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Pages 87-92
Epithelial TissuesLocations:
Body coveringsBody liningsGlandular tissue
Functions:ProtectionAbsorptionFiltrationSecretion
© 2015 Pearson Education, Inc.
Epithelium CharacteristicsCells fit closely together and often form sheets
The apical surface is the free surface of the tissueThe unattached surface
Can be exposed to exterior or cavity of an organ
The lower surface of the epithelium (the basal lamina) rests on a basement membraneConsists of reticular connective tissuesecures upper layers
© 2015 Pearson Education, Inc.
Epithelium CharacteristicsAvascular (no blood supply)
Relies on circulatory system to obtain food and oxygen Surrounding connective tissues supply via diffusion
from nearby capillaries
Regenerate easily if well nourished (through normal cell division)Cells on exterior of the skin are exposed to
friction and other hostile substances and are sloughed off
Classification of EpitheliaTwo name system:
First name = # of layersSecond name = shape of cells
Named using number of cell layers:Simple—one layer
Absorption/secretion/filtration are main functionsStratified—more than one layer
Ideal for protection Often found where there is friction or abuse; durable
© 2015 Pearson Education, Inc.
Figure 3.17a Classification and functions of epithelia.
Basalsurface
Apical surface
Basalsurface
Apical surface
Simple
Stratified(a) Classification based on number of cell layers
Epithelial shapesNames using shape of cells
Squamous Flattened, like fish scales
Cuboidal Cube-shaped, like dice
Columnar Column-like
© 2015 Pearson Education, Inc.
Figure 3.17b Classification and functions of epithelia.
Squamous
Cuboidal
Columnar
(b) Classification based on cell shape
Figure 3.17c Classification and functions of epithelia.
Remember these general characteristics and you will be able to classify each type a lot easier !!
Diffusion and filtrationSecretion in serous membranes
Protection
Secretion and absorption; ciliatedtypes propel mucus orreproductive cellsSecretion and absorption; ciliatedtypes propel mucus or reproductive cells
Protection; these tissue types are rarein humans
Protection; stretching to accommodatedistension of urinary structures
(c) Function of epithelial tissue related to tissue type
Number of layers
Cell shapeOne layer: simple epithelialtissues
More than one layer: stratifiedepithelial tissues
Squamous
Cuboidal
Columnar
Transitional
Pseudostratified ColumnarSingle layer
some cells are shorter than others, giving a false (pseudo) impression of stratification
© 2015 Pearson Education, Inc.
(d) Diagram: Pseudostratified(ciliated) columnar
Photomicrograph: Pseudostratifiedciliated columnar epithelium lining thehuman trachea (560×).
Basementmembrane
Basementmembrane
Pseudo-stratifiedepitheliallayer
Pseudo-stratifiedepithelial layer
Cilia
Connectivetissue
Transitional EpitheliumUnique because of its ability to become
temporarily modified in arrangement and shape
modified stratified squamous epitheliumCan stretch and reboundLocations: urinary system organs
© 2015 Pearson Education, Inc.
Figure 3.18f Types of epithelia and their common locations in the body.
Basementmembrane
Basementmembrane
Connectivetissue
Transi-tionalepithelium
Transitionalepithelium
(f) Diagram: TransitionalPhotomicrograph: Transitional epithelium lining ofthe bladder, relaxed state (270×); surface rounded cellsflatten and elongate when the bladder fills with urine.
Glandular EpitheliumTwo major gland types:
Endocrine gland Ductless; secretions diffuse into blood vessels All secretions are hormones Examples include thyroid, adrenals, and pituitary
Exocrine gland Secretions empty through ducts to the epithelial
surface Include sweat and oil glands, liver (bile duct), and
pancreas (digestive enzymes), mammary glands (milk) Includes both internal and external glands
© 2015 Pearson Education, Inc.