Structural Organization of the Human Body
(in order of complexity with definitions)
- Chemical Level: Smallest units of matter that participate in chemical reactions; Atoms (C, H, N, O, P) and molecules (DNA).
- Cellular Level: Molecules combine to form structures at the next level; Cells (muscle, nerve, blood).
- Tissue Level: Groups of cells/materials surrounding them to perform a particular function; Tissues (Epithelial, Connective, Muscle, Nervous).
- Organ Level: Different kinds of tissues join together to form body structures; Organs (Stomache, Heart, Liver, Lungs, Brain).
- System Level: Related organs that come together to perform a common function; Digestive system.
- Organism Level: Largest level; all systems combine together to make a human being.