In botany, parenchyma is the primary tissue of higher plants composed of thin-walled cells that remain capable of cell division, even when mature. These cells are often almost as broad as long, and are permeated by a system of intercellular spaces containing air. Parenchyma makes up the greater part of leaves, roots, the pulp of fruits, and the pith of stems. It constitutes fundamental plant tissues as opposed to more highly differentiated tissues.
In zoology, parenchyma is (a) loose tissue consisting of irregularly-shaped vacuolated cells, forming a large part of the body of flatworms (Platyhelminthes), or (b) the specific cells of an organ, as contrasted with the organ's blood vessels, nerves, and connective tissue.