L1.2: Structural Organization

• Level of structural organization

  atoms → molecules → cells → tissues → organs → organ systems → organism
• Levels of structural organization

  • Chemical/molecular level
  • Cellular level
  • Tissue level
  • Organ level
  • Organ system level
  • Organismal level
• • Presence of the basic unit of matter known as Atoms.
  • Atoms are individual entities within the body that when combined, creates chemical reactions to form molecules.


  Chemical/Molecular Level
• • Cells are made up of molecules and are considered as the basic unit of life.
  • All cells have some common structures and functions but individual cells vary widely in size, shape, and their particular roles in the body.

  Cellular Level
• • Tissues are composed of similar types of cells or cells of similar function.
  • Ex: Blood = RBC + WBC + Platelets
  • Community or cluster of similar cells.
  • There are 4 basic types of tissue:
  • Connective tissue, epithelial tissue, muscle tissue, and nervous tissue.


  Tissue Level
• • A collection of tissues that structurally form a functional unit specialized to perform a particular function.
  • At his level, extremely complex functions become possible.


  Organ Level
• • An organ system is a group of organs that work closely together to accomplish a common purpose.
  • There are 11 organ systems.


  Organ system Level
• • The human organism is made up of many organ systems. The sum of all structural levels working together to keep them alive.
  • The organismal level is the highest level of organization.
  • Organism: living being that has a cellular structure and can independently perform all physiologic functions necessary for life.


  Organismal Level