This image is of the cross-section of a kidney.

Q. Define: Organ

A1. A chemical receptor site which responds to chemical stimuli and functions to keep the body in a state of homeostasis

A2. A structure of the body which is responsible for reactions with external environment e.g. hands

A3. A collection of various tissues integrated into a distinct structural unit to perform specific functions

A4. A specialized, functional collection of tissue built around a bone frame, for structural reinforcement