Structure: parts of the pharynx
The pharynx is a fibromuscular tube, about 12 to 14 cm long, running from the skull base to the lower border of the cricoid cartilage at C6, where it becomes the oesophagus. It has three parts, named by what lies in front of each.
| Part | Extent | Opens forward into |
|---|---|---|
| Nasopharynx | Skull base to soft palate | Nasal cavity, through the choanae |
| Oropharynx | Soft palate to upper border of epiglottis | Mouth, through the oropharyngeal isthmus |
| Laryngopharynx | Upper border of epiglottis to lower border of cricoid | Larynx, through the laryngeal inlet |
The nasopharynx and oropharynx meet at the pharyngeal isthmus, the opening between the soft palate and the posterior pharyngeal wall. The oropharynx has the back of the tongue and the valleculae as its anterior wall, the tonsillar fossae as its lateral walls and the soft palate as its roof.
Lateral wall of the nasopharynx
The lateral wall of the nasopharynx carries the opening of the auditory (pharyngotympanic) tube and the folds its cartilage raises.
- Auditory tube opening: a triangular opening level with the inferior concha, connecting the nasopharynx with the middle ear.
- Tubal ridge (torus tubarius): the elevation arching over the top and back of the opening, raised by the medial end of the tubal cartilage.
- Salpingopharyngeal fold: descends from the back of the ridge over salpingopharyngeus, which helps open the tube in swallowing.
- Pharyngeal recess (fossa of Rosenmüller): the deep slit behind the tubal ridge.
- Pharyngeal tonsil (adenoid): lymphoid tissue on the roof and posterior wall. It is prominent in children and regresses after puberty, so in an adult specimen it appears as a fibrosed patch.
Palatine arches and the tonsillar fossa
The tonsillar fossa is the recess in the lateral wall of the oropharynx between two mucosal arches that run down from the soft palate.
- Palatoglossal arch (anterior pillar): raised by palatoglossus, running from the soft palate down to the side of the tongue. The two arches mark the oropharyngeal isthmus, the boundary between the mouth and the oropharynx.
- Palatopharyngeal arch (posterior pillar): raised by palatopharyngeus, running from the soft palate down the lateral pharyngeal wall.
- Palatine tonsil: lymphoid tissue in the fossa between them. Its bed is the superior constrictor and pharyngobasilar fascia, with the glossopharyngeal nerve and styloglossus lateral to that.
The palatine, pharyngeal, tubal and lingual tonsils form Waldeyer's ring around the entrance to the airway and gut.
Blood supply and innervation
The pharynx is supplied by branches of the external carotid artery and innervated through the pharyngeal plexus on the middle constrictor. The main tonsillar artery is the tonsillar branch of the facial artery, entering the lower pole; the ascending palatine, lingual, ascending pharyngeal and lesser palatine arteries contribute. The external palatine (paratonsillar) vein descends on the lateral surface of the tonsil and is the usual source of bleeding after tonsillectomy. Tonsillar lymph drains to the jugulodigastric node below the angle of the mandible.
| Function | Nerve |
|---|---|
| Motor to constrictors, palatopharyngeus, salpingopharyngeus, palatoglossus, levator veli palatini | Vagus, via the pharyngeal plexus |
| Motor to stylopharyngeus | Glossopharyngeal |
| Motor to tensor veli palatini | Mandibular nerve (V3) |
| Sensory to nasopharynx | Pharyngeal branch of maxillary nerve (V2) |
| Sensory to oropharynx and tonsil | Glossopharyngeal |
| Sensory to laryngopharynx | Internal laryngeal branch of vagus |
The gag reflex uses the glossopharyngeal nerve as its afferent limb and the vagus as its efferent limb.
Clinical relevance
The oropharynx and nasopharynx are common sites of infection, bleeding and cancer.
- Peritonsillar abscess (quinsy): pus collects between the tonsil capsule and the superior constrictor, pushing the tonsil and uvula towards the midline and causing trismus.
- Post-tonsillectomy haemorrhage: usually from the paratonsillar vein; the internal carotid artery lies posterolateral to the tonsillar bed and is a rare, serious hazard.
- Referred ear pain: tonsillitis and tonsillar cancer cause ear pain because the glossopharyngeal nerve also supplies the middle ear.
- Adenoid hypertrophy: blocks the choanae and auditory tubes, leading to mouth breathing, snoring and glue ear.
- Oropharyngeal carcinoma: often associated with human papillomavirus, arising in the tonsil and tongue base, and may first present as a neck lump.
- Nasopharyngeal carcinoma: often starts in the pharyngeal recess.
On the specimen
The specimen is a sagittal section of the head, so the pharyngeal walls are seen from the midline.
- Palatoglossal or palatopharyngeal fold: both leave the soft palate; the palatoglossal fold is anterior and ends at the side of the tongue, while the palatopharyngeal fold is posterior and fades down the pharyngeal wall.
- Salpingopharyngeal or palatopharyngeal fold: the salpingopharyngeal fold comes down from the tubal ridge, higher and further back; the palatopharyngeal fold comes from the soft palate.
- Tube opening or pharyngeal recess: the opening lies in front of the tubal ridge; the recess is the deep slit behind it.
- Adenoid: the irregular tissue on the roof and back wall of the nasopharynx; in adults it is small and fibrous.