glands, ducts, portions glands, ducts, portions

of kidney tubules, of kidney tubules, thyroid glandthyroid gland

FunctionFunction– Limited protection, Limited protection,

secretion and/or secretion and/or absorptionabsorption

Stratified cuboidal epitheliumStratified cuboidal epitheliumSame cells as simple, just several layersSame cells as simple, just several layers

Stratified cuboidal cont’dStratified cuboidal cont’d

LocationLocation– lining of some ducts (rare)lining of some ducts (rare)

FunctionFunction– protectionprotection– secretionsecretion– absorptionabsorption

Simple columnar epitheliumSimple columnar epitheliumThe cells are column shaped and generally The cells are column shaped and generally

have the nucleus in the lower half.have the nucleus in the lower half.

Simple columnar cont’dSimple columnar cont’d

Simple columnar cont’dSimple columnar cont’d

LocationLocation– lining of stomach, intestine, gallbladder, uterine lining of stomach, intestine, gallbladder, uterine

tubes, collecting ducts of kidneytubes, collecting ducts of kidney

FunctionFunction– protectionprotection– secretionsecretion– absorptionabsorption

Pseudostratified columnar Pseudostratified columnar epitheliumepithelium

Columnar cells whose nuclei fool you into thinking they are Columnar cells whose nuclei fool you into thinking they are stratified.stratified.

Pseudostratified columnar Pseudostratified columnar cont’dcont’d

This one is ciliated and pseudostratified

Pesudostratified columnar Pesudostratified columnar cont’dcont’d

LocationLocation– tracheatrachea– lining of nasal cavity, bronchilining of nasal cavity, bronchi

FunctionFunction– protectionprotection– secretionsecretion– mucous transportmucous transport

Stratified columnar epitheliumStratified columnar epitheliumStacked columnar cellsStacked columnar cells

Stratified Columnar Cont’dStratified Columnar Cont’d

Stratified columnar Cont’dStratified columnar Cont’d

LocationLocation– salavary gland ductsalavary gland duct– small areas of pharynx, epiglottis, anus, small areas of pharynx, epiglottis, anus,

mammary ducts, and urethramammary ducts, and urethra

FunctionFunction– protectionprotection

Transitional epitheilumTransitional epitheilumLook carefully at the cells, they appear Look carefully at the cells, they appear

different shapes and bunched up.different shapes and bunched up.

Transitional cont’dTransitional cont’d

LocationLocation– urinary bladderurinary bladder– renal pelvisrenal pelvis– uretersureters

FunctionFunction– permit expansion and recoil after stretchingpermit expansion and recoil after stretching

Test yourselfTest yourself

What type of epithelial tissue is this ?

The answerThe answer

If you guessed:

Ciliated Pseudostratified Columnar Epithelium

You were RIGHT !, Congratulations

End of showEnd of show

Stay tuned for our next exciting episode:

The Attack of the Ancient Connective Tissue