epithelial tissue

Epithelial Tissue

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GENERAL LOCATION

• Body coverings

• Body linings

• Glandular tissue

GENERAL FUNCTIONS

• Protection

• Absorption

• Filtration

• Secretion

GENERAL CHARACTERISTICS• Cells fit closely together

• Tissue layer always has one free surface

• The lower surface is bound by a basement membrane

• Avascular (no blood supply)

• Regenerates easily if well nourished

CLASSIFICATIONNumber of Cell Layers

-Simple: one cell layer

-Stratified: more than one cell layer

Cell Shape

-Squamous: flattened

-Cuboidal: cube-shaped

-Columnar: column like

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TYPES OF EPITHELIAL TISSUE

o Simple Squamous

Structure: single layer of flat cells

Function: forms membranes; lines

body cavities

Found in: capillaries, lining of lungs

SIMPLE SQUAMOUS

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Endothelium

• Specialized type of squamous cell that permits efficient diffusion of materials. Very fragile but this allows for rapid gas exchange. Found lining the heart, lungs, blood & lymph vessels.

TYPES OF EPITHELIAL TISSUE

o Simple Cuboidal

Structure: single layer of cube-like cells

often arranged around a space

(follicle)

Function: secrete fluids; absorption

Found in: kidney tubules; ovaries

SIMPLE CUBOIDAL

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TYPES OF EPITHELIAL TISSUE

o Simple Columnar

Structure: single layer of tall cells

Function: secrete mucus & enzymes;

absorption

Found in: the digestive tract lining

SIMPLE COLUMNAR

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Goblet cells

• Spherical cells that produce mucus - a lubricating material for the digestive tract

TYPES OF EPITHELIAL TISSUEo Psuedostratified (Ciliated)

Structure: hair-like projections

Function: absorption, secretion of mucus,

and aids in the movement of

particles

Found in: upper respiratory tract & reproductive

organs

PSUEDOSTRATIFIED (CILIATED)

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TYPES OF EPITHELIAL TISSUE

o Stratified

Structure: many cell layers

Function: protection in areas where friction

is common

Found in: skin, mouth, esophagus

STRATIFIED

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TYPES OF EPITHELIAL TISSUE

o Transitional

Structure: changes shape based on

amount of stretch

Function: allows for expansion

Found in: urinary tract/bladder lining

TRANSITIONAL

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SOURCES OF SLIDES

http://images.google.com/imgres?imgurl=http://www.stegen.k12.mo.us/tchrpges/sghs/ksulkowski/images/20_Simple_Columnar_Epithelial_Tissue.jpg&imgrefurl=http://www.stegen.k12.mo.us/tchrpges/sghs/ksulkowski/TissueSlides.htm&usg=__6bG6lRXNVq92ooXE_8vwTjeB25o=&h=467&w=700&sz=91&hl=en&start=3&um=1&tbnid=CJfwZ1avYGDPPM:&tbnh=93&tbnw=140&prev=/images%3Fq%3Depithelial%2Btissue%26hl%3Den%26sa%3DN%26um%3D1

http://www.unomaha.edu/hpa/2740epithelium.html#ss

Gland

• One or more cells that secrete a particular product

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TYPES OF GLANDS

Endocrine - ductless; secretions are

hormones that enter the blood

vessels

ex: thyroid, adrenal, pituitary

TYPES OF GLANDS

Exocrine - empty through ducts to the

epithelial surface

ex: sweat, oil, mammary, salivary

End.