The Pharynx extends from the basis cranii to the lower border of the sixth cervical vertebra. It is about 5 inches long, and is very distensible. It is common to both respiratory and digestive tracts, and may be divided into naso-pharyngeal, byccal, and laryngeal portions.
The naso-pharyngeal portion is situated above the soft palate and behind the nasal fossae. Its postero-superior wall is formed by the basis cranii, anterior arch of the atlas, and body of the axis, together with their muscles and ligaments. The Eustachian tubes project on the lateral walls, while from their lower borders folds of mucous membrane, known as the salpingopharyngeal folds, extend downwards. Behind the Eustachian tubes, and beneath the petrous bones, are lateral recesses known as the fossce of Rosenmullef, and here the pharynx is widest.
The buccal portion extends from the arch of the soft palate to the epiglottis and upper extremity of the larynx. In front it communicates with the mouth through the isthmus of the fauces, below which it is bounded by the dorsum of the tongue, while laterally it is bounded by the pillars of the fauces and tonsil.
The laryngeal portion extends the whole length of the larynx from its upper extremity to the lower border of the cricoid. It is the longest but least capacious portion. On each side, in front, below the great cornu of the hyoid and between the larynx and pharyngeal wall is the pyriform fossa. The pharynx is narrowest at its junction with the oesophagus, just at the cricoid cartilage, and here, therefore, foreign bodies are most apt to lodge. This point is about 6 inches from the teeth, and cannot be reached by the finger. The walls of this portion of the pharynx are in contact, save in swallowing, forming a crescentic slit, with the concavity directed forwards.
The pharyngeal wall consists of mucous membrane, pharyngeal aponeurosis, and muscles. Outside of these is the thin bucco-pharyngeal fascia, which invests the buccinator in front. The mucous membrane is vascular, prone to inflammatory affections, which may spread to the Eustachian tube, and so to the ears, and contains much lymphoid tissue, which-in the child, at least-forms a distinct mass in the posterior wall of the pharynx, stretching between the Eustachian tubes, known as the pharyngeal tonsil of Luschka. It frequently becomes hypertrophied, giving rise to post-nasal adenoids, which may block the posterior nares or Eustachian tubes, causing deafness.
The pharyngeal aponeurosis is a thin fibrous sheet, which is best developed posteriorly where the muscles are weakest. The muscles consist of the stylo- and palato-pharyngei, together with the three constrictors, which latter overlap one another from below upwards. The bucco-pharyngeal fascia has very lax connections with the surrounding parts, and so permits of considerable movement, while it also favours the spread of inflammatory affections, which may extend to the posterior mediastinum, or even to the diaphragm.
A retro-pharyngeal lymphatic gland is situated in the loose tissue opposite the axis, which receives lymph from the nares, and is prone to suppuration. An acute post- or retro-pharyn-geal abscess may originate in the cellular tissue or from this gland, in front of the prevertebral layer of deep cervical fascia, and present on the posterior pharyngeal wall, causing difficulty in respiration and in swallowing. Chronic abscess in this situation generally arises from cervical caries, and is, therefore, behind the prevertebral layer of the deep cervical fascia. Retro-pharyngeal abscesses generally burst into the mouth, but may pass behind the great vessels, and present to one side or other of the sterno-mastoid. The acute abscess is best treated by a vertical mesial incision through the mouth, keeping the head low to prevent the pus reaching the larynx. In order to prevent sepsis, the tubercular abscess is best evacuated through an incision along the posterior border of the sterno-mastoid, beginning at the tip of the mastoid process. The deep structures are divided by a blunt dissector, care being taken to avoid the great vessels, until the abscess is reached. Lateral pharyngeal abscess may be similarly treated, care being necessary to diagnose between abscess and aneurism of the internal carotid.
Posteriorly the pharynx is in relation to the six upper cervical vertebrae, anterior common ligament, prevertebral muscles and fascia, and retro-pharyngeal glands. Laterally it is related to the internal carotid artery, internal jugular vein, and ninth, tenth, eleventh, and twelfth cranial nerves and sympathetic. These structures may be wounded by instruments, introduced through the mouth, penetrating the pharynx. The pharynx is also in relation to the styloid process and muscles which arise from it, the posterior belly of the digastric and internal pterygoid muscles, and the parotid gland. Toward its lower extremity it is more superficial, and is related to the common carotid and its branches, the first portions of the lingual and facial arteries, the laryngeal nerves, and lateral lobe of the thyroid. Pharyngotomy may be performed for the removal of tumours, either laterally, through an incision similar to that for ligature of the lingual artery, or mesially. The tumours likely to occur are nasopharyngeal fibroma and sarcoma, the latter frequently invading the nasal cavities and orbit.