Classification of Epithelial Tissues: Stratified Epithelium

The stratified epithelium is a multi-layered tissue covering exposed body surfaces.

Cells at the bottom layer continuously divide to replace the old, damaged cells that wear off from the exposed surface.

Stratified epithelia can be squamous..., cuboidal..., and columnar....

Squamous epithelia have flattened cells at the surface and cuboidal or columnar cells in deeper layers.

Squamous epithelia on the skin epidermis have anucleated surface cells densely packed with keratin filaments. Such keratinized epithelia make surfaces like the foot sole or palm sturdy and water-resistant.

Non-keratinized epithelia have nucleated surface cells containing less keratin. They line moist surfaces of the oral cavity, esophagus, and anus.

The cuboidal epithelia form the ducts of sweat and mammary glands, while the columnar epithelia line and protect specific areas of the pharynx and epiglottis.

Transitional epithelium is a specialized lining on organs like the urinary bladder. When the organ is stretched, the apical cells change their shape from cuboidal to squamous, allowing the epithelium to thin out. This transition enables the bladder to expand while storing urine.