Illustration of a section through the head and upper neck. The frontal sinus is in the forehead and the sphenoid sinus is behind the nose. The sinuses are membrane-lined air-filled spaces in the bones of the face. Above the bony hard palate (roof of the mouth) is the nasal cavity. Here, air breathed in through the nose is warmed and filtered. Below the palate is the oral cavity (mouth) and tongue. Above the soft palate (posterior roof of the mouth) is the nasopharynx, a passage for air to pass from the nasal cavities to the laryngopharynx (back of throat). Air flows into the larynx (voice box) and down the trachea (windpipe) into the lungs. Food passes through the oropharynx (back of the mouth) into the oesophagus, which is behind the trachea and leads to the stomach.