Page 308 - My FlipBook

318 ANAT03IY.

of the liyoid bone, and is distributed to the crico-thyroid muscle. It
also sends branches to the interior constrictor of the pharynx and the
arytenoid muscles. It receives communicating filaments from the
upper cervical sympathetic ganglion, and interlaces with branches from
the inferior laryngeal nerve. It also sends communicating or cardiac
branches to the cardiac plexus. Occasionally communicating branches
from tins nerve pass to the pharyngeal plexus, distributing branches to
the thyroid body, the mucous membrane of the true vocal cords, and
the depressor muscles of the hyoid bone.
The Internal Laryngeal Brandt is shorter though thicker than the
externa] laryngeal. It passes forward along the thyro-hyoid membrane
to the median line of the neck, pierces that membrane in company with
the superior thyroid artery, and enters the internal portion of the larynx,
being situated beneath the mucous membrane. Here it divides into
numerous branches, which are distributed as folloM's :
1. A branch which passes upward in the aryteno-epiglottic fold to
the posterior surface of the epiglottis. Some writers claim that a few
filaments of this nerve pass through the epiglottis to its anterior surface.
2. A branch which passes to the base of the tongue as far as the cir-
cunivallate pa})illce.
3. Several small branches which pass downward and supply the
mucous menil)rane of the aryteno-epiglottic fold in the region of the
glottis, and as far downward as the false vocal cords and the back of
the larynx.
4. There is also a long branch which passes beneath the ala of the
thyroid cartilage, and unites with a branch from the recurrent or infe-
rior laryngeal nerve at the lower pt)rtion of the larynx.
The Inferior or Reeiwrent Lrtrr/ngeal Nerve is the principal motor
nerve of the larynx, and supplies all its intrinsic muscles excepting the
crico-thyroid. The right and left inferior laryngeal nerves differ in
their origin and in their relation to the tissues of the neck.
The Rif/lit Inferior Lariingeal Nerve arises from the main trunk of
the pneumogastric, close to the point where this nerve crosses the right
subclavian artery. It curves around the under and posterior surface
of tliis artery, passes obliquely upward and inward behind the common
carotid and inferior thyroid arteries, and reaches a groove between the
trachea and tlie (esojihagus, ascending in this groove to the level of the
crico-thyroid articulation.
The Left Inferior Laryngeal Nerve arises from the main trunk of the
pneumogastri(! as that nerve ])asses over the left extremity of the trans-
verse jiortion of the arcii of the aorta. It curves around the lower sur-
face of tlie arch just external to the ductus arteriosus or its remains after
birth, when it bec^omes a ligament. It then passes upward on its pos-
terior surface, and similarly to the nerve of the right side; extends
Vx'hind the common carotid and inferior thyroid arteries to the groove
between the ti-aclica and the (esoj)iiagus, terminating on a level with the
crico-thyroid articulation, where botli nerves break up into branches.
Their terminal branches are distributed to all the intrinsic muscles of
the larynx excepting tiie ci'ico-thvroids, tiiese muscles being supplied
by the superior laryngeal. It also distributes a few filaments to the