(_a_) The =kerato-pharyngeus= is a small and inconstant muscle which
arises from the inner surface of the great cornu of the hyoid bone near
its lower end. It passes upward and backward, turns inward toward the
raphé, and spreads out under the next muscle.
(_b_) The =chondro-pharyngeus=, broad and fleshy, arises from the
thyroid cornu of the hyoid bone and by a thin fasciculus from the wing
of the thyroid cartilage and ends at the median raphé.
5. The =thyro-pharyngeus= arises from the lateral surface of the wing of
the thyroid cartilage. Its fibers pass forward and inward to the median
raphé.
6. The =crico-pharyngeus= arises from the cricoid cartilage and ends at
the raphé. The fibers are directed upward, forward, and inward; they
blend behind with the longitudinal fibers of the œsophagus.
The last three muscles are constrictors of the pharynx.
The =pharyngeal aponeurosis= is attached to the base of the cranium. It
is well developed on the inner face of the palato-pharyngeus muscle and
forms a median raphé (Raphé pharyngis) dorsally, which is wide in its
posterior part.
The =mucous membrane= of the pharynx is continuous with that of the
several cavities which open into it. It is thin and closely adherent to
the base of the skull in the vicinity of the posterior nares, where the
muscular wall is absent. Behind the Eustachian openings is a median
cul-de-sac, the =pharyngeal recess=. The recess is somewhat variable,
but is usually about an inch in depth and will admit the end of the
finger. In the ass and mule it is much deeper. Here also the muscular
wall is absent and the mucous membrane lies against the guttural
pouches. From the Eustachian opening a fold of the mucous membrane
(Plica salpingo-pharyngea) passes toward but does not reach the
laryngeal opening. Below, a horizontal fold, the =posterior pillar of
the soft palate= (Arcus pharyngopalatinus), passes along the lateral
wall and unites with its fellow over the entrance to the œsophagus. The
upper part of the cavity (the naso-pharynx) is lined with a ciliated
epithelium, while the lower part (oro-pharynx) has a stratified squamous
epithelium. The communication between the two is oval and is bounded by
the free edge of the soft palate and its posterior pillars; it is termed
the =pharyngeal isthmus=. On either side of the laryngeal opening is a
narrow deep depression, the =pyriform sinus= (Recessus piriformis).
The submucous tissue contains numerous mucous glands (Glandulæ
pharyngeæ). In the young subject the lymph follicles are numerous and
form a collection dorsally and between the Eustachian openings, known as
the pharyngeal tonsil.
=Blood-supply.=—External carotid, external maxillary, and
thyro-laryngeal arteries.
=Nerve-supply.=—Glosso-pharyngeal, vagus, and sympathetic nerves.