ABSTRACT
The systems and organs of the body are composed of epithelial, connective, muscular and nervous tissues.
EPITHELIAL TISSUE Epithelium forms a protective covering over the internal and external surfaces of the body. It is derived from all three primitive embryonic layers. The ectoderm forms the skin; the mesoderm forms the pleura, pericardium and peritoneum; and the endoderm forms the endothelial lining of the blood vessels and gut.
