the.com/epithelium
The body's wallpaper, lining every surface that touches the outside or a hollow inside.
means The tightly packed sheet of cells covering your skin, organs, and the insides of your tubes and cavities.
from Greek epi (upon) plus thele (nipple), coined when anatomists first spotted it draped over nipple tissue.
No bloodAvascular; it feeds by diffusion from below.
Fast turnoverGut lining renews itself every few days.
GatekeeperControls what enters and exits the body.