What are the structures in the pharynx? What are the functions of these structures?

The pharynx is the same channel between the respiratory tract and the upper digestive tract, with a total length of about 12cm. It is wide at the top and narrow at the bottom, flat and slightly funnel-shaped, starting from the skull base to the lower edge of the sixth cervical vertebra. The front wall communicates with nasal cavity, oral cavity and larynx from top to bottom, and is divided into nasopharynx, oropharynx and larynx. The posterior wall is adjacent to the anterior fascia of vertebrae, and the two sides are adjacent to great vessels and nerves.

Nasopharynx, also known as upper pharynx, is located under the base of sphenoid bone and occipital bone and communicates with nasal cavity through posterior nostril. It has six walls: the front wall, the back wall, the left and right sides and the bottom wall. There are adenoids at the junction of the top wall and the back wall, and the pharyngeal orifice and recess of the eustachian tube are on the side wall. Pharyngeal recess is the most common site of nasopharyngeal carcinoma, the anterior wall is the posterior nostril and the posterior edge of nasal septum, and the bottom wall is composed of the back of soft palate and nasopharyngeal isthmus. Oral pharynx, also called middle pharynx, is a backward continuation of oral cavity, commonly called pharynx. It communicates with oral cavity through pharyngeal isthmus, including soft palate, uvula, glossopharyngeal arch, tonsil between glossopharyngeal arch and glossopharyngeal arch, lateral pharyngeal cords on both sides and lingual tonsil at the base of tongue. Laryngopharyngeal pharynx, also known as hypopharynx, is shaped like a funnel, the bottom of which is connected with the esophagus and communicates with the laryngeal cavity through the throat. The epiglottic valley and pear-shaped fossa on both sides are places where foreign bodies are easy to remain.

The pharyngeal wall has four layers from inside to outside: mucosa layer, fiber layer, muscle layer and adventitia layer. Mucosal mucosa is continuous with eustachian tube, nasal cavity, oral cavity and throat. Nasopharyngeal mucosa is mainly pseudostratified ciliated columnar epithelium, and oropharynx and laryngopharynx mucosa are stratified squamous epithelium.

There are abundant lymphoid tissues under the pharyngeal mucosa, some of which gather into rings to form lymphatic rings, mainly including pharyngeal tonsils (adenoids), pharyngeal tonsils, palatal tonsils, lateral pharyngeal cords, lymphoid follicles in the posterior pharyngeal wall and lingual tonsils. The fibrous layer, also called aponeurosis layer, is located between mucosa and muscularis, with a thick upper end and a thin lower part, and a pharyngeal suture is formed in the middle of the posterior wall, which is the attachment of the two pharyngeal constrictors.

The muscular layer is divided into three groups, including pharyngeal constrictor group consisting of upper pharyngeal muscle, middle pharyngeal muscle and hypopharyngeal muscle, pharyngeal ascending muscle group consisting of stylopharyngeal muscle, palatopharyngeal muscle and eustachian tube pharyngeal muscle, and palatine sail muscle group consisting of levator veli palatini, tensor veli palatini, palatopharyngeal muscle and uvula muscle. The adventitia, also known as fascia, is located outside the pharyngeal constrictor and consists of connective tissue, which is the continuation of buccal fascia and pharyngeal fascia. There is a loose tissue space between the pharyngeal fascia and the adjacent fascia to form the pharyngeal fascia space, especially the retropharyngeal space and the parapharyngeal space, which is beneficial to the movement of the pharyngeal cavity and the free movement of the neck during swallowing, that is, the lesion can be limited to a certain range, which may become a way for the lesion to spread.

As the same channel for breathing and digestion, pharynx has the following physiological functions:

1. Swallowing function;

2. Speech formation;

3. Defense and protection functions;

4. The function of regulating middle ear pressure;

5. Immune function of tonsil;

6. Breathing function: when breathing, air enters and exits the channel, which can adjust the temperature and humidity and clean the inhaled air.

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