Final answer:
In stratified epithelia, cell shapes vary among the layers with squamous shapes on the surface and possibly columnar or cuboidal in deeper layers. Transitional epithelia demonstrates variability in cell shape, illustrating this variation as it adapts to the filling and emptying of the urinary bladder.
Step-by-step explanation:
Stratified Epithelia Cell Shapes
In stratified epithelia, the cell shapes usually differ among the several stacked layers of cells that make up the tissue. The stratified epithelium is named after the shape of the most apical layer of cells, which is closest to the free space. Stratified squamous epithelium, the most common type found in the human body, has squamous apical cells, while the deeper basal layer may contain either columnar or cuboidal cells. For instance, in transitional epithelium, found in the urinary system, the shapes of the apical cells can vary significantly depending on whether the bladder is full or empty, transitioning from cuboidal to squamous as the bladder extends with urine.
In cases like the skin, the apical layers may have dead cells filled with keratin (keratinized), while in the lining of the mouth, the tissue is non-keratinized. Other forms such as stratified cuboidal or columnar epithelia are less common and are typically found in specific glands and ducts. It is essential to understand that in stratified epithelial tissues, very few capillaries penetrate these tissues, which is why they rely on the basal layers for nutrition and waste removal.