Representation of a human head and neck in a cross-section in front of a blue and white background. By means of the cross-section parts of the cranium and facial bone (white-yellow-ish) which are particularly recognizable as the maxilla and the mandibula. The backbone is shown with the spinal discs (gray). The choana (nasal cavities) as well as the oral cavity and the esophagus and trachea are red because of the mucosa. In the oral area, muscles are hinted. The cartilage and the larynx are blue. Yellow bolus passes during deglutition from the oral cavity into the esophagus, while the trachea is closed by the epiglottis. If this fails to take place, respective person swallows something up and parts of the food can enter the trachea.