Lateral pterygoid muscle
Citation, DOI & article data
The lateral pterygoid muscle, also known as pterygoideus externus or external pterygoid muscle, is one of the muscles of mastication.
The lateral pterygoid is a short, thick muscle, somewhat conical in form, which extends almost horizontally, posteriorly and laterally between the infratemporal fossa and the condyle of the mandible. It arises by two heads: an upper (superior) and a lower (inferior).
The superior part is active during retrusion (opposite of protrusion) and ipsilateral jaw movement. It is also essential in pulling the capsule and disc forward during mouth opening, thereby maintaining normal relationship between the condyle of the mandible and the TMJ disc.
The inferior part is responsible for opening of the mouth, protrusion and contralateral jaw movement.
Hyperactivity of the LPM muscle has been described in TMJ internal derangement, especially with longstanding anterior displacement of the disc without recapture. Thickening of the tendon (inferior part) can give rise to the "double disc sign".
Anatomical variants of the lateral pterygoid include:
- Fusion with temporalis or digastric muscle
- Variation in number of heads
- Three headed variant with an inner head originating at the greater wing of the sphenoid
- Single headed variant
- Variation in number of insertions
- Three insertion sites: articular disc, TMJ capsule, condyle of the mandible
- Single insertion site at the condyle only
- 1. Standring S (editor). Gray's Anatomy (39th edition). Churchill Livingstone. (2011) ISBN:0443066841. Read it at Google Books - Find it at Amazon
- 2. Gray H. Anatomy of the Human Body, 20th edition. (1918) ISBN:1587341026. Read it at Google Books - Find it at Amazon
- 3. Sommer O, Aigner F, Rudisch A et al. Cross-Sectional and Functional Imaging of the Temporomandibular Joint: Radiology, Pathology, and Basic Biomechanics of the Jaw. Radiographics. 2003;23(6):e14. doi:10.1148/rg.e14 - Pubmed
- 4. Tomas X, Pomes J, Berenguer J et al. MR Imaging of Temporomandibular Joint Dysfunction: A Pictorial Review. Radiographics. 2006;26(3):765-81. doi:10.1148/rg.263055091 - Pubmed
- 5. R. Shane Tubbs, Mohammadali M. Shoja, Marios Loukas. Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. (2016) ISBN: 9781118430354 - Google Books