The =guttural pouches=, right and left (Figs. 255, 256, 569), are large
mucous sacs, each of which is a ventral diverticulum of the Eustachian
tube (Diverticulum tubæ auditivæ); they are not present in the
domesticated animals other than the equidæ. They are situated between
the base of the cranium and the atlas above and the pharynx below.
Medially they are in apposition in great part, but are to some extent
separated by the intervening ventral straight muscles of the head. The
anterior end is a small cul-de-sac which lies below the body of the
presphenoid between the Eustachian tube and the median recess of the
pharynx. The posterior extremity lies near or below the atlantal
attachment of the longus colli. The pouch is related dorsally to the
base of the cranium, the atlanto-occipital joint capsule, and the
ventral straight muscles. Ventrally it lies on the pharynx and the
origin of the œsophagus. Laterally the relations are numerous and
complex. They comprise the pterygoid, levator palati, tensor palati,
stylo-hyoideus, and digastricus muscles; the parotid and submaxillary
glands; the external carotid, internal maxillary, and external maxillary
arteries; the internal maxillary and jugular veins; the pharyngeal or
guttural lymph glands; the glosso-pharyngeal, hypoglossal, and superior
laryngeal nerves. The vagus, accessory, and sympathetic nerves, the
superior cervical ganglion, the internal carotid artery, and the
inferior cerebral vein are situated in a fold of the upper wall of the
pouch. The pouch is reflected around the anterior border of the great
cornu of the hyoid bone so as to clothe both surfaces of the upper part
of the latter. It thus forms an outer compartment, which extends
backward external to the great cornu and the occipito-hyoideus muscle;
it is related externally to the parotid gland, the articulation of the
jaw, the ascending part of the internal maxillary artery, the
superficial temporal artery, and the facial nerve; dorsally it covers
the mandibular nerve and its chief branches, and is attached to the
styloid process of the conchal cartilage.
Each pouch communicates with the pharynx through the pharyngeal orifice
of the Eustachian tube, and is in direct continuity with the mucous
membrane of the latter.
The wall of the pouch is a delicate mucous membrane which is in general
rather loosely attached to the surrounding structures. It is covered
with ciliated epithelium and is supplied with mucous glands.
[Illustration: