The pharynx is a muscular, funnel-shaped organ located behind the oral and nasal cavities. It connects the nasal and oral cavities with the larynx and esophagus. The pharynx is about 5 - 5.5 inches (12 - 14 cm) long, extending between the external cranial base and the sixth cervical vertebra (C6).

The pharynx is an intersection site of the digestive and respiratory systems. Therefore, it can be classified as a structure of both the upper respiratory tract and gastrointestinal tract. As a part of the digestive system, the pharynx allows the swallowed solids and liquids to reach the esophagus from the oral cavity.

Superior and anterior to the pharynx is the nasal cavity, while it continues with the esophagus inferior. Anterior to it is the oral cavity and larynx, but posterior is the cervical part of the spine, deep muscles of the neck and deep cervical fascia, as well as the retropharyngeal space. The pharynx is composed of three parts:

Nasopharynx
Oropharynx
Laryngopharynx

Nasopharynx

The nasopharynx is the most superior portion or the nasal part of the pharynx. It is located posterior to the nasal cavity at the level of the first and second cervical vertebrae (C1 - C2). The nasopharynx extends from the external cranial base to the uvula of the soft palate. As it is responsible only for respiratory processes, it is classified as a part of the respiratory system.

Oropharynx

The oropharynx is located at the back of the oral cavity. It is the middle portion of the pharynx, extending from the uvula to the superior border of the epiglottis. It is situated at the level of the third and fourth cervical vertebrae (C3 - C4).

The oropharynx has only one opening called the oropharyngeal isthmus (opening). It connects the oropharynx with the oral cavity and houses one lingual and two palatine tonsils. The oropharynx is involved in both respiratory and digestion processes, and it is considered as part of the respiratory and digestive systems.

Laryngopharynx

The laryngopharynx, also called the hypopharynx, is the most distal and final portion of the pharynx. It is located at the level of the fifth and sixth cervical vertebrae (C5 - C6), extending from the superior border of the epiglottis to the esophagus. It ends at the inferior border of the cricoid cartilage of the larynx. Anterior to the laryngopharynx is the larynx, while it continues as the esophagus inferiorly.

The laryngopharynx has two openings - the laryngeal inlet or aditus and the esophageal opening. The laryngeal aditus leads into the larynx, while the esophageal opening connects the laryngopharynx with the esophagus.

On the sides of the laryngeal inlet are paired pear-shaped fossae called the piriform sinuses. They are common sites for the entrapment of foreign bodies. Within the submucosa of the piriform sinus pass the internal and recurrent laryngeal nerves.

The laryngopharynx is involved in respiratory and digestion processes. Therefore, it is considered a part of the respiratory and digestive systems.

Muscles of pharynx

The pharynx is composed of very well-developed paired skeletal muscles. All muscles can be classified into two groups:

Circular muscles (constrictors) - muscles that constrict the pharynx; this group includes the superior, middle and inferior pharyngeal constrictors;
Longitudinal muscles (levators) - muscles that lift the pharynx; it includes the stylopharyngeus, palatopharyngeus and salpingopharyngeus muscles.

Together with the tongue, soft palate, and larynx, the pharyngeal muscles provide swallowing and digestion.

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Pharynx