Page 183 - My FlipBook

AREOLAR TISSUE, TENDONS, AND MUSCLES. 193
fibres from these various points of origin pass baclvMard and curve inward
until they meet those of the opposite side, where many of the fibres inter-
lace. The remainder are inserted into the median line of the pharyngeal
raph6, in front of the cervical vertebrse, and a few of the fibres are inserted
in the pharyngeal spine and the aponeurosis attached t(j tlie basilar process
of the occipital bone.
The upper margin of the muscle is concave, being suspended at its
corners by the pterygoid process in front and the pharyngeal aponeurosis
behind. The surface between the border of the muscle and the base of
the brain-case is occupied by the pharyngeal aponeurosis, the lower
border of which becomes part of the wall of the pharynx, and is covered
by the middle constrictor muscle.
YariaUons.—The different heads of origin may be from various mus-
cles. The azygos pharvngis (Meckel) is a slip arising from the pharyn-
geal spine and inserted into the posterior pharyngeal wall.
Relations.—To the outer surface of the muscle are the cervical verte-
brae, the internal curotid artery, the pneumogastric, the glosso-pharyn-
geal, and spinal accessory nerves, the middle constrictor and the stylo-
pharyngeus muscles ; related to its inner surface are the palato-pharyn-
geus muscle and the tonsils. The origin of the levator palati muscle
and the Eustachian fossa are also near to this surface.
Nerves—The nerve-supply is derival from the pharyngeal plexus.
Actions.—When it contracts, the pterygoid portion, l)eing fixed at
both its origin and insertion, straightens the curvature of the superior
border and, at the same time, narrows the diameter of the naso-
pharynx. The pterygo-maxillarv and inferior maxillary portions assist
in drawing the posterior wall of the pharynx forward,
Tlte Middle Constrictor of the Pltarynx is a flattened radiating muscle
situated on a plane below the superior constrictor. It arises from the
greater and lesser cornua of the hyoid bone and the stylo-hyoid ligament.
The fibres radiate as they pass backward, and, curving inward, are
inserted in the posterior median raphe, some of them interlacing with
those of the opposite muscle. The extent of their insertion is from
below the level of the hyoid bone to a position near the occipital bone.
The lower portions descend beneath the inferior constrictor as it passes
backward, while the upjier fibres ascend and overlap those of the supe-
rior constrictor, the middle portion passing directly backward.
Variations.—As in the previous muscle, the slips arising from differ-
ent points of origin, as those from the greater and lesser cornua, may
serve as separate and distinct muscles. Fibres may be received from the
body of the hyoid bone, and a slip (cyndesmo-pharyngeus, Douglas)
from the thyro-hyoid ligament is frequently present. Fibres may also
arise from the tongue and posterior ])art of the mylo-hyoid ridge of the
inferior maxilla, and interlace with the genio-glossus, as does the superior
constrictor. The upper fibres may reach the occipital bone.
Belations.—The external and posterior surface with the longus colli
and rectus anticus major ; laterally, the carotid vessels, the pharyngeal
plexus, and some lymphatic glands. The inferior constrictor overlaps
its lower portion. The stylo-pharyngeus muscle passes between the
superior and middle constrictors, and the superior laryngeal nerve lies
Vol. 1.-13