Matching Pairs Tissues, Organs, and Body SystemsOnline version Review the tissue, organ, and body systems. by Janelle Ruiz 1 Connective Tissue 2 Circulatory System 3 Muscular System 4 Nervous System 5 Respiratory System 6 Epithelial Tissue 7 Digestive System Responsible for gas exchange (oxygen- carbon dioxide) with the outside environment Heart, veins, capillaries Brain, spinal column, axons Supports organs and joins tissue Lines organs and protects inside of body from outside world