a MUSCLES OF MASTICATION. 381 
Muscures oF MASTICATION. 
The muscles of mastication comprise the masseter, temporal, external and 
internal pterygoids, and buccinator (described above). 
The masseter arises (1) superficially from the lower border of the zygoma in 
its anterior two-thirds, and (2) more deeply from the deep or inner surface of the 
Epicranial aponeurosis a 
Temporal fascia 
Temporal fascia (deep 
layer) 
OCCIPITO-FRONTALIS - 
TEMPORAL MUSCLE — 
\ _ ORBICULARIS 
Auriculo-temporal = Sor \\ Wii), PALPEBRARUM 
nerve iy 
Superficial temporal 
I c Dae Tip, — ZXGOMATICUS MAJOR 
artery 
MAsseETER (deep fibres) ¥ 
___ MAssETER (superficial 
fibres) 
Parotid gland -—~Stenson’s duet 
~~ BUCCINATOR 
~~DEPRESSOR ANGULI ORIS 
Facial artery 
Fria. 280.—Muscies oF MAstTIcaTIon (superficial view). 
zygoma in its whole length. The superficial fibres are directed downwards and 
backwards towards the angle of the jaw; the deeper fibres are directed vertically 
downwards. The muscle is inserted into the outer surface of the ramus of the 
lower jaw and coronoid process. The deepest fibres blend with the fibres of the 
subjacent temporal muscle. 
The masseter muscle occupies the posterior part of the cheek. It is covered by 
the parotid gland, and is crossed by Stenson’s duct and the branches of the facial 
nerve, and it conceals the lower jaw and a part of the temporal muscle. 
The temporal muscle is a fan-shaped muscle arising from the whole area of 
the temporal fossa, as well as from the temporal fascia which covers it. Its 
converging fibres pass beneath the zygomatic arch. In the pterygoid region the 
muscle is inserted into the deep surface and apex of the coronoid process, and into 
the anterior border of the ramus of the lower jaw. 
The muscle is concealed by the temporal fascia, zygoma, the masseter muscle, 
and the coronoid process. It crosses over the external pterygoid muscle and the 
internal maxillary artery. 
The external pterygoid muscle arises by two heads, upper and lower. The 
upper head is attached to the under surface of the great wing of the sphenoid ; the 
lower head takes origin from the outer surface of the external pterygoid plate. The 
muscle is directed outwards and backwards, to be inserted into (1) the depression in 
front of the neck of the lower jaw, and (2) the inter-articular fibro-cartilage and 
capsule of the temporo-maxillary articulation. 
The muscle is placed deeply in the pterygoid region ; being covered by the 
temporal muscle and coronoid process, it partially conceals the internal pterygoid 
muscle and the trunk and branches of the inferior maxillary nerve. The internal 
