pharynx

pharynx It is a fibro-muscular funnel-shaped tube extending from the base of the skull to the lower border of C. 6 where it continues as the oesophagus. It lies behind the nose, mouth, and larynx.

Subdivision of the Pharynx I. Naso-pharynx - It extends from the base of the skull to the upper surface of the soft palate. - It communicates anteriorly with the nose through the posterior nasal aperature. - It communicates inferiorly with the oropharynx through the pharyngeal isthmus.

Features of the nasopharynx 1. Pharyngeal opening of the auditory tube (Eustachian or pharyngotympanic): 2. Tubal elevation: 3. Salpingo-pharyngeal fold: 4. Salpingo-palatine fold: 5. Pharyngeal recess: 6. Pharyngeal tonsil: - It is a collection of a lymphoid tissue on the posterior wall of the pharynx. - If enlarged it is called the adenoids. Tubal elevation Pharyngeal recess Salpingopharyngeal fold

II. Oro-pharynx - It extends from the lower surface of the soft palate to the upper border of the epiglottis at. - It communicates anteriorly with the oral cavity by an opening called the oropharyngeal isthmus made by the palatoglossal arch on each side (each arch is made by palatoglossus muscle covered by mucous membrane). - It also contains the palatopharyngeal arch (made by palatopharyngeus muscle covered by mucous membrane). - Between the palatoglossal and palatopharyngeal arches there is the “palatine tonsil”.

III. Laryngopharynx - It extends from the upper border of the epiglottis to the level of the cricoid cartilage (C. 6) where it continues as the oesophagus. - Its upper part lies behind the inlet of the larynx. * Pyriform fossa - It is a depression on each side of the inlet of the larynx. - The nerve supply of the mucous membrane of the pyriform fossa is the internal laryngeal nerve.

Muscles of Pharynx - The pharynx is formed of three constrictor muscles (superior, middle, and inferior), and three small muscles (stylopharyngeus, palatopharyngeus and salpingopharyngeus). - The three constrictor muscles encircle the pharynx and all insert posteriorly into the “median fibrous raphe” which is attached upwards into the pharyngeal tubercle. - The muscles don’t extend up to the base of the skull, here the wall consists of the pharyngobasilar fascia.

Nerve supply of the pharynx 1. Motor supply: All muscles of the pharynx are supplied by the “pharyngeal plexus” (cranial part of accessory nerve through the pharyngeal branch of vagus nerve). EXCEPT stylopharyngeus which is supplied by glossopharyngeal nerve. 2. Sensory supply: - Nasopharynx is supplied by pharyngeal branch of maxillary nerve through sphenopalatine ganglion. - Oropharynx is supplied by glossopharyngeal nerve and lesser palatine nerves. - Laryngopharynx is supplied by internal laryngeal nerve.