Question

What is the relationship between a cell, a tissue, an organ and an organ system?

Answer 1

Cell is the basic structural and functional unit of a multicellular organism. Different groups of cells perform different functions.
Tissue is a group of similar cells performing a specific function. Different tissues that work together form an organ. Different organs that work together constitute an organ system.
Thus, cell, tissue, organ and organ system are inter-related and represent the hierarchy of organisation in the body.