: All systems working together to form a complete human being. II. The 11 Major Body Systems Human body systems: Overview, anatomy, functions | Kenhub

: Related organs coordinating for a common purpose (e.g., the digestive system).

: Supports and binds body parts (e.g., bone, blood). Muscle : Enables movement through contraction. Nervous : Transmits electrical impulses for communication.

: The foundation where atoms (like carbon and oxygen) combine to form molecules (such as water, DNA, and glucose).

: Molecules form the basic functional units of life— cells .

The human body is organized into a hierarchy of increasing complexity:

: Groups of similar cells that perform a specific function. The four primary types are: Epithelial : Covers surfaces and lines organs.