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Functional Organization of the Human Body

Evolution of the Human Body
  • Life started as unicellular organism millions of years ago.

  • In this form, it was in direct contact with the external environment i.e. it took all the nutrients directly from its external surrounding and also released the waste products directly back into the external environment.

  • To overcome problems with the unicellular form, the multiple cells started teaming up, forming multicellular organisms. And eventually, life evolved over millions of years, into its present form.

What Happened During Evolution - a Schematic Understanding
  • The cells built a home i.e. skin and separated themselves from the external environment.

  • The environment inside this home is called the internal environment of the body.

  • Now the cells do not have to worry much about the external environment. They just need to take care of the internal environment i.e. keeping enough nutrients and oxygen in the home so that all the cells can get them easily, maintaining proper temperature, etc.

  • The maintenance activity of this home is called homeostasis.

  • To do different tasks, the cells made different teams, and each team started getting specialized in its work. Eventually, this resulted in the development of different organ systems.

Main Role of Each Organs System
  • Musculoskeletal System: Move the entire body to grab nutrients in the external environment.

  • Digestive System: Digest the food and move the nutrients from the external to the internal environment.

  • Respiratory System: Get oxygen and remove carbon dioxide.

  • Urinary System: Remove waste products.

  • Nervous System and Endocrine System: Control the activity of different organ systems depending on the changing internal and external conditions.

  • Integumentary System & Immune System: Protection of the body.

  • Reproduction: Maintain life beyond the lifetime of a single human being, by generating new ones who replace those who die.


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