Craniofacial Muscles

176 C.L. Ludlow
a
MH
HG
Bolus
aspiration
GH
Effects of hyo-laryngeal elevation
on Airway protection
HG
b
MH
GH
UES
UES
Effects of hyo-laryngeal elevation
on opening the UES
Fig. 10.1 ( a ) Schematic illustration of the muscle vectors to raise the hyo-laryngeal complex to
close the laryngeal vestibule and protect the airway from bolus entry. ( b ) A schematic illustration
of how hyo-laryngeal elevation can stretch the cricopharyngeus to assist with the movement of the
bolus through the upper esophageal sphincter. The muscles are mylohyoid (MH), geniohyoid
(GH), hyoglossus (HG), and thyrohyoid (TH). The upper esophageal sphincter is labeled UES
pharyngeal constrictor functions as part of the upper esophageal sphincter along
with the cricopharyngeus (Mu and Sanders 2001 ) .
The upper esophageal sphincter is a complex structure. First, Mu and Sanders
have recently described the cricothyropharyngeus muscle found only in human specimens
(Mu and Sanders 2008 ) . This muscle originates from the anterior arch of the
cricoid cartilage, courses between the inferior pharyngeal constrictor and cricopharyngeus
muscles to insert into the median raphe at the posterior midline of the pharynx
with separate innervation of two compartments; a laryngeal portion innervated
by the external superior laryngeal nerve, and a pharyngeal portion innervated by the
pharyngeal plexus. The cricopharyngeus forms the major part of the upper esophageal
sphincter and is of great importance to swallowing—this muscle is normally
tonically active keeping the sphincter closed to prevent spillage of the contents of the
upper esophagus into the hypopharynx and the upper airway. Relaxation is essential
to allow the bolus to be cleared out of the hypopharynx and into the esophagus.
Without relaxation and bolus clearance there is the collection of residual of the bolus
which will collect in the pyriform sinuses, and spillage back into the glottis and
through the vocal folds places the person at risk of aspiration of food or liquid into