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Chemistry LibreTexts

Levels of Organization

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    Let's take a little time to review the levels of organization in the human body. There are five levels of organization in the human body.

    • Cells
    • Tissues
    • Organs
    • Organ systems
    • Organism

    Specialized cells develop from a single zygote. Zygote's begin by dividing into embryonic stem cells. These cells can become any type of specialized cell in the body. 

    Determination - happens after the first few divisions, and this is when cells are committed to becoming a particular type of specialized cell. 

    Differentiation - occurs after determination and is the process where committed cells acquire the specialized structure and functions they will need. 

    Specialized cells function together in tissues, organs, organ systems, and the whole organism. Tissues are groups of similar cells working together. Organs are different tissues working together, and organ systems involve two or more organs working together. An organism is all organ systems working together. 


    There are 11 major organ systems in the human body that you will be studying over the next few weeks.

    • Circulatory
    • Digestive
    • Endocrine
    • Excretory
    • Immune
    • Integumentary
    • Muscular
    • Nervous
    • Reproductive
    • Respiratory
    • Skeletal