Cross-section of a human head and neck in front of a red background. The cut shows parts of the cranium and facial bones (white-yellowish), especially maxilla and mandible. The spine is depicted with its intervertebral disks (grey). The nasal cavities, oral cavity, trachea, and esophagus are red due to their mucosal lining. Some muscles of the oral area are depicted. Cartilage (of the larynx) in blue. During the process of swallowing, the food bolus is supposed to get from the oral cavity into the esophagus, while the trachea is closed by the epiglottis. If that doesn`t happen sufficiently, the person chokes on the bolus.