Pharynx | Muscles of Pharynx | Wall of Pharynx | NEET PG | FMGE | NEXT | USMLE

#rajithavanga #clinicalanatomy #fmge #mbbs #neet #headandneckanatomy #grossanatomy #usmle
• The pharynx acts as a common channel for both food (deglutition) and air (respiration). It conducts food to the esophagus and air to the larynx. It has three parts; Nasopharynx, oropharynx and laryngopharynx.
• Nasopharynx is present behind the nasal cavity above the soft palate and communicates with the nasal cavities through the nasal choanae
• Oropharynx extends between the soft palate above and the superior border of the epiglottis below and communicates with the mouth through the oropharyngeal isthmus.
• Laryngopharynx is also called hypopharynx and extends from the upper border of the epiglottis to the lower border of the cricoid cartilage.
The features seen in the nasopharynx are:
 Nasopharyngeal (pharyngeal) tonsil: It is a collection of lymphoid tissue beneath the mucous membrane atthe junction of the roof and posterior wall of the nasopharynx.
 A mucous diverticulum called nasopharyngeal bursa (pouch of Luschka) extends upwards into the substance of nasopharyngeal tonsil from its apex. It is provided with mucous glands.
 This bursa develops due to adhesion of notochord to the dorsal wall of the pharyngeal part of the foregut.
 Sometimes a small dimple is seen in the mucous membrane above the pharyngeal tonsil. It represents the remains of Rathke’s pouch. A craniopharyngioma may arise from it.

 Orifice of the pharyngotympanic tube or auditory tube (eustachian tube): This lies on the lateral wall at the level of the inferior nasal concha and 1.25 cm behind it.

 The upper and posterior margins of this opening are bounded by a tubal elevation, which is produced by the collection of lymphoid tissue called tubal tonsil. Two mucous folds extend from this elevation:

(i) Salpingopharyngeal fold extends vertically downwards and fades on the side wall of the pharynx. It contains salpingopharyngeus muscle.
(ii) Salpingopalatine fold extends downwards and forwards to the soft palate. It contains the levator palati muscle.
 Pharyngeal recess: It is a deep depression behind the tubal elevation; it is called pharyngeal recess (fossa of Rosenmüller).
 Structurally and functionally the nasopharynx resembles the nose. It is respiratory in function and lined by pseudostratified ciliated columnar epithelium. Its walls are rigid and non-collapsible to keep the air passage patent.
 Adenoids: The nasopharyngeal tonsils are prominent in children up to the 6 years of age, then gradually undergo atrophy till puberty and almost completely disappear by the age of 20.
 The nasopharyngeal tonsils when enlarge due to infection are known as adenoids, which block the posterior nares making ‘mouth breathing obligatory’.
 Nasopharyngeal Isthmus and Passavant’s Ridge Some fibres of the palatopharyngeus muscle (arising from palatine aponeurosis) sweep horizontally backwards and join the upper fibres of the superior constrictor muscle to form a U-shaped muscle-loop in the posterior pharyngeal wall underneath the mucosa, which is pulled forward during swallowing to form the Passavant ridge.

The features seen in the oropharynx are:
(a) Lateral wall presents palatine tonsils, one on either side. It is located into a triangular fossa (tonsillar fossa) bounded anteriorly by palatoglossal arch and posteriorly by palatopharyngeal arch.
The palatoglossal arch runs downwards and forwards from palate to the lateral margin of the tongue. The palatopharyngeal arch runs downwards and backwards to the pharyngeal wall where it fades out (for details of palatine tonsil
(b) Anterior wall presents:
 Lingual tonsil, formed by numerous nodules of lymphoid tissue underneath the mucous lining of the pharyngeal part of the dorsum of the tongue.
 Upper free end of epiglottis, behind the tongue.
 Median and lateral glossoepiglottic folds, connecting the anterior surface and edges of the epiglottis, respectively to the tongue.
 Epiglottic valleculae are shallow fossae between the median and lateral glossoepiglottic folds
The features seen in the laryngopharynx are:
• Anterior wall presents laryngeal inlet and below the inlet it is supported by cricoid and arytenoid cartilages.
• Lateral wall presents piriform fossa one on each side of laryngeal inlet. The piriform fossa is described in detail below.
Piriform fossa
 It is a deep recess broad above and narrow below in the anterior part of lateral wall of the laryngopharynx, on each side of the laryngeal inlet. These recesses are produced due to bulging of larynx into laryngopharynx.
The internal laryngeal nerve and superior laryngeal vessels pierce the thyrohyoid membrane and traverse underneath the mucous membrane of the floor of the fossa to reach the medial wall.