Constitution of the Body
From the smallest to the largest dimension of its components, six levels of organization are relevant for understanding anatomy and physiology: the chemical, cellular, tissue, organic, systemic and organismic levels .
Chemical Level: Includes atoms (smallest units of matter that participate in chemical reactions) and molecules (two or more atoms linked together).
Cell Level: The union of molecules forms cells. Cells are the basic, structural and functional units of the human body.
Tissue Level: Tissues are groups of cells and materials around them, which work together to perform a certain cellular function. There are four basic types of tissue in your body: epithelial, connective, muscular and nervous tissue.
Organic Level: Organs are structures composed of two or more different types of tissue. They have specific functions and usually have recognizable shapes.
Systemic Level: A system consists of related organs that have the same function.
Organismic Level: It is the highest organizational level. The organism is a living individual. All parts of the body, functioning with each other, constitute the total organism – a living person.