types of epithelium. © 2013 pearson education, inc. classification of epithelia all epithelial...
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© 2013 Pearson Education, Inc.
Classification of Epithelia
• All epithelial tissues have two names– One indicates number of cell layers
• Simple epithelia = single layer of cells• Stratified epithelia = two or more layers of cells
– Shape can change in different layers
– One indicates shape of cells• Squamous• Cuboidal• Columnar
• In stratified epithelia, epithelia classified by cell shape in apical layer
© 2013 Pearson Education, Inc.
Figure 4.2a Classification of epithelia.
Basal surfaceStratified
Classification based on number of cell layers.
Basal surfaceSimple
Apical surface
Apical surface
SIMPLE SQUAMOUS EPITHELIUM
Single layer of thin, flattened cells Broad thin nucleus (disc shaped)
Fxn: allows passage of materials by diffusion and filtration where protection is not important
Examples: air sacs (alveoli) Capillary walls, lining the heart, lining of ventral body
cavity, kidney glomeruli
Simple Cuboidal Epithelium
Single layer of cube shaped cellsCentrally located, spherical nucleus
FXN: Secretion and absorption
Ex: ovaries, kidney tubules, salivary glands, thyroid, pancreas, liver
Simple Columnar Epithelium
Elongated (longer than they are wide)
Nuclei located near/on basement membrane
(often you will find microvilli on surface)
(also find goblet cells)
Simple Columnar
Found: Lining most of Digestive tract (non-ciliated type), gallbladder, excretory ducts of some glands; small bronchi, uterine tubes, regions of uterus
Function: Absorption, secretion of mucous, enzymes and other substances
Stratified Squamous Epithelium
Multiple layer of squamous cells Two Main Types 1. Keratinizedouter layer of epidermis of the
skin.2. Non-keratinized Ex: mouth, throat, anus(cells on free surface remain alive) Definitely Protection!!
Stratified cuboidal Epithelium
2-3 layers of cuboidal cells (form lining of lumen)
-protection -sweat glands, mammary glands, salivary
glands, glands of pancreas
Stratified Columnar
RARE!!!
2-4 layers of elongated cellsProtectionEx: Male urethra, Vas deferens, parts of
pharynx
Pseudostratified Columnar
Appears to be stratified or layered. (BUT THEY ARE NOT)!!
Cell nuclei are actually at different levels in the row, but all cells are attached to the basement membrane.
Usually, but not always ciliated. Protection and Secretion
Ex: Trachea lining in the respiratory system
Transitional Epithelium
Specialized epithelium designed to change in response to increased tension. Stretches, changing apical cuboidal cells into squamous cells.
Many Layers
Ex: Bladder, ureters, parts of urethra