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- Widespread throughout body, covers most surfaces inside and out,
major tissue of glands.
- Cells reproduce readily
- Cells are tightly packed with little intercellular material
Epithelial tissues are classified according to the arrangement, shape and function
of their cells.
Arrangement of Cells
- A single layer of cells is called 'simple'.
- Many layers of cells are called 'stratified'.
Shape of cells
- Squamous -thin irregular shaped cells.
- Cuboidal -Cube shaped cells.
- Columnar -parallel thin cells.
- Transitional -cells which change shape
Examples of Epithelial tissues
Simple Squamous Epithelium
Single layer of thin irregularly shaped cells, with centrally located nuclei.
Allows movements of substances through membranes such as filtration or rapid
diffusion of gases.
Alveoli in the lungs, lining of lymph and blood vessels, glomerulus of kidney,
Simple Cuboidal Epithelium
Low magnification image Note: centrally located nuclei.
High magnification image
Note: cells in upper right hand corner show typical cuboidal shape.
See notes above
Lining of kidney tubules, lining of glands, surface of ovary.
Simple Columnar Epithelium
Note: The columnar epithelium is the lower half of the (purple) tissue.
Column shaped cells, nuclei located in the lower 1/3 of cell. Often this tissue
has cilia and goblet cells present (not seen here).
Lining of digestive tract (from stomach to rectum). Lines uterine tubes and parts of
uterus. Lines some of the smaller bronchii.
These cells appear stratified or layered but are not. Cells all reach the
but some may not contact the free surface. Note nuclei in
a row at the bottom of the tissue, but also scattered throughout. Cell walls
hard to see in this image. Often possess cilia (seen here on outer -top- surface)
and goblet cells (also visible).
- Movement of Mucus
Lining of trachea, parts of reproductive system (male urethra),
ducts of some glands.
Stratified Squamous Epithelium
Note: Tissue is the darker purple band making up roughly the central third
of the image.
Many layers of cells, therefore quite thick. Individual cell walls are not
visible, cells are indicated by nuclei. Usually 10+ layers thick.
Outer epidermis of skin, lining of anal canal, lines esophagus, pharynx, mouth
note: Low magnification. Tissue is darker band roughly halfway down image -lower half of tissue.
Several layers thick, cells change shape as tissue is distended.
Cell walls not
visible, so count the individual nuclei to determine the number of layers of cells.
In this image, the tissue is 3 -4 cells thick.
- distensibility (stretchiness)
Lining of parts of urinary tract: parts of urethra, ureter