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by C.V.Rajan

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Pharynx is the part of the throat that is common to both digestive system and respiratory system. It starts behind the nose and ends in the beginning of the voice box (larynx) and the oesophagus. It is a muscular tube lined by mucous membranes that connects the nose with the wind-pipe (trachea) and the mouth with the food-pipe (esophagus) and thus acts as a common passage for both food and air.

Structure of Pharynx:

Pharynx is a soft collapsible tube. It is about 13 cm long in humans and lies in the front of the spinal column. The pharynx contains tonsils and adenoids (in children). Pharynx is divided into three parts namely the oropharynx, nasopharynx and laryngopharynx. Let us now discuss each of these in detail:

OROPHARYNX;

The oropharynx lies just behind the oral cavity. The anterior wall of the oropharynx consists of the base of the tongue and the vallecula (it is the depression behind the root of the tongue). The lateral wall contains the tonsils. The superior wall consists of the interior surface of the soft palate (the posterior portion of the roof of the mouth which is fleshy)and Uvula (a conic projection of the soft palate which is responsible for the articulation of sound to form speech)

NASOPHARYNX:

As the name suggests, the nasopharynx lies behind the nasal cavity and extends from the junction of hard palate (the anterior bony part of the roof of the buccal cavity) and soft palate to the base of the skull in the postero-superior direction.

LARYNGOPHARYNX:

This is also known as the hypopharynx. This serves as the main passage for both air and food. It is present just above the epiglottis (muscular flap present in the trachea preventing passage of food into it by closing it when food is swallowed) and extends to the larynx (voice box) where the respiratory and digestive pathways diverge.

Functions of Pharynx:

The main function of pharynx is to act as a common passage for both food and air. Thus the pharynx should channel food without choking. Pharynx plays a major role in the first phase of swallowing. As the food bolus is pushed by the tongue into the pharynx, it pushes the food down by muscular contraction down the esophagus.

The other important function of Pharynx is to equalize pressure that gets built near the ear drums. This is made possible by the two eustachian tubes (one from each ear) that connect the middle ear with pharynx.

Pharynx is very soft and can be easily collapsed. Thus any physical structure can cause an obstruction in the pharynx. Pharynx is easily susceptible to infections. The inflammation or infection of pharynx is known as pharyngitis which is caused by micro organisms that enter through nose or mouth. The pharynx might collapse during sleep and the resulting condition is known as Obstructive Sleep Apnea (OSA). Any failure in the normal functioning of pharynx can cause breathing, swallowing or voice problems.

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