1 2 CHEMICAL LEVEL CELLULAR LEVEL 3 TISSUE LEVEL Smooth muscle cell Atoms (C, H, O, N, P) Molecule (DNA) Smooth muscle tissue 5 SYSTEM LEVEL Epithelial and connective tissues 4 ORGAN LEVEL Salivary glands Pharynx Mouth Smooth muscle tissue layers Esophagus Epithelial tissue Stomach Liver Stomach Gallbladder Pancreas (behind stomach) Large intestine 6 ORGANISMAL LEVEL Small intestine Digestive system Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.