Final answer:
Epithelial tissues are classified by cell shape (squamous, cuboidal, columnar) and layering (simple, stratified, pseudostratified, transitional). Simple epithelia have one layer, whereas stratified epithelia have multiple layers for extra protection. These tissues perform various body functions like absorption, filtration, secretion, and protection.
Step-by-step explanation:
The classification of cell layers in the covering & lining epithelium, known as epithelial tissues, is determined by both the shape of the cells and the number of cell layers. These tissues can be categorized based on their cellular shapes and arrangements: squamous, cuboidal, or columnar epithelia.
Simple epithelia consist of a single cell layer, while stratified epithelia are comprised of stacked cells forming multiple layers.
Simple epithelia have all cells resting on the basal lamina and are found where absorption, filtration, and secretion are prominent. Stratified epithelia contain more than one layer of cells, providing protection where needed, such as in the skin.
A special kind of simple epithelium called pseudostratified appears to have multiple layers due to the varying cell heights, but actually consists of only one layer. Another unique form is transitional epithelium, which allows for stretching, as seen in the bladder.
The simple squamous epithelium is a layer of flat cells, often found where diffusion or filtration takes place, like in lung alveoli. The stratified squamous epithelium provides protection and is located in areas prone to abrasion, such as the skin, mouth, and vagina.
Cuboidal epithelial cells are cube-shaped and commonly found in glandular tissues where secretion occurs. Lastly, simple columnar epithelium consists of taller cells, primarily lining the small intestine, involved in absorption and mucus secretion.