Final answer:
The single layer of cells where some are tall and thin indicates a simple columnar epithelium, a simple epithelium where each cell contacts the basal lamina and is involved in functions such as absorption.
Step-by-step explanation:
The single layer of cells described, where some are tall and thin and others are not reaching the free surface, refers to a type of epithelial tissue known as simple epithelium. In particular, the specification of the tall and thin cells suggests that this is simple columnar epithelium. Simple epithelium is characterized by a single layer of cells, with each cell being in contact with the basal lamina. On the other hand, stratified epithelium has more than one layer of cells, but only the basal layer touches the basal lamina. The term pseudostratified pertains to tissue with a single layer of cells that gives the illusion of being stratified due to the arrangement of nuclei at different levels within the cells. Simple columnar epithelial cells are notably taller than they are wide and are typically found lining organs such as the small intestine, where they are involved in absorption, and contain microvilli on their free surface to increase the surface area.