ABSTRACT
Human cells vary greatly in sophistication and function from relatively simple skin cells to highly specialised nerve cells. There are over 200 different types of cell in the human body including skins cells, bone cells, blood cells and nerve cells. For the most part, human cells require three basic components: a cell membrane, cytoplasm and a nucleus. All cells need some form of plasma membrane in order to maintain structural integrity. Anyway, in human cells, amphipathic phospholipid molecules are arranged in a continuous bi-layer and provide a highly impermeable barrier. This chapter looks at the body on an atomic, molecular and a cellular level. In terms of size and complexity, the next functional unit of the body is tissue. There are four distinct categories of tissue: epithelial, connective, muscular and nervous. Loose connective tissue is typically found beneath epithelial membranes and glandular epithelium. It binds loose connective tissues to other tissues and contributes to the formation of organs.
