Origin from the whole surface of the internal pterygoid fossa ([Fig. 40], s).
Insertion by fleshy fibres into the ventral surface of the external pterygoid and its tendon, into the medial surface of the angular process of the mandible and caudad of the angular process for about one centimeter into a fascia common to it and the masseter muscle, and into the stylomandibular ligament.
[Fig. 66].—Obliquely Ventral View of the Deep Muscles of the Lower Jaw and Palate.
![[Fig. 66]](#3418956513767812439_illo112lg.jpg.id-3123138378288292735.wrap-0.html.html){kind=link}
The tongue and other structures forming the floor of the mouth have been removed, showing the roof of the mouth. On the right side the masseter and pterygoideus internus have been removed, a, a′, M. masseter; b, M. pterygoideus externus; c, M. pterygoideus internus; d, d′, M. tensor veli palatini; e, e′, M. levator veli palatini; f, M. constrictor pharyngis superior. 1, aponeurosis of the velum palatinum; 2, ridges formed by the palatines and pterygoid portions of the sphenoid; 3, hamular processes; 4, free caudal border of the velum palatinum; 5, bulla tympani.
Relations.—Ventral surface with the styloglossus and the soft palate. Dorsal surface with the bulla tympani (5) and base of the skull. Cranial surface with the pterygoideus externus (b), with which it is partly united.
Action.—Assists the pterygoideus externus.
(b) Muscles of the Hyoid Bone.
M. stylohyoideus ([Fig. 65], d).—The stylohyoid is a ribbon-like muscle about three millimeters wide. It lies on the superficial surface of the digastric, caudad and ventrad of the angle of the jaw.
Origin by fleshy fibres from the outer surface of the stylohyal bone near its middle. The muscle curves over the outer surface of the digastric (b), and ends about one centimeter from the middle line in a slender flat tendon.