A biological system is a complex network which connects several biologically relevant entities. Biological organization spans several scales and are determined based different structures depending on what the system is.[1] Examples of biological systems at the macro scale are populations of organisms. On the organ and tissue scale in mammals and other animals, examples include the circulatory system, the respiratory system, and the nervous system. On the micro to the nanoscopic scale, examples of biological systems are cells, organelles, macromolecular complexes and regulatory pathways. A biological system is not to be confused with a living system, such as a living organism.

Organ and tissue systems

An example of a system: the brain, the cerebellum, the spinal cord, and the nerves are the four basic components of the nervous system.

Further information: Organ system and List of systems of the human body

These specific systems are widely studied in human anatomy and are also present in many other animals.


The notion of system (or apparatus) relies upon the concept of vital or organic function:[2] a system is a set of organs with a definite function. This idea was already present in Antiquity (Galen, Aristotle), but the application of the term "system" is more recent. For example, the nervous system was named by Monro (1783), but Rufus of Ephesus (c. 90–120), clearly viewed for the first time the brain, spinal cord, and craniospinal nerves as an anatomical unit, although he wrote little about its function, nor gave a name to this unit.[3]

The enumeration of the principal functions - and consequently of the systems - remained almost the same since Antiquity, but the classification of them has been very various,[2] e.g., compare Aristotle, Bichat, Cuvier.[4][5]

The notion of physiological division of labor, introduced in the 1820s by the French physiologist Henri Milne-Edwards, allowed to "compare and study living things as if they were machines created by the industry of man." Inspired in the work of Adam Smith, Milne-Edwards wrote that the "body of all living beings, whether animal or plant, resembles a factory ... where the organs, comparable to workers, work incessantly to produce the phenomena that constitute the life of the individual." In more differentiated organisms, the functional labor could be apportioned between different instruments or systems (called by him as appareils).[6]

Cellular organelle systems

See also: Organelle

The exact components of a cell are determined by whether the cell is a eukaryote or prokaryote.[7]

See also


  1. ^ F. Muggianu; A. Benso; R. Bardini; E. Hu; G. Politano; S. Di Carlo (2018). "Modeling biological complexity using Biology System Description Language (BiSDL)". 2018 IEEE International Conference on Bioinformatics and Biomedicine (BIBM). pp. 713–717. doi:10.1109/BIBM.2018.8621533. ISBN 978-1-5386-5488-0. S2CID 59233194. ((cite book)): |website= ignored (help)
  2. ^ a b Fletcher, John (1837). "On the functions of organized beings, and their arrangement". In: Rudiments of physiology. Part 2. On life, as manifested in irritation. Edinburgh: John Carfrae & Son. pp. 1-15. link.
  3. ^ Swanson, Larry (2014). Neuroanatomical Terminology: A Lexicon of Classical Origins and Historical Foundations. Oxford: Oxford University Press. link Archived 2023-09-28 at the Wayback Machine. p. 489.
  4. ^ Bichat, X. (1801). Anatomie générale appliquée à la physiologie et à la médecine, 4 volumes in-8, Brosson, Gabon, Paris, link. (See pp. cvj-cxj).
  5. ^ Cuvier, Georges. Lecons d'anatomie comparée 2. éd., cor. et augm. Paris: Crochard, 1835-1846. link Archived 2009-03-02 at the Wayback Machine.
  6. ^ R. M. Brain. The Pulse of Modernism: Physiological Aesthetics in Fin-de-Siècle Europe. Seattle: University of Washington Press, 2015. 384 pp., [1] Archived 2023-07-03 at the Wayback Machine.
  7. ^ "Human Anatomy And Physiology". PressBooks. Archived from the original on 2020-10-20. Retrieved 2019-02-19.