Concepts of organs and systems Organ: composed of four kinds of the tissues in a particular way Hollow organs: studied from inside to outside vpes parenchyma Substantial organs: Interstitium System: composed of many organs which have relationship with each other in structure and functionConcepts of organs and systems Organ: composed of four kinds of the tissues in a particular way Types Hollow organs: studied from inside to outside Substantial organs: System: composed of many organs which have relationship with each other in structure and function. parenchyma interstitium