The Cytoplasm

Abstract

Cells and extracellular material together comprise the tissues that make up animal organs. In all tissues, cells are the basic structural and functional units, the smallest living parts of the body. Animal cells are enclosed by cell membranes and are eukaryotic, each with a distinct, membrane-enclosed nucleus surrounded by cytoplasm, fluid containing a system of membranous organelles, nonmembranous molecular assemblies, and a cytoskeleton. In contrast, the smaller prokaryotic cells of bacteria typically have a cell wall and lack nuclei and membranous cytoplasmic structures.