The cells of the epithelial tissue have what we call 'polarity'. This means that the cells have both an apical and basal surface. The basal surface of the cell is attached to the basal lamina of the basement membrane. Note that the apical surface may bear microvilli(microscopic cellular membrane protrusions that increase the area of a cell) and cilia(latin for 'eyelashes' which are hair-like structures that help moves the cell around or tiny substances around the cell).
The cells of the epithelial tissue are also closely packed. These cells are held together by intercellular connections. If you notice the diagram above, you find that the epithelial tissue is supported by the reticular lamina(a thin extracellular layer that lies below the basal lamina which comprises mainly of collageneous fibers).
The epithelial tissue is avascular. It also rapidly divides via mitosis, thus, damaged or dead cells are quickly(not so fast but fast enough) replaced by new ones.
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