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The pharynx
cartilage and the cricoid and arytenoid cartilages. It is important be-
This is an incomplete striated muscular tube, opening in front into the
cause a carcinoma in this region can remain ‘silent’ until it has spread
nasal cavity, the mouth and the larynx, thus being made up of the
to the cervical lymph nodes whereas a tumour of the vocal cords pro-
nasopharynx, the oropharynx and the laryngopharynx. The muscular • Pyriform fossa: the fossa between the posterior border of the thyroid
coat (Fig. 62.1) is formed by: duces early voice changes.
• The superior constrictor: arises from the pterygomandibular liga- • Mucous membrane: mostly respiratory epithelium (ciliated colum-
ment (which spans between the pterygoid hamulus and the mandible nar) but over the vocal cords it changes to stratified squamous so that
just behind the third molar tooth). the cords have a pearly appearance (Fig. 62.5).
• The middle constrictor: arises from the stylohyoid ligament and the • Vestibular folds: a pair of additional folds above the vocal folds
lesser and greater horns of the hyoid bone. ( false cords). The space between the vocal and vestibular folds is the
• The inferior constrictor: arises from the thyroid and cricoid sinus of the larynx.
cartilages.
The constrictors encircle the pharynx and interdigitate posteriorly. The intrinsic muscles of the larynx
The gaps between the constrictors are filled in by fascia. There is also • Cricothyroid (Figs 62.1 and 62.3): situated on the outside of the
an inner longitudinal layer of muscle. The nasopharynx is lined by cili- larynx. Tenses the vocal cords.
ated columnar epithelium and on its posterior wall is situated a mass of • Thyroarytenoid (Fig. 62.4): from the back of the thyroid cartilage to
lymphatic tissue, the pharyngeal tonsil or adenoid. The pharyngotym- the vocal process of the arytenoid. Relaxes the vocal cords.
panic (Eustachian) tube opens into the nasopharynx at the level of the • Posterior cricoarytenoid (Figs 62.3 and 62.4): from the back of the
floor of the nose, the cartilage of the tube producing a distinct bulge cricoid to the muscular process of the arytenoid. Abducts the vocal
behind the opening. cords.
• Nerve supply: • Lateral cricoarytenoid (Fig. 62.4): adducts the vocal cords.
• Motorapharyngeal branch of the vagus (p. 131). • Interarytenoids and aryepiglottic muscle: form a ‘sphincter’, to-
• Sensoryaglossopharyngeal (p. 131). gether with the epiglottis, in order to close off the entrance to the larynx
(glottis) during swallowing.
The larynx • Nerve supply:
Palpable components • Motorarecurrent laryngeal nerve, except for the cricothyroid
• Hyoid bone, level of C3. which is supplied by the external laryngeal nerve.
• Thyroid cartilage, level of C4 and 5. • Sensoryaabove the vocal cords, the internal laryngeal nerve
• Cricoid cartilage, level of C6. which enters the larynx through the thyrohyoid membrane. Below
the vocal cords, the recurrent laryngeal nerve (which is therefore a
Other components mixed nerve) which enters the larynx just behind the cricothyroid
• Arytenoid cartilages: attached to upper border of the cricoid by syn- joint.
ovial joints so that they can slide and rotate. Each has an anterior vocal
process and a lateral muscular process (Figs 62.2 and 62.3). Laryngoscopy (Fig. 62.5)
• Epiglottis: a leaf-shaped piece of elastic cartilage attached to the The vocal cords may be seen by means of a warmed, angled mirror
back of the thyroid cartilage (Fig. 62.2) and projecting upwards behind passed to the back of the throat. Only the edges of the cords can be seen
the hyoid. because of the shadow of the false cords. Adduction of the cords may be
• Thyrohyoid ligament: joins the hyoid and the thyroid (Fig. 62.1). observed by asking the patient to say a high-pitched ‘eeeee’ while
• Cricovocal membrane (cricothyroid ligament): attached to the abduction occurs when saying ‘Ahhh’. If one of the recurrent laryngeal
upper border of the cricoid and passes inside the thyroid to be attached nerves is divided, the cord lies in a position midway between adduction
to the back of the thyroid and to the vocal processes of the arytenoids and abduction but this does not produce very severe voice changes
(Fig. 62.2). The upper border is thickened to form the vocal ligament because the uninjured cord can cross the midline to reach the para-
which, with the mucous membrane that covers it, forms the vocal lysed cord. However, if both nerves are cut the cords lie in the cadaveric
cords. position, i.e. in the mid-position. If both nerves are damaged but not
• Cricothyroid joint: a small synovial joint between the inferior horn completely divided the cords are adducted since the abductors are
of the thyroid cartilage and the cricoid, permitting a hinge-like move- more affected than the adductors (Semon’s law). This may cause
ment (Fig. 62.3). breathing difficulties.

The pharynx and larynx 139