The pharynx is a shared tube where food always gets right of way
Every breath and every swallow pass through the same short stretch of throat. The pharynx channels air towards the lungs and food towards the stomach, and a flap of cartilage called the epiglottis keeps them from colliding. When you swallow, breathing briefly pauses, because food takes priority over air.
The pharynx sits behind the nose and mouth and above the oesophagus and windpipe, and it is found across vertebrates and many invertebrates. In humans it belongs to both the digestive system and the airway that filters, warms and moistens incoming air. Two layers of muscle, one running lengthwise and one circling, give it shape. Anatomists divide it into three sections stacked from top to bottom.
The nasopharynx runs from the base of the skull to the soft palate. Its back wall holds the adenoids, part of a ring of lymphoid tissue that also includes the tonsils lower down, and its lining carries tiny beating hairs. On each side opens the auditory tube from the middle ear. Opening and closing these tubes balances air pressure in the ear with the outside atmosphere, which is why congestion or mucus there can matter.
Below it, the oropharynx lies behind the mouth, reaching down from the uvula as far as the hyoid bone, with the palatine tonsils in its side walls and the base of the tongue in front. The lowest part, the laryngopharynx, sits roughly between the fourth and sixth neck vertebrae and is where the common passage finally splits: air heads forward into the larynx, food and drink backward into the oesophagus. Both lower sections have a tougher, layered lining suited to passing food.
The throat's wiring produces some surprises. A branch of the vagus nerve, known as Arnold's nerve, also supplies the ear canal, so touching the canal can trigger a cough, and problems in the lower throat may be felt as ear pain. The pharynx also helps shape speech, producing certain consonants and acting as a resonating chamber for the voice.
Source: Pharynx
