How do cells form tissues, organs, and organ systems?

In biology, the organization of multicellular organisms follows a hierarchical structure where cells differentiate to form specialized tissues, which then assemble into organs and organ systems.12

Cell Differentiation

The process begins with cell differentiation, where immature cells develop into specialized types with distinct structures and functions. This is driven by gene expression, which is influenced by environmental signals, hormones, and interactions with neighboring cells.3

Tissues

Once differentiated, cells with similar structures and functions aggregate with intercellular material to form tissues. In animals, these are generally categorized into four classes:4
* Epithelial: Covers surfaces and lines internal organs.14
* Muscle: Specialized for contraction and movement.14
* Nerve: Conducts electrical impulses for coordination.14
* Connective: Binds structures together and provides support.14

Organs and Organ Systems

An organ is a distinct structural unit composed of a group of different tissues working together to perform a specific function, such as the heart. Finally, multiple organs and tissues integrate to form organ systems, which function as a unit to sustain the organism, such as the circulatory or digestive systems.12