Tissues. The human body is a complex machine made up of many parts. Although diverse in structure and function, all body parts are constructed of four basic tissue types: 1) epithelia, 2) connective, 3) muscle, and 4) nervous tissues. Consider these basic tissue types as the lego building blocks of the human body. During development, these building blocks are put together in many different ways to build the anatomical elements of the body. Anatomy always relates to physiology or more concisely, structure relates to function. Remember this as you learn about these tissue types. The differences between tissues and how they might appear under the microscope always relates to the particular functions they provide.