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Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: M: Masseter, Pterygoideus Lateralis, Pterygoideus Medialis, Temporalis

Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: M

Masseter, Pterygoideus Lateralis, Pterygoideus Medialis, Temporalis

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD

Peer Review Status: Internally Peer Reviewed
The muscles of mastication are derivatives of a single muscle mass; indications of their common origin can be seen in partial unions of the various muscles. Thus, fibers from the posterior portion of the deeper head of the masseter may join the temporal, fibers from both the temporal and masseter sometimes pass to the anterior border of the fibrocartilage of the mandibular articulation (temporomandibular joint), and the temporal and lateral pterygoid have been observed in some cases to be connected.

The temporal muscle may have a more extensive cranial origin than usual. It may be formed of two superimposed layers and it may be more or less fused with the lateral pterygoid or send a fasciculus to the condylar process.

Fibers arise from the anterior edge of temporalis to form a distinct muscle named temporalis minor (Henle). It inserts onto the mandibular notch.

Pterygoideus proprius (Henle) is a nearly vertical band of muscular and tendinous fibers, sometimes entirely tendinous, passing from the infratemporal crest of the great wing of the sphenoid, over the surface of the lateral pterygoid muscle, to the lower part of the lateral pteygoid plate, or to the tuberosity of the palate or superior maxillary bone. It has been found sending a slip to the pterygomaxillary ligament or even to the lower jaw.

Pterygospinous is a muscular slip occasionally seen arising from the spine of the sphenoid or the adjoining part of the vaginal process, and inserted into the posterior margin of the lateral pterygoid plate, between the lateral and medial pterygoid muscles. A fibrous band connecting these parts (pterygo-spinous ligament) is frequently present, and may be converted to bone.

The significance of these muscles passing between immovable parts is obscure. The masseter may be divided into two distinct fasciculi; it may join the temporalis and digastricus. The medial pterygoid may send a fascicle to the masseter and give rise to the styloglossus.


References

Anson, B.J., Ed. (1966) Morris' Human Anatomy,12th ed., The Blakiston Division, McGraw-Hill Book Company, New York.

Bertelli, D. (1889) Le muscle temporal superficiel. Arch. Ital. Biol. 11:420.

Fleissig, J. (1910) Eine Varietät des Musculus masseter und der Mandibula. Anat. Anz. 36:505-510.

Fusari, R. (1897) Contribution a la connaissance morphologique du muscle temporal. Arch. Ital. Biol. 28:471-472.

Grant, P.G. (1973) Lateral pterygoid: two muscles? Am. J. Anat. 138:1-9.

Gruber, W. (1880) Musculus digastricus maxillae inferioris mit Ursprung seines vorderen Bauches an und hinter der Mitte des Seitentheiles der Maxilla im Bereiche der Strecke zwischen dem Ansatze des M. masseter und dem Ursprunge des M. depressor anguli oris. Arch. Path. Anat. Physiol. Klin. Med. 81:449-453.

Macalister, A. (1871) The varieties of the styloid muscles. J. Anat. Physiol. 5:28-31.

Macalister, A. (1875) Observations on muscular anomalies in the human anatomy. Third series with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-130.

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