LEARNING OBJECTIVE: Recall how organs and body systems are composed of two or more kinds of tissue that perform specialized functions within the body.

Figure 1-12.óNeuron.

As a group of similar cells forms tissues, two or more kinds of tissues grouped together and performing specialized functions constitute an organ. Organs are grouped together to form systems (such as the urinary system, composed of the kidneys, ureters, bladder, and urethra).