A Level Biology Practice Exam

Squamous epithelial cells are characterized by their flattened, scale-like shape. This specific morphology allows these cells to form a thin layer that is ideal for processes such as diffusion and filtration. The arrangement in a single layer provides a barrier and is commonly found lining surfaces that require minimal resistance to movement, such as the alveoli in the lungs or the lining of blood vessels. Their flat structure facilitates the exchange of gases and nutrients, making them essential in various biological contexts.

In contrast, the other options describe different types of epithelial cells: columnar epithelial cells are taller and often found in areas where absorption and secretion occur; cuboidal cells are box-like and typically involved in secretion and absorption as well; and ciliated epithelial cells have hair-like projections that help in moving substances across their surface. Each of these types has distinct shapes and functions that differentiate them from squamous cells.