The pharynx is a canal that connects the throat with the oesophagus. It is formed of a muscular-mucosal nature, and it represents both the first part of the digestive tract – receives the food bolus from the mouth through swallowing – and a part of the upper airway: the air that enters through the nose is entered from the pharynx into the larynx.
The pharynx is attached to the base of the skull and the surrounding structures through thick fibres of muscle and connective tissue. The walls of the pharynx contain both circular and longitudinal muscles. The circular muscles cause constrictions that assist in pushing food towards the oesophagus and prevent air from being swallowed. The longitudinal muscles lift the walls of the pharynx during swallowing.
What is the throat?
This channel, about 15 centimetres long, runs back to the nasal cavity, the mouth and the larynx, and extends vertically from the base of the skull until the sixth cervical vertebra. The shape resembles a funnel: wider at the top, and narrower as it goes down, gradually acquiring a tubular appearance.
The pharynx is generally divided into three sections: the rear portion of the nasal airways (nasopharynx), the throat (oropharynx) and the laryngeal part (laryngopharynx). The nasopharynx and oropharynx are separated by a specific portion of the palate, the soft palate (which is an extension of the hard palate).
The nasopharynx is located between the base of the skull and the soft palate. It performs a respiratory function that includes conditioning inhaled air and passing it onto the larynx. The oropharynx is located between the soft palate and the upper border of the epiglottis, making it the middle portion of the pharynx. Its function refers to the voluntary and involuntary process of swallowing. Lastly, the laryngopharynx is located between the upper border of the epiglottis and the inferior border of the cricoid cartilage (C6) where it connects to the oesophagus. The laryngopharynx contains the middle and inferior pharyngeal constrictors.
The nasal cavities communicate with the pharynx through the posterior nares, the mouth through the isthmus of the fauces (the narrow opening that represents the transition from the oral cavity to the pharyngeal portion delimited at the top by the free edge of the soft palate, by two pairs of mucosal folds on the sides and the base of the tongue) and the larynx through the laryngeal orifice. All of these communications are carried out in correspondence of the front wall of the organ, which is thus presented incomplete by many parts.
Furthermore, two small tubes, called Eustachian tubes, connect the middle ear to the pharynx in order to equalize the air pressure on the eardrum. The Eustachian tubes can sometimes be inflamed by colds and lead to earaches and hearing difficulties.
What function does the pharynx serve?
There are two key features of the pharynx:
- It acts as the first portion of the digestive tract: the pharynx connects the mouth with the oesophagus allowing the passage of the food bolus through swallowing.
- As part of the upper airways: the pharynx allows the passage of air from the nose to the larynx.
